Isolation, Antibiotic Resistance and Clonal Similarities of Salmonella Spp. in Catfish and Processing Facilities

Abstract

Salmonella spp. is a human pathogen that has been reported in catfish, but with conflicting results. Salmonella spp. was isolated from live catfish, catfish products and the processing environment during catfish production, followed by evaluation of their antibiotic resistance and clonal similarities. Distinction of Salmonella spp. was increased by lowering background microflora with the addition of the antimicrobial novobiocin to the agar media. More than ten Salmonella serotypes were isolated from catfish and catfish products, such as live, chilled fillets, frozen fillets, and conveyor belts in catfish processing facilities. The isolates that were recovered include Salmonella ser. Typhimurium, Barranquilla, Mbadaka, Putten, Infantis and Thompson among others. The number of isolated Salmonella spp. and serotypes varied between sampling in catfish facilities. Clonal similarities of Salmonella spp. were found within sampling but did not show persistency among sampling periods, suggesting the opportunistic nature of the pathogen. Salmonella ser. Typhimurium was the most predominant isolate in live catfish and similarities were found within sampling but were not persistent among sampling periods. Antimicrobial resistant Salmonella was identified from the recuperated isolates. All Salmonella spp. isolates, showed resistance to erythromycin, vancomycin and rifampin regardless of the serotype, but resistant genes were absent suggesting that resistance was due to the pathogen’s biological nature. These results suggest that it is possible to recover Salmonella spp. in catfish products, but its opportunistic nature makes it difficult to predict the source or incidence of this pathogen.