Lecture 11 - Shigellosis

Lecture 11 - Shigellosis - SHIGELLOSIS Shigella:...

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SHIGELLOSIS
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Shigella : Bacteriology Gram-negative, non-motile rods Facultative anaerobe Lactose negative Four serogroups or species A ( S. dysenteriae ) B ( S. flexneri ) C ( S. boydii ) D ( S. sonnei )
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Incidence of shigellosis Worldwide o 165 million cases/yr 163 million cases/yr in developing countries 1.1 million deaths/yr 1.5 million cases/yr in industrialized countries (See Kotloff et al, Bull. WHO, 77 :651, 1999)
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Shigellosis: Clinical Manifestations Abdominal pain Tenesmus Watery diarrhea Dysentery (multiple scanty, bloody, mucoid stools) Fever Vomiting Dehydration PMNs in stool Mucosal layer of colon is inflamed with small ulcers Symptoms last 7 to 10 days (untreated)
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Treatment Hydration Antibiotics o Will shorten duration of disease Ampicillin Trimethoprim/sulfamethoxazole Naladixic acid Ciprofloxacin o Shigella are commonly resistant to multiple antibiotics Makes use of antibiotics increasingly difficult Expensive
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Epidemiology Humans are primary reservoir of Shigella o Captive non-human primates are accidental hosts Very low infectious dose o Few as 10 organisms can cause infection Spread from human to human o Fecal-oral route Source/Mechanism o Contaminated food o Contaminated water o Fingers, feces, fomites o Flies
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Epidemiology, continued Endemic in developing countries o 1.1 million deaths/year o Inadequate sanitation o Overcrowding o >5 years of age – less likely to contract disease due to immunity o young, malnourished, old unhealthy most susceptible o prevalent species S. flexneri (60%) S. sonnei (15%) S. dysenteriae (6%) S. boydii (6%)
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Epidemiology, continued Industrialized countries o Sporadic, common-source outbreaks Camps Indian reservations Day-care centers Cruise ships Airlines o Everyone is susceptible o Prevalent species S. flexneri (16%) S. sonnei (77%) S. dysenteriae (2%) S. boydii (1%)
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Enteropathogens Isolated from U.S. Military Personnel During Desert Shield (Fall, 1990) Enterotoxigenic E. coli 125/432 28.9% Enteroinvasive E. coli 3/432 0.7% Shigella spp 113/432 26.1% Salmonella 7/432 1.6% Campylobacter 2/432 0.5% Summarized from Hyam et al, NEJM 325:1423, 1991
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Control and Prevention of Shigellosis Provide clean water Feces disposal Education on good hygiene o avoid contaminated water and food o hand washing Breast-feeding Good nutrition Vaccines?
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Shigella Vaccine Example #1. Higgins et al. Am J.Trop. Med. Hyg. 4 :281-288, 1955 S. flexneri 3. Heat-killed bacteria, 2.5 x 10 9 organisms/ml. Route: subcutaneous Dose: apx 1 ml spread out in three doses at 1 week intervals. Study subjects: Children, mean age of about 28 months.
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This note was uploaded on 04/29/2009 for the course BIOL 420 taught by Professor Edwardsoaks during the Fall '08 term at George Mason.

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Lecture 11 - Shigellosis - SHIGELLOSIS Shigella:...

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