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micro GI > Bacterial GI 2 > Flashcards

Bacterial GI 2 Flashcards

1
Q

MacConkey agar tests for?

A

Lactose fermentation

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2
Q

MacConkey results are red indicates?

A

Lactose fermentation POSITIVE

E. coli, some others

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3
Q

MacConkey results are white indicates?

A

Lactose fermentation NEGATIVE

Salmonella, Shigella, and others

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4
Q

Indole test tests for?

A

Indole production

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5
Q

Indole test results red indicates?

A

Indole production POSITIVE

E. coli, Vibrio spp., and others

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6
Q

Indole test results in no color change indicates?

A

Indole production NEGATIVE

Salmonella

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7
Q

Hydrogen sulfite test used to differentiate?

A

Salmonella from Shigella

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8
Q

H2S production test for Salmonella

A

Results in a black precipitate, indicating H2S production

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9
Q

H2S production test for Shigella

A

No precipitate formed, indicating no production of H2S

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10
Q

Enteropathogenic E. coli (EPEC) features and disease

A

Gram-negative, facultative anaerobe, moderately invasive

Causes watery diarrhea, pediatric cases are big

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11
Q

EPEC pathogenesis

A

BfpA
Type III secretion system

NO toxins

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12
Q

BfpA

A

“Bundle-forming pilus”

Adhesins

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13
Q

Type III secretion system

A

Injection of bacterial protein
For EPEC, this protein is called Tir (receptor for another protein called intimin)

F actin polymerization occurs, which results in increased efflux of water

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14
Q

EPEC diagnosis and treatment

A

Culture and biochemical tests
MacConkey positive

Indole positive

PCR

Supportive therapy

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15
Q

Enterotoxigenic E. coli (ETEC) features and disease

A

Gram-negative, facultative anaerobe, non-invasive

“Travelers diarrhea” - watery diarrhea from contaminated water and ice

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16
Q

ETEC pathogenesis

A

Fimbriae (pili)
LT toxin

ST toxin

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17
Q

Fimbriae

A

Adherence to epithelial cells

18
Q

LT toxin

A

Heat liable toxin
AB toxin

Increases cAMP, resulting in water efflux

Plasmid-encoded

19
Q

ST toxin

A

Heat stable toxin
Non-AB toxin, does NOT enter cell

Increases cGMP

Plasmid-encoded

20
Q

ETEC diagnosis and treatment

A

DNA probes to detect LT and ST encoding genes

Supportive therapy

21
Q

Salmonella spp. two types

A

S. typhi

Non-typhoidal Salmonella

22
Q

Non-typhoidal Salmonella

A

S. cholerasuis
S. enteritidis

S. typhimurium

23
Q

S. typhi features

A

Gram-negative rods, non-motile, facultative anaerobes, intracellular pathogen

24
Q

S. typhi transmission and resistance

A

Oral-fecal route

Acid tolerant

25
Q

Incubation for S. typhi

A

~13 days

26
Q

Progression of S. typhi

A 
Fever with headache, with increasing fever for 3 days
Typhoid fever (longer than ~4 weeks)

GI symptoms

Re-infection (shedding of S. typhi in stool)

27
Q

S. typhi pathogenesis

A

Adherence to M cells

28
Q

M cells

A

Found in the small intestine
Sample and present intestinal contents to immune cells

Associated with Peyer’s patches

29
Q

S. typhi adherence to M cells and dissemination

A

Type III secretion system
Invade vacuoles of M cells and escapes into cytosol

Can then invade macrophage and escape into lymphatics, resulting in bacteremia

30
Q

Diagnosis and treatment of S. typhi

A

Culture of stool samples

Antibiotics based on susceptibility profile

31
Q

Prevention of S. typhi

A

Avoid potential sources of infection

Vaccinations for travelers - Ty21A and ViCPS

32
Q

Nontyphoidal Salmonella features

A

Gram-negative rods, facultative anaerobe, motile/flagellated (H Ag), intracellular pathogens

33
Q

Incubation period for nontyphoidal Salmonella

A

6-48 hours post-ingestion

34
Q

Symptoms of nontyphoidal Salmonella

A

Nausea, vomiting, abdominal cramps, watery diarrhea with or without blood, sometimes fever

35
Q

Nontyphoidal Salmonella pathogenesis

A

Same as typhoidal, up to macrophage infiltration; two options -
Rapid killing of the macrophage, resulting in massive inflammation response that confines the infection to intestines OR

(immunocompromised patients) systemic dissemintation, bacteremia, focal infections

36
Q

Diagnose nontyphoidal Salmonella

A

Serology (anti-Vi Ag Ab)
Culture from blood and stool

MacConkeys negative

Production of H2S

37
Q

Treatment for nontyphoidal Salmonella

A

Confined to intestines - replace electrolytes, antibiotics NOT recommended
Systemic - antibiotics, based on resistance profile

38
Q

Campylobacter jejuni features and disease

A

Gram-negative curved rod, microanaerobic, invasive

Ulceration/acute enteritis, watery diarrhea, sepsis, Sequelae (Guillain-Barre syndrome)

39
Q

Incubation time for Campylobacter jejuni

A

2-11 days

40
Q

Pathogenesis of Campylobacter jejuni

A

Similar to Salmonella, but not much is known

41
Q

Diagnosis and treatment of Campylobacter jejuni

A

Culture

Supportive therapy, or antibiotics (invasive disease only, based on susceptibility profile)

micro GI (2 decks)

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