HEALTH SIGNIFICANCE OF PIGMENTED BACTERIA IN DRINKING-WATER

The purpose of this study was to determine the relative health risks o f pigmented bacteria found in drinking water samples. These pigmented bacteria include opportunistic pathogens such as Flavobacterium, Pseud omonas, Corynebacterium, Nocardia, Mycobacterium. Erwinia, Enterobacte r, Serratia, and Micrococcus. Flavobacterium meningosepticum is the mo st clinically important of the flavobacteria but causes <0.08% of meni ngitis eases in the US. Pseudomonas aeruginosa is an important opportu nistic pathogen causing >10% of nosocomial infections. Human feeding t ests show that oral doses of 10(6) to 10(8)CFU results in colonisation of the gastrointestinal (GI) tract but do not produce any morbidity i n healthy volunteers. Corynebacteria rarely cause disease except for t oxigenic C. diphtheriae which is non-pigmented on R2A agar. The most i mportant member of Nocardia is N. asteroides which is an opportunistic pathogen for certain immunocompromised population segments. National surveys show that only 9.2-19.2% of mycobacterial clinical isolates ar e pigmented with M. kansasii being the most frequent (4-10%). This bac terium is associated with disease but would not be detected as part of the HPC bacteria using a 7d incubation period. Pigmented strains of E rwinia, Enterobacter, Serratia, and Micrococcus can cause disease but they are relatively unimportant compared to other pathogenic bacteria as shown in ranking studies. (C) 1997 IAWQ. Published by Elsevier Scie nce Ltd.