Chen Liang, Xie Zeqiang, Jian Jiyong
Clin Lab. 2025 May 1;71(5). doi: 10.7754/Clin.Lab.2024.241040.
This study aimed to clarify the microbiological characteristics of carbapenem-resistant Escherichia coli (CRECO) due to New Delhi metallo-β-lactamase (NDM)-producing from recurrent urinary tract infection (RUTI) patients.
CRECO isolates were isolated from the urine of RUTI patients, identified with VITEK 2 compact system, and confirmed by MALDI-TOF MS. Antimicrobial susceptibility testing (AST) was performed with VITEK 2 compact system and Kirby-Bauer (K-B) method. Disk diffusion was used for extended spectrum beta-lactamase (ESBL) test. Phenotypic assays, including modified Hodge test (MHT), EDTA-modified carbapenem inactivation method (eCIM), and modified carbapenem inactivation method (mCIM), were performed to screen the carba-penemase. The antibiotic resistance genes were detected by polymerase chain reaction (PCR). Multilocus sequence typing (MLST) was performed for molecular typing of the strains.
Among 63 CRECO strains, 22 (34.9%) strains were NDM-positive, in which NDM-5 accounted for 68.2% (15/22), NDM-1 accounted for 22.7% (5/22), and NDM-3 accounted for 9.1% (2/22). Among the 22 strains, 20 (90.9%) strains were co-carrying ESBLs genes, 12 (54.6%) strains were co-carrying blaCTX and blaTEM, 8 (36.4%) strains were co-carrying blaCTX or blaTEM, and 5 strains were co-carrying AmpC genes. BlaCMY-6 and blaCMY-156 ac-counted for 9.1% (2/22) and blaCMY-42 and blaDHA-1 accounted for 4.5% (1/22). Ten (45.5%) strains were co-carrying quinolone resistance genes. Three (13.6%) strains were co-carrying colistin resistance genes mcr-1. Six (27.3%) strains showed OmpF-expressed loss. Fourteen strains were positive and 8 strains were negative in the MHT, but mCIM and eCIM were both positive; the results of double-disc synergy method for detection of ESBLs were all negative in NDM-positive CRECO strains. The NDM-producing CRECO strains showed high-resistant rate to most antibiotics.
The antibiotic resistance mechanisms of NDM-positive CRECO are the coexistence of multiple resistance genes and/or the loss of or lesser expression of OMP. The emergence of mcr-1 gene in CRECO should be paid more attention by clinicians and microbiologists. Further surveillance should be strengthened to study the microbiological characteristics in order to control infection caused by NDM-positive CRECO better.
本研究旨在阐明复发性尿路感染（RUTI）患者中产生新德里金属β-内酰胺酶（NDM）的耐碳青霉烯类大肠埃希菌（CRECO）的微生物学特征。
从RUTI患者尿液中分离出CRECO菌株，采用VITEK 2 compact系统进行鉴定，并通过基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）进行确认。使用VITEK 2 compact系统和 Kirby-Bauer（K-B）法进行药敏试验（AST）。纸片扩散法用于超广谱β-内酰胺酶（ESBL）检测。进行包括改良 Hodge试验（MHT）、EDTA改良碳青霉烯灭活法（eCIM）和改良碳青霉烯灭活法（mCIM）在内的表型分析以筛选碳青霉烯酶。通过聚合酶链反应（PCR）检测抗生素耐药基因。进行多位点序列分型（MLST）以对菌株进行分子分型。
在63株CRECO菌株中，22株（34.9%）为NDM阳性，其中NDM-5占68.2%（15/22），NDM-1占22.7%（5/22），NDM-3占9.1%（2/22）。在这22株菌株中，20株（90.9%）同时携带ESBLs基因，12株（54.6%）同时携带blaCTX和blaTEM，8株（36.4%）同时携带blaCTX或blaTEM，5株同时携带AmpC基因。BlaCMY-6和blaCMY-156占9.1%（2/22），blaCMY-42和blaDHA-1占4.5%（1/22）。10株（45.5%）菌株同时携带喹诺酮耐药基因。3株（13.6%）菌株同时携带黏菌素耐药基因mcr-1。6株（27.3%）菌株显示OmpF表达缺失。14株MHT结果为阳性，8株为阴性，但mCIM和eCIM均为阳性；NDM阳性CRECO菌株中ESBLs检测的双纸片协同法结果均为阴性。产NDM的CRECO菌株对大多数抗生素显示出高耐药率。
NDM阳性CRECO的抗生素耐药机制是多种耐药基因共存和/或外膜蛋白（OMP）缺失或表达减少。CRECO中mcr-1基因的出现应引起临床医生和微生物学家更多关注。应加强进一步监测以研究微生物学特征，以便更好地控制NDM阳性CRECO引起的感染。
