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Published bySilas Gordon Modified over 8 years ago
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Enterobacteria. Biological characteristic and classification of genera
Enterobacteria. Biological characteristic and classification of genera. Characteristics of genus Escherichia, Shigella and Salmonella
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Family Enterobacteriaceae Genus
Escherichia Shigella Edwardsiella Salmonella Citrobacter Klebsiella Enterobacter Hafnia Serratia Proteus Morganella Providencia Yersinia Ervinia
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Escherichia
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Antigenic structure O antigen K antigen H-antigen
These antigens detected by agglutination reactions.
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Biochemical reactions
They ferment most of the sugars Glucose Lactose Mannitol Maltose with production acid and gas. Indol reaction is positive. H2S is not formed. Gelatin is not liquified.
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Diarrhoea 1. Enteropathogenic E.coli (EPEC)
E.coli causing diarrheal diseases are of five groups. 1. Enteropathogenic E.coli (EPEC) 2. Enterotoxigenic E.coli (ETEC) 3.Enteroinvasive E.coli (EIEC) 4.Enterohaemorrhagic E.coli (EHEC) 5.Enteroaggregative E.coli (EAEC)
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Laboratory diagnosis Bacteriological method.
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Shigella Classification Subgroup A (S.dysenteriae)
Subgroup B (S.flexneri) Subgroup C (S.boydii) Subgroup D (S.sonnei)
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Morphology
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Laboratory diagnosis Bacteriological method.
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Salmonella Classification
Causative agents of enteric fever S.typhi , S.paratyphi A, S.schottmuelleri Causative agents of gastroenteritis S.typhimurium, S.enteritidis, S.newport, S.dublin and etc. 3. Salmonella causing septicemia S.cholerae-suis
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Morphology of salmonellae
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Antigenic structure Flagellae antigen – H Somatic antigen – O
Surface antigen – Vi, found in some species.
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Classification Kauffmann-White scheme
Salmonellae are classified into groups based on distinctive O antigen factors. Within each group, further identification and differentiation is by phase 1 and phase 2 H antigens.
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Culture Lactose-including media SS-agar Nutrient agar Bile broth
Wilson and Blair bismuth sulphite medium (BSA)
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Biochemical reactions
Salmonellae ferment: Glucose Mannitol Maltose forming acid and gas except S.typhi which produces only acid and no gas. Most salmonellae produce H2S. They do not ferment lactose. Indol is not produced.
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Laboratory diagnosis Isolation of bacilli Demonstration of antibodies
Demonstration of circulating antigen
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Vaccination TAB vaccine – Live oral typhoid vaccine
Purified Vi polysaccharide vaccine
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Salmonella typhi
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