Methodology
A-1 broth used for direct isolation of fecal coliforms
(Std Methods)
Once inoculated, vials are incubated for 3 hours at 35oC than
transferred to 44.5oC incubator
for 21 hours
Gas production in any vial indicates a positive result
and the presence of fecal
coliforms
Bacterial growth or turbidity
typically counted as positive
• result
MPN statistically calculated from
the number of positive vials
