Abstract:
Epidemic IncF plasmids have been pivotal in
the selective advantage of multidrug-resistant
(MDR) extraintestinal pathogenic Escherichia
coli (ExPEC). These plasmids have offered several
advantages to their hosts that allowed them
to coevolve with the bacterial host genomes and
played an integral role in the success of ExPEC.
IncF plasmids are large, mosaic, and often contain
various types of antimicrobial resistance
(AMR) and virulence associated factor (VAF)
genes. The presence of AMR, VAF genes, several
addition/restriction systems combined with
truncated transfer regions, led to the fixation of
IncF plasmids in certain ExPEC MDR clones,
such as ST131 and ST410. IncF plasmids entered
the ST131 ancestral lineage in the mid 1900s and different ST131 clade/CTX-M plasmid
combinations coevolved over time. The
IncF_CTX-M-15/ST131-C2 subclade combination
emerged during the early 2000s, spread
rapidly across the globe, and is one of the
greatest clone/plasmid successes of the millennium.
The ST410-B3 subclade containing
blaCTX-M-15 incorporated the NDM-5 carbapenemase
gene into existing IncF platforms, providing
an additional positive selective
advantage that included the carbapenems. A
‘‘plasmid-replacement’’ clade scenario occurred
in the histories of ST131 and ST410 as different
subclades gained different AMR genes on different
IncF platforms. The use of antimicrobial
agents will generate selection pressures that
enhance the risks for the continuous emergence
of MDR ExPEC clone/IncF plasmid combinations.
The reasons for clade/IncF replacements
and associations between certain clades and
specific IncF plasmid types are unknown. Such
information will aid in designing management
and prevention strategies to combat AMR.
