Detection of Aeromonas hydrophila in a drinking- water distribution system: a field and pilot study

A 16-month study was conducted on the presence of Aeromonas hydrophila in d rinking water in Indiana, U.S.A. Enumeration was conducted in source water, in various sites within a water treatment plant, and in the distribution s ystem in both bulk water and biofilm, as well as in a simulated (annular re actors) drinking-water distribution system. Presumptive Aeromonas spp. coun ts on source waters regularly approached 10(3)-10(4) CFU/100 mL, during sum mer months and granular activated carbon - filtered water counts ranged fro m <1 to 490 CFU/100 mL. In source water, presumptive Aeromonas levels were related to water temperature. Aeromonas hydrophila was never detected in th e treatment plant effluent or distributed bulk water, showing disinfectant efficiency on suspended bacteria; however, isolates of A. hydrophila were i dentified in 7.7% of the biofilm samples, indicating a potential for regrow th and contamination of drinking-water distribution systems.