Fitness effects of blaCTX-M-15-harbouring F2:A1:B- plasmids on their native Escherichia coli ST131 H30Rx hosts.

We conclude that F2:A1:B- plasmids pose low fitness costs in their E. coli ST131 H30Rx hosts. This plasmid-host fitness compatibility is likely to promote the maintenance of antibiotic resistance in this clinically important E. coli lineage.