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Aim of this study was to investigate the prevalence and genetic environment of the oxazolidinone resistance gene optrA in Streptococcus suis (S. suis) isolates from diseased pigs in China. A total of 178 S. suis isolates were screened for the optrA gene by PCR. The phenotypes and genotypes of optrA -positive isolates were investigated by antimicrobial susceptibility testing, core genome Multilocus Sequence Typing (cgMLST), capsular serotypes determination and whole-genome sequencing (WGS). Fifty-one (28.7%) S. suis isolates were positive for optrA. Phylogenetic analysis indicated that the spread of the optrA among S. suis isolates was primarily due to horizontal transfer. Analysis of S. suis serotypes from diseased pigs revealed substantial diversity. The genetic environment of optrA was complex and diverse and could be divided into 12 different types. Interestingly, we identified a novel integrative and conjugative element ICE Ssu 988S, carrying optrA and erm (T) genes. This is to the best of our knowledge the first report of the optrA and erm (T) co-located on an ICE in S. suis. Our results showed a high prevalence of optrA gene in S. suis isolates in China. Further research is needed to evaluate the importance of ICEs, as they horizontally propagate important clinical resistance genes. [ABSTRACT FROM AUTHOR]

Background: The plasmid-encoded multidrug efflux pump oqxAB confers bacterial resistance primarily to olaquindox, quinolones, and chloramphenicol. The aims of this study were to investigate the prevalence of oqxAB among Escherichia coli isolates from dogs, cats, and humans in Henan, China and the susceptibilities of E. coli 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 E. coli . All isolates were screened for oqxAB genes by PCR and sequencing. The MICs of 11 antimicrobial agents were determined by the broth microdilution method. A total of 30 representative oqxAB -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 oqxAB . Olaquindox resistance was found for 85.7%-100% of oqxAB -positive isolates. Of oqxAB -positive isolates from dogs, cats, and humans, ciprofloxacin resistance was inspected for 85.8%, 59.1%, and 93.8%, respectively. Several oqxAB -positive isolates were demonstrated by ERIC-PCR and MLST, and have high similarity. Phylogenetic analysis showed that oqxAB -positive isolates could be divided into 7 major clusters. OqxAB -positive conjugants were obtained, southern hybridization verified that the oqxAB gene complex was primarily located on plasmids., Conclusion: In conclusion, oqxAB -positive isolates were widespread in animals and humans in Henan, China. Carriage of oqxAB on plasmids of E. coli isolates may facilitate the emergence of multidrug resistant and its transmission via horizontal transfer, and might pose a potential threat to public health., Competing Interests: With regards to our study’s use of animals, this study protocol was reviewed and approved by the Henan Agriculture University animal ethics committee, and the experiment was performed in accordance with the regulations and guidelines established by this committee. For experiments involving human participants, this study was approved by the Chinese Academy of Sciences human ethics committee, and was carried out strictly in accordance with the approved guidelines. Informed consent was obtained from the hospital.Not applicable.The authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.