Enumeration of TC by membrane filtration is not
totally specific. When MF is associated with m-Endo
media containing lactose, atypical colonies which are
dark red, mucoid or nucleated and without a metallic
sheen may occasionally appear. Atypical blue, pink,
white or colorless colonies lacking sheen are not
considered as TC by this technique (APHA et al.,
1998). Furthermore, typical colonies with a sheen may
be produced occasionally by non-coliform bacteria
and, conversely, atypical colonies (dark red or
nucleated colonies without sheen) may sporadically
be coliforms. Coliform verification is therefore recommended
for both types of colonies (APHA et al.,
1998).