SURVIVAL OF AEROMONAS-HYDROPHILA, AEROMONAS-CAVIAE AND AEROMONAS-SOBRIA IN SOIL

The survival of mesophilic Aeromonas spp. in soil in the presence or a bsence of indigenous microflora was evaluated in a laboratory study. T wo cytotoxic (Aer. hydrophila and Aer. caviae) and one invasive (Aer. sobria) clinical isolate strains were selected for this study. After c ontamination of sterile or unsterilized soil with the three strains of Aeromonas, the number of living cells was determined over at least 5 months. For all strains the survival curves were characterized by an i nitial re-growth followed by a slow inactivation of bacteria, with sig nificant differences due to the presence of indigenous microflora. The times necessary to achieve a 95% reduction of the initial population were > 140, 113 and 62 d in sterilized soil respectively for Aer. cavi ae, Aer. hydrophila and Aer. sobria, while the corresponding times in unsterilized soil were 42, 38 and Il d. All strains preserved the viru lence factors for the entire period of the study. These results sugges t that the soil may be an important reservoir for Aeromonas spp. and, thus, may play an important role in the epidemiology of Aeromonas-asso ciated human infections.