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CLASSIFICATION.

CLASSIFICATION. Classified into 4 species or subgroups based on biochemical & serological characteristics. 1.Sh.dysenteriae. 2.Sh.flexneri 3.Sh.boydii. 4. Sh.sonnei . Colicin typing. Sh.dysenteriae . mannitol nonfermenting bacilli. 10 serotypes Indole -negative Catalase -negative.

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CLASSIFICATION.

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  1. CLASSIFICATION.

  2. Classified into 4 species or subgroups based on biochemical & serological characteristics. • 1.Sh.dysenteriae. • 2.Sh.flexneri • 3.Sh.boydii. • 4. Sh.sonnei. • Colicin typing.

  3. Sh.dysenteriae. • mannitolnonfermenting bacilli. • 10 serotypes • Indole-negative • Catalase-negative

  4. 10 serotypes. • Type 1-shiga toxin. • Type 2-indole negative(Sh.schmitzi) • Type 3-7(large sachs group)

  5. 3 types of toxic activities of shiga toxin. • 1.neurotoxicity. • 2.enterotoxicity • 3.cytotoxicity

  6. NEUROTOXICITY • Demonstrable by paralysis & death on injection into mice & rabbits. • Neurotoxin. • Primary site of action appears to be not nervous tissue but the blood vessels of the CNS

  7. ENTEROTOXICITY • Induction of fluid accumulation in ligated rabbit ileal loop. • Sh.ET 1&2

  8. CYTOTOXICITY • Cytopathic changes in cultured Vero cells. • Toxin consists of binding(B) & active(A) subunits. • Subunit A is divided into A1 &A2 fragments.

  9. Sh.flexneri • Mannitol fermenting. • Antigenically most complex. • Based on type specific & group specific antigens-6 serotypes. • Two antigenic variants-X&Y.

  10. Sh.boydii • Consists of Dysentery bacilli similar to Sh.flexneri biochemically but not antigenically. • 15 serotypes

  11. Sh.sonnei • Late fermenters of lactose & sucrose • Indole negative. • Antigenically homogenous-but may occur in 2 forms phase1& phase2

  12. Mildest form of bacillary dysentery • Most common shigellosis in advanced countries.

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