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 car cass disinfectants I[EXP 1: 20, 400, and 800 ppm sodium hypochlorite; EXP 2: 5% acetic acid (AA), 8% trisodium phosphate (TSP), and 1% sodiu m metabisulfite (SS)] during simulated scalder (50 C for 2 min), chill er (0 C for 60 min), or post-process dip (23 C for 15 s) application. Efficacies of treatments were determined against populations of Salmon ella typhimurium that were ''loosely'' or ''firmly'' attached to chick en breast skin (10 cm diameter). For comparison, activity of the six d isinfectants was also determined against S. typhimurium in aqueous sus pension. All disinfectants except SS reduced numbers of freely suspend ed S. typhimurium by greater than or equal to 4.5 log(10) cfu/mL. The sodium metabisulfite did not reduce populations of salmonellae. In bot h EXP, there were disinfectant by application interactions (P < 0.05) on activity against loosely and firmly attached cells. Sodium hypochlo rite at 20 ppm had little activity regardless of application, whereas higher levels were more effective (P < 0.001), particularly in the chi ller application, in which loosely and firmly attached populations wer e reduced by 2.3 to 2.5 and 1.3 to 1.9 log(10) cfu per skin, respectiv ely. In EXP 2, SS showed no activity regardless of application. Trisod ium phosphate was similarly effective (reduction by 1.2 to 1.8 log(10) cfu per skin) in all applications (P > 0.05). In contrast, AA activit y was affected by the application method (P < 0.05). Against loosely a ttached cells, AA was most effective in the chiller application (2.5 l og(10) reduction), whereas against firmly attached cells, AA was effec tive only in the scalder application (2.0 log(10) reduction). Attachme nt of S. typhimurium to poultry skin apparently increased the ability of the bacteria to resist various disinfectants, and efficacy was infl uenced by extent of attachment of bacteria to skin and method of disin fectant application.