Term
What is the primary causative agent of tooth decay? |
|
Definition
|
|
Term
What causes cariogenic dental plaques? |
|
Definition
|
|
Term
What is periodontal disease? |
|
Definition
Inflammation of the gums in response to plaque bacteria such as in dental calculus or gingivitis Responsible for tooth loss in the elderly |
|
|
Term
|
Definition
|
|
Term
What causes trench mouth? |
|
Definition
Synergistic infection of spirochetes (oral spirochete of Treponema genus; T. pallidum is the cause of syphilis) and anaerobic bacteria |
|
|
Term
What causes watery diarrhea? |
|
Definition
Pathogenic mechanisms that attack the proximal small intestine (more than 90% of physiologic net fluid absorption occurs) |
|
|
Term
What organisms cause the purest form of watery diarrhea? |
|
Definition
Enterotoxin-secreting bacteria such as Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC), which cause fluid loss without cellular injury |
|
|
Term
Which causes of watery diarrhea are uniquely not self limiting to 1-3 days? |
|
Definition
V. cholerae, which usually produces a more severe illness
Giardia lamblia, which produces a watery diarrhea that may last for weeks |
|
|
Term
|
Definition
Rapid onset of frequent intestinal evacuations, but the stools are of smaller volume than in watery diarrhea and contain blood and pus |
|
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Term
|
Definition
Inflammatory and/or destructive changes in the colonic mucosa either by direct invasion or by production of cytotoxins |
|
|
Term
What causes enteric fever? |
|
Definition
Penetration by the organism of the cells of the distal small bowel with subsequent spread outside the bowel to the biliary tract, liver, mesentery, or reticuloendothelial organs |
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|
Term
What is the only infection causing enteric fever that is well studied? |
|
Definition
Typhoid fever caused by Salmonella enterica serotype Typhi |
|
|
Term
What are the most common causes of traveler's diarrhea? |
|
Definition
50% caused by ETEC 10%-20% by Shigella species Ingestion of uncooked or incompletely cooked foods is the most likely source of infection |
|
|
Term
What are the most common causes of food poisoning? |
|
Definition
Salmonella, Clostridium perfringens, and S. aureus Most often due to improper storage temperature |
|
|
Term
What are the most common causes of hospital associated diarrhea? |
|
Definition
E. coli (in infants) C. difficile (patients on antibiotics) |
|
|
Term
Which hepatitis virus is "silent" and often goes undetected? |
|
Definition
|
|
Term
How is liver cell damage present? |
|
Definition
Hepatic cell degeneration and necrosis, cell dropout, ballooning of cells, acidophilic degeneration of hepatocytes forming Councilman or apoptotic bodies |
|
|
Term
What are the unique features of Hep A? |
|
Definition
Single stranded RNA picornavirus Resists inactivation and is stale at -20C with low pH Never becomes chronic, has only one serotype, no animal reserve, vaccine existence is leading to eradication of the virus |
|
|
Term
What kind of abnormal liver cells are characteristic of liver disease? |
|
Definition
|
|
Term
What are the symptoms of Hep A? |
|
Definition
Fever, anorexia, nausea, pain in upper right abd, jaundice, dark urine and clay-colored stool, enlarged, tender liver, elevated serum aminotransferase and bilirubin Will never cause cancer or progress to chronic liver disease |
|
|
Term
|
Definition
Almost all are self limiting to a few weeks-months |
|
|
Term
How is Hep A detected in serology studies? |
|
Definition
Fecal HAV detected 4-6 weks IgM Anti-HAV detected early on but then drops IgG is inclusive because it increases over time, needs to see the trend |
|
|
Term
How long in advance must immune serum globulin be given to confer temporary immunity to Hep A? |
|
Definition
Protective if given before or during the incubation period of the disease Not indicated once symptoms have appeared |
|
|
Term
What are the unique features of Hep B? |
|
Definition
Member of hepadnaviridae family Smallest DNA virus known All newborns become chronic, 50% of children become chronic |
|
|
Term
What is present in the nuclei of cells infected with Hep B? |
|
Definition
HBcAg, HBeAg, and hepatitis B DNA |
|
|
Term
What is present in the cytoplasm of cells infected with Hep B? |
|
Definition
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|
Term
The HBV S gene codes for what? |
|
Definition
The "major" envelope protein HBsAg |
|
|
Term
What does the HBV P gene code for? |
|
Definition
Largest gene, codes for DNA polymerase |
|
|
Term
What does the HBV C gene code for? |
|
Definition
Two nucleocapsid proteins, HBeAg, a soluble, secreted protein and HBcAg, the intracellular core protein |
|
|
Term
What does the HBV X gene code for? |
|
Definition
HBxAg, which can transactivate the transcription of cellular and viral genes; its clinical relevance is not known, but it may contribute to carcinogenesis by binding to p53 |
|
|
Term
How do infants acquire HBV from their mother? |
|
Definition
Not vertically, accquired intrauterally via ingestions or abrasions during birth |
|
|
Term
What are the consequences of chronic HBV infection? |
|
Definition
Necrosis of hepatocytes, Collapse of the reticular framework of liver Progressive fibrosis Leads to syndrome of postnecrotic hepatic cirrhosis |
|
|
Term
What causes extrahepatic manifestations of HBV? |
|
Definition
Deposition of HBsAg-anti-HBs circulating immune complexes in tissue blood vessel walls results in prodromal serum sickness-like syndrome, glomerulonephritis, and nephritic syndrome |
|
|
Term
Polyarteritis nodosa is associated with which Hep virus? |
|
Definition
HBV Develops in considerably fewer than 1% of patients with chronic HBV infection However, 20 to 30% of patients with PAN have HBsAg in serum |
|
|
Term
Essential mixed cryoglobulinemia is associated with which Hep virus? What are its features? |
|
Definition
HBV, HCV Precipitates at cold temp Arthritis Cutaneous vasculitis (palpable purpura) Glomerulonephritis (occasional) Circulating cryoprecipitable immune complexes (more than one immunoglobulin class) |
|
|
Term
What are the characteristics of HBsAg? |
|
Definition
HBV surface antigen formed in excess and seen in serum |
|
|
Term
What are the characteristics of HBcAg |
|
Definition
HBV core antigen found in nucleus of infected hepatocytes by immunofluorescence |
|
|
Term
What are the characteristics of HBeAg |
|
Definition
HBV glycoprotein associated with the core antigen, used as a marker of potential virus activity, only seen when HBsAg is also present |
|
|
Term
What are the characteristics of Anti-HBs |
|
Definition
Ab to HBsAg, correlates with past infection or immunization |
|
|
Term
What are the characteristics of Anti-HBc |
|
Definition
Ab to HBcAg, seen in acute infection and chronic carriers, can be either IgM or IgG (acute vs. chronic) |
|
|
Term
Anti-HBc IgM indicates what? |
|
Definition
|
|
Term
Anti-HBc IgG indicates what? |
|
Definition
|
|
Term
Presence of Anti-HBe indicates what? |
|
Definition
Virus is not actively reacting and is in recession |
|
|
Term
What is the best diagnostic measure for HBV detection? |
|
Definition
IgM antibody to HBcAg along with or without HBsAg in the serum |
|
|
Term
How is vertical transmission of HBV to newborns prevented? |
|
Definition
Use of combined HBIG and HBV vaccine |
|
|
Term
How do you treat chronic HBV? |
|
Definition
Interferon-alpha, Lamivudin, Adefovir |
|
|
Term
What is the leading cause for liver transplants in the US? |
|
Definition
Liver failure due to Hep C |
|
|
Term
|
Definition
Commonly transmitted through blood contact (blood transfusion or needle sharing) than through transfer of body fluids; vertical transmission is possible |
|
|
Term
What is the most common complication of HCV? |
|
Definition
Chronic liver disease (80% of cases with a course of intermittent inflammation and normality) 10-20% of chronic patients develop cirrhosis or cancer in the long run |
|
|
Term
What is the average time from infection to the development of chronic hepatitis in HCV patients? |
|
Definition
10-18 years Often asymptomatic |
|
|
Term
What are the extra-hepatic manifestations of HCV? |
|
Definition
Essential mixed cryoglobulinemia (EMC) Circulating immune complexes containing HCV RNA Immune-complex glomerulonephritis |
|
|
Term
|
Definition
Detection of HCV antibody May remain negative for 1-3 weeks after clinical onset May never become positive in up to 20% of patients with acute, resolving disease |
|
|
Term
|
Definition
Combination treatment with interferon-a and ribavirin |
|
|
Term
The protein-RNA complex of Hep D is surrounded by what? |
|
Definition
|
|
Term
|
Definition
IgM or IgG antibodies or both to the delta antigen in serum IgM antibodies appear within 3 weeks of infection and persist for several weeks IgG antibodies persist for years |
|
|
Term
|
Definition
|
|
Term
|
Definition
Interferon alpha Response to treatment in patients with delta hepatitis (and hepatitis B) is less than in those with hepatitis B alone |
|
|
Term
The majority of GI pathogenic bacteria grow on what medias? |
|
Definition
Majority are gram-neg and grow on MacConkey agar which inhibits gram-pos growth |
|
|
Term
How is Hektoen agar used to diagnostically distinguish GI pathogenic bacteria? |
|
Definition
Inhibits common colon flora Selective to recover Salmonella and Shigella spp. Indicators to detect H2S production (black centers to colony) |
|
|
Term
What does Campylobacter spp. grow on? |
|
Definition
|
|
Term
What is acute diarrhea and what are its causes? |
|
Definition
Diarrhea lasting 7-14 days caused by: Drugs Infectious Agents (Virus, Bacteria, Parasite) Feeding after a long fasting Fecal Impaction |
|
|
Term
Which GI bacteria have vaccines? |
|
Definition
|
|
Term
What makes distinguishing E. coli so difficult? |
|
Definition
Many strains are a part of the normal GI flora and basic diagnostics will not discriminate between normal and pathogenic E. coli |
|
|
Term
What are the most common causes of Enterotoxigenic E. coli (ETEC)? |
|
Definition
Ingestion of contaminated water or food Major cause of travelers diarrhea |
|
|
Term
What is the most common progression of a GI infection? |
|
Definition
Bacteria pass through to intestines Attachment to mucous layer or intestinal epithelia Secretion of toxins Induction of diarrhea and potentially other symptoms Clearance by host immune system |
|
|
Term
What are the symptoms of an Enterotoxigenic E. coli (ETEC) infection? |
|
Definition
Watery diarrhea, cramps, vomiting, malaise, fever More severe symptoms if the infecting ETEC strain secretes both types of toxins |
|
|
Term
What toxins are secreted by Enterotoxigenic E. coli (ETEC)? |
|
Definition
Either one or both: ST (small toxin) LT (heat labile toxin pierces the membrane of target cell) |
