Term
Enterobacteriaceae general characteristics/epidemiology |
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Definition
gram-
oxidase-
non-motile OR motile w/ peritrichous flagella
non-fastidious
all except 1 ferment glucose (some ferment lactose; some non-fermenters can be pathogenic? not a good rule)
normal animal/human intestinal flora
>70% UTIs
significant cause: food poisoning |
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Term
common genera of the Enterobacteriaceae family (6): |
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Definition
1. Escherichia coli
2. Shigella
3. Proteus
4. Salmonella
5. Yersinia
6. Klebsiella
*all GNB |
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Term
predominant GNB of colonic flora |
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Definition
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Term
enterobacteriaceae: lactose fermenters |
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Definition
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Term
Enterobacteriaceae: Lactose non-fermenters |
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Definition
Proteus
Salmonella
Shigella
Yersinia |
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Term
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Definition
pink colonies => lactose fermenters
used when testing for enterobacteriaceae |
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Term
GNB have LPS as an integral part of the cell wall & is released after cell death; typical LPS includes: |
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Definition
1. lipid A: w/in mem; toxic activity
2. conserved core polysaccharide: common antigen
3. variable O-polysaccharide: serologic diversity |
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Term
virulence of enterobacteriaceae (4) |
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Definition
1. capsule (antiphag/poor antigen; inhib opson/complement activation)
2. antigenic variation: K&H antigens (alternatively expressed or not at all; evade host defense)
3. nutrient trap: Fe chelators (siderophores enterobactin, aerobactin)
4. ~20 bact proteins => "syring" (deliver virulence factors to host) *Yersinia, Salmonella, EPEC, Pseudomonas* |
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Term
the strains causing extra-intestinal & intestinal infections are different; what part of the host's immune system are important? |
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Definition
humoral & innate immunity
incr susceptibility w/ dysfunction/deficiencies of these parts of the immune system |
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Term
most common cause of septic shock? |
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Definition
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Term
name the organism w/ major sites of infection: CNS, LRT, bloodstream, GIT, & UTI |
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Definition
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Term
name the organism w/ major sites of infection: LRT, bloodstream, UTI |
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Definition
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Term
name the organism w/ the major sites of infection: LRT & bloodstream |
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Definition
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Term
name the organism w/ the major sites of infection: GIT |
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Definition
Salmonella
Shigella
Yersinia |
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Term
name the organism w/ the major sites of infection: UTI |
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Definition
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Term
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Definition
motility test semi-soft medium inoculated w/ straight neele
motile bacteria swim away from the line of inoculation to find nutrients/cause turbidity
=> + is cloudy/line of inoculation not visible
and - is clear/line of inoculation visible (bacteria are growing along)
*used to test enterobacteriaceae |
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Term
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Definition
-citrate utilization test (citrate is sole carbon source & ammonium salts sole N source)
-organisms that metabolizae citrate use ammonium salts --> release ammonia/incr pH
-bromothymol blue: green at neutral & deep blue above pH 7.6
*all salmonella (except S. typhi are +) |
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Term
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Definition
this tests for the bacteria that produce urease (these organisms will break the C-N bond of amides => co2, nh3, & h20 => basic solution)
results: + is pink
examples: E. coli- & Proteus+ |
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Term
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Definition
+ result: bacterial tryptophanase (converts tryptophan --> indole); adding Kovac's reagent leads to formation of red ring (pink color)
*E. coli+; P. vulgaris+; S. typhimurium- |
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Term
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Definition
combined test to determine production of: indole & H2S AND motility
inoculate organism in tube: organism w/ cysteine desulfurase (cysteine --> pyruvate + NH3 + H2S); Fe in medium rxs w/ H2S => black precip; motility (growth away from stab) is difficult to see w/ the H2S rxns
Ex: 1) E. coli does not produce H2S (no black color) & DOES prod indole (red ring)
2) Salmonells prod H2S (black color) & does NOT prod indole (no red ring)
3) Proteus vulgaris produces both H2S & indole (black color and red ring) |
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Term
triple-sugar-iron (TSI) test
[medium contains: 1% sucrose, 1% lactose, 0.1% glucose, and Fe] |
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Definition
no fermentation (obligate aerobe): slant & butt remain red
