Clinical Significance and Molecular Characterization of Nonsporulating Molds Isolated from the Respiratory Tracts of Bronchopulmonary Mycosis Patients with Special Reference to Basidiomycetes

Abstract

dNonsporulating molds (NSMs), especially basidiomycetes, have predominantly been reported as human pathogens responsible for allergic and invasive disease. Their conventional identification is problematic, as many isolates remain sterile in culture. Thus, inconclusive culture reports might adversely affect treatment decisions. The clinical significance of NSMs in pulmonary mycoses is poorly understood. We sequenced the internal transcribed spacer (ITS) region and D1/D2 domain of the larger subunit (LSU) of 52 NSMs isolated from respiratory specimens. The basidiomycetes were the predominant NSMs, of which Schizophyllum commune was the most common agent in allergic bronchopulmonary mycosis (ABPM), followed by Ceriporia lacerata in invasive fungal disease. Porostereum spadiceum, Phanaerochaete stereoides, Neosartorya fischeri, and Marasmiellus palmivorus were the other molds observed. Application of ITS and LSU region sequencing identified 92% of the isolates. The antifungal susceptibility data revealed that all basidiomycetes tested were susceptible to amphotericin B and resistant to caspofungin, fluconazole, and flucytosine. Except for 3 isolates of S. commune and a solitary isolate of M. palmivorus, all basidiomycetes had low MICs for itraconazole, posaconazole, and voriconazole. Basidiomycetes were isolated from patients with ABPM, invasive pulmonary mycosis/pneumonia, or fungal balls. In addition, the majority of the basidiomycetes were isolated from patients with chronic respiratory disorders who were sensitized to one of the basidiomycetous fungi and demonstrated precipitating antibodies against the incriminating fungi, indicating an indolent tissue reaction. Thus, isolation of basidiomycetes from the lower respiratory tract could be significant, and it is important to monitor these patients in order to prevent subsequent lung damage.

Schizophyllum radiatum, an Emerging Fungus from Human Respiratory Tract

“…This precludes their morphological identification. In routine laboratories, the induction of sporulation usually requires about 3 weeks and is associated with high failure rates (34). Therefore, molecular methods, such as DNA sequence analysis, are required for accurate identification of this kind of fungus that fails to sporulate (13).…”

“…Therefore, molecular methods, such as DNA sequence analysis, are required for accurate identification of this kind of fungus that fails to sporulate (13). The most commonly sequenced markers in Schizophyllum are the ITS and D1/D2 regions of the LSU (13,33,34). However, Schizophyllum has a highly conserved ITS region, which is often difficult to amplify and to sequence.…”

“…However, Schizophyllum has a highly conserved ITS region, which is often difficult to amplify and to sequence. Singh et al (34) reported this difficulty, being unable to amplify 3 of 27 strains that (35). It would seem clear, then, that other, more appropriate markers need to be adopted for reliable species identification.…”

“…for future comparison. The optimum management of infections by S. commune has not yet been determined (14,31,34). However, treatment with antifungal drugs has given encouraging results.…”

“…In addition, some species, such as S. commune and S. radiatum, have long been considered conspecific due to their morphological similarity (2). Recently, molecular methods have more successfully discriminated between various basidiomycetous molds (13,33,34). Singh et al (34) proposed sequencing the internal transcribed spacer (ITS) and D1/D2 regions for the identification of basidiomycetes.…”