Different impacts of naturally occurring variants of the globally disseminated carbapenemase-encoding plasmid pKpQIL on the biology of host strains

Abstract

SynopsisKlebsiella-associated plasmid pKpQIL and its variant have been isolated globally. Our study aimed to determine whether a naturally occurring variant has altered host range and impacts on the fitness of different bacterial host strains. The plasmids pKpQIL-UK and pKpQIL-D2 were transferred from the original clinical isolate host strains of Klebsiella pneumoniae into Escherichia coli, Salmonella Typhimurium, Enterobacter cloacae and Serratia marcescens strains by filter-mating and conjugation frequencies determined and compared. The fitness of the resulting transconjugants was assessed by determining growth kinetics, ability to form a biofilm and persistence of the plasmids in each host was also measured. Transfer of either plasmid into Salmonella and S. marcescens was similar. However, pKpQIL-UK transferred into E. coli at a higher rate than did pKpQIL-D2; the reverse was found for E. cloacae. Both plasmids were rapidly lost from the E. coli population. Plasmid pKpQIL-UK, but not -D2, was able to persist in Salmonella. Although pKpQIL-UK imposed a greater fitness cost (inferred from an increased generation time) than -D2 on E. cloacae, it was able to persist as well as pKpQIL-D2 in this host. The pKpQIL-D2 plasmid did not confer any fitness benefit on any of the hosts under the conditions tested. Variants of the globally important pKpQIL plasmid have arisen in patients due to recombination. The impacts of the pKpQIL-UK plasmid and the -D2 variant in various Enterobacteriaceae are host-dependent. Continuing evolution of pKpQIL may alter its host range in the future.