New host record of Vibrio anguillarum associated with haemorrhagic septicaemia in golden mahseer, Tor putitora (Hamilton, 1822) from India

Vibrio strains (n=5) were isolated from a pooled liver samples of golden mahseer, Torputitora (n=10) showing symptoms of hemorrhagic septicemia in cultured conditions. From biochemical analysis, partial PCR amplification of 16S rRNA genes (~1400bp) and sequencing, the isolates were identified as Vibrio anguillarum. One of the 5 isolates was designated as a strain number MHJL 248 and submitted to the NCBI (MN900589). The phylogenetic analysis of the V. anguillarum MHJL 248 showed >99% similarity with V. anguillarum strain HA (KF413427). V. anguillarum MHJL 248 was positive to arginine, oxidase, catalase, string test, ONPG, siderophore, sensitive to O/129 vibriostatic disc (10 and 150 pg) grown on medium containing varying NaCl concentrations (0.5% to 2.0%), showing intermediate resistance to ampicillin (10 pg) and a-hemolytic on 5% sheep blood agar plate. The major histopathological changes recorded in the kidney, liver, gill and intestine collected from natural infection were cellular degeneration, necrosis, cytoplasmic vacuolation, degeneration of glomerulus, dilation and increasing Bowman's space and glomerular contraction. Vibrio anguillarum MHJL 248 was found resistant to cefoxitin (30 pg), ciprofloxacin (5 pg), imipenem (10 pg), levofloxacin (5 pg) and nalidixic acid (30 pg). The minimum inhibitory concentration of oxytetracycline, erythromycin and florfenicol against V. anguillarum MHJL 248 were 16, 0.5 and 0.125 pg mL⁻¹, respectively. Transmission electron microscopy (negatively stained) of V. anguillarum MHJL 248 demonstrated the presence of monotrichous polar flagellum and capsular structure that can be correlated to the pathogenicity of the bacterium. This is the first case of a new host (T. putitora) record of V. anguillarum infection in coldwater aquaculture practices in India. Seeing the severity of infection of V. anguillarum in aquaculture worldwide, further study needs to be focused on the development of efficient measures to control its infection in coldwater aquaculture.