Molecular Detection, Quantification, and Toxigenicity Profiling of Aeromonas spp. in Source- and Drinking-Water

Abstract

Aeromonasis ubiquitous in aquatic environments and has been associated with a number of extra-gastrointestinal and gastrointestinal illnesses. This warrants monitoring of raw and processed water sources for pathogenic and toxigenic species of this human pathogen. In this study, a total of 17 different water samples [9 raw and 8 treated samples including 4 basin water (partial sand filtration) and 4 finished water samples] were screened forAeromonasusing selective culturing and a genus-specific real-time quantitative PCR assay. The selective culturing yieldedAeromonascounts ranging 0 – 2 x 103CFU/ml and 15Aeromonasisolates from both raw and treated water samples. The qPCR analysis indicated presence of a considerable nonculturable population (3.4 x 101– 2.4 x 104cells/ml) ofAeromonasin drinking water samples. Virulence potential of theAeromonasisolates was assessed by multiplex/singleplex PCR-based profiling of the hemolysin and enterotoxin genesvizcytotoxic heat-labile enterotoxin (act), heat-labile cytotonic enterotoxin (alt), heat-stable cytotonic enterotoxin (ast), and aerolysin (aerA) genes. The water isolates yielded five distinct toxigenicity profiles, viz.act,alt,act+alt, aerA+alt, andaerA+alt+act. Thealtgene showed the highest frequency of occurrence (40%), followed by theaerA (20%),act(13%), andast(0%) genes. Taken together, the study demonstrated the occurrence of a considerable population of nonculturable Aeromonads in water and prevalence of toxigenicAeromonasspp. potentially pathogenic to humans. This emphasizes the importance of routine monitoring of both source and drinking water for this human pathogen and role of the developed molecular approaches in improving theAeromonasmonitoring scheme for water.