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SHIGELLA

SHIGELLA. Dr. Neha Haswani Assistant professor, Dept. of microbiology. A highly infectious organism. Causative agent for dsentery frequent passage of blood stained mucopurulent stools. 10-100 bacilli can cause disease. Can survive for upto 30 days in milk, eggs, cheese or shrimps.

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SHIGELLA

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  1. SHIGELLA Dr. Neha Haswani Assistant professor, Dept. of microbiology

  2. A highly infectious organism • Causative agent for dsentery • frequent passage of blood stained mucopurulent stools. • 10-100 bacilli can cause disease. • Can survive for upto 30 days in milk, eggs, cheese or shrimps. • Infection occurs mostly after ingestion of food or water contaminated with human fecal matter.

  3. Definition • Belongs to family enterobacteriaceae • Gram negative bacilli • Aerobic • Non motile, non sporing • Non acid fast

  4. Classification • Basd on biochemical and serological reactions there are 4 serogroups/species: • Shigelladysenteriae(15) • Shigellaflexneri(8) • Shigellaboydii(19) • Shigellasonnei(26)

  5. Classification • On the basis of mannitol fermentation • Mannitol Non fermentor • Shigelladysenteriae • Mannitolfermentor • Shigellaflexneri • Shigellasonnei • Shigellaboydii

  6. Pathogenicity & Epidemiology • Causes bacillary dysentery • Source-human being • Route of infection- ingestion • Modes of transmission • Direct • Fomites • Contaminated food and water • Flies • Sexual- seen in young male homosexuals • Infective dose---10-100 bacilli.

  7. In countries where sanitation is good, shigellosis seen in young children • Shigellasonnei is commonly associated • In countries where environmental sanitation is poor, disease is endemic and occurs in all age groups. • In India, Shigellaflexneri is common species.

  8. Pathogenesis • Resembles EIEC • Binds to the M cells • Invades lamina propria • Grows in the enterocyte • Induce actin polymerisation • Invades the neighbouring enterocytes • Cause cell death and inflammation • Necrosis of patches of epithelium. • Transverse superficial ulcers. • Bacteraemia may occur in malnourished or HIV

  9. Clinical features • Short incubation period (1-7 days) • Onset and clinical course determined by virulence of infecting starin. • Frequent passage of loose scanty feces with blood and mucus • Abdominal cramps • Tenesmus • Fever and vomiting

  10. Complications • More common with Shigelladysenteriae type I • Arthritis • Neuritis • Conjunctivitis • Parotitis • Intusseception • Hemolyticuraemic syndrome

  11. Laboratory diagnosis • Specimen • Enrichment media/Transport media • Microscopy: plenty of pus cells, RBC, nonmotile bacilli • Culture:Mucus flakes are best samples to inoculate • MacConkey and DCA and XLD • Shigella salmonella agar • Hektoen agar • Biochemical reactions • Serology

  12. Treatment & Control • Uncomplicated shigellosis is a self limiting. • Treat dehydration in appropriately in infant and young children. • Routinely, antibiotic treatment not given. • MDR common now a days. It is plasmid mediated. • Improve personal and environmental conditions • No vaccine available • Antibiotics not used for prophylaxis

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