EPIDEMIOLOGY, ECOLOGY, AND MOLECULAR GENETICS OF ANTIMICROBIAL RESISTANCE IN PATHOGENIC AND COMMENSAL BACTERIA FROM FOOD ANIMALS
Location: Bacterial Epidemiology and Antimicrobial Resistance
Title: Prevalence, Serotype, and Antimicrobial Resistance of Salmonella on Broiler Carcasses Postpick and Postchill in 20 U. S. Processing Plants
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2009
Publication Date: October 2, 2009
Citation: Berrang, M.E., Bailey, J.S., Altekruse, S.F., Shaw, Jr, W.K., Patel, B.L., Meinersmann, R.J., Cray, P.J. 2009. Prevalence, Serotype, and Antimicrobial Resistance of Salmonella on Broiler Carcasses Postpick and Postchill in 20 U. S. Processing Plants. Journal of Food Protection. 72(8):1610-1615.
Interpretive Summary: Salmonella is a human pathogen that can be found on poultry and poultry products. It is unknown how commercial broiler processing affects the prevalence, serotype and antimicrobial resistance profile of naturally occurring Salmonella. This study was a survey of 20 large commercial broiler processing plants in the US to measure the affect of processing on carcass Salmonella. Ten carcasses were collected from each plant early (before evisceration) and late (after chilling) in processing. Each plant was sampled four times over the course of one year. A total of 800 carcasses were examined. Salmonella was cultured, the serotypes were determined and the antimicrobial profiles were determined. Overall, processing was effective to reduce the prevalence of Salmonella from 72% before evisceration to 20% after chilling. Application of chlorine did not guarantee an increased reduction in Salmonella prevalence. A total of 849 isolates were subjected to serotyping, the most prevalent serotypes were S. Kentucky, S. Heidelberg, S. Typhimurium and S. Typhimurium var5-; processing affected each of these serotypes in a similar fashion. Antimicrobial resistance was noted, especially to older drugs that have been traditionally used in animal agriculture such as tetracycline, sulfonamides and streptomycin. No resistance was found to amikacin, ceftriaxone, ciprofloxacin or the combination of trimethoprim/sulfamethoxozole. The majority of the most prevalent serotypes were susceptible to all 15 drugs tested except for S. Typhimurium var5- 79% of which exhibited resistance to three or more drugs. This is not a surprising finding because S. Typhimurium var5- is notorious for acquiring drug resistance. Across all 20 plants, seven different chemical processing aids (including none) were applied in carcass washers. The data is not complete enough to come to a clear conclusion, but it suggests that those plants using no extra carcass wash chemical may have had higher prevalence of drug resistant Salmonella. This information is useful to poultry processors as a means to explain the affect of broiler processing on Salmonella and to scientists as a first step in the design of more focused studies to examine the affect of various chemical processing aids on antimicrobial resistance.
The objective of this study was to measure the effect of broiler processing on the prevalence, serotype and antimicrobial resistance profiles of salmonellae. Twenty US commercial processing plants representing eight integrators in thirteen states were included in the survey. In each of four replications, ten carcasses from one flock were collected at re-hang and ten more at post-chill; each carcass was sampled by whole carcass rinse. Salmonella were isolated from carcass rinses using standard cultural techniques, serotype was determined and the resistance to 15 antimicrobials was measured. Overall, Salmonella was detected on 72 % of carcasses at re-hang (ranging from 35 to 97 %) and 20 % post-chill (ranging from 2.5 to 60 %). In every instance, a significant (p < 0.05) decrease in Salmonella prevalence was noted between re-hang and post chill which can be attributed to processing interventions. The four most common serotypes accounting for 64 % of all Salmonella isolates were: Kentucky, Heidelberg, Typhimurium and Typhimurium var 5-; most isolates of Kentucky (52 %), Heidelberg (79 %) and Typhimurium (54%) were susceptible to all antimicrobial drugs tested. However, only 15 % of the Typhimurium var 5- isolates were pan-susceptible; more than half of the isolates of this serotype were resistant to 3 or more drugs. No isolate of any serotype exhibited resistance to amikacin, ceftriaxone, ciprofloxacin or the combination of trimethoprim/sulfamethoxozole. These data demonstrate that although processing lessens carcass contamination with Salmonella, antimicrobial resistant isolates may still be present.