Convergence of MCR-8.2 and chromosome-mediated resistance to colistin and tigecycline in an NDM-5-producing ST656 Klebsiella pneumoniae from a lung transplant patient

For infection caused by NDM-5-producing Klebsiella pneumoniae, tigecycline and colistin are the last treatment options. In this study, we characterized the first NDM-5 and MCR-8.2 co-harboring K. pneumoniae clinical isolate, combining with chromosomal gene-mediated resistance to colistin and tigecycline. The K. pneumoniae KP32558 was isolated from the bronchoalveolar lavage fluid from a lung transplant male patient. Whole genome sequencing was carried out using Illumina HiSeq sequencing platform as well as nanopore sequencing method. The K. pneumoniae KP32558 was identified as a pan-drug resistant bacteria, belonged to ST656, and harbored plasmid-encoded blaNDM-5 and mcr-8.2 genes. The blaNDM-5 gene was located on an IncX3 type plasmid, which was successfully transferred to Escherichia coli strain J53 without visible fitness cost. The mcr-8.2 gene was located on a conjugative plasmid pKP32558-2-mcr8. It had two replicons, IncFII(K) and IncQ1, harbored previously by another two mcr-8.2-carrying plasmids pMCR8_020135 and pMCR8_095845. These three plasmids were clustered into the same clade and derived from K. pneumoniae isolates of the same clonal complex, indicating that pKP32558-2-mcr8 may come from pMCR8_020135 and pMCR8_095845 related ancestor. The MIC of KP32558 for colistin was 256 mg/L, the 6 amino acid substitutions in the two-component system may involve in the high-level colistin resistance. The truncation in acrR gene, related to tigecycline resistance, was also identified. K. pneumoniae has evolved a variety of complex resistance mechanisms to the last-resort antimicrobials, close surveillance is urgently needed to monitor the prevalence of this clone.