GI bacteria I

Question 1

Which host defenses can trigger expression of bacterial virulence factors?

Answer 1

Mucous, bile

Question 2

What is characteristic of GI distress 1-8 hours after ingestion?

Answer 2

Preformed toxin

Question 3

What is characteristic of GI distress 8-16 hours after ingestion?

Answer 3

Production of toxin after ingestion

Question 4

What is characteristic of GI distress 16+ hours after ingestion?

Answer 4

Adherence, growth, and virulence factor production

Question 5

What pathogens infect with a preformed toxin 1-8 hours after ingestion?

Answer 5

1. Staphylococcus aureus 2. Bacillus cereus (emetic) 3. Clostridium botulinum

Question 6

What pathogens produce toxin 8-16 hours after ingestion?

Answer 6

1. Bacillus cereus (diarrheal) 2. Clostridium perfringens 3. Clostridium botulinum

Question 7

What pathogens adhere, grow, and produce virulence factors 16+ hours after ingestion?

Answer 7

1. Shigella spp. 2. Listeria monocytogenes 3. EHEC 4. EPEC 5. ETEC 6. EIEC 7. Campylobacter spp. 8. Vibrio spp.

Question 8

Is fever associated with bacterial food poisoning?

Answer 8

No

Question 9

What are the four bacterial causes of food poisoning?

Answer 9

1. Staphylococcus aureus 2. Clostridium botulinum 3. Clostridium perfringens 4. Bacillus cereus

Question 10

What are the characteristics of staphylococcus aureus?

Answer 10

1. Gram positive cocci in clusters 2. Non spore forming

Question 11

What is the disease progression of staphylococcos aureus food poisoning?

Answer 11

1. Ingestion of preformed toxin 2. Severe vomiting, diarrhea, constipation and abdominal pain 1-8 hours after ingestion

Question 12

What is the pathogenesis of staphylococcus aureus food poisoning?

Answer 12

Heat stable toxin

Question 13

What are the characteristics of clostridium botulinum?

Answer 13

1. Gram positive rod 2. Spore forming

Question 14

Does staphylococcus aureus produce spores?

Answer 14

No

Question 15

Does clostridium botulinum produce spores?

Answer 15

Yes

Question 16

What is the disease progression of clostridium botulinum food poisoning?

Answer 16

1. Mediated by botulinum toxin 2. Early - vomiting, diarrhea, abdominal pain 1-8 after ingestion 3. Late - flaccid paralysis, progressive muscle weakness and respiratory arrest

Question 17

What is the pathogenesis of clostridium botulinum food poisoning?

Answer 17

1. Ingestion of preformed toxin 2. Large number of spores germinate in intestine and produce toxin 3. Toxin acts at NMJ, blocks Ach release at synapses

Question 18

What are the characteristics of clostridium perfringens?

Answer 18

1. Gram positive rod 2. Spore forming

Question 19

What is the disease progression for clostridium perfringens food poisoning?

Answer 19

1. C. perfringens enterotoxin 2. Diarrhea and abdominal pain 8-16h after ingestion 3. Lasts for 24 hours

Question 20

Does clostridium perfringens produce spores?

Answer 20

Yes

Question 21

What are the characteristics of bacillus cereus?

Answer 21

1. Gram positive 2. Spore forming

Question 22

What is the disease progression for the emetic form of bacillus cereus food poisoning?

Answer 22

1. Vomiting, nausea, abdominal cramps 1-8 hours after ingestion of preformed heat stable enterotoxin 2. Associated with improper storage of cooked rice

Question 23

What is the disease progression for the diarrheal form of bacillus cereus food poisoning?

Answer 23

1. Diarrhea, nausea, abdominal pain 8-16 hours after ingestion of contaminated food 2. Production of heat labile enterotoxin in intestine

Question 24

What are the characteristics of helicobacter pylori?

Answer 24

1. Gram negative curved rod 2. Microaerophilic (5% oxygen)

Question 25

What is the pathogenesis of helicobacter pylori?

Answer 25

1. Penetrates mucosa of stomach, attracted to hemin and urea 2. Produces urease which breaks down urea into NH3 and CO2 to increase pH

Question 26

What is the treatment for H. pylori?

Answer 26

1. Antibiotics 2. Proton pump inhibitor to control acid / further mucosal damage

Question 27

What are the characteristics of listeria monocytogenes?

Answer 27

1. Gram positive short rods sometimes in pairs 2. Facultative anaerobe

Question 28

What are the key survival traits of listeria monocytogenes?

Answer 28

1. Wide growth range (cryophilic) 2. Resistant to high salt concentrations 3. Wide pH range

Question 29

What is the epidemiology of listeria monocytogenes?

Answer 29

1. Contamination common in ready to eat meats 2. High risk of infection in elderly, immunocompromised

Question 30

What is the clinical manifestation of listeria monocytogenes in immunocompromised individuals?

Answer 30

1. Bacteremia 2. Meningitis and encephalitis

Question 31

If a pregnant patient has a fever with no obvious focus, what pathogen should be included in the differential?

Answer 31

Listeria monocytogenes

Question 32

What is the clinical manifestation of neonatal listeria monocytogenes infection?

Answer 32

1. Granulomatosis infantiseptica - pyogenic granulomas distributed over the whole body 2. Early onset in utero - premature birth, abortion3. Late onset - 2-3 weeks after birth

Question 33

What is the pathogenesis of listeria monocytogenes?

Answer 33

1. Adherence via internalin A (IntA) 2. Internalized into a vacuole 3. Acidification of vacuole / phagosome 4. Listeriolysin produced in response to acidification of phagosome

Question 34

How does listeria monocytogenes adhere to the GI tract?

Answer 34

Internalin A

Question 35

What is activated by the acidification of the internalized vacuole in listeria monocytogenes infection?

Answer 35

Listeriolysin

Question 36

What is the role of listeriolysin in listeria monocytogenes infection?

Answer 36

Disrupts vacuole membrane to allow for escape into the cytosol

Question 37

What is the pathogenesis of listeria monocytogenes?

Answer 37

1. Replication in host cell cytosol 2. ActA mediated polymerization to induce motility 3. Disseminated infection to liver, spleen, CNS

Question 38

What is the diagnosis for listeria monocytogenes?

Answer 38

Culture of CSF and blood for 1. Cold enrichment selection 2. Weak B hemolysis on blood agar 3. Motility test

Question 39

What is the treatment for listeria monocytogenes?

Answer 39

Beta lactam or trimethoprim-sulfamethoxazole