Abstract
Performance of Petrifilm VRB and SM plates to enumerate different types of bacterial populations was evaluated. A total of 100 Petrifilms and 100 regular Petri plates were tested with each of 3 different bacterial populations in 4 experiments. The Petrifilm system was superior to the conventional pour plate methods, or at least not statistically different, in enumerating Escherichia coli (coliform) and a mixture of E. coli, Staphylococcus aureus and Serratia marcescens (total aerobic plate count). The Petrifilm method was superior to conventional plate counts in enumerating Pseudomonas aeruginosa (psychrotrophic plate count), when both incubations were at 21°-22° C for 96 h. If sustained in further experimentation, this last observation would mean that the Petrifilm SM system could be successfully used to detect bacterial populations in addition to those for which the system was originally intended.