The main goal of this study was to determine the prevalence of methicillin-resistant Staphylococcus aureus (MRSA), particularly livestock-associated MRSA (LA-MRSA) in pigs and pork. The genotypic relatedness of isolates on the farm, at slaughter, and at the retail level was assessed. Paired nasal and perianal swab samples were collected from 10 cohorts of market-age pigs (24 pigs per cohort) and carcasses at slaughterhouse, and pork samples were collected at retail. Staphylococci were isolated using selective enrichment method. Isolates were tested for antimicrobial resistance by broth microdilution. Duplex PCR was used to confirm MRSA using species-specific (nuc) and methicillin resistance (mecA) genes. The clonal relatedness of isolates was determined using pulsed-field gel electrophoresis (PFGE), Staphylococcus protein A (spa) typing, multilocus sequence typing (MLST), and staphylococcal cassette chromosome mec element (SCCmec) typing. MRSA was detected in 5 of the 10 cohorts (50%), with the prevalence ranging from 0% to 12.5% per cohort. Of all the pigs sampled on the farm before they went to market, 3% (7/240) were MRSA positive. A higher prevalence of MRSA was detected at holding pens at the slaughterhouse (11% [27/240]). MRSA was also detected in 2% (4/235) of the carcasses and 4% (5/135) of the retail pork. While the isolates appear predominantly to be highly clonal, PFGE had a relatively higher discriminatory power (discriminatory index [DI] ؍ 0.624). Four genotypic clusters were identified by PFGE; of the four clusters, clonal type B was predominant across the farm-to-retail continuum. MLST findings revealed that sequence type 5 (ST5) was the most predominant subtype (32/50). The livestock-associated MRSA (clonal complex 398 [CC398] or sequence type 398 [ST398]) was the second common type (12/50) and was detected at all stages from farm to retail. Nine of the 50 (18%) MRSA isolates belonged to spa type 539/t034 that were of ST398 based on MLST. The results of this study confirm that MRSA, including LA-MRSA, is common in herds of swine in Ohio and hereby shown to persist in the farm to processing and retail continuum.
This study was conducted to determine the occurrence and prevalence of methicillin resistant Staphylococcus aureus (MRSA) in finishing pigs on-farm, at lairage and assess the likelihood of carriage at slaughter and retail levels. A crosssectional study targeting ten cohorts of commercial swine farms was conducted for carriage of MRSA. Paired nasal and peri-anal swab samples (n=24/farm) were collected from market age pigs on-farm and the same batch of pigs were followed and sampled at the lairage before slaughter and carcass swabs at post evisceration stage before chilling. Pork samples from the same batch of pigs were collected at retail market. We assessed phenotypic and genotypic relatedness from the various sources. Conventional cultural methods using oxacillin resistance screening agar was used. Antimicrobial resistance was tested to a panel of 21 antimicrobials. PCR was used to detect the presence of species-specific gene (nuc) and methicillin resistance marker gene (mecA). The genotypic relatedness of isolates was determined using the Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). One or more MRSA positive pigs were detected in five of the ten herds (50%). The prevalence of MRSA in pigs was higher at lairage and ranged from 0% to 54.2% per farm compared to that same batch of pigs on-farm (0% to 12.5%). The proportion of MRSA positive isolates recovered from nasal swab samples was relatively higher (4.8%) compared to peri-anal samples (2.7%). We detected MRSA in 1.6% (4/240) of the carcass swab and 3.7% (5/135%) of the retail pork samples. Genotypically similar isolates were detected from farm to the retail chain based on PFGE. Using MLST, ST398 was detected from farm, lairage and retail pork. In addition ST5, ST9, ST39 and ST72 were detected at different points of sampling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.