The technique of enumerating coliforms by means
of multiple-tube fermentation (MTF) has been used for
over 80 years as a water quality monitoring method.
The method consists of inoculating a series of tubes
with appropriate decimal dilutions of the water sample.
Production of gas, acid formation or abundant growth
in the test tubes after 48 h of incubation at 35 C
constitutes a positive presumptive reaction. Both lactose
and lauryl tryptose broths can be used as presumptive
media, but Seidler et al. (1981) and Evans et
al. (1981) have obtained interference, with high numbers
of non-coliform bacteria, using lactose broth. All
tubes with a positive presumptive reaction are subsequently
subjected to a confirmation test. The formation
of gas in a brilliant green lactose bile broth
fermentation tube at any time within 48 h at 35 C
constitutes a positive confirmation test. The fecal coliform
test (using an EC medium) can be applied to
determine TC that are FC (APHA et al., 1998): theproduction of gas after 24 h of incubation at 44.5 C in
an EC broth medium is considered as a positive result.