Advantage of the F2:A1:B- IncF Pandemic Plasmid over IncC Plasmids in In Vitro Acquisition and Evolution of bla _CTX-M Gene-Bearing Plasmids in Escherichia coli

Abstract

Despite a fitness cost imposed on bacterial hosts, large conjugative plasmids play a key role in the diffusion of resistance determinants, such as CTX-M extended-spectrum β-lactamases. Among the large conjugative plasmids, IncF plasmids are the most predominant group, and an F2:A1:B- IncF-type plasmid encoding a CTX-M-15 variant was recently described as being strongly associated with the emerging worldwide Escherichia coli sequence type 131 (ST131)-O25b:H4 H30Rx/C2 sublineage. In this context, we investigated the fitness cost of narrow-range F-type plasmids, including the F2:A1:B- IncF-type CTX-M-15 plasmid, and of broad-range C-type plasmids in the K-12-like J53-2 E. coli strain. Although all plasmids imposed a significant fitness cost to the bacterial host immediately after conjugation, we show, using an experimental-evolution approach, that a negative impact on the fitness of the host strain was maintained throughout 1,120 generations with the IncC-IncR plasmid, regardless of the presence or absence of cefotaxime, in contrast to the F2:A1:B- IncF plasmid, whose cost was alleviated. Many chromosomal and plasmid rearrangements were detected after conjugation in transconjugants carrying the IncC plasmids but not in transconjugants carrying the F2:A1:B- IncF plasmid, except for insertion sequence (IS) mobilization from the fliM gene leading to the restoration of motility of the recipient strains. Only a few mutations occurred on the chromosome of each transconjugant throughout the experimental-evolution assay. Our findings indicate that the F2:A1:B- IncF CTX-M-15 plasmid is well adapted to the E. coli strain studied, contrary to the IncC-IncR CTX-M-15 plasmid, and that such plasmid-host adaptation could participate in the evolutionary success of the CTX-M-15-producing pandemic E. coli ST131-O25b:H4 lineage.

Plasmid- and strain-specific factors drive variation in ESBL-plasmid spread in vitro and in vivo

“…Sequencing of the ESBL-plasmids in transconjugants revealed no mutations after transfer (Supplementary Results and Supplementary Table S2 ). This is in agreement with earlier findings reporting the absence of mutations on ESBL-plasmids even after 112 days of evolution of transconjugants [ 97 ] but does not exclude that such adaptive processes have happened in the past. Regardless, these data suggest that contemporary clinical ESBL-plasmids are well adapted to Enterobacteriaceae and do not require clone-specific adaptations for successful spread.…”

Meta-analysis of Pandemic Escherichia coli ST131 Plasmidome Proves Restricted Plasmid-clade Associations

“…The contribution of Groups 1 and 2 IncF plasmids on E. coli ST131 superiority have yet to be studied. In E. coli K12, a non-ST131 E. coli background, the acquisition of IncF Group2 plasmid resulted in minor chromosomal modifications and fitness cost diminished after several generations, while acquisition of IncC-IncR plasmid lead to major genomic rearrangements with consistent high fitness cost 22 . In K. pneumoniae, adaption to IncF pKpQIL-like plasmids was associated mostly with changes in gene expression levels, together with variations in other physiological features such as conjugation rates, competitiveness, or biofilm formation levels 23 .…”

A large self-transmissible resistance plasmid from Nigeria contains genes that ameliorate a carrying cost

“…In practice, this is not always true but the co-evolutionary routes to reduced cost are often unknown. Some research has suggested that this burden is reduced or eliminated through compensatory mutations or acquisitions 14,39–43 . Alternatively, or in addition, plasmid-encoded resistance genes themselves could confer a fitness advantage in the absence of antimicrobials 14,41 .…”