阿萨希毛孢子菌和头状地霉菌血流感染的鉴别诊断初探

Differential diagnosis in bloodstream infection with Trichosporon asahii and Geotrichum capitatum

摘要:

目的为临床微生物实验室建立少见类酵母样真菌血流感染诊断和鉴别诊断方法提供参考。方法采用临床资料分析，形态学检查、生化反应和分子生物学技术相结合的方法，对阿萨希毛孢子菌和头状地霉菌血流感染进行诊断和鉴别诊断。结果病例1和病例2类酵母样真菌血流感染均发生于患者白血病化疗后粒细胞缺乏期，患者病情严重，相似度高。挑取病例1、2血平皿上培养菌落进行革兰染色镜检，前者可见菌丝、关节孢子和小分生孢子，菌丝分枝分隔粗细不等，关节孢子长短不一，多呈矩形和桶型；后者可见中隔透明的菌丝断裂成关节孢子，呈长方形，不产生芽生分生孢子。API 20C AUX鉴定，提示分别为阿萨希毛孢子菌、头状地霉菌。所得序列在NCBI上进行比对，结果分别为阿萨希毛孢子菌、头状双足囊菌头状地霉菌的有性期。结论综合应用多种技术手段有助于提高类酵母样真菌血流感染诊断的准确性。将毛孢子菌和地霉菌鉴定到种水平有利于提高临床对该类少见真菌感染的认识，合理选择抗真菌药物和改善预后。

Abstract:

ObjectiveTo provide reference for establishing diagnosis and differential diagnosis methods of rare yeastlike fungal bloodstream infection for clinical microbiology laboratory. MethodsTrichosporon asahii (T. asahii) and Geotrichum capitatum(G.capitatum) bloodstream infection was diagnosed and differentially diagnosed through clinical data analysis, morphological examination, biochemical reactions,and molecular biology technology.ResultsTwo types of yeastlike fungal bloodstream infections in case 1 and case 2 both occurred in leukemia agranulocytosis phase after chemotherapy, such infections were serious and highly similar. The cultivated colonies on blood agar plates of case 1 and case 2 were performed gram stain and microscopic examination. Hyphae, arthrospores and microconidia were visible in the former, thickness of hyphae branches and length of arthrospores were different, most presented rectangular and barrel shape; the latter can be seen hyphae with transparent septum broken up into arthrospores, presented rectangular shape, did not produce blastoconidia. Identification with API 20C AUX showed that they were T. asahii and G. capitatum. The PCR product sequences were compared with NCBI, suggesting that T. asahii  and G. capitatum were at sexual stage.  ConclusionComprehensive application of a variety of technical methods is helpful for improving the diagnosis accuracy of bloodstream infection with yeastlike fungi, identifying Trichosporon and Geotrichum to the species level may help physicians to understand such rare fungal infection, choose antifungal agents rationally, and improve clinical prognosis.［Key words］bloodstream infection; Trichosporon asahii; Geotrichum capitatum; yeastlike fungus; differential diagnosis