ANTIBIOTIC RESISTANT MOTILE AEROMONADS INDUCED SEPTICEMIA IN PHILIPPINE CATFISH Clarias batrachus (Linnaeus, 1758) FINGERLINGS

Philippine catfish, Clarias batrachus farming is receiving much attention in recent years so also the diseases in catfish aquaculture. During the disease surveillance in catfish farms, mortalities were observed in C. batrachus fingerlings in a nursery and this report describes the bacteriological and histopathological observations made on the diseased catfish. The gross and clinical signs observed were lethargy, anorexia, vertical movement, skin erosion, operculum erosion, pale gills, reddening of mouth, fin haemorrhage, red lateral line and distended abdomen. The bacteria isolated from the kidney were identified phenotypically as species belonging to classical motile aeromonad group (Aeromonas caviae, A. hydrophila, A. jandaei and A. sobria) and newly described aeromonad group (A. aquariorum, A. fluvialis and A. rivuli). Multiple antibiotic resistance (MAR) index was in the range of 0.3-0.8. These antibiotic resistant motile aeromonads caused septicaemia and 100% mortality. Histologically, haemocyte infiltration, necrosis, inflammation of epidermal tissue, rough epidermal layer and fibrosis in muscle tissue, and loss of typical tubular epithelial lining, necrosis of tubular tissue, inflammation of epithelial layer, cellular and nuclear hypertrophy, pycnotic nuclei, karyolysis and hypoplastic haematopoietic tissue in the kidney of diseased catfish were noted. The inflammatory responses observed in the kidney of C. batrachus were indicative of suppurative infection.