为了说明肺炎克雷伯菌Kpn_XM9的基因组和耐药性特征,该菌株具有转座子(Tn)As1,对头孢他啶-阿维巴坦(CZA)几乎不敏感。全基因组测序,基因缺失,抗菌敏感性,并进行了结合试验以说明Kpn_XM9的性状。正如全基因组测序所证实的那样,Kpn_XM9拥有一条5,523,536bp的染色体和五个质粒,长度分别为128,129,196,512,84,812,43,695和5,596bp,分别。质粒p1_Kpn_XM9(128,219bp)含有4个抗性基因,blaCTX-M-65,blaTEM-1B,rmtB,还有两份BlaKPC-2.基因blaKPC-2在新的复合Tn3样TnAs1中被ISKpn17和ISKpn16包围。两个串联重复,彼此相对,在p1_Kpn_XM9中间隔93,447bp。Kpn_XM9属于K64和序列类型(ST)11。Kpn_XM9对阿米卡星耐药,氨曲南,替卡西林/克拉维酸,哌拉西林/他唑巴坦,头孢他啶,头孢吡肟,亚胺培南,美罗培南,妥布霉素,环丙沙星,左氧氟沙星,多西环素,米诺环素,替加环素,粘菌素,和甲氧苄啶/磺胺甲恶唑;它对CZA几乎不敏感,最小抑制浓度为8/4µg/mL,在敲除18,555bp的核苷酸并在p1_Kpn_XM9上维持一个拷贝的blaKPC-2后,该值下降到2/4µg/mL。Kpn_XM9具有编码1型和3型菌毛的毒力基因,四个铁载体,和荚膜多糖锚定蛋白,但没有基因上调荚膜多糖合成。Kpn_XM9呈现具有极端耐药性的经典表型。来自主要的ST11K.肺炎克雷伯菌的单个质粒中blaKPC-2的双拷贝的出现代表了新的治疗挑战。随着头孢他啶-阿维巴坦对耐碳青霉烯类生物的广泛使用,它的抗性越来越多地记录在案;在相应的抗性机制中,迄今为止,blaKPC-2或blaKPC-3向其他亚型的突变占主导地位。然而,更多的blaKPC-2拷贝也可能大大增加头孢他啶-阿维巴坦的最低抑制浓度,这可以由转座子As1和插入序列26赋予,应该引起关注。
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, rmtB, 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.IMPORTANCEWith 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.