|
|
Term
How is Enterotoxigenic E. coli (ETEC) diagnosed? |
|
Definition
Characteristic symptoms with ONLY lactose fermenting organisms on differential media ELISA for toxins |
|
|
Term
How is Enteropathogenic E. coli (EPEC) contracted? |
|
Definition
Lack of good hygienic practices: fecal oral contamination Most often in infants (1 year old or less usually) with adults as carriers |
|
|
Term
How is the progression of Enteropathogenic E. coli (EPEC) unique? |
|
Definition
Secretes of factors that alter the “host” cells (Type III secretion) Changes epithelial cell cytoskeleton to create a “pedestal” for the bacterial cell |
|
|
Term
What are the symptoms of an Enteropathogenic E. coli (EPEC) infection? |
|
Definition
Fever, vomiting, watery diarrhea that may contain large amounts of mucus Associated with clusters in the US such as daycare, hospitals, nursery |
|
|
Term
How is Enterohemorrhagic E. coli (EHEC) most often contracted? |
|
Definition
Lack of good hygienic practices Ingestion of insufficiently cleaned or cooked foods Reservoir is usually adult cattle which are asymptomatic |
|
|
Term
How is the progression of Enterohemorrhagic E. coli (EHEC) unique? |
|
Definition
Also involved in Type III secretion and pedestal formation May result in temporary or permanent systemic damage |
|
|
Term
What are the signs and symptoms of Enterohemorrhagic E. coli (EHEC)? |
|
Definition
Watery diarrhea that progresses to *bloody diarrhea, abdominal cramps, +/- fever, may also develop hemolytic uremic syndrome (HUS) |
|
|
Term
What causes hemolytic uremic syndrome (HUS)? |
|
Definition
o Toxin release into the bloodstream leads to lysis of erythrocytes, thrombocytes, and destruction of glomerular capillary endothelial cells Children and elderly are more susceptible, can be fatal |
|
|
Term
Hemolytic uremic syndrome (HUS) is most commonly associated with what? |
|
Definition
|
|
Term
What toxins are secreted by Enterohemorrhagic E. coli (EHEC)? |
|
Definition
Functionally and structurally related to the Shiga toxin AB type toxins The A subunit interacts with cellular ribosomes cleaving a single adenine residue from the 28S rRNA* leading to a shut-down of host protein synthesis |
|
|
Term
What special consideration should be made in the treatment of Enterohemorrhagic E. coli (EHEC)? |
|
Definition
Monitoring for renal failure |
|
|
Term
How is Enterohemorrhagic E. coli (EHEC) diagnosed? |
|
Definition
Cultures that fail to ferment sorbitol MacConkey agar using sorbitol instead of lactose ELISA for toxins
MUG assay: EHEC typically do not produce b-glucoronidase while 92% of other strains do |
|
|
Term
How is Enteroinvasive E. coli (EIEC) contracted? |
|
Definition
Fecal to oral contamination Reservoirs involve human sources |
|
|
Term
What is unique about the progression of Enteroinvasive E. coli (EIEC) infections? |
|
Definition
Secretion of factors that induce uptake and transmission by M cells* Entry into the inferior or lateral sides of intestinal epithelial cells |
|
|
Term
What are the signs and symptoms of an Enteroinvasive E. coli (EIEC) infection? |
|
Definition
Many are asymptomatic or with transient fever Early: Fever, severe cramps, Watery diarrhea Late: Reduced fever, increased diarrhea with blood*, urgency, tenesmus |
|
|
Term
What additional treatment option can be used for Enteroinvasive E. coli (EIEC)? |
|
Definition
Antibiotics may be administered for more severe cases and will decrease the length of symptoms |
|
|
Term
How is Enteroinvasive E. coli (EIEC) diagnosed? |
|
Definition
HE (Hektoen enteric) agar, MacConkey DNA probes are commercially available |
|
|
Term
What is unique about the progression of Enteroaggregative E. coli (EAEC) infections? |
|
Definition
Bacteria replicate and aggregate in a unique “stacked brick” fashion (biofilm) |
|
|
Term
What is a unique symptom of Enteroaggragative E. coli (EAEC) infection? |
|
Definition
May cause a protracted course of diarrhea (>14 days) in adults and children in all parts of the world |
|
|
Term
What are the toxins secreted by Enteroaggragative E. coli (EAEC)? |
|
Definition
ShET1 (Shigella enterotoxin 1) similar to a toxin common in Shigella EAST1 shows similarity to ETEC toxin ST Pet: A serine protease that alters the enterocyte cytoskeleton (not in all strains) |
|
|
Term
Which E. coli strains cause watery diarrhea? |
|
Definition
EPEC, ETEC, most Viral, (EAEC) |
|
|
Term
Which E. coli strains cause bloody diarrhea? |
|
Definition
EHEC, Shigella spp./EIEC, (EAEC) |
|
|
Term
Which E. coli strains cause watery and mucoid diarrhea? |
|
Definition
|
|
Term
Which E. coli strains are associated with recent travels? |
|
Definition
|
|
Term
What is the appearance of Yersinia spp.? |
|
Definition
Gram negative bacillus motile at 25C but not 37C |
|
|
Term
What does Yersinia culture on? |
|
Definition
Most enteric media except Salmonella-Shigella agar Produces urease |
|
|
Term
Yersinia is very sensitive to levels of what mineral? |
|
Definition
|
|
Term
How is Yersinia contracted? |
|
Definition
Ingestion of contaminated food or water Handling infected animals or carcasses Very rarely blood transfusion Swine is the primary reservoir |
|
|
Term
What is unique about the pathogenesis of Yersinia infections? |
|
Definition
Bacteria invade the M cells of the gut and start replicating Phagocytic cells ingest Yersinia spreading them to the reticuloendothelial system, and are then killed by the bacteria delaying the immune response |
|
|
Term
What are the signs and symptoms of a Yersinia infection? |
|
Definition
Enterocolitis Mesenteric adenitis and terminal ileitis Exudative pharyngitis Tender red nodules on extensor surfaces of limbs |
|
|
Term
What symptoms does enterocolitis refer to? |
|
Definition
Fever lasting 1-3 weeks, diarrhea containing mucous and blood, abdominal cramps, anorexia, nausea and vomiting, Rectal bleeding in severe cases Potentially severe dehydration |
|
|
Term
What post-infectious syndrome is common in patients recovering from a Yersinia infection? |
|
Definition
|
|
Term
What is the general function of toxins secreted by Yersinia? |
|
Definition
Most of the virulence factors are regulated in expression by the local environment and are aimed at suppressing the immune system |
|
|
Term
How is Yersinia diagnosed? |
|
Definition
Stool culture on enteric media |
|
|
Term
What media is used to culture Francisella tularensis? |
|
Definition
Requires special media for growth that is enriched in cysteine |
|
|
Term
How is Francisella tularensis contracted? |
|
Definition
Insect bites (no human to human transmission) |
|
|
Term
What are the signs and symptoms of Francisella tularensis? |
|
Definition
Fever (up to 104), chills, headache, myalgias, possible delirium Inflamed blister that fills with pus and opens to form an ulcer, swollen lymph nodes Severe sore throat Chest and abdominal pain, fatigue, weight loss, diarrhea |
|
|
Term
How is Francisella tularensis diagnosed? |
|
Definition
Serology is negative the first week but still the best means for confirmation Diagnosis is usually based on clinical suspicion |
|
|
Term
How is Francisella tularensis treated? |
|
Definition
Antibiotics (gentamicin or ciprofloxacin) |
|
|
Term
How is Brucella melitensis contracted? |
|
Definition
Direct contact with infected animals or their secretions through skin breaks Ingestion of unpasteurized dairy products derived from infected animals |
|
|
Term
Describe the pathogenesis of Brucella melitensis |
|
Definition
Transport to regional lymph nodes and growth in lymphoid cells Spread from the lymph nodes to the reticuloendothelial system Bursts of bacteremia |
|
|
Term
What are the signs and symptoms of Brucella melitensis? |
|
Definition
Usually 1 of 3 categories: Febrile illness that resembles typhoid but is less severe Fever and acute monarthritis, typically of hip or knee, in a young child Long-lasting fever, misery, and low-back or hip pain in older men |
|
|
Term
How is Brucella melitensis diagnosed? |
|
Definition
Culture from blood, bone marrow, or other tissues Grows very slowly so allow extra time in cases of suspicion Serum agglutination test may also be used |
|
|
Term
Describe the appearance of Brucella melitensis |
|
Definition
|
|
Term
Describe the appearance of Bacteroides fragilis |
|
Definition
|
|
Term
What media is used to culture Bacteroides fragilis? |
|
Definition
Forms colonies overnight on blood agar |
|
|
Term
What are the virulence factors and toxins of Bacteroides fragilis? |
|
Definition
Capsule resists phagocytosis and can independently lead to abscess formation Secretes a heparinase that promotes clotting Some strains secrete a 20 kDa metalloprotease toxin (BFT) that causes disease without the need for epithelial breaks |
|
|
Term
How is Bacteroides fragilis contracted? |
|
Definition
Can be part of the normal flora and these strains require a break in the anatomic mucosal barriers (unless metalloprotease toxin is present) |
|
|
Term
How is Bacteroides fragilis treated? |
|
Definition
If causing acute diarrhea due to ingestion, is self limiting If due to epithelial break: Abscess drainage and antibiotics |
|
|
Term
What is the physical appearance of Helicobacter pylori? |
|
Definition
Gram negative curved rod with multiple sheathed flagella for motility |
|
|
Term
How is H. pylori cultured? |
|
Definition
Grows on Skirrow media Requires a microaerophilic atmosphere and is slow (3-5 days) to grow |
|
|
Term
How is H. pylori transmitted? |
|
Definition
Person to person by fecal-oral route |
|
|
Term
What is the most common cause of gastritis, gastric ulcer, and duodenal ulcer? |
|
Definition
H. pylori Considered a class I carcinogen |
|
|
Term
What mediates the virulence factor of H. pylori? |
|
Definition
VacA is toxic and directly influences inflammation CagA stimulates cytokine IL-8 and neutrophil-activating protein (NAP) Net effect is gastritis, thinning of gastric mucosa, ulcers |
|
|
Term
How are T and B lymphocytes involved in the creation of gastric ulcers? |
|
Definition
H. pylori infection causes lymphocyte infiltration which causes epithelial tissue damage rather than removal of the pathogen |
|
|
Term
What is the purpose of urease secreted by H. pylori? |
|
Definition
Converts urea to ammonia which tends to neutralize the gastric acid |
|
|
Term
What are the symptoms of H. pylori induced gastritis? |
|
Definition
Often symptom free In symptomatic: belching, nausea, anorexia, vomiting, epigastric pain, bleeding Possible pyloric stenosis |
|
|
Term
How is an H. pylori infection diagnosed? |
|
Definition
Endoscopic biopsy and culture Detection of urease activity via urease breath test with 13C- or 14C-labeled urea Serology for specific antibody |
|
|
Term
How is H. pylori treated? |
|
Definition
Combo of antimicrobials and acid reducers Metronidazole, tetracyclin, clarithromycin*, and amoxycillin* Proton pump inhibitor |
