Evaluation of E. coli as an indicator for the presence of Campylobacter jejuni and Yersinia enterocolitica in chlorinated and untreated oligotrophic lake water

Two enteric pathogens, Campylobacter jejuni and Yersinia enterocolitica, and the indicator bacterium Eschericiha coli, were investigated for survival in autoclaved lake water and susceptibility to chlorine at 4 and 10°C. In addition, survival of Y. enterocolitica was investigated in oligotrophic lake water. The 3-log reduction (99.9% inactivation) time for Y enterocolitica in lake water was 17–18 days at 4°C and 14–15 days at 10°C. After exposure to 0.2 mg/l Cl2 a 3-log reduction was obtained for C. jejuni in 10–15 s, for Y. enterocolitica in 20–180 s, and for E. coli in 20–25 s, depending on bacterial strain, plasmid content and temperature. The same reduction of C. jejuni was obtained with 0.02-0.04 mg/l of free chlorine in 12 min at 4°C and 2 min at 10°C. These results indicate that C. jejuni is more sensitive to chlorine than most other waterborne pathogens and E. coli, indicating that it may easily be controlled by present disinfection practices. Y. enterocolitica is about as sensitive to chlorine as E. coli, but may survive for a longer time in cold, clean surface waters. E. coli is an adequate indicator for C. jejuni both in water sources and in chlorinated drinking water. E. coli, however, is not a safe indicator for the presence of Y. enterocolitica O:3 under all conditions, and especially not in oligotrophic lake water. Furthermore, the results for Y. enterocolitica O:3 indicate an association between enhanced resistance to chlorine and the presence of a virulence plasmid.