TRACKING CLONAL AND PLASMID TRANSMISSION IN COLISTIN AND CARBAPENEM RESISTANT KLEBSIELLA PNEUMONIAE

The surveillance of mobile genetic elements facilitating the spread of antimicrobial resistance genes has been challenging. Here, we tracked both clonal and plasmid transmission in colistin- and carbapenem-resistant K. pneumoniae using short and long read sequencing technologies. We observed three clonal transmissions, all containing IncL plasmids and blaNDM-1, although not co-located on the same plasmid. One IncL-blaNDM-1 plasmid had been transferred between ST392 and ST15, and the promiscuous IncL-blaOXA-48 plasmid was likely shared between a singleton and a clonal transmission of ST392. Plasmids within clonal outbreaks and between clusters and STs had 0-2 SNP differences, showing high stability upon transfer to same or different STs. The simplest explanation of a single common IncL-blaNDM-1 plasmid spreading was in fact false, and we found blaNDM-1 in the context of five different plasmids, emphasizing the need to investigate plasmid-mediated transmission for effective containment of outbreaks. IMPORTANCEAntimicrobial resistance occupies a central stage in global public health emergencies. Recently, efforts to track the genetic elements that facilitate the spread of resistance genes to determine so-called plasmid outbreaks have been described, however, such short read sequencing hinders full knowledge about plasmid structure and makes this approach very challenging to implement. In this study we used both short and long read sequencing in clinical Klebsiella pneumoniae from University Hospital Centre Zagreb, Croatia which were resistant to both last resort antibiotics colistin and carbapenem. Our results show complex transmission networks and sharing of plasmids, emphasizing multiple transmissions of plasmids harbouring carbapenem and/or colistin resistance genes between and within K. pneumoniae clones. Only full length sequencing plus a novel way of determining plasmid clusters resulted in the full picture, showing how future active monitoring of plasmids as a vital tool for infection prevention and control could be implemented.