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Bacterial Causes of Diarrhea
Med school GI section, bacteria
65
Microbiology
Graduate
03/22/2011

Additional Microbiology Flashcards

 


 

Cards

Term
Invasion
Definition

- may not have any diarrhea or vomiting

- dysentary may be present

- fecal leukocytes present

- blood in stool

- fever

Term
Inflammatory gastroenteritis pathogens
Definition
  1. Salmonella sp.
  2. Shigella sp.
  3. Campylobacter sp.
  4. Yersinia enterocolitica
  5. Vibrio parahaemolyticus
  6. Francisella tularensis
  7. EIEC
  8. EHEC
Term
Salmonella sp. (general, habitat)
Definition

Gram -, rods, motile, facultative anaerobes, non-lactose fermenting

 

Habitat:

- typhi = human

- enteritidis and choleraesuis = intestines of animals

Term
Salmonella sp.: transmission
Definition

Fecal-oral route

animals to humans (Turtles)

animal food products to humans

Term
Salmonella sp: O Ag
Definition
somatic
Term
Salmonella sp: H Ag
Definition
Flagellar Protein
Term
Salmonella sp: Vi Ag
Definition
Capsular Polysaccharide
Term
Salmonella Pathogenesis
Definition

-sensitive to killing by gastric acid

-attach to gastric epithelial cells in sm. intestine and colon -> bacterial type III secretory system injects bacterial proteins into host cells -> internalization -> replication in vacuoles -> cell lysis -> enter mesenteric lymph nodes and blood stream -> fever, ab pain, diarrhea

Term
Type III Secretion
Definition

used by Salmonella sp.

-bacterial needle that injects effector proteins into host cell

Term
Salmonella enteritidis: Virulence
Definition

-inflammatory diarrhea due to invasion of intestinal epithelial cells

-controlled by vagocytic defenses

-risk in immunocompromised for disseminated disease

Term
Salmonella typhi: pathogenesis
Definition

-cause enteric fever (typhoid fever)

-fever, nonproductive cough, bloody diarrhea, ab pain, rose spots on skin

Term
Salmonella typhi: Virulence
Definition

-invasive intracellular pathogen

-reaches blood stream (better than other Salmonella sp.)

-little diarrhea

-enteric fever

-involvement of other organs

Term
Salmonella: Clinical manifestations - Enteritis
Definition

- most common form of salmonellosis

- symptoms occur 6 - 48 hrs after injestions

  • nausea, ab cramps, vomiting, nonbloody diarrhea
  • fever, headache, myalgias

Symptoms last 2 days - 1 wk

Term
Salmonella: Clinical manifestations - septicemia
Definition

- higher risk in pediatric, geriatric and immunocompromised

- clinical presentation like all Gram (-) sepsis

Term
Salmonella: clinical manifestations - Enteric fever
Definition

S. typhi = typhoid fever

others = paratyphoid fever

-bacteria pass through the gastric epithelial cells and are engulfed by macrophages

 

-Symptoms:

  • 10 - 14 days after ingestions
  • fever, headache, myalgias, malaise, anorexia for 1 wk followed by diarrhea
Term
Salmonella: detection
Definition

Non-lactose fermenter = colorless on MacConkey agar

 

motile

H2S+

 

enteritidis - isolated from stool

typhi - isolated from stool OR blood

 

fewer rectal leukocytes than shigellosis

Term
Shigella Sp.: general, habitat, transmission
Definition

General:

Gram -, bacilli, non-motile, non-lactose fermenter

resistant to stomach acids = only 10 - 20 bacilli needed to cause disease

 

Habitat:

human and primate intestines

invades and survives in cytoplasm

 

Transmission:

fecal-oral, P2P

 

 

 

Term
Shigella sp: virulence
Definition

-produces shiga toxin (exotoxin, cytotoxic to epithelial cell)

-attach and penetrate GI epithelial cells and M cells (use Type III)

-multiply intracellularly, spread to contiguous cells (use hemolysin to escape cell)

-use host cell actin for transport

Term
Shigella sp: detection
Definition

-isolation from stool

-nonlactose fementer

Distinctive features from Salmonella:

-non-motile

-H2S negative

Term
Shigellosis: clinical manifestations
Definition

-incubation period 36 - 72 hrs

-fever, cramping ab pain (both non specific)

-dysentary 2 days later

-watery diarrhea

Term
Shigellosis: treatment
Definition

-usually self limited

-prevent P2P spread

-fluid and electrolyte replacement for severe cases

-antidiarrheal compunds contraindicated (b/c they inhibit peristalsis = can't get rid of toxin)

Term
Campylobacter sp: general
Definition

General:

gram -, curved or comma shaped, microaerophilic, motile rods

can suvive intracellularly in monocytes and intestinal epithelial cells -> tissue necrosis and cell death

can travel to blood stream

 

Term
Campylobacter sp: habitat and transmission
Definition

habitat: intestinal tract of animals

 

transmission:

