Question
A. SMAC
B. Wilson and Blair medium
C. Potassium tellurite in Mcleod’s medium
D. Deoxycholate citrate agar (DCA)
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Correct Answer » A Explanation |
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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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