Which system is utilized to confidently confirm the presence of coliform bacteria in water?

The multi-tube fermentation system is a well-established method used to detect and confirm the presence of coliform bacteria in water. This system involves inoculating a series of test tubes with water samples and observing for gas production as an indicator of fermentation, which suggests the presence of coliforms. The presence of gas in the fermentation tubes indicates that coliform bacteria are metabolizing the nutrients present in the medium, providing a reliable assessment of bacterial contamination.

In contrast, other methods, while valid in their own contexts, do not provide the same level of confirmation. The membrane filter system is effective for detecting bacteria but typically requires specialized equipment and is often used for enumerating bacteria rather than confirming their presence. The Colilert system is a newer approach that utilizes a color change and fluorescence to identify coliforms and E. coli but may not be as universally employed or familiar as the multi-tube fermentation method. Direct microscopy, on the other hand, can identify bacteria based on their morphology but does not differentiate between viable and non-viable cells and may fail to confirm the specific presence of coliforms.

Thus, while other options have their applications, the multi-tube fermentation system is recognized for its reliability and specificity in confirming coliform bacteria.