Spread and evolution of blaKPC-plasmid between Serratia marcescens and Klebsiella pneumoniae

The emergence and prevalence of carbapenem-resistant Enterobacterales on a global scale has posed a serious challenge to global public health security. Clinical research has rarely reported the co-infection of multidrug-resistant Serratia marcescens and Klebsiella pneumoniae. In this study, we describe the case of a hospitalized patient infected with carbapenem-resistant S. marcescens and K. pneumoniae. The evolution and transmission of blaKPC-2 occurred during the treatment with ceftazidime-avibactam and trimethoprim-sulfamethoxazole. Analysis of the antimicrobial susceptibility and genetic profiles of the clinical strains showed that blaKPC-2 evolved into blaKPC-71 and blaKPC-44, together with resistance to ceftazidime-avibactam and carbapenems susceptibility recovery under antimicrobial pressure. Cloning and expression of blaKPC-44 & blaKPC-71 in E. coli DH5α showed that KPC-44 and KPC-71 resulted in a 64∼128-fold increase in the MIC value for ceftazidime-avibactam. Meanwhile, the kinetic assays also showed that the enzyme activity of KPC-44 and KPC-71 towards carbapenems was destroyed and couldn't be inhibited by avibactam. Based on the conjugation assay and whole genome sequence analyses, we provided evolutionary insights into the transmission pathway trace of blaKPC-bearing plasmids between S. marcescens and K. pneumoniae. Based on the sharp decrease in conjugation frequency and the loss of blaKPC-bearing plasmids during treatment, we predicted that the evolution of blaKPC has affected the efficiency and stability of plasmid transmission between species. Mixed-species co-infection is one of the risk factors leading to the spread of plasmids carrying carbapenem-resistant genes, and increased surveillance of multidrug-resistant Enterobacterales is urgently needed.