Genotyping of Fusarium Isolates from Onychomycoses in Colombia: Detection of Two New Species Within the Fusarium solani Species Complex and In Vitro Antifungal Susceptibility Testing

Abstract

Fusariosis have been increasing in Colombia in recent years, but its epidemiology is poorly known. We have morphologically and molecularly characterized 89 isolates of Fusarium obtained between 2010 and 2012 in the cities of Bogotá and Medellín. Using a multi-locus sequence analysis of rDNA internal transcribed spacer, a fragment of the translation elongation factor 1-alpha (Tef-1α) and of the RNA-dependent polymerase subunit II (Rpb2) genes, we identified the phylogenetic species and circulating haplotypes. Since most of the isolates studied were from onychomycoses (nearly 90 %), we carried out an epidemiological study to determine the risk factors associated with such infections. Five phylogenetic species of the Fusarium solani species complex (FSSC), i.e., F. falciforme, F. keratoplasticum, F. lichenicola, F. petroliphilum, and FSSC 6 as well as two of the Fusarium oxysporum species complex (FOSC), i.e., FOSC 3 and FOSC 4, were identified. The most prevalent species were FOSC 3 (38.2%) followed by F. keratoplasticum (33.7%). In addition, our isolates were distributed into 23 haplotypes (14 into FOSC and nine into FSSC). Two of the FSSC phylogenetic species and two haplotypes of FSSC were not described before. Our results demonstrate that recipients of pedicure treatments have a lower probability of acquiring onychomycosis than those not receiving such treatments. The antifungal susceptibility of all the isolates to five clinically available agents showed that amphotericin B was the most active drug, while the azoles exhibited lower in vitro activity.

Development of a polymerase chain reaction-restriction fragment length polymorphism method for identification of the Fusarium genus using the transcription elongation factor-1α gene

“…Guevara-Suarez et al (15) used a TEF-1α gene fragment and performed a multi-locus sequence analysis of the ITS region with the RNA-dependent polymerase subunit II (Rpb2) genes, and recognized the phylogenetic species and circulating haplotypes for Fusarium isolates from onychomycosis. The pathogenic isolates to the pecan tree were identified, based on the TEF-1α gene, as belonging to the F. chlamydosporum species complex, F. graminearum species complex, F. proliferatum, and F. oxysporum (16).…”

Challenges in Fusarium, a Trans-Kingdom Pathogen

“…They used multi-locus sequence analysis-the gold standard-to identify known lineages in the F. solani and F. oxysporum species complexes and also identified two new lineages with members capable of human infection. Based on these outcomes, it seems that in the Americas as well as in Europe [12][13][14][15] members of these two complexes predominate in onychomycosis, while for instance in Thailand species of the F. incarnatum-equiseti complex are also frequently observed [4]. Interestingly the authors [12] show that pedicure treatment is not a predisposing factor, but rather seems to limit these infections.…”

“…Based on these outcomes, it seems that in the Americas as well as in Europe [12][13][14][15] members of these two complexes predominate in onychomycosis, while for instance in Thailand species of the F. incarnatum-equiseti complex are also frequently observed [4]. Interestingly the authors [12] show that pedicure treatment is not a predisposing factor, but rather seems to limit these infections. Most importantly, Guevara-Suarez et al [12] show that the different lineages vary in susceptibility to antifungal drugs and that the only approved antifungal agent for treating nail infections in Colombia, fluconazole, is exactly the one for which all isolates have minimum inhibitory concentrations higher than 64 lg/ml.…”

“…Interestingly the authors [12] show that pedicure treatment is not a predisposing factor, but rather seems to limit these infections. Most importantly, Guevara-Suarez et al [12] show that the different lineages vary in susceptibility to antifungal drugs and that the only approved antifungal agent for treating nail infections in Colombia, fluconazole, is exactly the one for which all isolates have minimum inhibitory concentrations higher than 64 lg/ml. This explains the limited success in onychomycosis treatment.…”

“…In this issue Guevara-Suarez et al [12] characterized 89 isolates of Fusarium from Colombia, the majority having been isolated from onychomycoses. They used multi-locus sequence analysis-the gold standard-to identify known lineages in the F. solani and F. oxysporum species complexes and also identified two new lineages with members capable of human infection.…”