Bacterial isolates with multiple plasmids harbouring different carbapenemase genes have emerged and been identified repeatedly, despite a general notion that plasmids confer fitness cost in bacterial host. In this study, we investigated the effects of plasmids with carbapenemase genes on the fitness and virulence of bacteria. Different plasmids harbouring the carbapenemase genes, blaNDM-1 and blaOXA-232, were isolated from a carbapenem-resistant K. pneumoniae strain. Each plasmid was conjugated into the Escherichia coli strain DH5α, and a transconjugant with both plasmids was also obtained by transformation. Their in vitro competitive ability, biofilm formation, serum resistance, survival ability within macrophage and fruit fly, and fly killing ability were evaluated. The transconjugants with a single plasmid showed identical phenotypes to the plasmid-free strain, except that they decreased fly survival after infection. However, significantly increased fitness, virulence and biofilm production were observed consistently for the transconjugant with both plasmids, harbouring blaNDM-1 and blaOXA-232. Our data indicate that bacteria carrying multiple plasmids encoding different carbapenemases may have increased fitness and virulence, emphasizing the need for diverse strategies to combat antimicrobial resistance.

中文翻译：

---

共同导入带有碳青霉烯酶基因的质粒bla _NDM-1和bla _OXA-232，可提高细菌宿主的适应性和毒力

尽管普遍认为质粒会增加细菌宿主的适应性成本，但带有多个带有不同碳青霉烯酶基因的质粒的细菌分离物已经出现并被反复鉴定。在这项研究中，我们调查了碳青霉烯酶基因质粒对细菌适应性和毒力的影响。从耐碳青霉菌的肺炎克雷伯菌菌株中分离出带有碳青霉烯酶基因的不同质粒blaNDM-1和blaOXA-232。将每个质粒缀合到大肠杆菌菌株DH5α中，并且还通过转化获得了具有两个质粒的转导结合体。对它们的体外竞争能力，生物膜形成，血清抗性，巨噬细胞和果蝇内的存活能力以及杀蝇能力进行了评估。具有单个质粒的转导结合体表现出与不含质粒的菌株相同的表型，不同之处在于它们降低了感染后果蝇的存活率。但是，对于带有blaNDM-1和blaOXA-232两种质粒的转导结合体，一致观察到适应性，毒力和生物膜产量显着提高。我们的数据表明，携带多种编码不同碳青霉烯酶的质粒的细菌可能具有更高的适应性和毒力，从而强调需要采取多种策略来对抗抗菌素耐药性。