Question

In Eijkman's test, incubation is done at

• A. 37 °C ± 1°C for 48 h±2 h
• B. 40 °C ± 1°C for 24 h±1h
• C. 42.5 °C ± 0.2°C for 24 h±1h
• D. 44.5 °C ± 0.2°C for 24 h±2h

Hint:

Coliform Testing Temperatures:
Total Coliforms (Presumptive Test) = $35^\circ - 37^\circ\text{C}$ for 24--48 h.
EIJKMAN TEST (Fecal Coliforms E. coli) = $44.5^\circ\text{C} \pm 0.2^\circ\text{C}$ for 24 h.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Thermotolerant coliform identification: the Eijkman test detects fecal E. coli by gas production from lactose fermentation at the selective elevated temperature of $44.5^\circ ext{C} \pm 0.2^\circ ext{C}$ for $24 ext{ h} \pm 2 ext{ h}$.
Key Formula or Approach:
\[ \text{Eijkman Fecal Coliform Test: EC Broth / Brilliant Green Bile Broth at } \mathbf{44.5^\circ\text{C} \pm 0.2^\circ\text{C} \text{ for } 24 \pm 2\text{ h}} \]

Step 2: Detailed Explanation:
In water and dairy bacteriological quality testing (Eijkman Test Elevated Temperature Fecal Coliform Test):
- Devised by Christiaan Eijkman to differentiate true fecal Escherichia coli (warm-blooded mammalian origin) from non-fecal environmental coliforms (Enterobacter aerogenes):
- The test culture (inoculated into EC Broth or MacConkey broth containing Durham inverted gas vials) is incubated in a circulating thermostatic water bath calibrated strictly at 44.5°C ± 0.2°C for 24 hours ± 2 hours (D):
1. Environmental soil coliforms cannot grow or ferment lactose at this high temperature.
2. Fecal {E. coli ferments lactose with vigorous production of gas and indole at $44.5^\circ ext{C}$, confirming direct fecal contamination.

Step 3: Final Answer:
Therefore, incubation in Eijkman's test is done at 44.5 °C ± 0.2°C for 24 h±2h, matching option (D).