only glucose is fermented: acid in butt turns it yellow (insuff to affect slant)
sucrose or lactose ferments: butt & slant both yellow
gas forms during fermentation: agar cracks (displaced upwards)
H2S is produced: black in butt |
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Term
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Definition
triple sugar iron (TSI) test results:
red-no fermentation
yellow-acid prod from fermentation
YG-gas produced |
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Term
testing for enterobacteriaceae on macconkey agar |
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Definition
selective medium
bile salts & crystal violet inhib GPB growth
lactose (fermentable sugar) allows differentiation
neutral dye: red @ pH<6.8 & colorless @ pH>6.8 |
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Term
Enterobacteriaceae: lactose-fermenters |
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Definition
Escherichia coli
Klebsiella pneumoniae
(considered to be usually non-pathogenic) |
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Term
Enterobacteriaceae: lactose non-fermenters |
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Definition
Salmonella
Shigella
Proteus
(considered to be usually pathogenic) |
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Term
extra-gastrointestinal infections caused by Escherichia coli are usually: |
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Definition
endogenous and different strains than those causing intestinal infections |
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Term
How is a gastroenteritis infection due to Escherichia coli from the environment usually transferred? |
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Definition
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Term
virulence factors of Escherichia coli (5) |
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Definition
1. surface antigens (confer variability)
2. adhesins (indicates cell identity: p fimbriae/pili~UTI; colonization factors~GI; aggregative adherence fimbriae~UTI)
3. capsule
4. endotoxin: LPS
5. Exotoxins: ETEC (enterotoxigenic)~heat stable & heat labile; EHEC (enterohemorrhagic)~shiga-like toxins |
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Term
most common extra-intestinal Escherichia coli infection & presentation |
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Definition
UTI
-dysuria, frequency, suprapubic pain
-fever and/or back px => progression to pyelonephritis |
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Term
name the 2 most common bacterial causes of meningitis in neonates |
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Definition
1. Streptococcus agalactiae
2. Escherichia coli |
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Term
what characteristics of E. coli promote UTI? |
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Definition
serotypes w/ P pili
attaches bacteria to cell linings of the bladder and prevents them being "flushed" out with the urine |
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Term
2nd most common site of extra-intestinal E. coli infection: |
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Definition
abdomen/pelvis
may => peritonitis, diverticulitis, appendicitis or visceral abscess |
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Term
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Definition
more common occurrence in hospital borne pneu
(GNBs cause ~70% nosocomial pneumonia)
(E. coli is rarely a cause of community pneumonia) |
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Term
E. coli causes cellulitis |
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Definition
frequently infects decubitus ulcer
also infects extremities in diabetic pts |
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Term
1. Where does bacteremia/septicemia arise (w/ E. coli infection)?
2. What is the most common source of bacteremia? |
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Definition
1.at any extra-intestinal site
2. Escherichia coli UTIs |
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Term
top three bacterial causes of UTIs |
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Definition
1. Escherichia coli (60%)
2. Klebsiella (20%)
3. Proteus (15%) |
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Term
name the 5 strains of E. coli that cause Gastroenteritis |
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Definition
1. enteropathogenic E. coli (EPEC)
2. enterotoxigenic E. coli (ETEC)
3. enterohemorrhagic E. coli (EHEC)
4. enteroinvasive (EIEC)
5. enteroaggregative (EAEC) |
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Term
major cause of non-bloody INFANT diarrhea in the underdeveloped countries, describe the mechanism |
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Definition
EPEC (enteropathogenic E. coli)
mechanism: Bfp, intimin, Tir allow attachment to intest epithel cells => destruction of microvillus => malabsorption/watery diarrhea |
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Term
major cause of non-bloody diarrhea worldwide, especially in children, also called "traveler's diarrhea"-describe virulent factors |
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Definition
enterotoxigenic E. coli (ETEC)
virulence: heat-labile (LT1-cholera like toxin incr cAMP) & heat-stable (STa toxin incr cGMP) => fluid loss |
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Term
organism that causes the most GI infections in the US, describe |
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Definition
enterohemorhagic E. coli (EHEC) O157:H7 serotype most common in the US
transmission: undercooked meat, vegetables, unpasteurized milk, fruits, water
virulence: shiga toxins (Stx-1) => disrupt protein synthesis => inflammation/lesions/destruction of intestinal villus => fluid secretion
presentation: mild --> bloody diarrhea, severe abdominal px
progression: may => HUS & kidney failure |
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Term
describe enteroinvasive E. coli (EIEC) |
