Evaluation of Three Different Selective Media for Enumeration of Clostridium perfringens in Untreated and Treated Wastewater.

Current and emerging legislation in North Carolina and other regions calls for the enumeration of Clostridium perfringens as a surrogate indicator for protozoan parasites in various types of waters. Past studies that have evaluated selective media for the detection of this bacterium have provided limited, conflicting, and inconclusive results. In this study, membrane filtration was used to enumerate C. perfringens as culturable spores or total culturable cells in 19 samples of untreated and 25 samples of partially treated wastewaters on 3 candidate media, Tryptose Sulfite Cycloserine Agar (TSC), CP ChromoSelect Agar (CPCS), and membrane Clostridium perfringens Agar (m-CP) in parallel, and the results were compared. Presumptive isolates from each agar were further subjected to phenotypic confirmation tests for acid phosphatase production and stormy fermentation to further determine the performance of each agar. The CPCS agar was determined to have the highest enumerative capacity of total C. perfringens cells when compared to both TSC agar and m-CP agar ( p -value < 0.05), but there was no significant difference in its ability to detect spores when compared to TSC agar ( p -value > 0.05). The overall specificity of CPCS agar as determined by agreement of results from both confirmation tests was 0.81, while the specificity of TSC agar was only 0.28. Based on its performance, ease of preparation and use and consistency of colony characteristics, CPCS agar is recommended as the preferred medium for C. perfringens enumeration in wastewater.