Culture media used for E.coli 0157:H7 is
a) SMAC
b) Wilson and Blair medium
c) Potassium tellurite in Mcleod’s medium
d) Deoxycholate citrate agar (DCA)
Correct Answer - A
Answer- A- SMAC
An enterohemorrhagic bacterial strain, E. coli O157: H7 infects the
alimentary tract and induces abdominal cramps with hemorrhagic
diarrhea. Transmission of E. coli O157: H7 occurs via the fecal-oral
route after consumption of contaminated, undercooked liquids and
foods.
Mac Conkey-Sorbitol ChromoSelect Agar (SMAC) is recommended
for selective isolation of Escherichia coli 0157:H7 from food and
animal feeding stuffs.
MacConkey Sorbitol Agar is based on the formulation described by
Rappaport and Henigh. The medium contains sorbitol instead of
lactose and it is recommended for the detection of enteropathogenic
strains of E. coli 0157:H7 which ferments lactose but does not
ferment sorbitol and hence produce colorless colonies.
Sorbitol fermenting strains of E. coli produce pink-red colonies. The
red color is due to the production of acid from sorbitol, absorption of
neutral red and a subsequent colour change of the dye when the pH
of the medium falls below 6.8.
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