|
|
Term
What is the general pathogenic mechanism of bacterial intestinal diseases? |
|
Definition
Attachment by pili or other adhesion Some bacteria transfer substances into host cell that mediate bacterial attachment Toxin production Cell division Loss of microvilli |
|
|
Term
What is the physical appearance of Vibrio cholera? |
|
Definition
Curved gram neg rod commonly found in salt water Highly motile with single polar flagellum Cells may be linked end to end forming S shapes and spirals |
|
|
Term
How is Vibrio cholera cultured? |
|
Definition
Oxidase positive and can grow both in aerobic and anaerobic conditions Grown on Thiosulfate Citrate Bile Salt Sucrose (TCBS) medium which inhibits gram pos |
|
|
Term
What is the major virulence factor for Vibrio cholera? |
|
Definition
Cholera toxin Colonizing factor known as the toxin-coregulated pilus (TCP) |
|
|
Term
How is Virbrio cholera detected by serology? |
|
Definition
H and O antigens (especially enterobacteriae) |
|
|
Term
What is the mechanism of action of cholera toxin? |
|
Definition
Catalyzes the ADP-ribosylation of the GS (stimulatory) regulatory protein, "locking" it in the active state Causes persistent activation of adenylate cyclase which causes cAMP accumulation for active secretion of Na+, K+, HCO3-, and water out of the cell |
|
|
Term
How does Vibrio cholera cause fluid loss? |
|
Definition
Increased adenylate cyclase via cholera toxin |
|
|
Term
What is the osmotic make up of diarrheal fluid? |
|
Definition
Can amount to many liters per day, with approximately the same sodium content as plasma but two to five times the potassium and bicarbonate concentrations |
|
|
Term
What regulates the virulence factors of Vibrio cholera? |
|
Definition
Transmembrane protein (ToxR ) that "senses" environmental changes in pH, osmolarity, and temperature which convert it to an active form |
|
|
Term
What are the symptoms of cholera? |
|
Definition
Rapid onset, abd pain, rushes of peristalsis, loose, watery stool containing mucus flecks- the “rice-water stool” Muscle cramp due to electrolyte imbalance In severe, hypotension, shock and death may occur within hours if untreated |
|
|
Term
How is cholera diagnosed? |
|
Definition
Isolation of the organism from stool by culture on common bacteriological medium (e.g. blood agar and MacConkey agar) or on a selective medium (thiosulfate-citrate-bile salt-sucrose agar) Latex agglutination test |
|
|
Term
|
Definition
Immediate fluid replacement Antimicrobials: tetracycline or TSX and erythromycin Usually self-limiting |
|
|
Term
Less common vibrio species?? |
|
Definition
|
|
Term
Describe the physical appearance of Campylobacter jejuni (dysentery) |
|
Definition
Curved motile gram neg rod Have polar flagella that are often attached to the ends giving an “S” or a “seagull” appearance |
|
|
Term
How is Campylobacter jejuni cultured? |
|
Definition
Microaerohilic (requires low oxygen tension), oxidase positive Slow growing (2-4 days, sometimes as long as one week) in selective medium (Campy-blood agar or Skirrow agar) at higher temperature (42C) |
|
|
Term
What is the leading bacterial diarrheal illness in the US? |
|
Definition
|
|
Term
How is campylobacter usually contracted? |
|
Definition
Domestic animals or consumption of contaminated meat (poultry) Ingestion of non-pesteurized cow and goat milk as well |
|
|
Term
How is campylobacter associated with Guillain-Barre syndrome |
|
Definition
Antibody elicited by ganglioside-like structures in the C. jejuni LPS core oligosaccharide cross-reacts w/ molecules in the host nerve myelin These abs are found in the serum of pts w/Guillain-Barre syndrome Similar to molecular mimicry in rheumatic fever |
|
|
Term
What are the symptoms of a campylobacter infection (dysentery)? |
|
Definition
Fever Lower abd pain (may be severe enough to mimic acute appendicitis) Dysenteric stool containing blood and pus Vomiting (often not present) Is invasive Usually self-limiting, recovers within 3-5days |
|
|
Term
How is campylobacter diagnosed? |
|
Definition
Stool isolation and culture via Campy-blood agar or Skirrow agar Plates are to be incubated in microaerophilic condition |
|
|
Term
How is campylobacter contraction prevented? |
|
Definition
Pesteurization of milk and beverages and chlorination of water is helpful in preventing outbreaks Proper cooking and handling of poultry products |
|
|
Term
How is campylobacter treated? |
|
Definition
Macrolides (erythromycin is the drug of choice) and fluoroquinolones Resistant to beta-lactams |
|
|
Term
What are the relevant species of salmonella that causes diarrhea? |
|
Definition
|
|
Term
What is the physical appearance of salmonella? |
|
Definition
Gram-negative enterobacteria, motile |
|
|
Term
How is salmonella cultured? |
|
Definition
Ferment glucoses with acid and sometimes gas; most of them produce hydrogen sulfide (H2S) not urease Grows on most common bacteriological media, resistant to chemicals such as bile and dyes |
|
|
Term
Describe the pathogenesis of S. enterica |
|
Definition
Attaches to the enterocytes and M cells in the small and large intestine by pili Initiates a cytoskeletal change with formation of ruffles (extension of plasma membrane) Passes through the cells to the lamina propria to produce inflammation |
|
|
Term
How does S. enterica avoid phagocytosis? |
|
Definition
Inducing macrophage apoptosis |
|
|
Term
What are the symptoms of salmonella infection? |
|
Definition
Often described as “food poisoning” Nausea Vomiting Abdominal pain Loose motion Fever |
|
|
Term
What is the classic contaminated food consumed in the contraction of salmonella poisoning? |
|
Definition
|
|
Term
What causes typhoid fever? |
|
Definition
Salmonella typhi Transmitted by contaminated drinking water, usually associated with travel Requires a large infecting dose |
|
|
Term
Describe the pathogenesis of Salmonella typhii |
|
Definition
Similar to that of S. enterica Also kills macrophages by inhibiting phagosome fusion with lysosomes Capsular Vi antigen inhibits PMN phagocytosis |
|
|
Term
How does the virulence of Salmonella typhii differ from other strains of salmonella? |
|
Definition
Prolonged survival within the macrophages due to its ability to inhibit oxidative burst Infected macrophages are carried in the lymphatic circulation to mesenteric nodes, spleen, liver and bone marrow |
|
|
Term
What are the symptoms of typhoid fever? |
|
Definition
Involves multiple organs Incubation 13 days Fever, headache, faint rash on abd Diarrhea Relative bradycardia is characteristic |
|
|
Term
What are the most important complications of typhoid fever? |
|
Definition
Intestinal (terminal ileum or proximal colon) perforation* and cholecsystitis* are the most important complications Chronic bacteremia and effects of endotoxins may lead to myocarditis, encephalopathy, or IVC |
|
|
Term
How is Salmonella poisoning diagnosed? |
|
Definition
Hektoen enteric agar medium Bile salts and the indicator dyes inhibit the Gram-pos Fails to ferment lactose H2S forms black colonies |
|
|
Term
How do common GI pathogens present on Hektoen enteric agar cultures? |
|
Definition
Fermenters produce yellow-pink colonies (e. g. E. coli) H2S producers (salmonella) form colonies with black precipitate Shigella colonies are green or transparent |
|
|
Term
How is salmonella poisoning treated? |
|
Definition
Fluid and electrolyte replacement is the primary therapeutic approach Chemotherapy includes chloramphenicol (bone marrow depression is an important side effect, dangerous), STX, ampicillin, ceftriaxone, and quinolones |
|
|
Term
Describe the physical appearance of Shigella |
|
Definition
Gram-negative straight rods, nonmotile and non-spore-forming |
|
|
Term
How is shigella cultured? |
|
Definition
Selective Hektoen enteric agar Does not produce urease or H2S, most do not ferment |
|
|
Term
How is shigella contracted? |
|
Definition
Strictly a human disease with no animal reservoirs Person to person transmission by fecal-oral route |
|
|
Term
How does shigella differ in its pathogenesis from other intestinal bacteria? |
|
Definition
Invades the cells of the large intestine rather than the small intestine |
|
|
Term
Describe the pathogenesis of Shigella |
|
Definition
Bacteria transcytose through the M cells in large intestine into the underlying phagocytic cells Infects the adjacent cells directly The cell by cell extension radially creates focal ulcers in the mucosa Intense acute inflammation in the lamina propria cause the characteristic dysenteric stool |
|
|
Term
What is the significance of Shigella toxin? |
|
Definition
Not in all strain, increases severity Has a strong association with the hemolytic uremic syndrome characterized by break up of RBCs in the tiny blood vessels of the body resulting in anemia and kidney failure with occasional nervous system injury |
|
|
Term
What are the characteristics of dysentery syndrome? |
|
Definition
Cramps Painful straining to pass stools (tenesmus) A frequent, small-volume, bloody mucoid discharge |
|
|
Term
Most cases of shigella are due to S. sonnei, which presents with what symptoms? |
|
Definition
Fever Malaise, anorexia Myalgia (sometimes) Diarrhea (may become dysenteric) |
|
|
Term
How is shigella diagnosed? |
|
Definition
Culture on selective Hektoen enteric agar Slide agglutination tests using O group specific antisera (A, B, C, D) |
|
|
Term
|
Definition
Usually self limiting Antimicrobials help shortening the period of illness and excretion of the organisms Antispasmodics are contraindicated |
|
|
Term
What are the characteristics of Picornaviruses? |
|
Definition
Poliovirus (3 serotypes) Hepatitis A Virus Coxsackievirus groups A and B |
|
|
Term
Describe the pathogenesis of picornaviruses |
|
Definition
Initial infection is of intestinal epithelia or pharynx, persists throughout disease Spreads to submucosal lymphoid tissues (Peyer’s patches or tonsils) and regional lymph nodes Spreads to and replicates in organs of the reticuloendothelial system |
|
|
Term
What diseases processes/complications are seen with Group A Coxsackievirus infections? |
|
Definition
Asceptic Meningitis, Encephalitis, muscle weakness and paralysis (Poliomyelitis-like disease), cerebellar ataxia, exanthems and enanthems |
|
|
Term
What disease processes/complications are seen with Group B Coxsackievirus infections? |
|
Definition
Asceptic Meningitis, Encephalitis, Pericarditis, Myocarditis, Epidemic Mylagia, Orchitis |
|
|
Term
What disease processes/complications are seen with Echovirus and Enterovirus infections? |
|
Definition
Asceptic Meningitis, Encephalitis, muscle weakness and paralysis (Poliomyelitis-like disease), Exanthems and enanthems |
|
|
Term
What are the disease states of poliovirus? |
|
Definition
Abortive poliomyelitis, asceptic meningitis, paralytic poliomyelitis |
|
|
Term
