What is the correct sequence of growth in a multiple-tube fermentation method?

In the multiple-tube fermentation method used for water quality testing, the correct sequence of growth is based on the selective media used to detect the presence of coliforms and other microorganisms.

The process begins with a selective enrichment medium, Lactic Thiocyanate Broth (LTB), which allows the growth of target organisms while inhibiting other bacteria. This step is important as it enhances the recovery of potentially low levels of coliforms in a sample.

Following the LTB incubation, the next medium is Brilliant Green Broth (BGB). This medium is selective for the presence of coliforms, specifically E. coli, and helps to provide an additional layer of confirmation of their presence after preliminary enrichment in LTB.

Lastly, the Embden-Meyerhof-Bo共等 (EMB) agar serves as differential media that allows for the differentiation of coliforms based on their biochemical reactions, particularly regarding their ability to ferment lactose and produce acid or gas.

This sequential approach is critical for ensuring accurate detection and differentiation of coliform microorganisms, as it progressively selects and confirms the growth of the target organisms. Each step plays a vital role in delivering reliable results in water quality assessments, making option B the correct sequence.