Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2008
Publication Date: 6/1/2008
Citation: Alali, W.Q., Scott, H.M., Harvey, R.B., Norby, B. 2008. Longitudinal study of antimicrobial resistance among Escherichia coli isolated from integrated multi-site cohorts of humans and swine. Applied and Environmental Microbiology. 74(12):3672-3681. Interpretive Summary: Increasingly, bacteria are becoming antimicrobial resistant (AR). This has serious implications for human and animal health. Some in the medical community believe that the use of antibiotics in animal agriculture has promoted AR in bacteria and these bacteria may be transferred from animals to humans. In the present study, we determined that bacteria from swine workers had greater AR than those from non-workers. This is the first study to demonstrate the possible transfer of AR from animals to humans. This information could potentially change current agriculture practices away from antibiotic usage.
Technical Abstract: We examined the relationship between the prevalence of antimicrobial-resistant (AR) E. coli isolated from human wastewater and swine fecal samples and the risk factors: (host species, production type (swine), vocation (human swine workers, non-workers, and slaughter-plant workers), and season) in a multi-site housing, vertically integrated swine and human population agri-food system. Human and swine E. coli (N = 4048 and 3485, respectively) isolated from wastewater and fecal samples were tested for antimicrobial susceptibility using the Sensititre**TM broth microdilution system. There were significant (P < 0.05) differences in AR isolates: 1) between host-species with swine at higher risk for tetracycline, kanamycin, ceftiofur, gentamicin, streptomycin, chloramphenicol, sulfisoxazole, and ampicillin, 2) swine production group was significantly associated with AR with purchased boars, nursery piglets, and breeding boars at a higher risk of resistance to streptomycin and tetracycline, and 3) human swine worker cohorts exhibited lowered sulfisoxazole and cefoxitin prevalence compared to non-workers, while slaughter-plant workers exhibited elevated cefoxitin prevalence compared to non-workers. High variability among seasonal samples over the 3-year period was observed. There were significant differences in multiple resistance isolates between host species, with swine at higher risk than humans of carrying multi-resistant strains, slaughter-plant workers at higher risk than swine non-workers; however, there were no significant differences in multiple resistance isolates within swine by production group. Occupational exposure to slaughter facilities appeared to be associated with an increased relative odds for the prevalence of cefoxitin resistance and multiple resistance compared to swine non-workers.