Isolation and characterization of motile aeromonads from Chilean freshwaters and their potential use as water quality indicators

This report documents the motile Aeromonas incidence in water and their potential health risk in Chile. Samples were collected from three different water sources: Drinking water supplies (n = 24), irrigation waters (n = 11), and runoff waters receiving sewage (n = 15). No correlation with conventional fecal pollution indicators (total and fecal coliforms) was observed. Average counts of Aeromonas in slightly and heavily polluted waters were 1.5 . 10(3) and 2.0 . 10(8) colony forming units/100 mL, respectively. The biochemical speciation of 172 isolates showed a predominance of A. hydrophila in all aquatic environments sampled. The phenotypic characterization of these isolates showed striking differences between the isolates recovered from slightly and heavily polluted sources. Slightly contaminated water strains were typically aerogenic nonlactose fermenters (50%), while anaerogenic lactose fermenters were predominant in heavily contaminated waters (68%). Furthermore, gluconate oxidation and acetoin production were significantly different for each population (chi-squared, p < 0.001). We propose the use of motile aeromonads as complementary water pollution indicators to ensure the safety of water, and to consider the above described biochemical traits to clarify the role of water as a reservoir of enterotoxigenic Aeromonas spp. in diarrheal diseases in Chile. (C) 1996 by John Wiley & Sons, Inc.