How are picornavirus infections prevented? |
|
Definition
Both Inactivated virus (IPV) and Live-attenuated virus (OV) vaccines exist for poliovirus IPV is now the standard for use in the US |
|
|
Term
How are picornaviruses treated? |
|
Definition
Most picornavirus infections are mild and resolve on their own Injection of Ig to the infecting virus is used in severe cases of neonates or those with Ig deficiency Supportive care for cardiac or CNS |
|
|
Term
How are picornaviruses contracted? |
|
Definition
|
|
Term
Describe the pathogenesis of rotaviruses |
|
Definition
24-48 hour incubation period Initial infection is of the mature villis tip cells of the small intestine Tip cell death leads to cell replacement by cells that cannot absorb nutrients as efficiently leading to osmotic diarrhea |
|
|
Term
What is the leading cause of severe dehydrating diarrhea in those under 3 years? |
|
Definition
|
|
Term
What are the general symptoms of rotavirus? |
|
Definition
Vomiting (typically the first symptom) Abdominal cramps Watery diarrhea May frequently occur along with a respiratory tract infection Lasts 2-8 days, a form of traveler's diarrhea |
|
|
Term
How is rotavirus immunity mediated? |
|
Definition
VP4 and VP7 (outer shell) are targets for neutralizing antibodies and humoral immunity plays a large role in viral clearance |
|
|
Term
How is rotavirus infection prevented? |
|
Definition
A live-attenuated vaccine is available. The 3 shot course must be completed by 32 months of age due to concerns over a potentially fatal complication |
|
|
Term
How is rotavirus diagnosed? |
|
Definition
Shed in large amounts in the stool (only during an active infection), and a variety of molecular and enzymatic tests can confirm infection |
|
|
Term
How is rotavirus treated? |
|
Definition
Usually self limiting, can be treated with oral fluids |
|
|
Term
How are Norwalk agent and Noroviruses contracted? |
|
Definition
Fecal-oral route, associated with Foodborne outbreaks associated with unsanitary restaurant workers Waterborne outbreaks of viral gastroenteritis Uncooked shellfish |
|
|
Term
How do Norwalk agent and Norovirus infections progress? |
|
Definition
Intestinal villi and microvilli become blunted and shortened Malabsorption of carbohydrates and fats leads to osmotic diarrhea without involvement of adenylate cyclase Gastric motor function is delayed and may be the cause of nausea symptoms Lasts 12 to 60 hours |
|
|
Term
What are the symptoms of a Norwalk agent or Norovirus infection? |
|
Definition
Nausea, vomiting, cramps, and watery diarrhea Vomiting is more common in children, and diarrhea in adults Headache, fever, chills, and myalgias |
|
|
Term
How is immunity to Norwalk agents and Norovirus mediated? |
|
Definition
Short term immunity to infection by the same strain (2-3 months) Lasting immunity is not achieved to any strain |
|
|
Term
How are Norwalk agent and Norovirus infections treated? |
|
Definition
Treatment is usually not necessary as the disease is of short term, self-limiting, and is not severe |
|
|
Term
What symptoms appear in Picornavirus infections but no in Norovirus infections? |
|
Definition
Rashes, lesions, photophobia, tachycardia |
|
|
Term
Calicivirus infections are more common among what demographic? |
|
Definition
Older children and adults and have nausea as a primary symptom |
|
|
Term
|
Definition
Nematodes (roundworms) Cestodes (tapeworms) Trematodes (flukes) |
|
|
Term
How does the reproduction of helminths correlate with disease severity? |
|
Definition
Adult worms do not multiply in human hosts Symptoms are usually linked with “worm burden” (number of adults present) |
|
|
Term
|
Definition
Trichuris trichiura (Whipworm) Enterobius vermicularis (Pinworm) Ascaris lumbricoides (Roundworm) Necator americanus and Ancylostoma duodenale (Hookworm) Strongyloides stercoralis (Threadworm) |
|
|
Term
How is Trichuris trichiura (Whipworm) contracted? |
|
Definition
Ingestion of fecal contaminated soil or foods |
|
|
Term
What are the symptoms of Trichuris trichiura (Whipworm)? |
|
Definition
Light infections are asymptomatic Heavy infections can have Epigastric pain, vomiting, distention, flatulence, anorexia and weight loss may occur, severe cases have Trichuris dysentary syndrome, blood and mucous in stools |
|
|
Term
How is Trichuris trichiura (Whipworm) diagnosed? |
|
Definition
|
|
Term
What kind of complications are seen with Trichuris trichiura (Whipworm)? |
|
Definition
Parasites typically induce an IgE response and hypereosinophilia Mast cell activation may lead to the increase in allergic responses and symptoms coincide with GI complaints Prolapse of rectum |
|
|
Term
How is Enterobius vermicularis (Pinworm) contracted/spread? |
|
Definition
Fecal-oral route of infection Person to person transmission is high, especially in children and institutionalized individuals Female lays eggs in perianal region causes intense itching, leading to scratching, leading to hand and nail contamination, etc. |
|
|
Term
How do Enterobius vermicularis (Pinworm) infections progress? |
|
Definition
Self-infection occurs by scratching perianal area without hand washing Larvae hatch in the small intestine after ingestion of infective eggs Adults grow in the colon Pregnant females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area |
|
|
Term
What are the symptoms of Enterobius vermicularis (Pinworm)? |
|
Definition
Intense nocturnal perianal itching Insomnia Can migrate to urogenital tract in females causing a vaginitis and lead to secondary bacterial UTI Scratching may lead to secondary bacterial skin infections |
|
|
Term
How is Enterobius vermicularis (Pinworm) diagnosed? |
|
Definition
Tape test from perianal region reveals eggs |
|
|
Term
How is Ascaris lumbricoides (Roundworm) contracted? |
|
Definition
|
|
Term
How does a Ascaris lumbricoides (Roundworm) infection progress? |
|
Definition
Adult worms live in the lumen of the small intestine, passes eggs in small intestines Larva penetrates the intestinal mucosa, carried via the portal vein, then systemic circulation to the lungs The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed Egg ingestion to new egg passage takes approximately 9 weeks |
|
|
Term
What are the symptoms of Ascaris lumbricoides (Roundworm) infection? |
|
Definition
Usually asymptomatic Fever, jaundice, chachexia and mental retardation due to malnutrition, pulmonary symptoms, abdominal tenderness due to obstruction or bowel perforation, Loeffler's syndrome, Larva migrans |
|
|
Term
What is Loeffler's Syndrome? |
|
Definition
Originally reported as a benign, acute eosinophilic pneumonia of unknown cause characterized by migrating pulmonary infiltrates and minimal clinical manifestations |
|
|
Term
|
Definition
Dog and cat ascarid larvae (Toxocara spp.) hatched from eggs that are accidentally swallowed Larvae migrate and encyst as second-stage larvae, terminating development Produces tracts with hemorrhagic necrosis and eosinophilic and lymphocytic infiltration Can migrate to the liver causing enlargement and studded nodules |
|
|
Term
How is Ascaris lumbricoides (Roundworm) diagnosed? |
|
Definition
Eggs in stool (negative in early infection) |
|
|
Term
How is Necator americanus and Ancylostoma duodenale (Hookworm) contracted? |
|
Definition
Direct contact (walking barefoot) or ingestion of soil contaminated with human fecal matter |
|
|
Term
How does a Necator americanus or Ancylostoma duodenale (Hookworm) infection progress? |
|
Definition
On contact with the human host, the larvae penetrate the skin and are carried through the veins to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed Larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they feed on erythrocytes of the host. |
|
|
Term
What are the symptoms of Necator americanus and Ancylostoma duodenale (Hookworm)? |
|
Definition
Infecting larvae induce pruritic maculopapular dermatitis at site of entry ("ground itch") Transient pneumonitis Epigastric pain, inflammatory diarrhea with eosinophilia Primary Syndrome: Iron deficiency anemia Occult blood in stool Larva migrans |
|
|
Term
How is Necator americanus and Ancylostoma duodenale (Hookworm) diagnosed? |
|
Definition
Eggs in fresh stool, larvae in old stool |
|
|
Term
How is Strongyloides stercoralis (Threadworm) contracted? |
|
Definition
Direct contact of contaminated soil (walking barefoot) or ingestion of contaminated soil |
|
|
Term
How does a Strongyloides stercoralis (Threadworm) infection progress? |
|
Definition
Colonization of bowel and maturation Can spread through lymphatics to blood stream and other organs leading to abscesses, granulomas, or sepsis Can cause reinfection by maturing in bowel and re-entering through skin in perianal region |
|
|
Term
What are the symptoms of a Strongyloides stercoralis (Threadworm) infection? |
|
Definition
"Ground itch", cough and Loeffler’s syndrome, chronic watery diarrhea with mucous, may contain blood, urticaria, Larva currens |
|
|
Term
|
Definition
• Occurs on the trunk or near the anus and is a linear eruption in which the larvae migrate under the skin causing an itchy, non-indurated wheal with a red flare that moves rapidly and disappears in a few hours |
|
|
Term
What are the cestodes (tapeworm)? What are their features? |
|
Definition
Taenia solium (pig tapeworm) Taenia saginata (beef tapeworm) Have proglottids and Cystercerci (tissue cysts) |
|
|
Term
How are Cestodes (tapeworms) and Taenias contracted? How does the infection progress? |
|
Definition
Ingestion of cystercerci in meat Ingestion of eggs Invasion of tissues and cystercerci formation, most commonly in brain |
|
|
Term
What are the symptoms of a Cestode (tapeworms) or Taenias infection? |
|
Definition
Likely to be asymptomatic Epigastric discomfort Nausea Sensation of hunger Diarrhea Cysticercosis if eggs are ingested |
|
|
Term
How are Cestode (tapeworms) or Taenias diagnosed? |
|
Definition
Detection of eggs or proglottids in stool Cystercerci: plain films reveal calcified “puffed rice” lesions |
|
|
Term
How are Trematodes (Fluke) contracted? |
|
Definition
Biliary infections: Ingestion of poorly cooked, pickled, or smoked fish Liver infections: Ingestion of metacercariae encysted on aquatic plants (watercress) |
|
|
Term
How does a trematode (fluke) infection progress in the biliary tract? |
|
Definition
Excyst in small intestines, migrate through ampulla of Vater into biliary ducts Worms lead to adenomatous hyperplasia, inflammation, and duct obstruction |
|
|
Term
How does a trematode (fluke) infection progress in the liver? |
|
Definition
Excyst in duodenum, pass through intestine into peritoneum, invade liver through Glisson’s capsule Granulomatous reactions, duct obstruction, etc. may occur |
|
|
Term
How does a biliary trematode (fluke) infection manifest? |
|
Definition
