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T. Dolgorsuren T. Dolgorsuren

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Shigella

Belong to Enterobacteriaceae

Non motile, non capsulated

Deoxycholate citrate agar (DCA) selective media (pale color colonies)

Gram negative bacilli

4 SPECIES/SUBGROUPS BASED ON

BIOCHEMICAL AND SEROLOGICAL CHARACTERS /

SHIGELLA DYSENTERIAE SHIGELLA FLEXNERI SHIGELLA BOYDII SHIGELLA SONNEI

Classifications

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Shigella species

Non Fermentation Fermentation

S dysentriae S flexneri

S boydii

S sonnei

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Epidemiology and Clinical Syndromes

Major cause of bacillary dysentery

Estimated 15% of pediatric diarrhea in U.S.

Leading cause of infant diarrhea & mortality

in developing countries

Epidemics of S. dysenteriae type 1 have occurred in Africa and Central America with case fatality rates of 5-15%.

Common in Pediatric age group (1-10 yrs)

Developed world – S sonnei,

developing world – S flexneri

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Shigellosis = Generic term for disease

Transmission by fecal-oral route

Incubation period = 1-3 days

Watery diarrhea with fever; changing to dysentery

Bacillary Dysentry

Passing blood & mucus in the stool

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Infection cycle of Shigella

Shiga toxin exacerbate inflammation by causing ischemia & hemorrhage

Ulcers

Rarely lead to bacteremia

Organisms adhere to colonic lymphoid follicles

Undergo parasite directed phagocytosis

Resist intracellular killing

Move directly from cell to cell

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Pathogenesis Two-stage disease

Early stage

Second stage

Fever attributed to neurotoxic activity of toxin

Dysentery due to adherence and tissue invasion of large intestine (cytotoxic activity of Shiga toxin)

Watery diarrhea attributed to the enterotoxin activity of Shiga toxin in the small intestine

Enterotoxic, neurotoxic and cytotoxicShiga toxin

04/12/23 Dr B V Navaneeth, Dept of Microbiology 10

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Clinical manifestation

Fever

Abdominal cramping & tenderness

Diarrhea / Dysentry

Tenesmus (straining at stools)

Sigmoidoscopy: ulceration Shigellosis in the cecum tissue

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Lab Diagnosis of Dysentry

Specimens Stool, rectal swab from an ulcer

In Xylose lysine deoxycholate agar(XLD) they appear pinkish to reddish colonies while in Heaktoen Enteric Agar (HEA), they give green to blue green colonies

Growth on Selective Growth on Selective MediumMedium

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Treatment

Oral vaccines of Shigella hybrids or Shigella mutants offers immunity for six months to one year

For adults:

Rehydration if necessary

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For childrenCo-trimoxazole or ampicillin + rehydration

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Yet No Licenced

Vaccine

Preventation

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Hand Washing Can Still Save Hand Washing Can Still Save Many from ShigellosisMany from Shigellosis

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www.wikipedia.comwww.slideshare.comwww.polioeradication.orgwww.webmd.comhealthrecent.blogspot.comconxz.blogspot.comwww.findarticles.comEnglish Mongolian medical dictionary“ Халдварт өвчин судлал ” Я. Дагвадорж“ Анагаах ухааны бичил амь судлал”

Sources

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Thank you for

your attention 04/12/23 20