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25 Cards in this Set
- Front
- Back
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What does the blood and mucus in the stool imply?
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Inflammatory invasion of the colonic mucosa
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What is the Hallmark of inflammatory diarrhea?
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the presence of neutrophils and other leukocytes in clumps of mucus in
fecal sample |
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- An invasive infection that is almost always limited to the superficial mucosal membranes of the terminal ileum and large intestine; blood invasion is rare
- Spread by the fecal-oral route; humans are the only reservoir - Sudden onset of abdominal pain and cramps, diarrhea fever. Stools are liquid and scant but after the first bowel movement contain mucus, pus and occasionally blood |
Shigella
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The infectious dose of Shigella is
very low (10-100 organisms). Why? |
Shigella is highly resistant to stomach acid
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Ten kids in a day care center in
Kentucky came down with abdominal cramps, fever, urgency and bloody, mucoid feces. What is the diagnosis? 1. Shigella dysenteriae 2. Shigella flexneri 3. Shigella boydii 4. Shigella sonnei |
Shigella sonnei
(most common in industrialized countries; worse in kids) |
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Most severe shigella infection that possesses the shiga toxin
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S. dysenteriae
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How does the shiga toxin lead to cell death?
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Cleaves the 60S ribosomal subunit = apoptosis
**Shiga toxin is an N-glycosidase** |
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What is shigella's only portal of entry into the enterocytes?
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It invades the M CELL
-Then it moves laterally into enterocytes |
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Name the bug:
_____ is a Gram-negative bacillus, non-motile and a facultative anaerobe. It is a non-lactose fermenter and does not produce H2S |
Shigella
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When macrophages take up Shigella bacteria, what do they secrete to attract PMNs?
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IL-1β and IL-18
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When enterocytes are infected with Shigella, what do they secrete to attract PMNs?
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IL-8
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What features of the M cell make it
accessible to Shigella? 1. Small number of M cells relative to enterocytes 2. Reduced glycocalyx 3. High net negative charge on surface 4. Rudimentary brush border |
Reduced glycocalyx
Rudimentary brush border |
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1. An invasive organism that infects the mucosal membranes of the ileum
2. Two clinical syndromes: gastroenteritis and typhoid (enteric) fever 3. Many different O and H antigens (flagellar antigen) 4. Vi (Virulence) capsule that interferes with phagocytosis 5. Ingested in food (eggs, poultry etc.) or water contaminated with feces from an infected host |
Salmonella
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What strains of Salmonella subspecies cause typhoid fever?
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Typhi
Paratyphi |
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What strains of Salmonella subspecies cause gastroenteritis?
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Cholerasuis
Enteritidis Dublin Typhimurium |
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Genus = Salmonella
Causes 70% of infection in U.S. |
Enteritidis
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What is the most common manifestation of Salmonella infection?
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GASTROENTERITIS
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Are Salmonella ssp. sensitive to stomach pH?
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Yes!
You need a higher inoculum than Shigella! |
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• Protracted, systemic illness due to infection with S. typhi or S. paratyphi, which lead to bacteremia and septicemia
• Spread through lymphatics and blood results in focal infections in any body site (ex. osteomyelitis, endocarditis) |
Typhoid Fever
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- Prevent the rapid recruitment of neutrophils and they are able to evade what neutrophils are present, resulting in systemic spread
• Hypertrophy of intestinal RES, including Peyer’s patches, mesenteric lymph nodes, spleen and bone marrow |
Typhoid Fever
(S. typhi or S. paratyphi) |
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How can S. typhi and S. paratyphi cause recurrent typhoid fever?
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Eventually organisms infect the gallbladder, grow actively in bile and reseed the GI tract
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What enables S. typhi and S. paratyphi to evade being killed by macrophages?
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- Type III secretion system
-bacterial proteins enable Samonella to prevent phagolysosome fusion and escape from vacuole |
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What toll-like receptor ligands do
Salmonella contain? |
-LPS --> TLR4
-Flagellin --> TLR5 |
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When considering typhoid fever, how do these Salmonella cause systemic infection?
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-Infected macrophages transport bacteria to the mesenteric lymph nodes.
- Only the serotypes that cause typhoid fever (S. typhi or S. paratyphi) survive in the macrophages to establish systemic infection |
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Name the bug:
____ is a Gram-negative bacillus, motile (flagella) and a facultative anaerobe. It is a nonlactose fermenter and produces H2S |
Salmonella
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