Acute infections noted by fever, eosinophilia, and hepatomegaly Heavy worm burden may lead to constitutional complaints and symptoms associated with cholelithiasis and pancreatitis |
|
|
Term
How does a liver trematode (fluke) infection manifest? |
|
Definition
Fever, hepatomegaly and/or abdominal pain Nausea, cough, diarrhea, and urticaria are also common Periods of jaundice |
|
|
Term
How is a biliary trematode (fluke) infection diagnosed? |
|
Definition
Ova can be identified in stools, dilation of ducts by imaging |
|
|
Term
How is a liver trematode (fluke) infection diagnosed? |
|
Definition
Fever, hepatomegaly or liver pain, proper clinical setting Serology, as ova may not be detected in stool |
|
|
Term
What are the general characteristics of Staphylococcus aureus? |
|
Definition
Ferments mannitol, coagulase-positive, catalase-positive Gram-positive, cocci in clusters Non-motile, non-sporeformer Facultative anaerobe |
|
|
Term
What causes Staph aureus food poisoning? |
|
Definition
Results from bacterial toxin in food, not an infection by the bacteria itself |
|
|
Term
What foods are commonly contaminated by Staph aureus? |
|
Definition
Usually by improper handling of meats Ham, salted pork (can grow in high salt content Custard-filled pastries Potato salad Ice cream |
|
|
Term
What are the toxins secreted by Staph aureus? |
|
Definition
Enterotoxin A and B Can lead to severe metabolic alkalosis |
|
|
Term
What types of media are capable of culturing Staph aureus |
|
Definition
Β-hemolytic sheep’s blood agar
Selective media: Mannitol salt agar Phenylethylalcohol agar (PEA |
|
|
Term
What are the general characteristics of Clostridium perfringens |
|
Definition
Gram-positive, spore-formers Can be found in the intestinal flora of humans and in the soil |
|
|
Term
How is Clostridium perfringens food poisoning contracted? |
|
Definition
Ingestion of contaminated food via dirt or feces Often occur in institutions or after large gatherings, can incubate at moderate temps Most commonly in meat cooked in bulk and then left in warming trays |
|
|
Term
What increases the likelihood of food poisoning by Clostridium perfringens? |
|
Definition
The longer the meat is allowed to sit, more likely of getting sick |
|
|
Term
What types of media are capable of culturing Clostridium perfringens? |
|
Definition
EYA (egg yolk agar) with anti-toxin A in ½ of the plate: precipitation forms around colonies to indicate lecithinase activity
Double-zone of hemolysis on blood agar |
|
|
Term
How does Clostridium perfringens cause food poisoning? |
|
Definition
|
|
Term
What are the effects of clostridium enterotoxin? |
|
Definition
Maximum effect in the ileum Minimum effect in the duodenum Inhibits glucose transport Damages intestinal epithelium Causes protein loss into the intestinal lumen |
|
|
Term
What causes Enteritis necroticans? |
|
Definition
Clostridium perfringens, type C |
|
|
Term
How is enteritis necroticans contracted? |
|
Definition
Occurs after large consumption of improperly cooked pork during native feasts |
|
|
Term
What are the symptoms of Enteritis necroticans? |
|
Definition
Severe necrotizing disease of the small intestine Intense abdominal pain, distension, bloody diarrhea, vomiting & shock High mortality due to intestinal perforation |
|
|
Term
How does Clostridium botulinum cause food poisoning? |
|
Definition
Ingestion of secreted botulin toxin |
|
|
Term
What are the effects of botulin toxin? |
|
Definition
Small amounts can produce paralysis and death Attaches to neuromuscular junction of affected nerves Prevents release of acetylcholine Approximately 1 microgram of toxin is lethal |
|
|
Term
What is the most common route of botulin toxin food poisoning? |
|
Definition
|
|
Term
What is the progression of botulin intoxication? |
|
Definition
Cranial nerve paralysis Respiratory muscle weakness which can be fatal Preceding or following onset of paralysis |
|
|
Term
How is botulin toxin food poisoning diagnosed? |
|
Definition
Presence of organism and/or toxin in vomitus, gastric fluid, or stool |
|
|
Term
How is botulin toxin food poisoning treated? |
|
Definition
A-B-E antitoxin Can slow progression of disease but will not neutralize toxin already bound to neuromuscular junctions |
|
|
Term
What are the possible pathologies caused by Bacillus cereus food poisoning? |
|
Definition
Gastroenteritis Ocular infections Intravenous catheter-related sepsis Diarrhea syndrome Vomiting syndrome |
|
|
Term
What are the general characteristics of Bacillus cereus? |
|
Definition
Spore-former Β-hemolytic on sheep blood agar Facultative anaerobe Motile, gram-positive rod |
|
|
Term
How does Bacillus cereus food poisoning cause diarrhea syndrome? |
|
Definition
Enterotoxin produced, adenylate cyclase is activated in intestinal cells Similar to action of cholera toxin |
|
|
Term
What foods are associated with Bacillus cereus induced diarrhea syndrome? |
|
Definition
Spaghetti sauces Dried potatoes, dried milk Foods are maintained at temperatures between 30-50 degC |
|
|
Term
What foods are associated with Bacillus cereus induced vomiting syndrome? |
|
Definition
Fried rice via a heat stable toxin that does not activate adenylate cyclase Large amounts can lead to liver failure |
|
|
Term
What are the toxins secreted by Bacillus cereus? |
|
Definition
Heat-stable, proteolysis-resistant enterotoxin: Emetic form Heat-labile enterotoxin: Diarrheal form |
|
|
Term
How is Bacillus cereus food poisoning diagnosed? |
|
Definition
Samples of contaminated food must be cultured Identification in stool specimens of symptomatic patients is strong evidence Grows rapidly on sheep blood aga |
|
|
Term
Cryptosporidium spp. infections are associated with what mode of contraction? |
|
Definition
|
|
Term
What are the general characteristics of Cryptosporidium spp.? |
|
Definition
A coccidian, subphylum, Sporozoa (protozoan) Lives on or just below the epithelial cells of the small intestine |
|
|
Term
What is significant about the life cycle of Cryptosporidium spp.? |
|
Definition
Asexual reproduction allows for continued autoinfection, oocysts are infective when passed Patients may remain infective after diarrhea ceases |
|
|
Term
What are the symptoms of a Cryptosporidium infection? |
|
Definition
Frequent, watery diarrhea Nausea, vomiting Abdominal cramps Low-grade fever |
|
|
Term
How does Cryptosporidium cause diarrhea? |
|
Definition
Alters osmotic pressure in the gut resulting in in influx of fluid, much like cholera Epithelial cells are damaged by Invasion of parasite T-cell mediated inflammation causing villus atrophy |
|
|
Term
How is Cryptosporidium infections diagnosed? |
|
Definition
Modified Ziehl-Nielsen acid-fast stain Microscopic observations of small, acid-fast oocysts in smears of fecal specimens |
|
|
Term
How is Cryptosporidium treated? |
|
Definition
Self limiting in most If immunocompromised, give Paromomycin |
|
|
Term
What are the general characteristics of Giardia lamblia? |
|
Definition
Flagellate Most commonly identified intestinal parasitic pathogen Cysts are resistant forms, survive in cold water for several months |
|
|
Term
How is Giardia lamblia most commonly acquired? |
|
Definition
Contaminated water and person contact in institutions or daycare centers |
|
|
Term
Describe the lifecycle of Giardia lamblia |
|
Definition
Trophozoites reproduce by longitudinal, binary fission in the lumen of the proximal small bowel Encystation occurs as parasites travel to the colon Cysts are passed out through nondiarrheal feces |
|
|
Term
What are the symptoms of acute Giardiasis? |
|
Definition
Diarrhea, abdominal pain, bloating, nausea, vomiting |
|
|
Term
How is Giardia lamblia diagnosed? |
|
Definition
Microscopic identification of cysts or trophozoites in feces |
|
|
Term
How is Giardia lamblia treated? |
|
Definition
Metronidazole, tinidazole |
|
|
Term
How is Entamoeba histolytica (a pathogenic amoeba) infection most commonly contracted? |
|
Definition
Oral/fecal route, contaminated water, food Cysts are found in formed stools Can survive for day-weeks in external environment, trophozoites die in the acidic stomach |
|
|
Term
What are the characteristics of invasive, intestinal amebiasis via Entamoeba histolytica? |
|
Definition
|
|
Term
What are the characteristics of extra-intestinal amebiasis via Entamoeba histolytica? |
|
Definition
Liver abscess Peritonitis Pleuropulmonary abscess Cutaneous and genital amebic lesions |
|
|
Term
What is the mechanism of GI infection by Entamoeba histolytica? |
|
Definition
Mediated by an adherence lectin in instestin Disruption of intestinal barrier by secretion of proteolytic enzymes and invasion of intestinal epithelial cells |
|
|
Term
What are the characteristic appearance of Entamoeba histolytica GI lesions? |
|
Definition
|
|
Term
E. histolytica is resistant to what immune mechanisms? |
|
Definition
Phagocytosis Complement-mediated cell lysis |
|
|
Term
What are the consequences of a heavy infection of Entamoeba histolytica? |
|
Definition
Causes vacuoles to coalesce Sloughing off of the lining causes bloody, mucus-filled stools |
|
|
Term
How does Entamoeba histolytica cause liver abscesses? |
|
Definition
May completely erode the intestinal mucosa Enters the circulation Organ most commonly colonized is the liver, causes abscess formation |
|
|
Term
How does Entamoeba histolytica cause lung abscesses? |
|
Definition
Penetration of the diaphragm from hepatic abscesses or from hematogenous spread |
|
|
Term
How is Entamoeba histolytica diagnosed? |
|
Definition
Microscopic evidence of trophozoites in stool specimens via wet mounts or trichrome-stained smears Sigmoid biopsies ELISA provides evidence of current infection but is not diagnostic |
|
|
Term
What are the general characteristics of Cyclospora cayetanensis? |
|
Definition
Spore-forming coccidia Unicellular, coccidian parasite Oocysts are passed in stools, not infective, distinguishes this organism from Cryptosporidium Sporulation occurs in the environment at temp. between 22-32 degC |
|
|
Term
How is Cyclospora cayetanensis most often transmitted? |
|
Definition
Fresh produce and water via contamination with sporozoites released asexually into the stool |
|
|
Term
How is Cylcospora cayetanensis infection prevented? |
|
Definition
Can be killed by washing or cooking Occurs primarily in the tropics and subtropics |
|
|
Term
How is a Cylcospora cayetanensis infection diagnosed? |
|
Definition
Evidence of oocysts in stool specimens by microscopy Stool specimens should be refrigerated or preserved in 10% formalin Requires 3 or more specimens collected at 2-3 day intervals due to intermittent release of oocysts Modified acid-fast stain |
|
|
Term
What are the symptoms of a Cylcospora cayetanensis infection? |
|
Definition
Watery diarrhea which can be severe Anorexia, nausea, vomiting, abd pain Low-grade fever, fatigue Flu-like symptoms Can persist for several weeks |
