Ecology of mesophilic Aeromonas spp. in aquatic environments of a temperate region and relationship with some biotic and abiotic environmental parameters.

The Ecology of mesophilic Aeromonas species has been investigated since January 1988 to examine their occurrence and distribution in aquatic environments of Okayama Prefecture. Water and plankton samples were quantitatively as well as qualitatively analyzed throughout the seasons from five selected stations including fresh, brackish, and saline environments. Analysis of variance and correlation coefficients among the biotic and abiotic parameters were sought. The organisms were found in all the environs with high densities through all the seasons. Plankton samples yielded higher counts of Aeromonas than the water samples in all the environs. Water temperature seemed to play a significant role on their growth during the winter months, however, no significant seasonal variation nor any correlation with fecal pollution were observed in most of the environments. A reciprocal relationship was seen with salt concentration in the saline environment. Among the currently recognized mesophilic species; A. caviae, A. hydrophila, A. sobria, and A. media were isolated with the predominance of anaerobic biovar. The present study reveals that Aeromonas are widely distributed in fresh, brackish and saline environments of this region. The study also reveals that Aeromonas are autochthonous members in aquatic ecosystems and are indigenous to these environs. Aeromonas species isolated from our environments were found to exhibit drug resistance potential which differed from that of isolates from diverse geographical locales. The high incidence of clinically significant Aeromonas species in this aquatic region could be of public health significance for the inhabitants of this region, as well as a challenge to their dependence on aquatic resources.