血培养奥默柯达酵母鉴定方法学比较及药物敏感性

Identification and antifungal susceptibility profile of Kodamaea ohmeri isolated from blood cultures

目的收集中国侵袭性真菌耐药监测网的血培养阳性奥默柯达酵母,进行表型鉴定方法学比较及体外抗真菌药物敏感性测定。方法收集7年间中国16所医院分离的34株血培养阳性的奥默柯达酵母分离株进行研究。以26S rDNA测序为金标准,对3种表型鉴定方法进行比较并回顾了当地参与医院提交的原始鉴定结果。采用标准微量肉汤稀释法(BMD)测定奥默柯达酵母体外对抗真菌药物的敏感性。结果使用VITEK 2-Compact和VITEK MS分别对34株奥默柯达酵母进行菌种鉴定,明确获得种鉴定结果分别达94.1%和100%。对于Bruker MS,用直接涂布法和甲酸-乙醇蛋白提取法分别有3株(8.8%)和33株(97.1%)分离菌株正确鉴定到种水平。然而只有20株(58.8%)分离株最初被当地医院正确鉴定为奥默柯达酵母。CHROM agar的鉴定错误率最高(6/6)。根据BMD结果,MIC90最高见于氟康唑(16mg/L),其次是米卡芬净、卡泊芬净、伊曲康唑和两性霉素B(1mg/L)、5-氟胞嘧啶和伏立康唑(0.5mg/L)、泊沙康唑(0.25mg/L)。结论奥默柯达酵母感染应引起重视,早期准确快速鉴定及抗真菌药物敏感性检测对其感染治疗至关重要。

Objective This study was conducted to compare different phenotypic methods in identification of Kodamaea ohmeri and investigate the antifungal susceptibility in vitro. Methods Thirty-four strains of K. ohmeri were isolated from blood cultures in16 hospitals across China over a seven-year period. Three phenotypic methods were assessed for their performance in identification of K. ohmeri against a gold standard, 26 S rDNA sequencing. Original identification results submitted by the participating local hospitals were reviewed. Standard broth microdilution(BMD) method was used to determine the in vitro antifungal susceptibility. Results Accurate species identification was achieved in 94.1% and 100% of the cases by VITEK 2-Compact and VITEK MS, respectively. For Bruker MS, 8.8% and 97.1% of the isolates were correctly identified to species level using direct streaking technique and protein extraction method, respectively. Only 20(58.8%) isolates were initially correctly identified as K. ohmeri by local hospitals. The highest misidentification rate(100%, 6/6) was observed in CHROM agar. According to BMD, the highest MIC90 was seen for fluconazole(16 mg/L), followed by 1 mg/L for micafungin, caspofungin, itraconazole and amphotericin B, 0.5 mg/L for 5-fluorocytosine and voriconazole, 0.25 mg/L for posaconazole. Conclusions This study highlights the importance of early accurate identification and antifungal susceptibility testing of K. ohmeri isolates for appropriate antifungal therapy.