Here we report a novel narrow-spectrum β-lactamase CTX-M-215 identified in an Escherichia coli clinical isolate in China and conferring high-level resistance to mecillinam but not to cefotaxime. CTX-M-215 differed from CTX-M-125, a CTX-M-ESBL by an N132D substitution, which decreased the hydrolytic activities towards penicillins and cephalosporins except for mecillinam. High similarity was observed between CTX-M-215- and CTX-M-125-bearing plasmids, carried by different isolates in the same patient, indicating in vivo evolution of CTX-M-215 from CTX-M-125.
The
qnrE
family was designated in 2017. To date, two
qnrE
alleles have been discovered that are carried by plasmids. Here, we identified a new quinolone resistance gene
qnrE3
in the chromosome of an
Enterobacter
mori
clinical isolate 08-091 in China.
qnrE3
conferred decreased susceptibility to fluroquinolones, similar to
qnrE1
and
qnrE2
. To investigate the precise origin of
qnrE1
,
qnrE2,
and
qnrE3
, 79
qnrE
-bearing strains producing 30
qnrE
variants were retrieved from the NCBI database. Phylogenetic analysis illustrated two major clusters, QnrE
Emo
and QnrE
Eas
, produced mainly by the
E. mori
and
E. asburiae
strains, respectively. Comparison of the genetic context of
qnrE
alleles demonstrated that
qnrE3
and
qnrE
Eas2
alleles were presumably captured by ISE
cp1
and mobilized from the
E. mori
and
E. asburiae
strains to the
E. xiangfangensis
and
E. coli
strains, respectively.
qnrE
Eas2
was proposed to be named as
qnrE4
since it has been spread to another genus. All the
qnrE
alleles were harbored by the
Enterobacter
species, except those captured by ISE
cp1
and mobilized into other species of
Enterobacterales
.
E. mori
is probably the source of
qnrE1
to
qnrE3
alleles and
E. asburiae
is the reservoir of
qnrE4
.
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