Pathogenic-bacterial water contamination in mountainous catchments

This space-time study of bacteriological response compared the presence of pathogens with indicators contained in surface and groundwater in mountaino us regions. A systematic search for bacteria such as Listeria, Salmonella, Campylobacter and Yersinia carried out simultaneously with a search for ind icators has shown that these waters can occasionally contain potentially pa thogens, though these are generally to be found in small quantities. The mo st common pathogens found are Campylobacter and Listeria. Salmonella has ne ver been isolated. The presence of pathogens is usually accompanied by the presence of classic indicators of contamination such as Escherichia coli, e nterococci and other aerobic bacteria. Exceptions are only to be observed i n cases of samples presenting very low numbers of pathogens. Such low patho gen levels have a minimal impact on human health; but we cannot exclude tha t, during periods affected by specific conditions, higher levels might temp orarily occur. Our research has demonstrated that classic indicators can be considered as efficient detectors of pathogens in most cases. When these i ndicators are used systematically and regularly, the human health hazard ca n be qualified as low but not negligible. The presence of pathogens, togeth er with their survival capacity, brings the protection measures currently a pplied to safeguard drinking waters sharply into question. (C) 2001 Elsevie r Science Ltd. All rights reserved.