Influence of catfish skin mucus on trisodium phosphate inactivation of attached Salmonella Typhimurium, Edwardsiella tarda, and Listeria monocytogenes

Abstract

This study examined the antimicrobial effectiveness of trisodium phosphate (TSP) on Edwardsiella tarda, Listeria monocytogenes, and Salmonella Typhimurium attached to catfish skin with and without mucus. Salmonella Typhimurium and E. tarda attached more readily to catfish skin than did L. monocytogenes. At high inoculum levels (107 CFU/ml), TSP treatments (at 2 to 6%) for 10 min reduced bacterial counts of E. tarda by >2.5 to >3.3 log10 CFU per skin sample for firmly attached cells and by 3.5 to 3.6 log10 CFU per skin sample for loosely attached cells. Counts of L. monocytogenes declined by 0.6 to >1.8 log10 CFU per skin sample for firmly attached cells and by 1.2 to 2.2 log10 CFU per skin sample for loosely attached cells. Counts of Salmonella Typhimurium were reduced by 3.6 to >3.8 log10 CFU per skin sample for firmly attached cells and by 3.5 to >3.8 log10 CFU per skin sample for loosely attached cells. Overall, counts of firmly attached bacteria on TSP-treated skins with mucus were higher than counts on skin without mucus. Firmly attached L. monocytogenes was more resistant to TSP than was firmly attached Salmonella Typhimurium or E. tarda. The presence of mucus on skins slightly decreased the antimicrobial effect of TSP. Significant (P < 0.05) reduction in the numbers of all three bacteria can be achieved by treatment with 6% TSP for 10 min.