The mycologist dilemma: Challenges in reporting and identifying histoplasma capsulatum in mycology laboratory, UMMC

Abstract

Background: Histoplasmosis are endemic in the eastern and central states of United States. However it is not a very common fungal pathogen found and isolated in Malaysia. Disease presentation can be varied from very mild symptoms to a full blown disseminated disease. Diagnosis of this dimorphic fungus in mycology laboratory can be challenging. Case description: A 27 year old Indonesian with HIV positive results presented with intermittent fever for two months followed by generalized maculopapular rash upon admission. Patient was started on amphotericin B when fungal hypae was identified by direct smear from blood culture bottles that was flagged positive by the Bactec. The antifungal was started on the presumptive assumption that it may be a common opportunistic fungal pathogen, Tarolomyeses marneffei which is endemic in Malaysia Discussion: Histoplasma capsulatum which is rarely isolated in clinical specimen and needs to be identified precisely for prompt treatment. Histoplasma capsulatum can take up two to three weeks to grow in its mycelia form. Typical microscopic morphology of this pathogen depends on the maturity of mycelia. Tuberculated macrconidia an important microscopic identification feature for this pathogen in prepared slide culture . In this clinical case the slide culture which was prepared shown, only few single small capsulated like macroconidia without any tuberculation on the surface of conidia. It was very in-conclusive findings from micoroscopic point of view and unable to diagnose the pathogen just looking at this nontypical features. In the suspicious growth of gross morphology colonies, which appears white chalky on Sabouraud Dextrose Agar (SDA) agar, we randomly performed MALDI-TOF MS analysis on this colonies with special prepartion for mold identification. Surprisingly it was excellent scores, 99.9% identified as histoplasma capsulatum within 20 minutes. Conclusion: Identifying rare fungal pathogen in mycology laboratory needs experience and experts. Alternative methods of diagnosis need to be established if common conventional methods failed especially in mycology laboratory. Fungal Species Identification by MALDI-ToF Mass spectrometry is very good alternative method for fast and efficient compare to molecular method.