Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/3/2005
Publication Date: 12/20/2005
Citation: Campbell, L.D., Scott, H.M., Bischoff, K.M., Anderson, R.C., Harvey, R.B. 2005. Prevelance of class 1 integrons and antimicrobial resistance gene cassettes among enteric bacteria found in multisite group-level cohorts of humans and swine. Journal of Food Protection. 68:2693-2697. Interpretive Summary: Bacterial antibiotic resistance has become increasingly important in the human and veterinary medical communities. Little is known about how bacteria transfer resistance and if antibiotic usage in animals contributes to resistance in humans. In the present study, we showed that when humans and swine have daily exposure to each other, there is no apparent transfer of resistance. This on-going study is the first of this particular design and if future data verify the present results, it would provide strong evidence that bacterial antibiotic resistance strains in swine (and possibly other livestock) have no significant likelihood of being transferred to humans.
Technical Abstract: The prevalence of antimicrobial resistance (AMR) genotypic characteristics (Class 1 integron and AMR gene cassettes) in commensal Escherichia coli (EC) isolated from humans and swine in a semi-closed, integrated farrow-to-fork population were evaluated in a cross-sectional study. The objective of this study was to establish baseline antimicrobial resistance patterns of enteric bacteria from animals and humans within the study population; specifically, genotypic traits which are both unique and common to commensal EC derived from the different sources. There were significant differences between host species with swine isolates having greater odds for the presence of integrons (OR=2.33, p=0.0487). No significant differences were found (p>0.05) for facility location, facility type, human housing cohort or time of day. There were significant differences (p=0.006) between swine production groups (boars, dry sows, finisher, grower, intake boars, lactating sows, lagoon, nursery piglets, influent and piglets) with the grower group having lower odds for the presence of a Class 1 integron than the nursery group (nursery as referent, OR=0.22, p=0.04). Among all isolates with an integron present, human isolates were at higher risk for the presence of an AMR gene cassette (OR=6.36, p=0.003). When isolates that possessed gene cassettes coding for specific resistance to antimicrobials were compared, no significant differences between host species (p>0.05) were observed.