Invasive fusariosis (IF) is considered an emerging fungal disease and an important problem worldwide that increasingly affects immunocompromised individuals. There is currently concern about establishing the genetic diversity and phylogenetic relationship of the species Fusarium causing invasive fusariosis.

The aim of this study was to characterize the molecular profile and morphological characteristics of Fusarium species isolated from 21 patients with invasive fusariosis. Multilocus sequence typing was performed for molecular identification of the following genes: the second largest subunit of the RNA polymerase gene (RPB2) and elongation factor 1 alpha (EF-1α). The morphological features of different species were carefully described and revised by experienced mycologists.

Morphological and molecular analyses revealed that the F. solani species complex (FSSC) and F. oxysporum species complex (FOSC) were the most common species isolated from patients with invasive fusariosis; FSSC-2 h (5), FSSC-1 (2) and FOSC-183 (2) were the most frequent haplotypes. The macroscopic characterization revealed great variation in the tonalities of the FSSC colonies and particularities amongst the species in relation to the macroconidia structures, while the FOSC was more homogeneous and presented shades from white to lilac.

Our study characterized the diversity, haplotypes, and morphological aspects of Fusarium species and the haplotypes prevalent in patients with invasive fusariosis. FSSC and FSSC-2 h were the predominant species and haplotype, respectively. Although we have described interesting morphological aspects in Fusarium species, particularly haplotypes, their identification cannot rely on phenotypical aspects. Molecular biology techniques are necessary and should be introduced for routine use in mycology laboratories.