GI bacteria I Flashcards
Which host defenses can trigger expression of bacterial virulence factors?
Mucous, bile
What is characteristic of GI distress 1-8 hours after ingestion?
Preformed toxin
What is characteristic of GI distress 8-16 hours after ingestion?
Production of toxin after ingestion
What is characteristic of GI distress 16+ hours after ingestion?
Adherence, growth, and virulence factor production
What pathogens infect with a preformed toxin 1-8 hours after ingestion?
- Staphylococcus aureus 2. Bacillus cereus (emetic) 3. Clostridium botulinum
What pathogens produce toxin 8-16 hours after ingestion?
- Bacillus cereus (diarrheal) 2. Clostridium perfringens 3. Clostridium botulinum
What pathogens adhere, grow, and produce virulence factors 16+ hours after ingestion?
- Shigella spp. 2. Listeria monocytogenes 3. EHEC 4. EPEC 5. ETEC 6. EIEC 7. Campylobacter spp. 8. Vibrio spp.
Is fever associated with bacterial food poisoning?
No
What are the four bacterial causes of food poisoning?
- Staphylococcus aureus 2. Clostridium botulinum 3. Clostridium perfringens 4. Bacillus cereus
What are the characteristics of staphylococcus aureus?
- Gram positive cocci in clusters 2. Non spore forming
What is the disease progression of staphylococcos aureus food poisoning?
- Ingestion of preformed toxin 2. Severe vomiting, diarrhea, constipation and abdominal pain 1-8 hours after ingestion
What is the pathogenesis of staphylococcus aureus food poisoning?
Heat stable toxin
What are the characteristics of clostridium botulinum?
- Gram positive rod 2. Spore forming
Does staphylococcus aureus produce spores?
No
Does clostridium botulinum produce spores?
Yes
What is the disease progression of clostridium botulinum food poisoning?
- Mediated by botulinum toxin 2. Early - vomiting, diarrhea, abdominal pain 1-8 after ingestion 3. Late - flaccid paralysis, progressive muscle weakness and respiratory arrest
What is the pathogenesis of clostridium botulinum food poisoning?
- 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
What are the characteristics of clostridium perfringens?
- Gram positive rod 2. Spore forming
What is the disease progression for clostridium perfringens food poisoning?
- C. perfringens enterotoxin 2. Diarrhea and abdominal pain 8-16h after ingestion 3. Lasts for 24 hours
Does clostridium perfringens produce spores?
Yes
What are the characteristics of bacillus cereus?
- Gram positive 2. Spore forming
What is the disease progression for the emetic form of bacillus cereus food poisoning?
- Vomiting, nausea, abdominal cramps 1-8 hours after ingestion of preformed heat stable enterotoxin 2. Associated with improper storage of cooked rice
What is the disease progression for the diarrheal form of bacillus cereus food poisoning?
- Diarrhea, nausea, abdominal pain 8-16 hours after ingestion of contaminated food 2. Production of heat labile enterotoxin in intestine
What are the characteristics of helicobacter pylori?
- Gram negative curved rod 2. Microaerophilic (5% oxygen)
What is the pathogenesis of helicobacter pylori?
- Penetrates mucosa of stomach, attracted to hemin and urea 2. Produces urease which breaks down urea into NH3 and CO2 to increase pH
What is the treatment for H. pylori?
- Antibiotics 2. Proton pump inhibitor to control acid / further mucosal damage
What are the characteristics of listeria monocytogenes?
- Gram positive short rods sometimes in pairs 2. Facultative anaerobe
What are the key survival traits of listeria monocytogenes?
- Wide growth range (cryophilic) 2. Resistant to high salt concentrations 3. Wide pH range
What is the epidemiology of listeria monocytogenes?
- Contamination common in ready to eat meats 2. High risk of infection in elderly, immunocompromised
What is the clinical manifestation of listeria monocytogenes in immunocompromised individuals?
- Bacteremia 2. Meningitis and encephalitis
If a pregnant patient has a fever with no obvious focus, what pathogen should be included in the differential?
Listeria monocytogenes
What is the clinical manifestation of neonatal listeria monocytogenes infection?
- Granulomatosis infantiseptica - pyogenic granulomas distributed over the whole body 2. Early onset in utero - premature birth, abortion3. Late onset - 2-3 weeks after birth
What is the pathogenesis of listeria monocytogenes?
- Adherence via internalin A (IntA) 2. Internalized into a vacuole 3. Acidification of vacuole / phagosome 4. Listeriolysin produced in response to acidification of phagosome
How does listeria monocytogenes adhere to the GI tract?
Internalin A
What is activated by the acidification of the internalized vacuole in listeria monocytogenes infection?
Listeriolysin
What is the role of listeriolysin in listeria monocytogenes infection?
Disrupts vacuole membrane to allow for escape into the cytosol
What is the pathogenesis of listeria monocytogenes?
- Replication in host cell cytosol 2. ActA mediated polymerization to induce motility 3. Disseminated infection to liver, spleen, CNS
What is the diagnosis for listeria monocytogenes?
Culture of CSF and blood for 1. Cold enrichment selection 2. Weak B hemolysis on blood agar 3. Motility test
What is the treatment for listeria monocytogenes?
Beta lactam or trimethoprim-sulfamethoxazole
