Clostridium perfringens as a water pollution indicator.

Abstract

Although Clostridium perfringens is con sistently associated with human fecal wastes,1-3 it is not used as a fecal indicator system in the U. S., and only peripherally in Europe. One important factor for this has been the absence of easy methods for the quantification of this obligate anaerobe in environmental waters. Another was the conflicting data produced in early studies with this organism. The findings of American workers through 1945 have been reviewed by Prescott et al.* and those from the European workers through 1960 by Bonde.5 In most of these studies, the judgment was made by comparing the densities of C. perfringens to those of Escherichia coli or by noting the detection of one of the indicators in the absence of the other. The findings and the conclusions drawn varied with the investi gator, the type of sample examined, and even the specific location from which the samples were collected. In general, the American investigators concluded that the C. perfringens indicator system was of little, if any, value in indexing the presence of fecal contamination. For example, Muhammed and Morrison6 recently reported the detection of C. perfringens in well and river water to be irregular when measured against that of fecal coliforms and concluded that the latter were better indicators of pollution. Contradictory findings and conclusions are not surprising in view of what is known concerning the ecology and physiology of the two indicator systems. At one extreme, one would expect to recover E. coli in the absence of C. perfringens in waters subject to small, immediate sources of pollution because the densities of E. coli in feces and wastewater are approximately two orders of magnitude greater than those of C. perfringens.7 At the other extreme, one would expect to isolate C. perfringens in the absence of E. coli in situations where there has been environmental stress caused by prolonged transit time in the aquatic environment or by disinfection because the spores of C. perfringens are much more resistant to those stresses than is E. coli. In between these two extremes, one would expect to recover both organisms from the sample and even, to obtain some general relationship of the density of one to the other. Nevertheless, for reasons discussed elsewhere,7 the absence of a consistent correlation of C. perfringens to E. coli densities in environ mental waters should not preclude its use as a water quality indicator. In fact, because C. perfringens produces both a ''resistant spore and a sensitive vegetative cell, there are situations that recommend its use. The purpose of this study was to reexamine these potential applications of the C. perfringens indicator system.