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Organism
- Hundreds of serotypes
- Typhoid bacillus
- S. typhi=strictly human
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Epidemiology
- industrialized societies and improper food handling
- High infecting dose (10,000)
- Poultry products
- Raw milk + exotic pets
- Industrial production = outbreaks
- Chronic carries
- Fecal-oral
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Pathogenesis
- Large and small intestine
- Adhesion causes membrane ruffling (actin cytoskeleton rearrangement)
- Internalized via pinocytosis
- Multiple effector proteins injected into cells
- profound inflammatory response
- S. Typhi: Vi Ag reduces infecting dose, proliferation inside intestinal macrophages, carried to nodes, liver, spleen; bacteria seed blood stream; LPS starts fever -> rises with infection; reinfection of the bowel via UTI
- Immunity: humoral, CMI
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Manifestations
- Gastroenteritis: 24-48 hrs post exposure, nausea, vomiting, abd cramps, diarrhea; persists 2-7 days; fever in 50%
- Bacteremia: Frank sepsis in poor CMI; osteomyolitis involves long bones, sites of trauma
- Enteric fever: multiorgan infection; prolonged fever, RES involvement; can persist for weeks; Most are constipated; chronic seeding of bloodstream leads to endotoxemia; biliary tree infections -> reseeding of bowels; Major complication is hemorrhage from perforations through wall of terminal ileum
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Diagnosis
Blood/fecal culture
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Treatment
- GI: fluid/electrolyte replacement, control of nausea/vomiting
- Enteric fever: ampicillin
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Other enterobacteriaceae
- Klebsiella: lobar pneumonia, polysaccharide capsule
- Enterobacter: less virulent than klebsiella, mixeed infections
- Yersinia: Plague
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