The occurrence of aerolysin-positive Aeromonas spp. and their cytotoxicity in Norwegian water sources

Aims:  The aim of the study was to investigate the occurrence of Aeromonas spp. and their aerolysin status in Norwegian natural water sources.
Methods and Results:  Seventy-one samples from 33 Norwegian water sources were examined for the presence of Aeromonas spp. From most of the sample sites, the strains were isolated on blood-ampicillin-agar and Difco Aeromonas agar simultaneously. The majority of the samples (73/77) contained Aeromonas spp., with an average of 35–100 cfu 100 ml^–1. The highest counts were found in faecally-contaminated water. Using PCR, 445 isolates were screened for the presence of aerolysin, and 79% of them were found to be carriers of the aerolysin gene. A selection of the isolated strains was tested on Vero cell cultures and 83% of them showed cytotoxicity.
Conclusions:  There is widespread occurrence of aerolysin-positive cytotoxic Aeromonas spp. in many different Norwegian natural waters, including drinking water sources.
Significance and Impact of the Study:  The widespread occurrence of potentially-pathogenic Aeromonas spp. in the environment demands that these bacteria should not be ignored in drinking water supplies and in the food industry.