Prevalence and molecular characterization of <italic>oqxAB</italic> in clinical <italic>Escherichia coli</italic> isolates from companion animals and humans in Henan Province, China.

Background: The plasmid-encoded multidrug efflux pump <italic>oqxAB</italic> confers bacterial resistance primarily to olaquindox, quinolones, and chloramphenicol. The aims of this study were to investigate the prevalence of <italic>oqxAB</italic> among <italic>Escherichia coli</italic> isolates from dogs, cats, and humans in Henan, China and the susceptibilities of <italic>E. coli</italic> isolates to common antibiotics. Methods: From 2012 to 2014, a total of 600 samples which included 400 rectal samples and 200 clinical human specimens were tested for the presence of <italic>E. coli</italic>. All isolates were screened for <italic>oqxAB</italic> genes by PCR and sequencing. The MICs of 11 antimicrobial agents were determined by the broth microdilution method. A total of 30 representative <italic>oqxAB</italic>-positive isolates were subjected to ERIC-PCR and MLST. Additionally, conjugation experiments and southern hybridizations were performed. Results: Of 270 isolates, 58.5% (62/106) of the isolates from dogs, 56.25% (36/64) of the isolates from cats, and 42.0% (42/100) of the isolates from humans were positive for the <italic>oqxAB</italic>. Olaquindox resistance was found for 85.7%-100% of <italic>oqxAB</italic>-positive isolates. Of <italic>oqxAB</italic>-positive isolates from dogs, cats, and humans, ciprofloxacin resistance was inspected for 85.8%, 59.1%, and 93.8%, respectively. Several <italic>oqxAB</italic>-positive isolates were demonstrated by ERIC-PCR and MLST, and have high similarity. Phylogenetic analysis showed that <italic>oqxAB</italic>-positive isolates could be divided into 7 major clusters. <italic>OqxAB</italic>-positive conjugants were obtained, southern hybridization verified that the <italic>oqxAB</italic> gene complex was primarily located on plasmids. Conclusion: In conclusion, <italic>oqxAB</italic>-positive isolates were widespread in animals and humans in Henan, China. Carriage of <italic>oqxAB</italic> on plasmids of <italic>E. coli</italic> isolates may facilitate the emergence of multidrug resistant and its transmission via horizontal transfer, and might pose a potential threat to public health. [ABSTRACT FROM AUTHOR]