Utility of molecular techniques in the diagnosis of histoplasmosis

Abstract

Histoplasmosis is a systemic mycosis distributed worldwide, associated to birds and
bats guano. Diagnosis is achieved through the isolation of Histoplasma capsulatum var.
capsulatum in clinical samples and complemented with immunodiagnostic procedures;
however, both isolation and immunodiagnosis pose limitations, such as the slow growth of
the fungus to perform the mycological diagnosis and the immune cross-reaction with other
fungal species causing similar nosologies. These handicaps have demanded more efficient
methods to detect accurately the presence of the pathogen in infected individuals. Recently,
molecular tests have been introduced to reveal small amounts of genetic material of the
fungus in clinical samples. For the detection of H. capsulatum, hybridization techniques of
the fungal DNA through Southern blot and in solution have been developed, as well as
Polymerase Chain Reaction (PCR) with an adequate probe. PCR is the most used technique,
because it facilitates a sensitive and fast diagnosis. Although these techniques have been
widely accepted in the clinical practice, they also present handicaps that have not allowed
replacing the classical techniques used in the mycology laboratory. Therefore, it is
recommended to combine both techniques to ensure an accurate diagnosis.