|
|
Term
How are Cylcospora cayetanensis infections treated? |
|
Definition
Usually self-limiting in both immunocompetent and immunocompromised individuals, give fluids Trimethoprim-sulfamethoxazole can reduce symptoms |
|
|
Term
|
Definition
Noncontagious inflammation of the lower portion of the eyelids and eyelashes caused by Poor eyelid hygiene Excess oil Staphylococcus aureus Allergic reaction |
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|
Term
|
Definition
Inflammation of the lacrimal sac caused by partial or complete obstruction within the sac or nasolacrimal duct Bacteria are trapped initiating acute or chronic infection Older patients are predisposed |
|
|
Term
|
Definition
Inflammation of the conjunctiva, the outermost layer of the eye covering the sclera Progressive keratitis can lead to ulceration, scarring, and blindness |
|
|
Term
What are the three causes of conjunctivitis? |
|
Definition
Bacterial (most common) viral, or allergies |
|
|
Term
What are the characteristics of viral conjunctivitis? |
|
Definition
Usually due to an upper respiratory infection Watery discharge Red eye Irritation Can spread to other eye |
|
|
Term
What symptoms of bacterial conjunctivitis help differentiate it from viral conjunctivitis? |
|
Definition
Stringy discharge Other symptoms: Swelling of the conjunctiva Redness, tearing Irritation (gritty feeling) Can spread to other eye |
|
|
Term
What is the most common cause of bacterial conjunctivitis? |
|
Definition
Adults: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae Infants: Neisseria gonorrhoeae, Streptococcus pneumonia, Haemophilus influenzae |
|
|
Term
How do you treat bacterial conjunctivitis? |
|
Definition
Antibiotic ointments or eyedrops Neomycin, polymyxin, bacitracin Gentamicin, tobramycin against gram-neg microorganisms |
|
|
Term
What is Ophthalmia neonatorum? |
|
Definition
Severe conjunctivitis of newborns, can acquire the infection at birth, typically due to STD pathogens Neisseria gonorrhoeae, Chlamydia trachomatis, Herpes simplex virus |
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|
Term
What is Endophthalmitis? What causes it? |
|
Definition
Rare, intraocular infection of the aqueous or vitreous humor caused by normal flora of the eyelids: Staphylococcus epidermidis Rarely by pseudomonas (poor prognosis) |
|
|
Term
|
Definition
Inflammation or swelling of the eye structures responsible for the eye’s blood supply |
|
|
Term
What are the symptoms of Iritis (anterior uveitis)? |
|
Definition
Redness, pain, photophobia due to painful movement of inflamed iris Blurred vision in severe inflammation |
|
|
Term
What are the symptoms of Intermediate uveitis (cyclitis)? |
|
Definition
Blurring, presence of floaters (black dots or wispy lines which move across the field of vision) |
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|
Term
What are the symptoms of posterior uveitis |
|
Definition
Blurring, gradual or sudden reduction in vision Usually painless |
|
|
Term
What is periorbital cellulitis? what are potential complications? |
|
Definition
Acute infection of the tissues surrounding the eye Can lead to orbital cellulitis and protrusion of the eyeball, meningitis if severe |
|
|
Term
What causes periorbital cellulitis? |
|
Definition
Absence of an effective drainage system, predisposes the parasinuses to invasion Bacteria, fungi, or parasites can gain access via trauma, surrounding infection, or upper respiratory infection |
|
|
Term
Haemophilus influenza is grown on what type of media? |
|
Definition
Chocolate agar Requires the 2 erythrocyte growth factors X (hemin) and V (nicotinamide adenine dinucleotide) for growth |
|
|
Term
What is the appearance of Haemophilus influenza? |
|
Definition
Gram-negative, bacillus (rod) Non-motile, non-spore forming Fastidious, facultative anaerobe |
|
|
Term
What mediates pathogenesis for Haemophilus influenza? |
|
Definition
Attachment to respiratory epithelial cells is accomplished using pili Endotoxin in the cell wall is toxic to ciliated respiratory cells |
|
|
Term
What is the most virulent strain of H. influenza which is responsible for infections such as bacteremia, meningitis, cellulitis, septic arthritis, and pneumoniae? |
|
Definition
Haemophilus influenzae type b (HiB) |
|
|
Term
Which H. influenza strain causes mucosal infections such as otitis media, conjunctivitis, bronchitis, and pneumoniae? |
|
Definition
Nonencapsulated (or non-typeable) strains 80% of individuals are colonized with the non-typeable strains COPD and cystic fibrosis pts particularly susceptible |
|
|
Term
What are the general characteristics of Streptococcus pneumonia |
|
Definition
Gram-positive, cocci Usually seen in pairs**(diplo) but not always Non-spore formers, non-motile |
|
|
Term
Strep pneumonia is cultured on what media? |
|
Definition
Blood agar medium results in alpha-hemolysis (partial hemolysis) Can grow very quickly under optimal conditions |
|
|
Term
What determines the virulence of Strep pneumonia? |
|
Definition
Capsule interferes phagocytosis by blocking C3b opsonization |
|
|
Term
What is the Quellung reaction? |
|
Definition
Serotyping used to identify a particular capsule type of strep pneumo Antibody reacts with a particular capsule type, causes capsular swelling |
|
|
Term
What allows Staph aureus to avoid phagocytosis? |
|
Definition
Protein A, a cellular component in the cell wall |
|
|
Term
What are the virulence factors of Staph aureus? |
|
Definition
Cytolytic toxins (alpha and beta hemolysin, staphylococcal leukocidin) Enzymes (coagulase, hyaluronidase, lipase) Protein A |
|
|
Term
How do you differentiate Staph epidermidis from Staph aureus? |
|
Definition
Staph epidermidis is coagulase-negative whereas Staph aureus is positive |
|
|
Term
What type of infections are caused by Staph epidermidis? |
|
Definition
Hospital acquired UTIs Osteomyelitis at prosthetic joints Native valve endocarditis due to catheters Bacteremia Almost ALL cases of infection are hospital acquired |
|
|
Term
What mediates the antibiotic resistance of Staph epidermidis? |
|
Definition
Plasmid-mediated, can also transfer to Staph aureus |
|
|
Term
What are the general characteristics of Chlamydia trachomatis? |
|
Definition
Obligate intracellular parasites Most common STD in the world, causes blindness and infertility |
|
|
Term
|
Definition
Chlamydia infection of the eye transmitted through eye secretions and eye-seeking flies Inflammatory reactions results in scarring on the conjunctiva Eyelid to turns inward where the eyelashes can rub the cornea |
|
|
Term
What is unique about the life cycle of Chlamydia trachomatis? |
|
Definition
Alternates between a non-replicating, infectious elementary body and a replicating, noninfectious reticulate body |
|
|
Term
How is Chlamydia trachomatis diagnosed? |
|
Definition
|
|
Term
|
Definition
mycobacteria other than tubercle bacilli Associated with contact lenses, trauma, and wound contamination with soil Causes Keratitis and Corneal ulcers |
|
|
Term
What are the most common MOTT pathogens? |
|
Definition
Mycobacterium chelonae Mycobacterium fortuitum |
|
|
Term
What are the general characteristics of Eikenella corrodens? |
|
Definition
Microaerophilic, gram-negative rods Normal flora of human, mucosal surfaces Culture requires CO2 environment and hemin in the medium, lab must be notified in advance Usually a part of a mixed infection with Streptococcus sp. Gets its name from the fact that it forms pits on the surface of agar medium |
|
|
Term
How is Francisella tularensis contracted? |
|
Definition
Primarily a pathogen of squirrels and rabbits. Humans are infected by the bite of an infected deer fly or tick or eating undercooked infected meat or handling infected rabbit carcasses |
|
|
Term
What are the symptoms of tularemia (Francisella tularensis infection) |
|
Definition
Highly infectious Skin ulcers Swollen, painful lymph nodes Inflamed eyes, sore throat, mouth sores |
|
|
Term
How is Francisella tularensis cultured? |
|
Definition
|
|
Term
What causes "cat scratch fever"? |
|
Definition
Bartonella henselae: Gram-negative bacillus |
|
|
Term
What are the characteristics of cat scratch fever (Bartonella henselae infection)? |
|
Definition
Parinaud’s Oculoglandular Syndrome, manifests as conjunctivitis, neuroretinitis Vitritis, posterior uveitis Discrete foci of retinitis manifested as white retinal or choroidal lesions |
|
|
Term
What are the characteristics of HSV blepharitis? |
|
Definition
Vesicles appear on lid margins and around the eyes Vesicles can break open forming lesions which can become superinfected by skin flora |
|
|
Term
What is ocular herpes and what are its characteristics? |
|
Definition
HSV infection of the conjunctiva Swelling of the eyelids If cornea is involved (Herpes Simplex Keratitis) Destructive ulceration and perforation of the cornea possible |
|
|
Term
What is Herpes Simplex Keratitis? |
|
Definition
Dendritic keratitis Secondary herpetic infections Virus branches out in a dendritic pattern** Virus deadens the nerves – no pain |
|
|
Term
What are the characteristics of varicella-zoster blepharitis? |
|
Definition
Vesicles may appear on the lid margins Wartlike lesions can form (molluscum contagiosum) from the pox virus Can cause keratitis, scleritis, infections of the lacrimal apparatus, endophthalmitis |
|
|
Term
What ocular infections are caused by adenovirus? |
|
Definition
Conjunctivitis and epidemic keratoconjunctivitis |
|
|
Term
What are the characteristics of CMV retinitis? |
|
Definition
Floaters, flashes, and blind spots Pizza pie retinopathy (CMV infiltrates the vascular endothelium) More common among immunocompromised or neonates from infected mothers |
|
|
Term
What are the characteristics of Aspergillus sp? |
|
Definition
Most commonly encountered genus of fungi in the clinical laboratory Erects conidiophores from a “foot cell” with a vegetative hyphae |
|
|
Term
What are the characteristics of Acremonium sp.? |
|
Definition
Filamentous fungi isolated from plant debris and soil Rare cases of keratitis and endophthalmitis Known to cause opportunisitic infections in immunocompromised Possess fine, narrow, septate hyphae |
|
|
Term
What are the characteristics of Penicillium sp.? |
|
Definition
Filamentous fungi Found in soil, decaying vegetation, air May cause infections in immunocompromised hosts Has a bottle brush look Can cause Keratitis and Endophthalmitis |
|
|
Term
What are the characteristics of Rhizopus sp? |
|
Definition
Causative agent for a group of fungal infections classified as zygomycosis, frequently fatal Causes rhinocerebral infections Also known as the black bread mold |
|
|
Term
What predisposes someone to a rhinocerebral infection? |
|
Definition
Diabetic ketoacidosis Immunosuppression |
|
|
Term
Nosocomial rhinocerebral infections are usually contracted through what means |
