GI bacteria II Flashcards Preview

Year 1 Microbiology > GI bacteria II > Flashcards

Flashcards in GI bacteria II Deck (35):
1

What is the main ingredient in MacConkey agar?

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

2

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

E. coli

3

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

Salmonella, shigella

4

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

E. coli, vibrio spp.

5

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

Salmonella

6

What test is used to differentiate between salmonella and shigella?

Hydrogen sulfite production

7

Is salmonella a hydrogen sulfite producer?

Yes

8

Is shigella a hydrogen sulfite producer?

No

9

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

1. Gram negative 2. Facultative anaerobe 3. Mmoderately invasive

10

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

Water diarrhea

11

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

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

12

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

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

13

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

1. Gram negative 2. Facultative anaerobe 3. Non-invasive

14

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

1. "Traveler's diarrhea" 2. Watery diarrhea

15

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

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

16

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

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

17

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

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

18

What are the characteristics of salmonella typhi?

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

19

What is the epidemiology of salmonella typhi?

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

20

What is the disease progression for salmonella typhi?

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

What is the pathogenesis for salmonella typhi?

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

What is the function of M cells?

1. Sample and present intestinal contents to immune cells 2. Associated with Peyer's patches in ileum

23

What causes the typhoid fever symptoms in salmonella typhi infection?

Endotoxin released into blood stream from bacteremia

24

What is the treatment for salmonella typhi?

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

25

What are the characteristics of non-typhoidal salmonella?

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

What is the epidemiology of non-typhoidal salmonella?

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

27

What is the clinical manifestation of non-typhoidal salmonella?

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

What is the pathogenesis of non-typhoidal salmonella?

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

29

What characterizes non-typhoidal salmonella infection with macrophage killing?

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

30

What characterizes non-typhoidal salmonella infection with macrophage hijacking?

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

31

What is the diagnosis for non-typhoidal salmonella?

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

32

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

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

33

What are the characteristics of campylobacter jejuni?

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

34

What is the disease progression for campylobacter jejuni?

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

35

What are the features of Guillain-Barre syndrome?

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