ABSTRACT: Aeromonads are aquatic bacteria associated with frequent outbreaks of diarrhea in coastal Bangladesh, but their potential risks from environmental sources have remained largely unexplored. This study, over 2 years, examined homestead pond waters in the region for monthly dynamics and diversity of Aeromonas spp. The bacterial counts showed bi-modal annual growth peak, pre- and post-monsoon, strongly correlating (p < 0.0005) with temperature. Of 200 isolates characterized, Aeromonas veronii bv. sobria (27%) was predominant among co-existent Aeromonas schubertii (20%), Aeromonas hydrophila (17%), Aeromonas caviae (13%), and three more. PCR screening of virulence-related genes identified 15 genotypes (I to XV), however, enterotoxigenicity in animal model was observed for five genotypes, ca. 18% (nine of 50) strains, prevalent in A. veronii bv. sobria, A. hydrophila, and A. caviae. Pathogenic strains were distinguishable by possessing at least three of the major virulence genes: ascV, hlyA, ela, ast, and alt, together with accessory virulence factors. PFGE of XbaI-digested genomic DNA revealed high genetic diversity and distant lineage of potentially toxigenic clones. Therefore, along with increased global warming, Aeromonas spp. having multi-factorial virulence potential in coastal ponds that serve as drinking water sources pose a potential health risk, and underscores the need for routine monitoring.
