Stenotrophomonas maltophilia as an opportunistic pathogen in cultured African catfish Clarias gariepinus (Burchell, 1822)

Abstract

Indian catfish production is increasing over the years so as the frequency of diseases. In this report, the isolation of Stenotrophomonas maltophilia from the kidney of Clarias gariepinus juvenile with distended abdomen along with its phenotypic, molecular and phylogenetic characteristics was described. The diseased catfish juveniles in an earthen pond (1500m3) with high stocking density (≈60nos/m3) had body discoloration, fin/tail rot, focal cutaneous hemorrhage, distended abdomen, inflammation of internal organs and visceral hemorrhage. The abdominal cavity was filled with transparent jelly-like mass. The bacterial strain isolated from the kidney of catfish formed a monophyletic group with other strains of S. maltophilia based on genotypic characters and phylogenetic analyses. The strain S. maltophilia SK1 (NCBI accession number KP898215) was alpha-hemolytic, protease and lipase positive and weakly pathogenic to C. gariepinus juveniles. It caused only 35±5% mortality at a level of 1.40×107 cells/fish via intraperitonial injection. While the intramuscular injection caused only 10% mortality. The dead fish up on challenge had distended abdomen with jelly-like mass. Understanding the pathology and pathogenesis of this emerging pathogen in cultured catfish would help manage the disease. Statement of relevance1Stenotrophomonas maltophilia is considered as an opportunistic pathogen of human and fish.2This species is emerging as a pathogen in cultured catfish Clarias gariepinus (Burchell, 1822).3Understanding the pathology and pathogenesis of this species would help manage the disease.