Identification and characterization of virulent <i>Aeromonas hydrophila</i> Ah17 from infected <i>Channa striata</i> in river Cauvery and in vitro evaluation of shrimp chitosan

Abstract

<i>Aeromonas hydrophila</i>, an inhabitant in the aquatic ecosystem is considered as an important foodborne bacterial zoonotic pathogen in aquaculture. The present study aimed to identify virulent <i>A. hydrophila</i> from naturally infected <i>Channa striata</i> in river Cauvery and in vitro evaluation of shrimp chitosan. Rimler Shotts (RS) and blood agar medium identified the presence of pathogenic <i>Aeromonas</i> sp. from the infected <i>C. striata</i>. <i>A. hydrophila</i> Ah17 was identified using 16S rRNA nucleotide sequence. Extracellular enzymes such as amylase, lipase, and protease were screened in <i>A. hydrophila</i> Ah17. Antibiotic susceptibility tests showed <i>A. hydrophila</i> Ah17 was highly resistant against <i>β</i>-lactam, glycopeptide, macrolides, phosphonic, fucidin, and oxazolidinone classes of antibiotics. Virulent genes such as hemolysin (<i>aer</i> and <i>hly)</i>, heat-labile enterotoxin (<i>act</i>), cytotonic heat-stable enterotoxin (<i>ast</i>), elastase (<i>ahyB</i>), and lipase (<i>lip</i>) were identified. Growth and the viable cell population of virulent <i>A. hydrophila</i> Ah17 were significantly reduced in a dose-dependent manner against shrimp chitosan (CHS) from <i>Penaeus indicus</i> (<i>P. indicus</i>). Thus, the present study isolated virulent <i>A. hydrophila</i> Ah17 from the environmental source and characterized in vitro with shrimp chitosan.