Comparison of methods for the enumeration of Clostridium perfringens spores in water

Abstract

Four methods for enumerating Clostridium perfringens spores in water were evaluated: (1) the IMM (Iron Milk Medium) method (MPN); (2) the LS (Lactose Sulfite Broth) method (MPN); (3) the m-CP (membrane filtration Clostridium perfringens Agar) method (membrane filtration); and (4) the TSC (Tryptose Sulfite Cycloserine Agar) method (membrane filtration). The performance of these methods was compared with that of the DRCM (Differential Reinforced Clostridium Medium) method (MPN) as adopted by CETESB (Brazil's Environmental Sanitation Technology Company) for the analysis of C. perfringens spores in water. Statistical analysis was performed according to ISO 17994:2004 (Water Quality - Criteria for Establishing Equivalence between Microbiological Methods). The LS, m-CP, and TSC methods were considered not equivalent to the DRCM method, as they gave significantly lower results. The IMM showed inconclusive results and, according to ISO 17994:2004, analysis of a greater number of samples is needed to draw definitive conclusions comparing IMM and DRCM.