Shang Weilong,Hu Qiwen,Hu Zhen,Zhu Junmin,Yang Jie,Yuan Wenchang,Cheng Hang,Yuan Jizhen,Zhang Xia,Rao Qing,Rao Xiancai.Mechanisms in replacement of major methicillin-resistant Staphylococcus aureus epidemic clones in Chongqing[J].J Amry Med Univ (J Third Mil Med Univ),2014,36(08):735-739.
Shang Weilong,Hu Qiwen,Hu Zhen,Zhu Junmin,Yang Jie,Yuan Wenchang,Cheng Hang,Yuan Jizhen,Zhang Xia,Rao Qing,Rao Xiancai.Mechanisms in replacement of major methicillin-resistant Staphylococcus aureus epidemic clones in Chongqing[J].J Amry Med Univ (J Third Mil Med Univ),2014,36(08):735-739.DOI:
Mechanisms in replacement of major methicillin-resistant Staphylococcus aureus epidemic clones in Chongqing
Objective To explore the mechanisms underlying the replacement of methicillin-resistant Staphylococcus aureus (MRSA) straim ST239-MRSA-Ⅲ-t037 by ST239-MRSA-Ⅲ-t030 in Chongqing
China. Methods Eight ST239-MRSA-Ⅲ-t030 and ST239-MRSA-Ⅲ-t037 isolates collected from Chongqing were divided into four t030/t037 pairs. The independent growth rates of all isolates were then determined. The competitive growth rates of the bacterial pairs were detected in vitro and in vivo
and cross inhibition assays were also performed. Results The ST239-MRSA-Ⅲ-t030 isolates were rifampicin-resistant
whereas the ST239-MRSA-Ⅲ-t037 strains were all rifampicin-sensitive and trimethoprim/sulfamethoxazole-resistant. The ST239-MRSA-Ⅲ-t030 strains had shorter lag phases than the ST239-MRSA-Ⅲ-t037 isolates. The ST239-MRSA-Ⅲ-t030 strains could out-compete their rivals in a competition assay in vitro as well as in a mouse model. No significant cross-inhibition effect was observed between ST239-MRSA-Ⅲ-t030 and ST239-MRSA-Ⅲ-t037. The growth of ST239-MRSA-Ⅲ-t037 strains on the BHI nonselective plates had smaller colonies as compared to ST239-MRSA-Ⅲ-t030 strains. Conclusion ST239-MRSA-Ⅲ-t030 replacing ST239-MRSA-Ⅲ-t037 as the first predominant clone may result from its higher growth rate and the specific drug resistance profiles.