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Definition
prevalence: mostly underdeveloped countries
virulence: plasmid mediated invasion & destruction of colonic epithelial cells
presentation: fever, cramp, watery diarrhea --> dysentery w/ scant bloody stools; progresses like Listeria & Shigella |
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Term
describe enteroaggregative Escherichia coli (EAEC) |
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Definition
=> infant bloody diarrhea (underdeveloped countries)
presentation: persistent watery diarrhea w/ vomiting, dehydration & fever
virulence: stacked bricks (plasmid-encoded behavior of rods) => short microvilli => poor reabsorption |
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Term
what are the two most common gastroenteritis causing strains of Escherichia coli? |
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Definition
-ETEC: traveler's diarrhea; organism in feces; toxins; LT & ST genes
-EHEC: serotype O157:H7; low amt of organism in feces; shiga toxins/genes; usually sorbitol non-fermenters |
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Term
Which organism is an oxidase negative, citrate & urease test negative, lactose fermenting motile rod? |
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Definition
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Term
age groups most commonly infected by salmonelosis |
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Definition
<5 yr
older adults >60 yr |
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Term
name the important species & serovars of Salmonella: |
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Definition
1. Salmonella enterica - clinically more significant
Serovars: Typhimurium & Typhi & Paratyphi
2. Salmonella bongori |
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Term
common transmission of Salmonella |
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Definition
poultry & dairy products & undercooked meat
-Salmonella enterica infects the ovaries/upper oviduct tissues of hens |
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Term
pathogenesis of Salmonella: bacteria can traverse the intestinal layer through... |
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Definition
-phagocytic microfold (M) cells in peyer's patch => membrane ruffles in intest epithel cells => trap salmonella/induce their endocytosis (w/ salmonella present, epithelial cells secrete IL8 => attract PMNs --> PMN's toxic substances damage intest mucosa => inflammatory diarrhea)
*NTS => massive PMN infiltration (large/small bowel mucosa)
*TTSS play key role in endocytosis/intracell surviv |
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Term
describe the most common form of salmonellosis |
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Definition
gastroenteritis
symptoms: fever, vomiting, water diarrhea, cramps
tx: NO antibiotics, usually self-limiting |
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Term
most common NTS that causes bacteremia |
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Definition
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Term
most common Salmonellas that causes bacteremia |
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Definition
Salmonella Paratyphi & Salmonella Typhi |
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Term
pathogenesis of typhoidal salmonella |
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Definition
invade: epithelium like other Salmonella --> disseminate through body via macrophages traveling through lymphatics
colonize: reticuloendothelial tissues (liver, spleen, bone marrow) --> re-enter GI tract => re-exposure => intestinal ulcers & necrosis
*Salmonella Typhi => mononuclear cell infiltration (not same as GI PMN infil during NTS infections) |
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Term
Enteric fever: presentation, progression, w/o tx? |
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Definition
Salmonella Typhi
early presentation: rose spots on trunk & chest (rash where bacteria is present), hepatosplenomegaly, epistaxis
progression: bradycardia @ peak of fever
w/o tx: severely ill (GI bleeding/perforation <= hyperplasia & ulceration) |
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Term
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Definition
gram-
oxidase-
motile rod
lactose non-fermenter
produce H2S
SS agar: grilliant green, ox bile, high thiosulfate & citrate inhib normal flora (H2S production detected by using thiosulfate & iron - colonies -> black color) |
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Term
name the 4 species of Shigella |
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Definition
Shigella dysenteriae
Shigella boydii
Shigella flexneri
Shigella sonnei |
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Term
1. Name the 5 F's
2. What organism is this associated w/? |
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Definition
1. Food, Flies, Feces, Fingers, Fomites
2. Shigella |
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Term
Where does the Shigella bacteria invade the colonic mucosa? |
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Definition
through M cells of Peyer's Patches
causes mucosal destruction/inflammation
rarely invades the bloodstream
Shigella dysenteriae => shiga toxin (inhib protein synthesis => cell death)
*remember, once these bacteria are inside the cells, they will stay there |
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Term
what are the two Shigella most common in the US? |
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Definition
Shigella sonnei
Shigella Flexneri
*neither => shiga toxin => less severe disease (watery diarrhea)
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Term
What specifically do the shiga toxin+ strains (Shigella) damage? |
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Definition
glomerular epithelium => HUS |
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Term
