Prevalence, Antimicrobial resistance and Virulence profile of Salmonella from Aquaculture farms of central Kerala, India

Abstract

Salmonella belonging to Enterobacteriaceae is considered as the leading cause of food borne illness all over the world and products from aquaculture often act as vehicles of their transmission. In this study, a total of 150 samples including mud, water, fish/ shrimp and feed from 38 aquaculture farms from three districts of central Kerala viz., Thrissur, Ernakulam and Kottayam were screened for the presence of Salmonella. The overall prevalence of Salmonella in aquaculture farms was 7.9%. By serotyping, 100% of Salmonella isolates (n=8) from aquaculture were identified as Salmonella enterica subspecies enterica serovar Typhimurium with antigenic formulae 4,5,12: i: 1,2. None of the shrimp farms selected in this study harboured Salmonella. Antibiotic sensitivity testing revealed that 100% of S. Typhimurium were sensitive to the 17 antibiotics tested. Screening of the S. Typhimurium isolates for 11 virulence genes; invA, fimA, stn, spvC, sopB, mgtC, bcfC, csgD, avrA, hilA and phoP/phoQ belonging to Salmonella Pathogenicity Islands (SPI) 1 to 5 by PCR revealed that the isolates carried all the virulence genes except spvC gene, indicating its pathogenic potential. This study suggests that finfish farms are probable reservoirs of Salmonella with high virulence potential and can pose a potential threat to public health safety. Proper policies and regulations are to be adopted to control the occurrence of Salmonella in finfish culture systems.