Patterns of antimicrobial resistance among enteric bacteria found in multi-site group-level cohorts of humans and swine

The prevalence of antimicrobial resistance (AMR) phenotypes and genotypic characteristics (Class 1 integron and AMR gene cassettes) in commensal Escherichia coli (EC) and vancomycin resistant Enterococcus faecium (EF) isolated from humans and swine in a semi-closed, integrated farrow-to-fork population were evaluated in a crosssectional study. Our objective was to establish baseline antimicrobial resistance patterns and to evaluate the stability of isolate recovery phenotype within multiple grab samples per collection day and over multiple biweekly samples collected during a period of several months. This data will serve as a baseline for continuing longitudinal studies within the population. These continuing studies should produce the first comprehensive epidemiological data to document the transmission dynamics of antimicrobial resistance in the farrow-to-fork continuum. Outcome variables assessed included: phenotypic resistance in EC, pan-susceptibility, multi-resistance and genotypic resistance. Potential predictor variables included: 1) host species, 2) unit, 3) unit type, 4) housing cohort by species, and 5) time of day. There were significant differences (p<0.05) between host species with swine at higher odds for both single and multiple resistance. There were also differences in resistance based on unit location, unit-type, and housing cohort within both humans and swine. Our study found no significant differences (p>0.05) in resistance between swine workers and non-swine workers with the sole exception of resistance to cephalothin, with non-swine workers at 1.89 higher odds for resistance (p=0.02). A total of 17 VRE were isolated from human wastewater samples, and to the author??s knowledge these represent the first environmentally isolated VRE in the U.S. Several unique multi-resistance phenotypes were observed and future evaluation of AMR phenotype in continuing longitudinal studies provides a unique opportunity to study phenotypic patterns and dissemination through the study population.