Genetic diversity, virulence attributes and antimicrobial resistance of Aeromonas hydrophila isolated from fishes and water in Puducherry

Abstract

Aeromonas hydrophila is one of the emerging foodborne pathogens that are autochthonous to aquatic ecosystems. The present investigation was undertaken to study the occurrence, virulence properties and antimicrobial drug resistance pattern of A. hydrophila in fishes (n = 100) and water (n = 100) in Puducherry. About 15 Aeromonas spp. isolates were obtained by standard bacteriological methods which were presumptively confirmed by morphological and biochemical tests. All the 15 isolates (10%) were confirmed as A. hydrophila by PCR targeting species specific 16S rRNA gene. Eight out of fifteen isolates (53.33%) produced β-haemolysis. Also 6 isolates (40%) were positive for gelatinase activity. Molecular detection of virulence genes revealed that haemolysin (hly) gene and cytotoxic enterotoxin (act) gene was present in 5 (33.33%) and 3 isolates (20%) respectively. Antimicrobial sensitivity test showed that all the isolates were resistant to co-trimoxazole (100%) and penicillin G (100%) and sensitive to gentamicin (100%). Multidrug resistant was found in 46.67% of isolates (n = 7) as they showed resistance against more than 3 antimicrobial classes tested. Molecular detection of antimicrobial resistance genes showed that tetA gene and blaTEM gene was present in 3 (20%) and 4 isolates (26.67%) respectively. Molecular typing by ERIC-PCR revealed grouping of isolates into four different clusters and two isolates remained outgroup. A wide genetic diversity of isolates irrespective of their source of isolation was noticed and no particular clone was predominant. The study documented the presence of multidrug resistant, virulent Aeromonas hydrophila among fishes and its environment (water) which is of public health concern.