Bacteria from different pollution sources may consist of essentially the same species but with different strains predominating. Therefore, sub-typing of bacterial strains recovered in the polluted water and comparison with those present in possible pollution sources is a valuable tool for identification of the source. Since such studies require investigations of large numbers of isolates, simple laboratory methods combined with automated data evaluation and presentation are necessary. The Phene Plate (PhP) system for biochemical fingerprinting of bacteria is based on measurements of the kinetics of biochemical tests, performed in micro-plates. The system also includes mathematical models to calculate the diversity (Di) of the bacterial flora within samples, as well as the similarities between bacterial populations in different samples as the population similarity coefficient (Sp). We have used the PhP system to type coliform bacteria isolated from a polluted river in Sweden and from the outlets from three paper mills that were suspected contamination sources. From each of 27 river water samples and 8 samples from factory outlets, collected on eight sampling occasions, between 10 and 50 coliforms were typed, yielding altogether 1,027 isolates. The diversity among the bacteria in river water samples was generally high (mean Di = 0.95) compared with factory outlets (mean Di = 0.63) which usually were dominated by isolates belonging to a few PhP types. These PhP types were very rarely recovered from the river water samples which is also reflected in low similarities between bacterial populations in river water and factory outlets (mean Sp = 0.03). Thus the bacteria from factory outlets did not seem to have spread downstream. In contrast, bacterial populations from sampling sites close to each other in the river were more similar to each other (mean Sp 0.13), indicating the presence of several, diffuse contamination sources, possibly from animal or human faecal material.

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