-fecal-oral route

-transmitted ny contraminated food; more common in summer

Term
Campylobacter sp: incidence
Definition

leading cause of bacterial diarrheal illness in US

 

most common cause in udnerdeveloped countries

 

3-5 days after ingestion; diseasse only if penetrates the mucouse layer and invades GI epithelial cells

Term
Campylobacter sp: virulence
Definition

-flagella

-adherence factors

-heat labile toxin = watery diarrhea

-ingestion by host cells = inflammatory colitis

-can also produce shiga toxin

-inflammatory and bloody diarrhea

Term
Campylobacter sp: clinical manifestations
Definition

anywhere from 7 days to chronic infection

 

periumbilical cramping, intense abdominal pain that mimics appendicitis, malaise, myalgias, headache, vomiting

 

watery diarrhea = most common

 

inflammatory bowel disease

Term
Campylobacter sp: detection
Definition

Detection:

-WBC in feces

-isolation in stool: requires growth on Campy or Skirrow media

 

Term
Yersinia enterocolitica: general, habitat, transmission
Definition

general:

aerobic, gram (-), bacilli

 

habitat: domestic and farm animals

 

transmission: fecal-oral route

Term
Yersinia enterocolitica: pathogenesis
Definition

invades mucosa of terminal ileum -> painful enlargement of mesenteric lymp nodes

- mistaken for appendicitis

- causes inflammatory and bloody diarrhea

 

transmitted by contaminated meat products, mostly during winter (can grow at 4 degrees C)

Term
Yersinia enterocolitica: virulence and clinical manifestations
Definition

virulence:

-heat stable enterotoxin -> inflammatory and bloody diarrhea

 

clinical:

-febrile illness with abdominal pain

-can mimic appendicitis

-lasts 2 - 3 weeks

-common in infants, occasional septicemia

Term
Yersinia enterocolitica: detection
Definition
isolation from stool and blood
Term
Aeromonas sp.
Definition

gram (-), motile, bacilli

 

found in fresh, salt and chlorinated water habitats

 

very resistant to temperatures and chemicals

 

Aerolysin cytotoxic toxin (ACT)

 

opportunistic pathogen in immune compromised

Term
Vibro sp: general
Definition
small, curved, gram (-), bacilli, single flagellum
Term
V. cholerae: virulence, transmission
Definition

virulence:

-produces cholera toxin - activates adenylate cyclase to increase cAMP -> voluminous, watery diarrhea

 

transmission:

-contaminated water or food (shellfish or crabs)

Term
Vibro cholerae: pathogenesis
Definition

-colonizes small bowel

-acute illness due to enterotoxin production

    -severe form: rapid loss of liquid and electrolytes; hypovolemic shock, metabolic acidosis and death

-acid sensitive = requires a lot to cause disease

Term
Cholera toxin (enterotoxin)
Definition

- A-B type toxin

- A increases adenylate cyclase activity -> increase in cAMP

Term
Vibro cholera: clinical manifestations
Definition

-abrupt, watery diarrhea (rice water)

-vomiting following diarrhea

-cyanotic, sunken eyes, high voice, unobtainable BP, etc. all because of severe dehydration

Term
Vibrio cholera: diagnosis
Definition

-rice water stools

-stool culture on thiosulfate-citrate-bile salt-sucrose agar (TCBS); colonies are yellow, other Vibrio are green

Term
Vibrio parahaemolyticus:
Definition

-hemolytic strains are most virulent

-enterotoxin production -> moderate bowel inflammation; mild to moderately severe diarrhea

-halophilic (salt-loving); grows in marine environments

-found in raw or undercooked shellfish

-colonizes small intestine

Term
Vibrio parahaemolyticus: Transmission, clinical manifestions, diagnosis
Definition

Transmission:

-ingestion of inadequately cooked seafood or sushi

 

clinical: watery diarrhea, ab cramps, nausea, vomiting, bloody diarrhea (sometimes)

 

diagnosis: green on TCBS agar

Term
Enterotoxigenic E. Coli (ETEC)
Definition

-Non-invasive = do not see fecal WBC's

-colonize sm. intestine

-common cause of traveler's diarrhea

-produce cholera-like (heat-labile) toxin and a heat-stable toxin -> both lead to watery diarrhea (secretion of Cl- -> osmotic diarrhea)

-abrupt onset watery diarrhea, lasts less than 24 hrs after initiation of fluid replacement

Term
Enteropathogenic E. Coli (EPEC)
Definition

-non-invasive = do not see WBC in stool

-no known toxin

-adheres to epithelial cells in Sm. intestine and disrupts microvilli (effacement)

-type III secretory system

   -makes its own receptor

        - when it binds to cell it forms pedestals

-watery diarrhea with mild inflammation, infants <6 m.o.