|
Definition
Contaminated adhesive tape Contaminated, wooden tongue depressors |
|
|
Term
What is responsible for approximately 90% of rhinocerebral infections classified as zygomyosis? |
|
Definition
|
|
Term
What causes endophthalmitis due to candida infections? |
|
Definition
Exogenously following surgery or trauma (rare) Endogenoushly due to embolic seeding in the retina (most common cause) |
|
|
Term
What pathogens can cause corneal ulcers due to improper contact lens use? |
|
Definition
Pseudomonas, Bacillus cereus, Acanthamoeba |
|
|
Term
Keratitis due to Acanthamoeba is associated with what kind of behavior? |
|
Definition
Wearing of nondisposable lenses Use of homemade sodium chloride solutions Wearing of contacts while swimming |
|
|
Term
Toxoplasma gondii is most often contracted via what vectors? |
|
Definition
Exposure to contaminated water containing tissue cysts Exposure to oocysts shed by infected cats Eating meat contaminated with oocysts Congenital transmission |
|
|
Term
Congenital infections by Toxoplasma gondii targets what organs? |
|
Definition
Retina (chorioretinitis) Brain |
|
|
Term
What are the different morphological forms of Toxoplasma gondii? |
|
Definition
Oocysts in intestines of members of the cat family (primary host) Tachyzoite – the invasive form responsible for acute disease Sporulated and unsporulated oocysts |
|
|
Term
How is Toxoplasma gondii diagnosed? |
|
Definition
Indirect immunofluorescent assay (IFA) Ring enhancing lesions on imaging is indicative |
|
|
Term
How is Loa loa (eyeworm) transmitted? |
|
Definition
Chrysops fly Confined to the rain forest and swamp forest areas of West Africa |
|
|
Term
How is Onchocerca volvulus transmitted? |
|
Definition
Spread by the vector, Simulium (the black fly) |
|
|
Term
What is caused by infection by Onchocerca volvulus? |
|
Definition
River Blindness Microfilaria can migrate into peripheral blood and the eyes during heavy infections, infects the cornea, optic nerve, choroid Dead microfilaria induce an inflammatory response in the eyes |
|
|
Term
|
Definition
Infection of tissues or organs of animals or man by fly larvae Oestrus ovis (sheep botfly) Can cause severe conjunctivitis |
|
|
Term
What are the most common manifestations of a hematological infection? |
|
Definition
Anemia Pancytopenia Lymphocytosis Neutrophilia Eosinophilia |
|
|
Term
|
Definition
A decrease in all blood cell lineages due to toxic effects causing bone marrow necrosis, inflammatory mediators, and hemophagocytic syndrome |
|
|
Term
What causes Pancytopenia? |
|
Definition
Congestive splenomegaly due to infections such as: Salmonellosis, infectious mono Tularemia, hepatitis Syphilis Toxoplasmosis Schistosomiasis, malaria |
|
|
Term
|
Definition
AKA glandular fever, rabbit fever, tick fever, and deer fly fever Caused by infection by Francisela tularensis acquired from the bite of an infected tick (Ixodes, Dermacentor) |
|
|
Term
What are the general characteristics of Francisela tularensis? |
|
Definition
Gram-negative, non-motile rod Strict aerobe, fastidious Intracellular parasite Acquired from the bite of an infected tick (Ixodes, Dermacentor) |
|
|
Term
What is the most common clinical manifestation of Tularemia? |
|
Definition
Ulceroglandular tularemia Skin lesion (from a tick bite) is a painful papule which ulcerates having a necrotic center Leads to lymphadenopathy and bacteremia |
|
|
Term
How is Tularemia diagnosed? |
|
Definition
Direct immunofluorescent staining |
|
|
Term
What causes Toxoplasmosis? |
|
Definition
Toxoplasma gondii, an intracellular blood and tissue parasite Definitive host is the cat Infective oocysts are shed in cat feces Human infection is due to ingestion of improperly cooked meat or oocysts from cat feces |
|
|
Term
What is the infective form of Toxoplasma gondii? |
|
Definition
Trophozoites Responsible for initial infection and tissue damage |
|
|
Term
What are some of the more rare causes of Toxoplasmosis? |
|
Definition
Transplacental infections Transfusion infection via contaminated blood |
|
|
Term
T. gondii has a predilection for infecting which organs? |
|
Definition
Heart and lymphoid organs especially Lung, CNS, and eyes as well |
|
|
Term
An infant suffering from a congenital case of Toxoplasmosis experiences what symptoms? |
|
Definition
Anemia Jaundice, epilepsy, encephalitis, other neurological disorders |
|
|
Term
What are the symptoms of Hemophagocytic Syndrome (aka hemophagocytic lymphohistiocytosis (HLH)) |
|
Definition
Fever, splenomegaly* Jaundice Presence of activated macrophages phagocytizing erythrocytes, leukocytes, platelets, and other blood cell precursors Phagocytosis is detectable in the bone marrow |
|
|
Term
What is reactive hemophagocytic syndrome? |
|
Definition
Hemophagocytic syndromes secondary to an underlying infection |
|
|
Term
Sporadic and familial cases of HLH are caused by what? |
|
Definition
|
|
Term
Hemophagocytic Syndrome can interfere with the diagnosis of what treatable infectious disease? |
|
Definition
|
|
Term
What initial diagnostic tests should be performed if Hemophagocytic syndrome is suspected? |
|
Definition
Blood and urine cultures Chest radiography to screen for tuberculous infections Serological assays for viral infections Throat and rectal swabs for viral culture Fungal antigen testing Determine if an underlying T-cell lymphoma is present |
|
|
Term
Hemophagocytic syndrome is associated with HIV patients with what kind of underlying infections? |
|
Definition
Pneumococcal disease Pneumocystosis Histoplasmosis |
|
|
Term
What kind of infections associated with animal infections or travel need to be considered in cases of hemophagocytic syndrome? |
|
Definition
Leshmaniasis Brucellosis Rickettsioses Malaria |
|
|
Term
What are the most common symptoms of hemophagocytic syndrome? |
|
Definition
|
|
Term
What are the most common lab abnormalities associated with hemophagocytic syndrome? |
|
Definition
**Anemia, thrombocytopenia, neutropenia, hypertriglyceridemia, hypofriboginemia |
|
|
Term
How can the overactivation of macrophages cause hemophagocytic syndrome (HLH)? |
|
Definition
High levels of activating cytokines due to viral or nonviral causes Associated with EBV infection and the presence of episomal EBV genome in T cell lymphocytes |
|
|
Term
|
Definition
Infection caused by Brucella sp. |
|
|
Term
What are the general characteristics of Brucella sp.? |
|
Definition
Small, nonmotile, gram-negative rods Requires complex growth media Strict aerobe Slow growth (at least 1 week) An intracellular parasite of the reticuloendothelial system |
|
|
Term
What are the two types of colony morphology of Brucella? What is it based off of? |
|
Definition
Based on the O antigen of LPS Smooth (translucent, homogeneous, more virulent) Rough (opaque, granular, or sticky) O chain of the smooth strain LPS is a marker for virulence |
|
|
Term
Describe the pathogenesis of Brucella |
|
Definition
An intracellular parasite of the reticuloendothelial system Microorganisms are phagocytosed by macrophages and monocytes Acidic environment of the phagolysosome induces virulence genes Phagocytosed bacteria are carried to the spleen, liver, bone marrow, lymph nodes, and kidneys, forms granulomas |
|
|
Term
How is Brucellosis contracted? |
|
Definition
Consuming contaminated, unpasteurized milk and other dairy products |
|
|
Term
What is Leishmaniasis? What causes Leishmaniasis? |
|
Definition
Infection by Leishmania sp. Vector-borne disease transmitted by sandflies |
|
|
Term
What causes the symptoms of a Leishmania infection? |
|
Definition
Amastigote forms found in reticulo-endothelial cells of the viscera Spleen, lymph nodes, liver, intestines |
|
|
Term
What is distinctive about the incubation period of Leishmaniasis? |
|
Definition
Incubation can be as short as 10 days or as long as a year |
|
|
Term
What are the symptoms of Leishmaniasis? |
|
Definition
Anemia, protrusion of abdomen due to splenomegally, and bleeding mucus membranes are most important* Low grade fever, malaise, wasting, facial edema, diarrhea, breathing difficulties |
|
|
Term
What causes Rickettsioses? |
|
Definition
Rickettsia sp. Transmitted by tick vectors |
|
|
Term
What are the general characteristics of Rickettsia? |
|
Definition
Obligate intracellular, aerobic, gram-negative rods |
|
|
Term
How is Rickettsia diagnosed? |
|
Definition
Giemsa stain is preferred |
|
|
Term
Describe the pathogenesis of Rickettsia? |
|
Definition
Enters eukaryotic cells by stimulating phagocytosis Degrades the phagosome membrane using a phospholipase to enter the cytoplasm, necessary for survival |
|
|
Term
What is the characteristic site of pathologic lesions of Rocky Mountain Spotted Fever? |
|
Definition
Small blood vessels Vessels may be blocked by thrombi causing vasculitis in the heart*, spleen*, skin, liver, kidneys, lungs, or CNS |
|
|
Term
Severe cases of Rocky Mountain Spotted Fever are in danger of what complication? |
|
Definition
Disseminated Intravascular Coagulopathy (DIC) |
|
|
Term
What is Rocky Mountain Spotted Fever |
|
Definition
Rickettsioses due to Rickettsia rickettsii transmitted through the tick |
|
|
Term
|
Definition
Rickettsioses caused by Rickettsia prowazekii transmitted by exposure to human body louse feces (Pediculus humanus) |
|
|
Term
What are the symptoms of epidemic typhus? |
|
Definition
Splenomegaly*, hypotension*, vascular collapse* if severe High fever, headache, maculopapular rash |
|
|
Term
|
Definition
Rickettsioses caused by Rickettsia tsutsugamushi Transmitted to humans by chigger (mite larva) bites Occurs in Asiatic-Pacific areas |
|
|
Term
What are the clinical symptoms of scrub typhus? |
|
Definition
*Splenomegaly, *interstitial myocarditis Fever, headache, macular rash Delirium, stupor, muscle twitching |
|
|
Term
What causes increased levels of hepcidin with release of cytokines in cases of anemia due to chronic infection? |
|
Definition
Iron is trapped in the reticuloendothelial system Erythropoietin levels decrease Cytokines suppress hematopoiesis in the bone marrow |
|
|
Term
What is the function of Hepcidin? |
|
Definition
Key regulator in iron metabolism Regulates absorption of iron from foods and iron transport across the placenta Regulates the release of iron from macrophages and the recycling of aged RBCs |
|
|
Term
How does inflammation affect the actions of Hepcidin and cause anemia? |
|
Definition
Production is 100x higher than normal Results in increased sequestration of iron in macrophages |
|
|
Term
What are the best known parasitic infections that cause hemolytic anemia? |
|
Definition
Malaria (Plasmodium falciparum) Bartonellosis (Bartonella bacilliformis) Babesiosis (Babesia microti) |
|
|
Term
|
Definition
Sporozoites of Plasmodium falciparum in the salivary glands of mosquitoes that have ingested blood infected with malarial gametocytes |
