Isolation and identification of Malassezia furfur from lower respiratory tract secretions / 中华检验医学杂志

ABSTRACT

Objectives To culture and isolate Malassezia furfur which were suspected in sputum smears,and then to identify the isolates systematically.Methods From March 2010 to September 2011,133 lower respiratory tract secretion samples were collected in Beijing Hospital of the Ministry of Health which were suspected containing Malassezia furfur by Parker ink staining.The samples were inoculated and cultured on CHROMagar mediums containing 1％ Tween 60 ( which was modified from Candida chromogenic media) in the atmospheric environment at 35 ℃.The suspected colonies were selected and cultured on both SDA plates containing 0.5％ Tween 40 and SDA plates containing 0.5％ Tween 60.The traditional phenotypic identification methods were used to identify the pure colonies,including staining,growth on Sabouraud agar plates,Tween test,decomposing Escalin,Catalase test,Tween precipitation test and castor oil test.Then the suspected colonies were identified by analyzing the sequences of 18s rRNAs.Results The isolation rate of Malasseziafurfur from lower respiratory tract secretions was 47.4％ (63/133) and 63 strains were also identified as Malassezia furfur by traditional phenotypic identification methods combined with the 18s rRNA gene sequence analysis.Malassezia can be significantly distinguished from Candida by direct smear of the specimen with Parker ink staining.Conclusions Malassezia furfur was found as pink colonies on modified Candida chromogenic media which were significantly different from other Candida colonies.The isolation rate of lower respiratory tract secretions can be improved by modified Candida chromogenic media.The identification accuracy can be further improved by combining traditional phenotypic identification methods with 18s rRNA sequence analysis.