Yamochi Tadanori, Ugajin Kazuhisa, On Rintaro, Inoue Sho, Ikeda Hiromi, Yamochi Toshiko, Takimoto Masafumi, Tokimatsu Issei
Department of Pathology, Showa University School of Medicine, Tokyo, Japan.
Clinical Laboratory, Showa University Hospital, Tokyo, Japan.
J Glob Antimicrob Resist. 2025 Mar;41:163-168. doi: 10.1016/j.jgar.2024.12.029. Epub 2025 Jan 14.
In Pseudomonas aeruginosa isolates, emerging meropenem resistance beyond imipenem resistance has become a problem. In this study, we aimed to investigate the relationship between the in vivo acquisition of antimicrobial resistance in fluoroquinolone- and carbapenem-resistant P. aeruginosa clinical isolates, the underlying molecular mechanisms, and exposure to antimicrobial agents.
Pulsed-field gel electrophoreses were performed to study the molecular relatedness of nine clinical isolates from a Japanese hospital. The minimal inhibitory concentrations of clinically relevant antibiotics were determined. Quantitative PCR was performed to analyze oprD, mexB, mexC, mexE, and mexY expression. DNA sequencing was performed to identify mutations.
Eight of nine strains were metallo-β-lactamase (MBL) negative, and one strain was MBL positive. All eight non-MBL-resistant strains harbored mutations in the quinoline-resistance-determining regions (QRDR) of gyrA, gyrB, or parC. Five of the eight non-MBL strains had T83I, two had D87N, and one had both T83I and D87N mutations in gyrA. Of these eight strains, three carrying gyrA mutations had another QRDR mutation in subunits, gyrB or parC, associated with mexY overexpression. Additionally, seven of eight dual fluoroquinolone and carbapenem-resistant isolates carried a premature termination codon within oprD, containing either F170L or L7 shortening.
In dual fluoroquinolone- and carbapenem-resistant P. aeruginosa, alterations in the OprD porin and the presence of an active EP are primary resistance mechanisms. Meropenem exposure within the past 59 days may have contributed to the selection of the oprD mutant overexpressing mexB, and meropenem exposure within the past 6 months may have contributed to meropenem resistance.
在铜绿假单胞菌分离株中，美罗培南耐药性超过亚胺培南耐药性已成为一个问题。在本研究中，我们旨在调查耐氟喹诺酮和碳青霉烯的铜绿假单胞菌临床分离株体内获得性抗菌药物耐药性、潜在分子机制与抗菌药物暴露之间的关系。
采用脉冲场凝胶电泳研究日本一家医院的9株临床分离株的分子相关性。测定临床相关抗生素的最低抑菌浓度。进行定量PCR分析oprD、mexB、mexC、mexE和mexY的表达。进行DNA测序以鉴定突变。
9株菌株中有8株金属β-内酰胺酶（MBL）阴性，1株MBL阳性。所有8株非MBL耐药菌株在gyrA、gyrB或parC的喹诺酮耐药决定区（QRDR）均存在突变。8株非MBL菌株中有5株在gyrA中有T83I突变，2株有D87N突变，1株同时有T83I和D87N突变。在这8株菌株中，3株携带gyrA突变的菌株在与mexY过表达相关的亚基gyrB或parC中存在另一个QRDR突变。此外，8株耐氟喹诺酮和碳青霉烯的双重耐药分离株中有7株在oprD内携带一个提前终止密码子，包含F170L或L7缩短。
在耐氟喹诺酮和碳青霉烯的双重耐药铜绿假单胞菌中，OprD孔蛋白的改变和活性外排泵（EP）的存在是主要耐药机制。过去59天内的美罗培南暴露可能有助于选择过表达mexB的oprD突变体，过去6个月内的美罗培南暴露可能导致了美罗培南耐药性。
