The aim of this study was to detect CMY-type beta-lactamases in E. coli isolates obtained from paediatric patients. In total, 404 infection-causing E. coli isolates resistant to third and fourth generation cephalosporins (3GC, 4GC) were collected from paediatric patients over a 2 years period. The identification and susceptibility profiles were determined with an automated microbiology system. Typing of blaCMY and other beta-lactamase genes (blaTEM, blaSHV, blaCTX-M, blaVIM, blaIMP, blaKPC, blaNDM, blaOXA and blaGES) was realized by PCR and sequencing. Phenotypic detection of AmpC-type enzymes was performed using boronic acid (20 mg/mL) and cloxacillin (20 mg/mL) as inhibitors, and the production of extended-spectrum beta-lactamases was determined with the double-disk diffusion test with cefotaxime (CTX) and ceftazidime (CAZ) discs alone and in combination with clavulanic acid. The CarbaNP test and modified carbapenem inhibition method (mCIM) were used for isolates with decreased susceptibility to carbapenems. The clonal origin of the isolates was established by pulsed-field gel electrophoresis (PFGE), phylotyping method and multilocus sequence typing. CMY-type beta-lactamases were detected in 18 isolates (4.5%). The allelic variants found were CMY-2 (n = 14) and CMY-42 (n = 4). Of the E. coli strains with CMY, the AmpC phenotypic production test was positive in 11 isolates with cloxacillin and in 15 with boronic acid. ESBL production was detected in 13 isolates. Coexistence with other beta-lactamases was observed such as CTX-M-15 ESBL and original spectrum beta-lactamases TEM-1 and TEM-190. In one isolate, the CarbaNP test was negative, the mCIM was positive, and OXA-48 carbapenemase was detected. Phylogroup A was the most frequent (n = 9) followed by B2, E and F (n = 2, respectively), and through PFGE, no clonal relationship was observed. Eleven different sequence types (ST) were found, with ST10 high-risk clone being the most frequent (n = 4). Seventy-two percent of the isolates were from health care-associated infections; the mortality rate was 11.1%. This is the first report in Mexico of E. coli producing CMY isolated from paediatric patients, demonstrating a frequency of 4.5%. In addition, this is the first finding of E. coli ST10 with CMY-2 and OXA-48.

中文翻译：

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墨西哥一家三级医院儿科患者大肠杆菌分离株中 CMY 型 β-内酰胺酶的检测

本研究的目的是检测从儿科患者获得的大肠杆菌分离株中的 CMY 型 β-内酰胺酶。在 2 年的时间里，总共从儿科患者中收集了 404 株对第三代和第四代头孢菌素（3GC、4GC）耐药的大肠杆菌分离株。鉴定和敏感性曲线是用自动微生物系统确定的。blaCMY 和其他 β-内酰胺酶基因（blaTEM、blaSHV、blaCTX-M、blaVIM、blaIMP、blaKPC、blaNDM、blaOXA 和 blaGES）的分型通过 PCR 和测序实现。使用硼酸 (20 mg/mL) 和氯唑西林 (20 mg/mL) 作为抑制剂进行 AmpC 型酶的表型检测，使用头孢噻肟 (CTX) 和头孢他啶 (CAZ) 圆片单独和与克拉维酸联合使用双圆片扩散试验测定超广谱 β-内酰胺酶的产生。CarbaNP 测试和改良的碳青霉烯抑制方法 (mCIM) 用于对碳青霉烯类药物敏感性降低的分离株。通过脉冲场凝胶电泳（PFGE）、系统发育法和多位点序列分型确定了分离物的克隆来源。在 18 个分离株（4.5%）中检测到 CMY 型 β-内酰胺酶。发现的等位基因变体是 CMY-2 (n = 14) 和 CMY-42 (n = 4)。在带有 CMY 的大肠杆菌菌株中，11 株含有氯唑西林的分离株和 15 株含有硼酸的 AmpC 表型生产试验呈阳性。在 13 个分离株中检测到 ESBL 产生。观察到与其他 β-内酰胺酶共存，例如 CTX-M-15 ESBL 和原始光谱 β-内酰胺酶 TEM-1 和 TEM-190。在一个分离株中，CarbaNP 测试为阴性，mCIM 为阳性，并检测到 OXA-48 碳青霉烯酶。系统群 A 是最常见的（n = 9），其次是 B2、E 和 F（分别为 n = 2），并且通过 PFGE，没有观察到克隆关系。发现了 11 种不同的序列类型 (ST)，其中 ST10 高风险克隆是最常见的 (n = 4)。72% 的分离株来自卫生保健相关感染；死亡率为11.1%。这是墨西哥首次报道从儿科患者中分离出的产生 CMY 的大肠杆菌，显示频率为 4.5%。此外，这是首次发现带有 CMY-2 和 OXA-48 的大肠杆菌 ST10。