Genetic diversity of Histoplasma capsulatum isolated from infected bats randomly captured in Mexico, Brazil, and Argentina, using the polymorphism of (GA)n microsatellite and its flanking regions

Abstract

The genetic diversity of 47 Histoplasma capsulatum isolates from infected bats captured in Mexico, Brazil, and Argentina was studied, using sequence polymorphism of a 240-nucleotides (nt) fragment, which includes the (GA)n length microsatellite and its flanking regions within the HSP60 gene. Three human clinical strains were used as geographic references. Based on phylogenetic analyses of 240-nt fragments achieved, the relationships among H. capsulatum isolates were resolved using neighbour-joining and maximum parsimony methods. The tree topologies obtained by both methods were identical and highlighted two major clusters of isolates. Cluster I had three sub-clusters (Ia, Ib, and Ic), all of which contained Mexican H. capsulatum samples, while cluster II consisted of samples from Brazil and Argentina. Sub-cluster Ia included only fungal isolates from the migratory bat Tadarida brasiliensis. An average DNA mutation rate of 2.39 × 10−9 substitutions per site per year was estimated for the 240-nt fragment for all H. capsulatum isolates. Nucleotide diversity analysis of the (GA)n and flanking regions from fungal isolates of each cluster and sub-cluster underscored the high similarity of cluster II (Brazil and Argentina), sub-clusters Ib, and Ic (Mexico). According to the genetic distances among isolates, a network of the 240-nt fragment was graphically represented by (GA)n length haplotype. This network showed an association between genetic variation and both the geographic distribution and the ecotype dispersion of H. capsulatum, which are related to the migratory behaviour of the infected bats studied.