Supplemental utility of nested PCR for the pathological diagnosis of disseminated trichosporonosis

Abstract

Disseminated trichosporonosis is known to be a severe opportunistic mycosis and has a high mortality rate. In autopsy cases, it is often difficult to diagnose as trichosporonosis because the causative Trichosporon species are pathologically similar to other fungi, especially the Candida species. Immunohistochemical analysis is essential for the differential diagnosis, but an antibody to Trichosporon is not available commercially. In the present study, we investigated the supplemental utility of nested polymerase chain reaction (PCR) for the pathological diagnosis of trichosporonosis from formalin-fixed and paraffin-embedded tissues. Total DNA was purified from 30 major organs in three autopsy cases, and Trichosporon DNA was specifically amplified by nested PCR using three sets of primers. Of 22 organs in which Grocott's stain was positive for fungal infection, 170- and 259-bp PCR products were detected in 20 (91%) and 12 (55%) organs, respectively. In short-term fixation (about 1 day), these bands were highly detected in ten (100%) and nine (90%) organs, whereas the detection efficiency tended to decrease after long-term fixation and decalcification. No PCR product of 412 bp was detected in any organs. These findings suggest that nested PCR from short-term-fixed tissues is useful for supportive pathological diagnosis of disseminated trichosporonosis.

Current Knowledge of Trichosporon spp. and Trichosporonosis

“…Sano et al (158) extracted DNAs from 30 different tissue sections obtained from major organs of 3 autopsy cases of disseminated trichosporonosis. The fungemic patients had been previously diagnosed by blood cultures and analysis with the Vitek 2 compact system to be infected by T. asahii.…”

“…After 1 day of fixation, only one-third of the collected samples were positive by both Grocott staining and amplification of the 170-and 259-bp bands. Longer tissue fixation of between 6 and 21 days considerably diminished the amplification of the 259-bp fragment (2 of 12) (158).…”

“…Although there is no consensus on the route of infection of human beings, close contact with an incident case, hair humidity, and the length of the scalp hair have all been recognized as risk factors for acquiring white piedra (96,153,158,197).…”

The development of animal infection models and antifungal efficacy assays against clinical isolates ofTrichosporon asahii,T. asteroidesandT. inkin

“…[3][4][5][6][7][8][9][10][11][12] It is not clear how Trichosporonosis can be acquired, but the following possibilities can be envisaged: (i) poor hygiene, (ii) bathing in contaminated water, (iii) sexual transmission, (iv) hair humidity and the length of the scalp hair (more specifically in the case of acquiring white piedra), (v) gastrointestinal colonization and further translocation throughout the gut (deep-seated infections), and (vi) exogenously acquired through a percutaneously inserted intravascular catheter via colonized skin. [13][14][15][16][17][18] In spite of the fact that Trichosporon spp are probably the second or third most common non-Candida yeast infections causing invasive disease in patients with hematological cancer, there are few reports related to virulence factors of this genus. 2,[19][20][21] The main causes of infection by invasive Trichosporon spp.…”

Development of a Peptide Nucleic Acid Probe to Trichosporon Species and Identification of Trichosporonosis by Use of In Situ Hybridization in Formalin-Fixed and Paraffin-Embedded (FFPE) Sections

“…present certain morphological features in pathological specimens (14). However, their morphological similarities to other fungi, especially non-glabrata Candida species, lead to difficulties in the identification of trichosporonosis.…”