The primary objective of this study was to investigate the prevalence of Campylobacter spp. DNA by PCR in retail ground beef sold in Saskatchewan, Canada, and to identify the presence of individual Campylobacter species (C. coli, C. curvus, C. fetus, C. hyointestinalis, C. jejuni, C. rectus, and C. upsaliensis) using real-time quantitative PCR (qPCR). Secondary objectives were to assess potential differences in the prevalence of Campylobacter between ground beef offered for sale during cold and warm seasons as well as that offered for sale fresh and frozen, to investigate any association between the presence of Campylobacter spp. DNA and E. coli and/or aerobic bacterial counts, and finally to compare the prevalence of Campylobacter spp. DNA in ground beef originating from different production and retail environments. Out of the 309 total samples included in the study, 50 (16.2%) samples tested positive for Campylobacter spp. DNA, while 49 (15.9%) samples were determined positive for up to five individual species. Collectively, these assays determined that 14 (4.5%) samples were positive for C. coli, 11 (3.6%) for C. curvus, 6 (1.9%) for C. fetus, 24 (7.8%) for C. hyointestinalis, 12 (3.9%) for C. jejuni, 6 (1.9%) for C. rectus, and 9 (2.9%) for C. upsaliensis. There were 27 (8.7%) samples that were positive at the genus level that did not test positive for any of the seven Campylobacter species investigated (suggesting an alternate Campylobacter species). Also, 26 (8.4%) samples generated positive results by one of the species-specific qPCR assays, but returned no product in the conventional genus-level assay (suggesting a higher sensitivity for the species-specific qPCR assays). There was no significant association between the presence of Campylobacter spp. in Saskatchewan retail ground beef and any of the investigated risk factors.
The change in bacterial recovery and phenotypic antimicrobial susceptibility of 3 important bovine respiratory disease bacteria (Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni) between arrival and 90 to 120 days was observed in 295 healthy fall-placed feedlot calves in western Canada using deep nasal swabs. At the arrival sampling, 28%, 28%, and 9% of calves were culture positive for Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, respectively; these rates changed to 23%, 14%, and 16%, respectively, in the post-arrival period. A decrease in antimicrobial susceptibility was observed between the arrival and post-arrival sample periods, with numerically fewer pan-susceptible isolates and little change in multi-drug resistant isolates. Between the 2 sampling periods, statistically significant decreases in susceptibility to tilmicosin and tulathromycin were observed for Mannheimia haemolytica and tildipirosin for Pasteurella multocida isolates. Results of this study suggest that changes to both the proportions of bacteria isolated and the antimicrobial susceptibility of isolates occur between arrival and ~90 days post-arrival.
Antimicrobials are important tools in modern beef production. Antimicrobial drugs are often used for metaphylaxis to prevent and treat early cases of bovine respiratory disease complex (BRD) as well as for therapeutic purposes in feedlot cattle. Antimicrobial resistance of bovine respiratory pathogens can result in treatment failures and losses associated with increased treatment costs and mortalities. Mixing of cattle from multiple sources within auction markets has always been a significant risk factor for BRD. The stress of establishing a social dominance hierarchy along with the mixing of pathogens from a variety of farm sources can increase the risk of BRD in weaned calves. One method feedlots have used to mitigate this risk is to reduce mixing stress by purchasing calves directly from the ranch rather than through the auction market. The objective of this study was to describe the prevalence and antimicrobial sensitivity of 3 major bovine respiratory disease (BRD) bacterial pathogens at arrival and again later in the feeding period in feedlot calves derived from the auction market and from a single ranch source.
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