Detection, Conjugation And Genetic Environment Of Efflux Genes BcrB And Lsa(E) Among Enterococci Strains

Enterococci, a clinically important pathogens of humans and animals, have received widespread concern in the scientific and medical workers due to its diverse intrinsic resistance, acquired resistance and pathogenicity. Therefore, surveys on the resistance of enterococci strains and study on the resistance mechanism of these strains are important to the health of humans and animals, has important public health significance.In this study, detection of efflux pump genes bcrB and lsa (E), plasmid conjugation and transformation, the whole genome sequencing, genetic environment analysis of the resistance genes and overlaping PCR were performed based on acquired 102 enterococci strains derived from pigs and humans.The results showed that the detection rates of bcrB among swine and human enterococci strains were 57.5%(23/40) and 14.3%(4/28), respectively. While, the detection rates of lsa(E) among swine and human enterococci strains were 53.6%(37/69) and 30.3%(10/33), respectively.The conjugation experiments showed that transfer efficiency of bacitracin resistance gene bcrB among swine and human enterococci strains were 4.5×10-3and 6.0×10-5, respectively. While transfer efficiency of lincomycin-Pleuromutilin-streptogramin A resistance gene lsa (E) in swine enterococci strains was3 ×10-6.The transformation experiments indicated that the transformation can occur in lsa (E) postive enterococci strains.The genetic environment of bcrB revealed that bcrABDR resistance gene cluster located in two direct repeat insert sequence ISEnfal. transposition formed by composite transposon consisting of insertion sequence prompt horizontal dissemination of bcrABDR resistance gene cluster. The genetic environment of lsa (E) indicated that erm(B), aadE, spc and Lnu (B) co-existed with lsa(E). These resistance genes formed a multi-drug resistance gene cluster, which is flanked by the IS element and the transposase gene. These data suggested that horizontal dissemination of these resistance genes can occur by integration or transposition.In summary, the bacitracin efflux pump gene bcrB and lincomycin-Pleuromutilin-streptogramin A efflux pump gene lsa(E) were detected in human and swine Enterococci strains. The conjugation can occur in the bcrB- or lsa(E)-positive strains, while the transformation can occur in the lsa(E) strains. Further genetic environmental analysis of resistance gene revealed that bcrB and lsa(E) is related to the IS elements, suggesting that horizontal dissemination of these resistant genes can occur by integration or transposition, which provide the partial theoretical explanation for the rapid emergence of these resistance genes in clinic.