Purpose: The purpose of this study was to determine the prevalence and antimicrobial resistance (AR) of Salmonella in carcass rinses and environmental samples obtained from a commercial plant that processes antibiotic-free broilers using conventional (CP) and organic (OP) processing methods.
Methods: During four separate processing days (two CP and two OP), five carcass rinses were collected from four processing steps (n = 20 for CP; n = 15 for OP): post evisceration (PE), post inside/outside bird washer (I/O), post water chill (PWC), and post air chill (PAC). Each day, 55 environmental samples were collected (49 for OP). Isolates of Salmonella were recovered according to the USDA-FSIS protocols and two isolates per positive sample (a total of 186 isolates) were analyzed for AR using the NARMS protocol.
Results: A downward trend in Salmonella prevalence was observed from PE to post chill for both CP (from 40% PE to 30% PWC and 20% PAC) and OP birds (from 100% PE to 70% PAC). However, for CP birds, an increase in prevalence was observed from PE (40%) to I/O (80%). One hundred thirty-nine isolates (74%) were resistant to at least one antimicrobial, and fourteen isolates (8%) were resistant to three or more. The most common resistance was to tetracycline (130 isolates, or 70%), and the second most common was streptomycin (50 isolates, or 27%). These data indicate a high prevalence of Salmonella throughout PE processing steps for both CP and OP birds, although a lower prevalence was observed post-chill.
Significance: The presence of several isolates resistant to commonly used antimicrobials highlights the need to control Salmonella populations during processing and demonstrates that multidrug resistant isolates can be present even in flocks raised without antibiotics.