Utilization of the skin attachment model to determine the antibacterial efficacy of potential carcass treatments.

Two experiments (EXP), utilizing the skin attachment model (SAM), were conducted to determine the bactericidal activity of six potential carcass disinfectants [EXP 1: 20, 400, and 800 ppm sodium hypochlorite; EXP 2: 5% acetic acid (AA), 8% trisodium phosphate (TSP), and 1% sodium metabisulfite (SS)] during simulated scalder (50 C for 2 min), chiller (0 C for 60 min), or post-process dip (23 C for 15 s) application. Efficacies of treatments were determined against populations of Salmonella typhimurium that were "loosely" or "firmly" attached to chicken breast skin (10 cm diameter). For comparison, activity of the six disinfectants was also determined against S. typhimurium in aqueous suspension. All disinfectants except SS reduced numbers of freely suspended S. typhimurium by > or = 4.5 log10 cfu/mL. The sodium metabisulfite did not reduce populations of salmonellae. In both EXP, there were disinfectant by application interactions (P < 0.05) on activity against loosely and firmly attached cells. Sodium hypochlorite at 20 ppm had little activity regardless of application, whereas higher levels were more effective (P < 0.001), particularly in the chiller application, in which loosely and firmly attached populations were reduced by 2.3 to 2.5 and 1.3 to 1.9 log10 cfu per skin, respectively. In EXP 2, SS showed no activity regardless of application. Trisodium phosphate was similarly effective (reduction by 1.2 to 1.8 log10 cfu per skin) in all applications (P > 0.05). In contrast, AA activity was affected by the application method (P < 0.05). Against loosely attached cells, AA was most effective in the chiller application (2.5 log10 reduction), whereas against firmly attached cells, AA was effective only in the scalder application (2.0 log10 reduction). Attachment of S. typhimurium to poultry skin apparently increased the ability of the bacteria to resist various disinfectants, and efficacy was influenced by extent of attachment of bacteria to skin and method of disinfectant application.