|
|
Term
Describe the pathogenesis of Plasmodium falciparum (malaria) |
|
Definition
Sporozoites travel to the liver where they invade and replicate Merozoites leave the liver through the circulatory system and invade red blood cells Merozoites continue to replicate, lyse RBCs, and invade other RBCs |
|
|
Term
Plasmodium falciparum (most severe form of Malaria) feeds on what? |
|
Definition
Hemoglobin and other proteins Ultimately causes destruction of the spleen Merozoites adhere to glycophorin molecules on the red blood cell surface |
|
|
Term
Which organisms cause relapsing malaria? |
|
Definition
Plasmodium vivax and Plasmodium ovale After treatment, treatment-resistant parasites reside dormant in the liver Eventually they invade RBCs and begin a typical erythrocytic cycle |
|
|
Term
Which organism causes long-lasting malarial infections that are most often asymptomatic? |
|
Definition
|
|
Term
RBCs parasitized by Plasmodium vivax display small purplish red granules (with Wright’s stain) called what? |
|
Definition
|
|
Term
How is malaria diagnosed? |
|
Definition
Giemsa or Wright stains are gold standard |
|
|
Term
What are other forms of malarial diagnosis? |
|
Definition
Malarial RDTs (rapid diagnostic test) |
|
|
Term
|
Definition
Zoonosis caused by animal-specific protozoan parasites Parasites invade RBCs and induce a febrile disease Hemolytic anemia, hemoglobinuria, shock, death |
|
|
Term
What Babesia species are responsible for majority of human infections? |
|
Definition
Babesia microti Babesia divergens |
|
|
Term
What are the most common hosts for Babesia? |
|
Definition
White-footed mouse Deer tick Humans are accidental hosts, no human to human transfer |
|
|
Term
How is Babesiosis diagnosed? |
|
Definition
Direct blood smears show tetrad formation in RBCs Indirect fluorescent antibody test |
|
|
Term
What is Oroya fever (acute)? |
|
Definition
Infection by Bartonella bacilliformis (Bartonellosis) Motile by polar flagellum Adheres to and invades RBCs |
|
|
Term
What causes Bartonellosis (Oroya fever)? |
|
Definition
Transmitted by the nocturnal sandfly Limited to a small area in the Andes Mountains |
|
|
Term
How does intraerythrocytic Bartonella bacilliformis avoid the immune response? |
|
Definition
Lacks MHC molecules on the surface of mature erythrocytes Presentation of Bartonella antigens to the immune system is not possible |
|
|
Term
How is Bartonellosis diagnosed? |
|
Definition
Serologic testing Microscopic examination of Giemsa-stained blood smears |
|
|
Term
What alpha toxin is secreted by Clostridium perfringens? |
|
Definition
|
|
Term
*What are the actions of the alpha-toxin lecithinase secreted by Clostridium perfringens? |
|
Definition
Reacts with red blood cell membrane lipoproteins to produce lysolecithin Disrupts cell membranes of host cells including Erythrocytes and Leukocytes Mediates massive hemolysis, increased vascular permeability, and bleeding Causes myocardial dysfunction |
|
|
Term
What is the action of Theta-toxin (Θ-toxin) secreted by Clostridium perfringens? |
|
Definition
Is a heat-labile & oxygen-labile hemolysin Alters capillary permeability Toxic to heart muscle Pore-forming (cytolytic) |
|
|
Term
What is responsible for initial cell destruction in respiratory tract by Clostridium perfringens? |
|
Definition
Hydrogen peroxide Damages erythrocyte membranes* |
|
|
Term
How does Mycoplasma pneumoniae cause cold autoimmune hemolytic anemia? |
|
Definition
Auto-IgM antibodies are directed against the I antigen on red blood cells Cause agglutination of RBCs* transiently in the fingers, ears, nose |
|
|
Term
Mycoplasma pneumoniae is inherently immune to what types of antibiotics? |
|
Definition
Beta-lactams due to lacking a cell wall |
|
|
Term
What are the general characteristics of Mycoplasma pneumoniae? |
|
Definition
Slow rate of growth Obligate aerobe Receptor on Mycoplasma pneumoniae is integral in attachment to eukaryotic host cell membranes in the respiratory tract and RBCs |
|
|
Term
What are the possible complications of measles vaccination? |
|
Definition
|
|
Term
What are the characteristics of a Rubella infection? |
|
Definition
Respiratory transmission Viruses replicates in the nasopharynx & lymph nodes Viremia* with spread to other tissues |
|
|
Term
What are the hemorrhagic manifestations* of a Rubella infection? |
|
Definition
Rare, primarily children Low platelet count, vascular damage Thromobocytopenic purpura GI, cerebral, intrarenal hemorrhaging can occur |
|
|
Term
What are the IgG antibodies that react with RBCs in the cold (below body temperature) |
|
Definition
Donath-Landsteiner antibodies cause a rare form of cold-autoimmune hemolytic anemia referred to as Paroxysmal cold hemoglobinuria Can be idiopathic or associated with Syphilis, Varicella, Mumps, Measles, etc. |
|
|
Term
What kind of infection can cause Ag/Ab complexes bind to RBC surface and induce hemolysis? |
|
Definition
Hemophilus influenzae type b meningitis |
|
|
Term
What is Polyagglutination? |
|
Definition
A rare form of hemolysis caused by metabolites from infectious agents forcing RBCs to exposed normally hidden surface antigens Example: enteric bacteria can produce neuraminidase |
|
|
Term
What kinds of infections can cause a disruption of the gastrointestinal or genitourinary mucosa leading to anemia by blood loss? |
|
Definition
Helicobacter pylori Helminthic infections such as nematodes and trematodes |
|
|
Term
What is the most cause for blood loss anemia in developed countries? |
|
Definition
|
|
Term
How do Ancylostoma duodenale & Necator americanus (hookworms) cause blood loss? |
|
Definition
Due to feeding worms Microcytic, hypochromic anemia develops |
|
|
Term
Describe the pathogenesis of Schistosomiasis? |
|
Definition
Cercaria penetrate the skin and enter the venous system Travel to heart, lungs, and portal circulation |
|
|
Term
What are the symptoms of Acute schistosomiasis (Katayama’s fever) |
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Definition
*Diarrhea (bloody), *Hepatosplenomegaly, *eosinophilia, Cystitis, ureteritis with hematuria* (can lead to bladder cancer) Fever, cough, abd pain, occasional CNS lesions, pulmonary hypertension |
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Term
How is Fasciolopsis buski (intestinal fluke) contracted? |
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Definition
Ingestion of encysted larva in aquatic vegetation like water chestnuts Found only in China, Vietnam, Thailand, parts of Indonesia, Malaysia, India |
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Term
Attachment of the flukes (Fasciolopsis buski) to the small intestines causes what? |
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Definition
Hemorrhage* Marked eosinophilia* Inflammation and ulceration |
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Term
What parasite causes Megaloblastic Anemia? |
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Definition
Diphyllobothrium latum (Cestode) (Fish tapeworm) Common in areas where raw or pickled fish are eaten |
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Term
What is characteristic of carriers of Cestodes (fish tapeworm) suffering from megaloblastic anemia? |
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Definition
Low serum levels of vitamin B12 |
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Term
What are the characteristics of Trypanosoma? |
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Definition
Flagellated, insect-transmitted protozoa that infects RBCs and tissues |
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Term
What causes Chagas’ Disease? |
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Definition
Trypanosoma cruzi transmitted by feces of Triatomine (reduviid) bugs, the "kissing bug" |
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Term
What are the acute symptoms of Chaga's disease? |
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Definition
Romaña’s sign: Eye on one side swells (at location where triatomine bug fecal matter gets rubbed in) Occur in about 1% of cases |
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Term
What are prolonged symptoms of Chaga's disease? |
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Definition
Enlarged liver or spleen* Fever, fatigue, swollen lymph glands Brain damage and death in younger |
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Term
What causes African Sleeping Sickness? |
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Definition
Trypanosoma brucei gambiense (slow progressing) Trypanosoma brucei rhodesiense (rapidly progressing) Kinetoplastids (mitochondrial DNA) |
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Term
What is characteristic of the acute blood stage of infection for African Sleeping Sickness? |
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Definition
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Term
What causes relapses of African Sleeping Sickness? |
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Definition
Antigenic variation of trypanosomal surface Life cycle exhibits different morphologies |
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Term
What are the symptoms of African Sleeping Sickness? |
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Definition
Apathy, fatigue, confusion, motor changes (tics, slurred speech) Changes in sleep patterns Extreme fatigue during day, extreme agitation during night |
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Term
What are potential complications of African Sleeping Sickness? |
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Definition
Trypanosomes cross the blood-brain barrier resulting in meningoencephalitis Untreated can progress to coma or death |
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Term
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Definition
Caused by infections with nematodes (roundworms) Infective larvae are transmitted by arthropods |
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Term
How do nematodes (roundworms) cause filariasis? |
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Definition
Female worms produce microfilariae Microfilariae enter and circulate in the bloodstream |
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Term
What are the clinical manifestations of lymphatic filariasis? |
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Definition
Eosinophilia is prominent* Many are asymptomatic though some develop lymphatic dysfunction |
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Term
How is filariasis diagnosed? |
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Definition
Identify presence of microfilariae in blood Blood collection must be timed with periodicity of organism |
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