How is the multiple tube fermentation technique for fecal coliform performed?

The multiple tube fermentation technique for detecting fecal coliform is performed specifically in EC medium, which is designed to support the growth of coliform bacteria while inhibiting competing organisms. Incubation at a temperature of 44.5 ± 2 degrees Celsius is significant because this temperature range is optimal for the growth of fecal coliforms, especially E. coli, allowing for the differentiation from non-fecal coliforms that may not thrive at this elevated temperature.

This technique involves inoculating a series of tubes containing EC medium with diluted samples of water, followed by incubation to allow any coliform bacteria present to ferment the lactose contained in the medium, producing gas. The presence of gas indicates positive growth, suggesting contamination by fecal matter.

The other options do not reflect the standard practices used in this technique. For instance, using nutrient agar plates at room temperature does not align with the specific growth requirements for fecal coliforms, nor does sample filtration performed at a lower temperature, which would not provide an environment conducive to the growth of these bacteria. Similarly, the use of a single test tube at varying temperatures would not allow for a proper enumeration of coliform bacteria, as the multiple tube technique is designed to evaluate multiple samples or dil