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Phenotypic Switching and β‐ N ‐Acetylhexosaminidase Activity of the Pathogenic Yeast Trichosporon asahii
Author(s) -
Ichikawa Tomoe,
Sugita Takashi,
Wang Li,
Yokoyama Koji,
Nishimura Kazuko,
Nishikawa Akemi
Publication year - 2004
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.2004.tb03519.x
Subject(s) - trichosporon , biology , microbiology and biotechnology , virulence , corpus albicans , candida albicans , agar , enzyme , yeast , cryptococcus neoformans , fungi imperfecti , bacteria , biochemistry , gene , genetics
The pathogenic yeast Trichosporon asahii is the major causative agent of deep‐seated trichosporonosis in immunocompromised patients. Although infection by this microorganism is becoming increasingly frequent, information related to its pathogenicity and virulence factors is still limited. Therefore, we investigated phenotypic switching in colony morphology, and the production of extracellular enzymes as a virulence factor. Sixty‐one clinical isolates of T. asahii produced four different morphological types on Sabouraud dextrose agar (SDA): 69% WF (white farinose), 18% WP (white pustular), 10% Y (yellowish white), and 3% WC (white cerebriform). Strains of the three major types (WF, WP, and Y) produced two to five colony types when cultured on SDA at 37 C. The frequency of switching between colony types was 10 –2 to 10 –4 , as in Candida albicans and Cryptococcus neoformans . Notably, most of the colonies switched to the smooth (S) type irreversibly, at frequencies of 10 –2 to 10 –3 . No secreted aspartic proteinase or phospholipase activity was detected in T. asahii , while β‐ N ‐acetylhexosaminidase activity, which catalyzes the hydrolysis of terminal nonreducing N ‐acetyl‐ D ‐hexosamine residues in N ‐acetyl‐β‐ D ‐hexosaminides, was found. Furthermore, enzymatic activity of the S type was significantly greater than that of the parent type in all strains. No other clinically relevant Trichosporon species ( T mucoides, T inkin , and T ovoides ) produced this enzyme. These results provide basal information for understanding the pathogenic potential of T asahii .