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Definition
non-fermenters (white colonies on MacConkey)
H2S non-producer
neutrophils in fecal stain
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Term
differentiate bt/w Escherichia coli & Shigella & Salmonella |
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Definition
1. motility:
Shigella-not
E. coli-motile
2. H2S production (black colonies on SS agar)
Shigella-not a producer
Salmonella-yes a producer |
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Term
3 most important human pathogens of genus: Yersinia |
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Definition
1. Yersinia enterocolitica
2. Yersinia pseudotuberculosis
3. Yersinia pestis |
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Term
identify Yersinia enterocolitica |
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Definition
gram- rod
zoonotic pathogen
non-lactose fermenter
motile only @ 28* C |
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Term
epidemiology of Yersinia enterocolitica |
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Definition
transmission: oral route from raw meat, unpasteurized milk, fecally contained water |
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Term
Yersinia enterocolitica virulence |
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Definition
*70kb plasmid essential (at least 6 genes for outer mem proteins => cytotoxicity, resist phago, apoptosis of host cells)
-chrom inv prod => translocation across epithelium |
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Term
Bodily target of Yersinia enterocolitica: |
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Definition
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Term
main presentation of Yersinia enterocolitica diseases: |
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Definition
acute diarrhea <= enteritis or enterocolitis
also: low fever & cramping |
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Term
Identify: GNB w/ prominent capsule, non-fastidious, facultative, oxidase-, lactose fermenting, motile |
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Definition
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Term
most common/important Klebsiella species (1) |
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Definition
Klebsiella pneumoniae
-causes majority of Klebsiella infections in LTCF, hospitals & community |
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Term
Klebsiella pneumoniae diseases |
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Definition
1. Pneumonia: minor cause of community; usually lobar (acute, severe, destructive)
2. UTI: not that common
3. Soft-tissue infection: affects devitalized tissues (decubitus & diabetic ulcers & burn sites)
4. Bacteremia: can be caused from infection at any site |
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Term
Identify Klebsiella granulomatis |
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Definition
gram-
encapsulated rod
intracellular pathogen
(has never been cultured)
donovan bodies w/in macrophages (pathognomonic sign) |
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Term
cause of ~70% STI cases in age group 40-70 |
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Definition
Klebsiella granulomatis (but this pathogen is also seen in children and sexually inactive adults) |
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Term
diseases of Klebsiella granulomatis |
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Definition
-Granuloma inguinale: begins w/ 1 or more subcut nodules --> erode through skin => clean, granulomatou, sharply defined, painless lesions that slowly enlarge (progressive erosion may completely destroy penis/other organ) |
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Term
Significant Proteus species: |
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Definition
1. Proteus mirabilis: causes ~90% of Proteus infections
2. Proteus vulgaris
normal flora in GUT, soil, & water |
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Term
virulence factors for Proteus |
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Definition
adhesins
flagella
IgA protease
urease |
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Term
diseases caused by Proteus mirabilis |
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Definition
UTI
wound infections
kidney (from urinary tract; more commonly than E. coli) |
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Term
identify Proteus mirabilis |
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Definition
lactose non-fermenter
do not form regular colonies
"swarming colonies" from high motility
urease+ |
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Term
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Definition
three most common bacterial causes of UTIs and their distinguishing characteristics |
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Term
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Definition
3 common causes of GI infections and their distinguishing characteristics |
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Term
gram-
non-spore forming
anaerobic rods
(name the two genera) |
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Definition
1. Bacteroides prevotella and Bacteroides porphyromonas (rod or coccobacilli)
2. Fusobacterium (longer rods tapering end) |
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Term
Bacteroides fragilis diseases |
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Definition
most common cause of intra-abdominal infections
also: sinusitis, otitis, brain/liver abscesses, pneumonia, skin & soft-tissue infection |
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Term
identify Bacteroides fragilis |
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Definition
weakly gram- staining
small pleomorphic rod
strict anaerobe
foul smelling wound w/ presence of gas
Bile Esculin agar: B. fragilis (black growth) vs. Proteus mirabilis (no growth) |
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