Department of Microbiology, Intensive Care Unit and Unidad de Investigación, Hospital Universitari Son Espases, Instituto de Investigación Illes Balears (IdISBa), Palma de Mallorca, Spain.
Department of Microbiology and Infectious Diseases, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
Antimicrob Agents Chemother. 2017 Oct 24;61(11). doi: 10.1128/AAC.01589-17. Print 2017 Nov.
This study assessed the molecular epidemiology, resistance mechanisms, and susceptibility profiles of a collection of 150 extensively drug-resistant (XDR) clinical isolates obtained from a 2015 Spanish multicenter study, with a particular focus on resistome analysis in relation to ceftolozane-tazobactam susceptibility. Broth microdilution MICs revealed that nearly all (>95%) of the isolates were nonsusceptible to piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, imipenem, meropenem, and ciprofloxacin. Most of them were also resistant to tobramycin (77%), whereas nonsusceptibility rates were lower for ceftolozane-tazobactam (31%), amikacin (7%), and colistin (2%). Pulsed-field gel electrophoresis-multilocus sequence typing (PFGE-MLST) analysis revealed that nearly all of the isolates belonged to previously described high-risk clones. Sequence type 175 (ST175) was detected in all 9 participating hospitals and accounted for 68% ( = 101) of the XDR isolates, distantly followed by ST244 ( = 16), ST253 ( = 12), ST235 ( = 8), and ST111 ( = 2), which were detected only in 1 to 2 hospitals. Through phenotypic and molecular methods, the presence of horizontally acquired carbapenemases was detected in 21% of the isolates, mostly VIM (17%) and GES enzymes (4%). At least two representative isolates from each clone and hospital ( = 44) were fully sequenced on an Illumina MiSeq. Classical mutational mechanisms, such as those leading to the overexpression of the β-lactamase AmpC or efflux pumps, OprD inactivation, and/or quinolone resistance-determining regions (QRDR) mutations, were confirmed in most isolates and correlated well with the resistance phenotypes in the absence of horizontally acquired determinants. Ceftolozane-tazobactam resistance was not detected in carbapenemase-negative isolates, in agreement with sequencing data showing the absence of mutations. The unique set of mutations responsible for the XDR phenotype of ST175 clone documented 7 years earlier were found to be conserved, denoting the long-term persistence of this specific XDR lineage in Spanish hospitals. Finally, other potentially relevant mutations were evidenced, including those in penicillin-binding protein 3 (PBP3), which is involved in β-lactam (including ceftolozane-tazobactam) resistance, and FusA1, which is linked to aminoglycoside resistance.
本研究评估了 150 株广泛耐药（XDR）临床分离株的分子流行病学、耐药机制和药敏谱，这些分离株来自 2015 年西班牙多中心研究，特别关注与头孢洛扎他唑巴坦药敏性相关的耐药组分析。肉汤微量稀释 MIC 结果显示，几乎所有（>95%）分离株对哌拉西林-他唑巴坦、头孢他啶、头孢吡肟、氨曲南、亚胺培南、美罗培南和环丙沙星均不敏感。其中大多数对妥布霉素（77%）也耐药，而头孢洛扎他唑巴坦（31%）、阿米卡星（7%）和黏菌素（2%）的耐药率较低。脉冲场凝胶电泳-多位点序列分型（PFGE-MLST）分析显示，几乎所有分离株均属于先前描述的高危克隆。9 家参与医院均检出 175 型序列（ST175），占 XDR 分离株的 68%（=101），其次是 244 型（=16）、253 型（=12）、235 型（=8）和 111 型（=2），仅在 1 至 2 家医院中检出。通过表型和分子方法，在 21%的分离株中检测到水平获得的碳青霉烯酶，主要是 VIM（17%）和 GES 酶（4%）。每个克隆和医院至少选择 2 个有代表性的分离株（=44），在 Illumina MiSeq 上进行全序列测序。在大多数分离株中证实了导致β-内酰胺酶 AmpC 过表达、外排泵 OprD 失活和/或喹诺酮耐药决定区（QRDR）突变等经典突变机制，与无水平获得决定因素时的耐药表型相关性良好。在碳青霉烯酶阴性分离株中未检测到头孢洛扎他唑巴坦耐药，这与测序数据显示无突变相符。7 年前首次发现的导致 ST175 克隆广泛耐药表型的独特突变集被发现保持不变，这表明该特定 XDR 谱系在西班牙医院长期存在。最后，还发现了其他潜在相关的突变，包括参与β-内酰胺（包括头孢洛扎他唑巴坦）耐药的青霉素结合蛋白 3（PBP3）和与氨基糖苷类耐药相关的 FusA1 的突变。
