Liu Roushan, Zhang Jian, Du Xiaoli, Lv Yingying, Gao Xiangyu, Wang Yanyan, Wang Junrui
Department of Laboratory Medicine, Affiliated Hospital of Inner Mongolian Medical University, Hohhot, 010050, People's Republic of China.
Department of Laboratory Medicine, Bayannur People's Hospital, Bayannur City, 015000, People's Republic of China.
Infect Drug Resist. 2021 Feb 19;14:661-669. doi: 10.2147/IDR.S288991. eCollection 2021.
This study investigates the phenotypic and genotypic resistance features of OS-MRSA clinical isolates and their distinctive sensitivities to oxacillin.
1200 clinical isolates of were enrolled in this study. Automated antibiotics susceptibility tests on VITEK-2 and BD Phoenix-100, cefoxitin disc diffusion method, oxacillin broth microdilution method, , and gene detection were performed to identify OS-MRSA. MLST, PFGE, SCCmec, and spa typing methods were employed to determine genotypes of OS-MRSA isolates. Heterogeneous resistance of OS-MRSA isolates was detected using the population analysis profiling method, and PBP2a latex agglutination assay was used to detect the expression of PBP2a protein for 14 OS-MRSA isolates and their highly resistant subpopulations.
A total of 14 OS-MRSA isolates (1.17%, 14/1200) were identified, and all of the isolates were confirmed to be positive with the gene and negative with the gene. All of the 14 OS-MRSA isolates were identified as MSSA by VITEK-2, BD Phonenix-100, and oxacillin broth microdilution methods, while 21.43% (3/14) isolates were determined to be MRSA by the cefoxitin disk diffusion method. Genotypes of the 14 OS-MRSA isolates were diverse, and no dominant clones were identified. The prevalence of gene among 14 OS-MRSA isolates was high up to 64.29% (9/14). All of the isolates showed heterogeneous resistance to oxacillin, while frequencies of the oxacillin-resistant subpopulations ranged from 10 to 10 and differed significantly among different isolates.
The overall prevalence of OS-MRSA was relatively lower, but lower oxacillin MICs, low testing sensitivity of routine antibiotics susceptibility testing methods and weak PBP2a protein expression were observed in this study. 14 OS-MRSA showed diverse genotypes and universal heterogeneous resistance, and inaccurate laboratory identification and improper antimicrobial usage may promote the induction of highly resistant subpopulations and lead to treatment failure.
本研究调查了OS-MRSA临床分离株的表型和基因型耐药特征及其对苯唑西林的独特敏感性。
本研究纳入了1200株临床分离株。采用VITEK-2和BD Phoenix-100自动抗生素敏感性试验、头孢西丁纸片扩散法、苯唑西林肉汤微量稀释法以及基因检测来鉴定OS-MRSA。采用多位点序列分型（MLST）、脉冲场凝胶电泳（PFGE）、葡萄球菌染色体盒式Mec（SCCmec）和spa分型方法来确定OS-MRSA分离株的基因型。使用群体分析谱方法检测OS-MRSA分离株的异质性耐药，并使用PBP2a乳胶凝集试验检测14株OS-MRSA分离株及其高耐药亚群中PBP2a蛋白的表达。
共鉴定出14株OS-MRSA分离株（1.17%，14/1200），所有分离株的基因均为阳性，基因均为阴性。14株OS-MRSA分离株通过VITEK-2、BD Phonenix-100和苯唑西林肉汤微量稀释法均被鉴定为甲氧西林敏感金黄色葡萄球菌（MSSA），而通过头孢西丁纸片扩散法有21.43%（3/14）的分离株被判定为耐甲氧西林金黄色葡萄球菌（MRSA）。14株OS-MRSA分离株的基因型多样，未发现优势克隆。14株OS-MRSA分离株中基因的流行率高达64.29%（9/14）。所有分离株对苯唑西林均表现出异质性耐药，而苯唑西林耐药亚群的频率范围为10至10，不同分离株之间差异显著。
OS-MRSA的总体流行率相对较低，但本研究观察到苯唑西林最低抑菌浓度较低、常规抗生素敏感性试验方法的检测灵敏度较低以及PBP2a蛋白表达较弱。14株OS-MRSA表现出多样的基因型和普遍的异质性耐药，实验室鉴定不准确和抗菌药物使用不当可能会促进高耐药亚群的诱导并导致治疗失败。
