ABSTRACT
To illustrate the genomic and drug resistance traits of the
Klebsiella pneumoniae
Kpn_XM9, which harbors a transposon (Tn) As1 and was barely susceptible to ceftazidime–avibactam (CZA). Whole-genome sequencing, gene deletion, antimicrobial susceptibility, and conjugation tests were carried out to illustrate the traits of Kpn_XM9. As confirmed by whole-genome sequencing, the Kpn_XM9 harbored a 5,523,536 bp chromosome and five plasmids with lengths being 128,129, 196,512, 84,812, 43,695, and 5,596 bp, respectively. Plasmid p1_Kpn_XM9 (128,219 bp) contained four resistance genes,
blaCTX-M-65
,
blaTEM-1B
,
rmt
B, and two copies of
blaKPC-2
. Genes
blaKPC-2
were bracketed by ISKpn17 and ISKpn16 within a new composite Tn3-like TnAs1. The two tandem repeats, positioned opposite each other, were spaced 93,447 bp apart in p1_Kpn_XM9. Kpn_XM9 belonged to K64 and sequence type (ST) 11. The Kpn_XM9 was resistant to amikacin, aztreonam, ticarcillin/clavulanic acid, piperacillin/tazobactam, ceftazidime, cefepime, imipenem, meropenem, tobramycin, ciprofloxacin, levofloxacin, doxycycline, minocycline, tigecycline, colistin, and trimethoprim/sulfamethoxazole; it was barely susceptible to CZA with a minimum inhibitory concentration of 8/4 µg/mL, which declined to 2/4 µg/mL after a 18,555 bp nucleotide was knocked out and one copy of
blaKPC-2
was sustained on p1_Kpn_XM9. Kpn_XM9 had virulence genes encoding Types 1 and 3 fimbriae, four siderophores, and capsular polysaccharide anchoring protein but no genes upregulating capsular polysaccharide synthesis. The Kpn_XM9 presented a classical phenotype with extreme drug resistance. The emergence of double copies of
blaKPC-2
in a single plasmid from the predominant ST11
K. pneumoniae
represents a new therapeutic challenge.
IMPORTANCE
With the wide use of ceftazidime–avibactam against carbapenem-resistant organisms, its resistance is increasingly documented; among the corresponding resistance mechanisms, mutations of
blaKPC-2
or
blaKPC-3
into other subtypes are dominant to date. However, more copies of
blaKPC-2
may also greatly increase the minimum inhibitory concentration of ceftazidime–avibactam, which could be conferred by transposon As1 and insertion sequence 26 and should be of concern.