血液分离利奈唑胺耐药头状葡萄球菌耐药性及相关临床特征分析

Resistance mechanism and clinical feature of linezolid-resistant Staphylococcus capitis isolated from blood samples

目的了解利奈唑胺耐药头状葡萄球菌血流感染的临床及病原菌耐药特点。方法收集利奈唑胺耐药头状葡萄球菌血液分离株,并测定药敏;PCR及测序检测耐药基因cfr及23S rRNA耐药突变;临床分离株用脉冲场凝胶电泳(PFGE)进行同源性分析;病例资料分析。结果从3例患者血标本中分离到5株利奈唑胺耐药头状葡萄球菌;这些临床分离株对苯唑西林、左氧氟沙星、庆大霉素等常用抗菌药物耐药,仅对糖肽类、利福平和甲氧苄啶-磺胺甲唑敏感;5株耐药菌的23S rRNA均存在突变,4株携带cfr基因;PFGE显示5株临床株属同一谱型;3例患者均有留置深静脉导管,2例曾接受利奈唑胺治疗。结论利奈唑胺耐药头状葡萄球菌呈多重耐药表型;头状葡萄球菌对利奈唑胺耐药由23S rRNA突变及cfr基因导致;长疗程使用利奈唑胺及留置深静脉导管可能是此类耐药菌感染的危险因素。

Objective To understand the resistance mechanism and clinical feature of linezolid-resistant S. capitis isolated from blood samples. Methods Antimicrobial susceptibility testing was carried out to determine the susceptibility of clinical strains. PCR and sequencing analysis were used to analyze cfr gene and 23S rRNA mutation, which were associated with linezolid resistance. Patterns of pulsed-field gel electrophoresis （PFGE） were analyzed in combination with clinical data to understand the clinical feature of S. capitis strains. Results Five linezolid-resistant S. capitis strains were isolated from blood samples of 3 patients. These strains were resistant not only to linezolid, but also to most of the commonly used antimicrobial agents except glycopeptides, rifampin, and trimethoprim-sulfamethoxazole. Mutation was identified in 23S rRNA genes of all the five strains and cfr gene was found in four of the five strains. PFGE typing showed the same type, which supported the homology of the 5 strains. Three patients had deep vein indwelling catheter and two of them were treated with linezolid. Conclusions Linezolid-resistant S. capitis isolates showed the phenotype of resistance to multiple antimicrobial agents. Linezolid resistance may be mediated by cfr gene and 23 S rRNA mutations in S. capitis. Long-term use of deep vein indwelling catheter and linezolid treatment may increase the risk of linezolid-resistant S. capitis infection.