Question

A child comes with fever, cold, cough and a membrane over the tonsils. A nasal swab is taken. Culture should be done on which medium for the earliest diagnosis?

• A. Loeffler's serum slope
• B. L. J. medium
• C. MacConkey's agar
• D. Citrate medium

Hint:

Think of the medium on which diphtheria bacilli grow within 6 to 8 hours.

Answer 1

The Correct Option is A

Step 1: The clinical picture of a tonsillar pseudomembrane with upper respiratory symptoms in a child is classic for diphtheria. The bacterium responsible is Corynebacterium diphtheriae, and the question asks which medium yields the quickest result.

Step 2: Speed of growth is the deciding factor. Among standard media, Loeffler's serum slope supports extremely fast multiplication of this organism, with recognisable colonies forming within roughly 6 to 8 hours. This early growth advantage lets the lab report findings before competing flora overgrow the plate.

Step 3: Reviewing why the rest fail: Lowenstein-Jensen (L. J.) medium targets tubercle bacilli and needs weeks, MacConkey's agar selects for lactose-fermenting and non-fermenting enteric rods, and citrate medium is a confirmatory biochemical reagent rather than an isolation medium.

Step 4: Therefore the nasal swab is streaked on Loeffler's serum slope for the fastest confirmation.

\[\boxed{\text{Loeffler's serum slope}}\]