Question 1

Question

A 25-year-old male from a flood-affected area presents with sudden onset of profuse, painless, rice-water diarrhoea and severe dehydration. Stool is collected and inoculated onto selective media. The plate after 18 hours of incubation at 37°C is shown (Image 1). Which single biochemical or growth characteristic of the organism forming these colonies best explains why this selective medium differentiates it from other vibrios such as Vibrio parahaemolyticus?

Accepted Answer

A. Fermentation of sucrose, producing acid that shifts the pH indicator to yellow

Answer

B. Inability to tolerate bile salts, resulting in selective inhibition of competing enteric flora

Answer

C. Production of hydrogen sulphide, causing blackening of the colony centre

Answer

D. Fermentation of thiosulfate with release of free sulphur, yielding opaque white colonies

General Microbiology — MCQs

General Microbiology — MCQs

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