SHIGELLA

IT IS NAMED AFTER SHIGA ,WHO FIRST ISOLATED IT

IT IS A MEMBER OF ENTEROBACTERIACEAE IN ENTEROBACTERIACEAE THERE ARE FOUR TRIBES IT BELONGS TO TRIBE ESCHERICHIAE

DYSENTERY IS A CLINIC CONDITION OF MULTIPLE ORIGIN IT IS CHARACTERIZED BY THE FREQUENT PASSAGE OF BLOODSTAINED,MUCOPURULENT STOOLS TWO COMMON TYPES OF DYSENTERY ARE PRESENT 1. AMEBIC 2. BACILLARY

THE CASATIVE AGENTS OF BACILLARY DYSENTERY BELONG TO THE GENUS SHIGELLA THE OTHER BACILLI WHICH ALSO PRODUCE THE CLINICAL PICTURE OF DYSENTERY ARE EIEC VIBRIO PARAHAEMOLYTIUS CAMPYLOBACTER

MORPHOLOGY SHIGALLAE ARE SHORT ,GRAM-NEGATIVE RODS THEY ARE NONMOTILE,NONSPORING AND NONCAPSULATED FIMBRIAE MAY BE PRESENT

CULTURAL CHARACTERISTICS THEY ARE AEROBES AND FACULTATIVE ANAEROBES THEY GROW ON ORDINARY MEDIA AFTER OVERNIGHT INCUBATION,COLONIES ARE SMALL,CIRCULAR,CONVEX,SMOOTH AND TRANSLUCENT

CONTD COLONIES ON MACCONKEY AGAR ARE COLOURLESS DUE TO THE ABSENCE OF LACTOSE FERMENTATION BUT Sh Sonnei FERMENTS LACTOSE AND FORMS PALE PINK COLONIES SELECTIVE MEDIA-DCA

RESISTANCE SHIGALLE ARE NOT SPECIALLY RESISTANT THEY ARE KILLED AT 56 C IN ONE HOUR BY 1% PHENOL IN 30 MINUTES IN FECES THEY DIE WITHIN A FEW HOURS DUE TO THE ACIDITY PRODUCED BY THE GROWTH OF COLIFORMS Sh sonnei IS MORE RESISTANT THAN OTHER SHIGELLA SPECIES

BIOCHEMICAL REACTIONS SHIGALLAE ARE MR POSITIVE REDUCE NITRATES TO NITRITES DO NOT FORM H2S CATALASE IS PRODUCED, EXCEPT by sh dysenteriae Type 1

CONTD GLUCOSE IS FERMENTED WITH THE PRODUCTION OF ACID WITHOUT GAS NEWCASTLE AND MANCHESTER BIOTYPES OF Sh flexneri TYPE 6 AND SOME STRAINS OF Sh boydii FORMS GAS BASED ON THE FERMENTATION OF MANNITOL SHIGELLAE ARE DIVIDED INTO MANNITOL FERMENTING AND NON FERMENTING SPECIES

ANTIGENIC STRUCTURE IT POSSESS SOMATIC O ANTIGENS SOME STRAINS POSSESS K ANTIGENS FIMBRIAL ANTIGENS ARE ALSO PRESENT