ISOLATION AND CHARACTERIZATION OF Photobacterium damselae FROM MARINE FISH

Photobacterium damselae is a primary bacterial pathogen of marine fishes and an opportunistic pathogen in humans. Luminous and non-luminous Photobacterium sp. are pathogenic to fishes and cause wound infections and hemorrhagic septicemia. P. damselae is considered as an emerging pathogen that causes production and economic losses in marine aquaculture. Exposure to seawater and handling of infected fishes by the handlers with wounds increases the possibility of P.damselae infections. The objective of the study was to screen for the pathogenic P.damselae in the marine fish landings of Pulicat Lake, Tamil Nadu, India.

A total number of 113 samples which included various species of fishes (Table 1) were collected during June 2018 to August 2018 from the fish landings of Pulicat lake,  Tamilnadu (13°33′57″N 80°10′29″E).              Swabs of liver, kidney, gill, brain, skin and intestine of fish samples were collected aseptically and streaked on Thiosulfate citrate bile salt sucrose agar (TCBS) with 1.5% NaCl. Pin point colonies grown on TCBS agar were selected and subjected to biochemical tests. The isolates that were presumptive of P.damselae were subjected to PCR for confirmation of using primers targeting photobacterium-specific 16s rDNA and capsid gene. The amplified PCR products were sequenced  and analysed for nucleotide homology (NCBI, BLAST).

P.damselae were isolated and confirmed in Rastrelliger kanagurta (Mackerel) (13) and Saurida thumbil (9) by bio chemical and molecular method (Figure.1) there by demonstrating the presence of   P. damselae in 19.4% of the samples collected from the fish landings of Pulicat lake, Tamilnadu during the period of June 2018 to August 2018 (MK250484 & MK284529). The transmission of P.damselae infection to humans can be prevented by careful handling of fishes and proper cooking.