Term
Enteroaggregative E. Coli (EAggEC)
Definition

-non-invasive = do not see WBC in stool

3 stages:

  1. adhere to mucosa
  2. enhanced mucus production encases bacteria enabling biofilm formation
  3. elaboration of cytotoxin, damages intestinal cells

-may colonize sm. and lg. intestine

-cause of a more persistent diarrhea

Term
Diagnosis and treatment of inflammatory E. coli infections
Definition

Diagnosis:

-isolation on MacConkey's Agar (like Vibro)(lactose fementer)

Tx: fluid and electrolytes, antibiotics

Term
Enteroinvasive E. coli (EIEC)
Definition

-similar pathogenesis as for Shigella infections

-results in watery diarrhea and dysentery

-sporadic outbreaks in infants and children

Term
Enterohemorrhagic E. coli (EHEC)
Definition

-mostly infects lg. bowel

-kidney damage due to Shiga toxin

 

Clinical manifestations:

-Hemolytic colitis: severe crampy ab pain, watery diarrhea followed by bloody diarrhea, no fever

-Hemolytic Uremic Syndrome: triad of acute renal failure, thrombocytopenia and microangiopathic hemolytic anemia

Term
Diagnosis and Treament of Invasive E. coli infections: EHEC
Definition

Dx:

-carbohydrate sorbitol must be included in the medium

-inability to ferment sucrose

-ELISA detection of Shiga Toxins 1 and 2 in stool

 

Tx: Avoid antibiotics

Term
Listeria monocytogenes: Listeriosis
Definition

-usually mild diarrhea but systemic symptoms are prominent

-pathogen can break into cytoplasm and divide

-major risk is maternal infection during pregnancy

-serious in immunocompromised

Term
Three most common causes of acute infectious diarrhea
Definition
Salmonella, Shigella, Campylobacter
Term
E. coli: general
Definition
  • MOST common in uncomplicated outpatient UTI's
  • Gram (-), motile, bile tolerant, lactose fermenting
  • Lab ID: pink on MacConkey Agar
  • transmission: part of normal flora
Term
E. coli: Virulence Factors
Definition
  • adherence to urethroepithelial cells via fimbriae (pyelonephritis strains are the most adherent)
  • endotoxin
  • some strains have capsule adhesion
Term
E. coli: UTI strains
Definition

UPEC

  • adhere to urethroepithelial cells
  • increased serum resistance
  • increased hemolysin production
Term
Staphylococcus saprophyticus
Definition
  • 5-15% of cystitis cases in young, sexually active women
  • gram (+), cocci in clusters
  • transmission: normal flora of skin and GU mucosa
  • prevention: urination after intercourse
Term
Staphylococcus saprophyticus: Lab ID
Definition
  • white colonies on blood agar
  • catalase (+)
  • coagulase (-)
  • mannitol non-fermenter
  • Novobiacin resistant (distinguishes from other coagulase (-) staph)
Term
Staphylococcus epidermidis
Definition
  • nosocomial UTI pathogen
  • white colonies on blood agar
  • Catalase (+)
  • Coagulase (-)
  • mannitol non-fermenter
  • novobiacin sensitive
Term
Staphylococcus epidermidis: pathogenesis and tx/px
Definition
  • Pathogenesis: slime production and biofilm formation; colonizes catheters and prostheses
  • Tx/Px: MDR strains exist so use catheter care
Term
Enterococci
Definition
  • common in pts with recurrent infections, instrumented or have anatomic defects
  • normal flora of UG tract
  • MDR (vanco)
  • fomerly classified in Streptococcus
Term
Proteus mirabilis
Definition
  • produces ureases which cause pyelonephritis
  • Highly motile (swarmer) - able to ascend the ureter against the flow of urin
  • Gram (-), rod
Term
Proteus mirabilis: virulence and lab ID
Definition

Virulence Factors:

  • urease
  • endotoxin

Lab ID:

  • non-lactose fermenting
  • urease (+)
  • indole (-)
Term
Enterobacter sp.
Definition
  • common in pts with recurrent infections, instrumented or have anatomic defects
  • Gram (-) rod, motile
  • lactose fermenter
  • MDR
Term
Pseudomonas aeruginosa
Definition
  • common in pts with recurrent infections, instrumented or have anatomic defects
  • nosocomial pathogen
  • inherently resist to many antibiotics
  • Gram (-), rods, motile, aerobe
  • ubiquitous distribution in soil and water
Term
Psuedomonas aeruginosa: lab ID
Definition
  • oxidase (+) (distinguishes from E. coli)
  • pigment production
  • fimbriae for adherence
  • endotoxin
  • biofilm formation (attaches to catheters)
Term
Klebsiella sp.
Definition
  • nosocomial UTIs
  • Gram (-), non-motile, lactose fermenter
  • Transmission: normal flora, able to survive in moist environments (hands)
  • virulence: capsule, endotoxin, fimbriae
Term
Serratia marscescens
Definition
  • gram (-), bacillus, facultative anaerobe
  • normal GI flora in small numbers
  • environmental bacteria
  • opportunistic pathogen (nosocomial)
  • characteristic red pigment
  • lactose - , indole - , urease - , motile, H2S -
Term
Candida albicans
Definition
  • common in hospitalized pts who are on broad-spectrum antibiotics and have a bladder catheter
  • diabetic pts
  • immunosuppressed pts
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