No evidence of multidrug-resistant <i>Enterobacterales</i> transmission between healthy companion animals and pet owners in the greater Atlanta area: a pilot study

Antimicrobial resistance (AMR) is a global concern affecting both animals and humans. Pets share a close bond with humans and are exposed to human-related conditions that can, in many cases, facilitate the transmission of bacteria and mobile genetic elements. This prospective observational cohort pilot study aimed to determine the prevalence of multidrug-resistant Gram-negative bacteria (MDR-GNB) colonization in healthy individuals and their companion animals (dogs and cats) in the greater Atlanta area, as well as to understand the prevalence of enteric MDR-GNB. Serial fecal samples from paired humans and their pets were collected and analyzed over a 6-month period (at 0, 2, and 6 months). Thirty-four pet owners participated, with 26 providing stool samples at all three time points. A total of 226 fecal samples were collected from owners and their pets. Seven of 26 humans and 12 of 43 animals were found to carry MDR-GNB, specifically species such as <i>Escherichia coli, Enterobacter ludwigii, Enterobacter hormaechei,</i> and <i>Citrobacter pasteurii</i>. Whole-genome sequencing revealed nine different resistance genes in <i>E. coli</i> isolates from pets and eight from humans, six different plasmid replicons, and all were located in four different phylogroups. Phylogenetic analysis indicates species-specific clustering based on host. Our results demonstrate that while MDR Enterobacterales were present in both humans and their pets in this Atlanta population, there was no evidence of bacterial transmission between pets and their owners during the study period. This finding contradicts previous similar studies that have shown transfer of MDR bacteria. However, it aligns with research that suggests bacterial colonization depends on the strain and the host.IMPORTANCEAntimicrobial resistance in animals, particularly pets, may serve as a potential source of antimicrobial resistance. However, a definitive pathway for the transmission of clonal bacteria or horizontal gene transfer between humans and their pets has not yet been identified. This pilot study aimed to assess the risk of multidrug-resistant (MDR) Enterobacterales transmission between healthy humans and their companion animals (dogs and cats) in the greater Atlanta area. Additionally, it sought to explore any association between MDR bacterial colonization and transmission within participating households. Despite the lack of a fully defined method of transmission, our findings demonstrated that while MDR <i>Enterobacterales</i> were present in both humans and their pets in this Atlanta population, there was no evidence of bacterial transmission between pets and their owners during the study period.