Enterobacteriaceae I Flashcards Preview

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Flashcards in Enterobacteriaceae I Deck (40)
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1
Q

Are enterobacteriaceae gram+ or -?

A

NEG

2
Q

What are antibodies formed against in enterobacteriaceae?

A

O antigen of LPS

3
Q

What part of LPS is responsible for toxicity?

A

Lipid A (causes fever, diarrhea, shock)

4
Q

Where is the H antigen located?

A

peritrichous flagella

5
Q

Where is the K antigen located?

A

capsule

causes UTI, invasive disease

6
Q

What are the 7 virulence factors for enterobacteriaceae?

A

1) Endotoxins (LPS)
2) Capsule (no phagocytosis)
3) antigenic phase variation
4) type III secretory system
5) sequestration of growth factors (ex: iron)
6) resistance to serum killing
7) antimicrobial resistance

7
Q

Are enterobact obligative or facultative?

A

facultative

8
Q

What key enzyme are enterobact NEGATIVE for?

A

oxidase

9
Q

What is the energy source for enterobact?

A

ferment glucose

reduce nitrate to nitrite

10
Q

Do all bacteria ferment lactose?

A

NO, some do and some don’t

11
Q

What is special about macconkey agar?

A

only gram NEGATIVE grow on it

12
Q

What color do lactose fermenters turn on macconkey agar?

A

purple

13
Q

Is the normal flora in our body lactose positive or neg?

A

positive (streak a stool sample and if everything is purple, no infection)

14
Q

What are the 7 tribes of enterobacteriaceae?

A
I Escherichiae
II Edwardsielleae
III Salmonelleae
IV Citrobactereae
V Klebsielleae
VI Proteeae
VII Yersinieae
15
Q

What is the most common enterobacteriaceae isolated from human infection?

A

E. coli

16
Q

Where is E. coli found in the environment?

A

IT ISNT

if it is found in water, it is indicative of fecal contamination

17
Q

What are 6 clinical syndromes that E. coli can cause?

A

1) gram negative sepsis
2) UTI
3) wound infection
4) pneumonia in IC hospitalized patients
5) meningitis in neonates
6) gastroenteritis

18
Q

What are the 5 strains of E. coli causing gastroenteritis?

A

1) Enterotoxigenic (ETEC)
2) Enteropathogenic (EPEC)
3) Enteroinvasive (EIEC)
4) Enterohemorrhagic (EHEC)
5) Enteroaggregative (EAggEC)

19
Q

What strain of E. coli is associated with Traveler’s diarrhea? (profuse watery diarrhea)

A

ETEC

20
Q

What strain of E. coli is associated with infantile diarrhea?

A

EPEC (no gross blood)

21
Q

What kind of E. coli is associated with blood, mucus, and many leukocytes in the stool? And tenesmus

A

EIEC (invade epithelial cells)

22
Q

What kind of E. coli is associated with bloody diarrhea without WBCs? no fever

A

EHEC (caused by O157:H7)

23
Q

What kind of E. coli is associated with watery diarrhea with blood and mucus, less commonly associated with abdominal pain?

A

EAggEC

24
Q

What is the most common Shiga Toxin Producing E. coli (STEC)?

A

O157

25
Q

How is STEC transmitted?

A

feces of cattle, deer, sheep

humans get it via food (undercooked ground beef), water or direct contact with infected patient

26
Q

What 2 infections are associated with E.coli O157?

A
  • Hemolytic Uremic Syndrome (HUS)

- Hemorrhagic Colitis

27
Q

What 3 things are indicative of hemorrhagic colitis?

A

1) abdominal cramps, watery diarrhea, bloody discharge
2) no significant fever
3) absence of WBC in stool

28
Q

What is the triad of symptoms in HUS?

A
  • acute renal failure
  • thrombocytopenia
  • hemolytic anemia
29
Q

What is the leading cause of renal failure in kids?

A

HUS

preceded by bloody diarrhea

30
Q

What is the clinical trajectory followed by Enterohemorrhagic E. coli?

A

3-4 days nonbloody diarrhea w/ ab pain then bloody diarrhea w/ severe ab pain

either resolves in 4-10 days or HUS

31
Q

What does a CBC look like for an O157 E. coli patient?

A

RBCs are hypochromic (white) and fragmented (shisotcytes)

32
Q

What is responsible for toxicity seen in O157?

A

shiga toxin (builds up on kidney wall)

33
Q

What is the mechanism of action of Shiga toxin?

A

1) inhibit protein synthesis targets (of commensals and host cells)
2) damage microcirculation –> vasculitis –> mucosal damage
3) trigger signaling cascades (influence cytokines)
4) Hits endothelial and epithelial cells of the CNS

34
Q

What 2 settings can HUS occur in?

A

1) diarrheal related (classical)

2) non-diarrheal HUS (pneumococcal infection, chemo, transplant immunosuppression)

35
Q

What are 3 host risk factors that can increase chance of getting HUS?

A

1) young or old age
2) mental retardation
3) P antigen on RBCs (attachment site for shiga)

36
Q

Treatment with what can worsen an O157 infection?

A

anti-motility agents (increase susceptibility)

37
Q

True or false: serotypes other than O157 can cause disease

A

TRUE (still make shiga)

38
Q

What antigens are you looking for to diagnose positive O157 infection?

A
shiga
O157 antigen (LPS)
39
Q

What antibiotics do you treat STEC with?

A

NONE - will cause massive destruction of e. coli which will release all the shiga toxin and endotoxin

40
Q

How do you treat STEC diarrhea?

A

rehydration, dialysis

NO antimotility agents and NO antibiotics