Hu Dakang, Wang Shijie, Xu Mengqiao, Zhang Jin, Luo Xinhua, Zhou Wei, Ma Qinfei, Ma Xiaobo
Department of Laboratory Medicine, Taizhou Municipal Hospital, Taizhou, Zhejiang, China.
Department of Clinical Laboratory, Xiamen Humanity Hospital Fujian Medical University, Xiamen, Fujian, China.
Microbiol Spectr. 2024 Aug 6;12(8):e0033124. doi: 10.1128/spectrum.00331-24. Epub 2024 Jul 10.
To illustrate the genomic and drug resistance traits of the 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, , , B, and two copies of . Genes 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 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 in a single plasmid from the predominant ST11 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 or into other subtypes are dominant to date. However, more copies of 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.
为阐明携带转座子(Tn)As1且对头孢他啶-阿维巴坦(CZA)几乎不敏感的肺炎克雷伯菌XM9(Kpn_XM9)的基因组和耐药特性,开展了全基因组测序、基因缺失、药敏试验和接合试验以阐明Kpn_XM9的特性。全基因组测序证实,Kpn_XM9含有一条5,523,536 bp的染色体和5个质粒,长度分别为128,129、196,512、84,812、43,695和5,596 bp。质粒p1_Kpn_XM9(128,219 bp)包含4个耐药基因, 、 、B和2个 的拷贝。基因 在一个新的复合Tn3样转座子TnAs1中被ISKpn17和ISKpn16包围。两个串联重复序列彼此相对,在p1_Kpn_XM9中相隔93,447 bp。Kpn_XM9属于K64型和序列型(ST)11。Kpn_XM9对阿米卡星、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、黏菌素和甲氧苄啶/磺胺甲恶唑耐药;它对CZA几乎不敏感,最低抑菌浓度为8/4 μg/mL,在敲除18,555 bp核苷酸且p1_Kpn_XM9上保留一个 拷贝后降至2/4 μg/mL。Kpn_XM9具有编码1型和3型菌毛、4种铁载体和荚膜多糖锚定蛋白的毒力基因,但没有上调荚膜多糖合成的基因。Kpn_XM9呈现出具有极端耐药性的经典表型。在主要的ST11单一质粒中出现 的两个拷贝代表了新的治疗挑战。重要性随着头孢他啶-阿维巴坦广泛用于治疗耐碳青霉烯类微生物,其耐药情况越来越多地被记录;在相应的耐药机制中, 或 突变为其他亚型至今仍占主导。然而,更多拷贝的 也可能极大地增加头孢他啶-阿维巴坦的最低抑菌浓度,这可能由转座子As1和插入序列26导致,值得关注。