Objectives As part of an active MRSA surveillance programme in our neonatal ICU, we identified nares surveillance cultures from two infants that displayed heterogeneity in methicillin resistance between isolated subclones that lacked mecA and mecC. Methods The underlying mechanism for the modified Staphylococcus aureus (MODSA) methicillin-resistance phenotype was investigated by WGS. Results Comparison of finished-quality genomes of four MODSA and four MSSA subclones demonstrated that the resistance changes were associated with unique truncating mutations in the gene encoding the cyclic diadenosine monophosphate phosphodiesterase enzyme GdpP or a non-synonymous substitution in the gene encoding PBP2. Conclusions These two cases highlight the difficulty in identifying non-mecA, non-mecC-mediated MRSA isolates in the clinical microbiology laboratory, which leads to difficulties in implementing appropriate therapy and infection control measures.

中文翻译：

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在新生儿重症监护患者中检测到改良的耐甲氧西林金黄色葡萄球菌

目标 作为我们新生儿 ICU 中积极 MRSA 监测计划的一部分，我们从两个婴儿中鉴定出鼻孔监测培养物，这些培养物在缺乏 mecA 和 mecC 的分离亚克隆之间表现出甲氧西林耐药性的异质性。方法通过WGS研究修饰金黄色葡萄球菌（MODSA）耐甲氧西林表型的潜在机制。结果 比较四个 MODSA 和四个 MSSA 亚克隆的最终质量基因组表明，抗性变化与编码环二腺苷磷酸二酯酶 GdpP 的基因中的独特截短突变或编码 PBP2 的基因中的非同义替换有关。结论 这两个案例突出了在临床微生物实验室中识别非 mecA、非 mecC 介导的 MRSA 分离株的困难，