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

Abstract

2 Synopsis (240 words) 19Klebsiella-associated plasmid pKpQIL and its variant have been isolated globally. Our 20 study aimed to determine whether a naturally occurring variant has altered host range 21 and impacts on the fitness of different bacterial host strains. The plasmids pKpQIL-UK 22 and pKpQIL-D2 were transferred from the original clinical isolate host strains of Klebsiella 23 pneumoniae into Escherichia coli, Salmonella Typhimurium, Enterobacter cloacae and 24 Serratia marcescens strains by filter-mating and conjugation frequencies determined and 25 compared. The fitness of the resulting transconjugants was assessed by determining 26 growth kinetics, ability to form a biofilm and persistence of the plasmids in each host was 27 also measured. Transfer of either plasmid into Salmonella and S. marcescens was 28 similar. However, pKpQIL-UK transferred into E. coli at a higher rate than did pKpQIL-D2; 29 the reverse was found for E. cloacae. Both plasmids were rapidly lost from the E. coli 30 population. Plasmid pKpQIL-UK, but not -D2, was able to persist in Salmonella. Although 31 pKpQIL-UK imposed a greater fitness cost (inferred from an increased generation time) 32 than -D2 on E. cloacae, it was able to persist as well as pKpQIL-D2 in this host. The 33 pKpQIL-D2 plasmid did not confer any fitness benefit on any of the hosts under the 34 conditions tested. Variants of the globally important pKpQIL plasmid have arisen in 35 patients due to recombination. The impacts of the pKpQIL-UK plasmid and the -D2 variant 36 in various Enterobacteriaceae are host-dependent. Continuing evolution of pKpQIL may 37 alter its host range in the future. 38 39 40 370 This project was supported by the Elite Doctoral Researcher Scholarship of the University