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Year 1 Microbiology > GI bacteria II > Flashcards

GI bacteria II Flashcards

1
Q

What is the main ingredient in MacConkey agar?

A

Bile salts - inhibits growth of many bacteria except certain GI bacteria

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2
Q

Lactose fermentation on MacConkey agar is positive (red) with what bacteria?

A

E. coli

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3
Q

Lactose fermentation on MacConkey agar is negative (white) with what bacteria?

A

Salmonella, shigella

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4
Q

The indole test is positive (red color change) for what bacteria?

A

E. coli, vibrio spp.

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5
Q

The indole test is negative (no color change) for what bacteria?

A

Salmonella

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6
Q

What test is used to differentiate between salmonella and shigella?

A

Hydrogen sulfite production

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7
Q

Is salmonella a hydrogen sulfite producer?

A

Yes

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8
Q

Is shigella a hydrogen sulfite producer?

A

No

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9
Q

What are the characteristics of enteropathogenic E. coli (EPEC)?

A
  1. Gram negative 2. Facultative anaerobe 3. Mmoderately invasive
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10
Q

What are the disease symptoms of enteropathogenic E. coli (EPEC)?

A

Water diarrhea

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11
Q

What is the pathogenesis of enteropathogenic E. coli (EPEC)?

A
  1. Interacts with intestinal cells via BfpA (bundle forming pillus A) 2. Type III secretion system, injects Tir into host cytosol 3. Intimin binds to Tir 4. F actin causes loss of microvilli - diarrhea 5. No toxins
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12
Q

What is the diagnosis for enteropathogenic E. coli (EPEC)?

A
  1. Ferments lactose (red on MacConkey) 2. Indole positive 3. PCR
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13
Q

What are the characteristics of enterotoxigenic E. coli (ETEC)?

A
  1. Gram negative 2. Facultative anaerobe 3. Non-invasive
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14
Q

What are the disease characteristics of enterotoxigenic E. coli (ETEC)?

A
  1. “Traveler’s diarrhea” 2. Watery diarrhea
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15
Q

What is the pathogenesis of enterotoxigenic E. coli (ETEC)?

A
  1. Fimbriae - adherence 2. Toxins - increase cAMP and cGMP 3. Non-invasive, noninflammatory
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16
Q

What toxins are associated with enterotoxigenic E. coli (ETEC)?

A
  1. LT - heat labile - AB toxin - increases cAMP 2. ST - heat stable - non-AB toxin - increases cGMP 3. Plasmid encoded
17
Q

What is the diagnosis for enterotoxigenic E. coli (ETEC)?

A
  1. Clinical history 2. DNA probes to detect LT and ST encoding genes
18
Q

What are the characteristics of salmonella typhi?

A
  1. Gram negative 2. Facultative anaerobe 3. Motile flagellated rods 4. Acid tolerant 5. Intracellular pathogen 6. Inflammatory
19
Q

What is the epidemiology of salmonella typhi?

A
  1. Humans are the only reservoir 2. Fecal-oral transmission 3. Infectious dose 10^5 - 10^6 bacteria
20
Q

What is the disease progression for salmonella typhi?

A
  1. 13 day incubation 2. Fever with headache 3. Typhoid fever (4 weeks) with sustained bacteria 4. GI symptoms - colonization of gall bladder, reinfection of intestines 5. Shed in stool
21
Q

What is the pathogenesis for salmonella typhi?

A
  1. Adherence to M cells and enterocytes 2. Type III secretion system 3. Ssps - salmonella secreted invasion proteins cause membrane ruffling of M cell 4. Escape from vacuole 5. Bacteremia from T3SS invasion into macrophages
22
Q

What is the function of M cells?

A
  1. Sample and present intestinal contents to immune cells 2. Associated with Peyer’s patches in ileum
23
Q

What causes the typhoid fever symptoms in salmonella typhi infection?

A

Endotoxin released into blood stream from bacteremia

24
Q

What is the treatment for salmonella typhi?

A
  1. Antibiotics based on susceptibility profile 2. Fluoroquinolones, trimethoprim-sulfamethoxazole or broad spectrum cephalorsporin
25
Q

What are the characteristics of non-typhoidal salmonella?

A
  1. Gram negative facultative anaerobe 2. Motile flagellated rods 3. Acid tolerant 4. Intracellular pathogens 5. Same as typhoidal but not as human adapted 6. Inflammatory
26
Q

What is the epidemiology of non-typhoidal salmonella?

A
  1. Numerous animal reservoirs 2. Contaminated dairy / egg / poultry 3. Human to human transmission unlikely 4. Infectious dose 10^6 - 10^8
27
Q

What is the clinical manifestation of non-typhoidal salmonella?

A
  1. 6-48 hours post ingestion 2. Nausea and vomiting with abdominal cramps and watery diarrhea for 3-4 days 3. Fever 50% of cases 4. Dysentery type diarrhea possible 5. Spontaneous resolution of watery diarrhea within 7 days
28
Q

What is the pathogenesis of non-typhoidal salmonella?

A
  1. Initial stage similar to typhoidal 2. After entry can either kill macrophage or reside within macrophage
29
Q

What characterizes non-typhoidal salmonella infection with macrophage killing?

A
  1. Massive inflammatory response that aims to confine infection 2. Active fluid secretion
30
Q

What characterizes non-typhoidal salmonella infection with macrophage hijacking?

A
  1. Occurs in immunocompromised individuals 2. Systemic dissemination, bacteremia 3. Focal infections of arthritis, osteomyelitis, endocarditis
31
Q

What is the diagnosis for non-typhoidal salmonella?

A
  1. Serology - anti-Vi antigen Abs 2. Culture - non-lactose on MacConkey, H2S positive
32
Q

Why is antibiotic therapy not recommended for non-typhoidal salmonella gastroenteritis infection?

A
  1. Enhances carrier state 2. It is only for severe cases to prevent septicemia
33
Q

What are the characteristics of campylobacter jejuni?

A
  1. Gram negative rod, seagull shaped 2. Microaerophilic 3. Many animal reservoirs 4. Invasive - jejunum, ileum, colon
34
Q

What is the disease progression for campylobacter jejuni?

A
  1. Ulceration and acute enteritis - watery diarrhea 2. Sepsis 3. Long incubation time (2-11 days) 4. Sequelae - Guilliain-Barre syndrome
35
Q

What are the features of Guillain-Barre syndrome?

A
  1. Acute immune-mediated polyneuropathy 2. Progressive, fairly symmetric muscle weakness accompanied by absent or depressed deep tendon reflexes

Year 1 Microbiology (42 decks)

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