Discordant automated and conventional identification of invasive trichosporonosis: A case for enhanced laboratory practices

Background

Accurate identification of invasive fungal pathogens is crucial for appropriate antifungal therapy. The Department of Clinical Laboratory at Indus Hospital & Health Network, Karachi, Pakistan, reported two cases of invasive fungal infections between 1^st January and 31^st March 2024 in which conventional identification methods and automated systems produced discordant results, highlighting critical diagnostic challenges.

Case presentation

Two invasive yeast isolates initially showing budding yeast cells without pseudohyphae on Gram stain were subjected to conventional identification using cornmeal-Tween 80 agar, chrome agar, and BiGGY agar, followed by automated identification using the VITEK 2 ID-YST system and confirmatory API 20C AUX testing. Both isolates demonstrated typical soft, wrinkled, cream-colored colonies on Sabouraud dextrose agar, which on chrome agar appeared as dry, blue colonies and on BiGGY agar as dry, brown colonies. Characteristic arthroconidia and blastoconidia formation on cornmeal-Tween 80 agar were observed, consistent with Trichosporon species. However, the VITEK 2 ID-YST system identified both isolates as Cryptococcus laurentii with good confidence levels. India ink staining was negative for both isolates. Confirmatory API 20C AUX testing correctly identified both isolates as Trichosporon asahii (identification profile 3740734).

Conclusions

These cases demonstrate that while automated identification systems provide valuable diagnostic support, they cannot replace expert interpretation in resolving discordant results. Accurate species-level identification of uncommon invasive yeasts remains essential for optimal patient management. Clinical laboratories must maintain proficiency in conventional identification methods and implement confirmatory testing strategies when automated results conflict with morphological findings. The integration of morphological expertise, recognition of system limitations, and appropriate verification approaches is fundamental to maintaining diagnostic excellence in clinical mycology.

Full text

https://www.xiahepublishing.com/2771-165X/JCTP-2025-00032

The study was recently published in the Journal of Clinical and Translational Pathology.

Journal of Clinical and Translational Pathology (JCTP) is the official scientific journal of the Chinese American Pathologists Association (CAPA). It publishes high quality peer-reviewed original research, reviews, perspectives, commentaries, and letters that are pertinent to clinical and translational pathology, including but not limited to anatomic pathology and clinical pathology. Basic scientific research on pathogenesis of diseases as well as application of pathology-related diagnostic techniques or methodologies also fit the scope of the JCTP.

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