AFLP analysis reveals high genetic diversity but low population structure in Coccidioides posadasiiisolates from Mexico and Argentina

Abstract

BackgroundCoccidioides immitis and C. posadasii cause coccidioidomycosis, a disease that is endemic to North and South America, but for Central America, the incidence of coccidioidomycosis has not been clearly established. Several studies suggest genetic variability in these fungi; however, little definitive information has been discovered about the variability of Coccidioides fungi in Mexico (MX) and Argentina (AR). Thus, the goals for this work were to study 32 Coccidioides spp. isolates from MX and AR, identify the species of these Coccidioides spp. isolates, analyse their phenotypic variability, examine their genetic variability and investigate the Coccidioides reproductive system and its level of genetic differentiation.MethodsCoccidioides spp. isolates from MX and AR were taxonomically identified by phylogenetic inference analysis using partial sequences of the Ag2/PRA gene and their phenotypic characteristics analysed. The genetic variability, reproductive system and level of differentiation were estimated using AFLP markers. The level of genetic variability was assessed measuring the percentage of polymorphic loci, number of effective allele, expected heterocygosity and Index of Association (IA). The degree of genetic differentiation was determined by AMOVA. Genetic similarities among isolates were estimated using Jaccard index. The UPGMA was used to contsruct the corresponding dendrogram. Finally, a network of haplotypes was built to evaluate the genealogical relationships among AFLP haplotypes.ResultsAll isolates of Coccidioides spp. from MX and AR were identified as C. posadasii. No phenotypic variability was observed among the C. posadasii isolates from MX and AR. Analyses of genetic diversity and population structure were conducted using AFLP markers. Different estimators of genetic variability indicated that the C. posadasii isolates from MX and AR had high genetic variability. Furthermore, AMOVA, dendrogram and haplotype network showed a small genetic differentiation among the C. posadasii populations analysed from MX and AR. Additionally, the IA calculated for the isolates suggested that the species has a recombinant reproductive system.ConclusionsNo phenotypic variability was observed among the C. posadasii isolates from MX and AR. The high genetic variability observed in the isolates from MX and AR and the small genetic differentiation observed among the C. posadasii isolates analysed, suggest that this species could be distributed as a single genetic population in Latin America.

The habitat of Coccidioides spp. and the role of animals as reservoirs and disseminators in nature

“…Based on work by De Hoog [ 22 ], the Coccidioides genus consists of xerotolerant fungi because they can grow under extreme hostile conditions. Moreover, Coccidioides may be considered halotolerant organisms [ 23 ], because both species in this genus tolerate high salt concentrations of up to 8 % [ 2 , 24 , 25 ]. Nevertheless, little is known about the mechanisms that species of Coccidioides utilize to survive under high salinity conditions.…”

“…This dispersal method would also provide an explanation for a positive C. posadasii isolate that was obtained from a patient who acquired the disease from a non-endemic region (Campeche, Mexico) and who reported no excursions away from his site of residence [ 25 ]. Another observation seldom referenced but with great relevance for the epidemiology of coccidioidomycosis is a report from Nigeria of two chickens that were analysed post-mortem and showed positive Coccidioides spp.…”

“…It is speculated that marine currents may be able to drag the arthroconidia towards non-endemic zones. These facts suggest that the area of geographic distribution for Coccidioides is expanding and that the fungi responsible for coccidioidomycosis are adapting to new habitats that may have characteristics different from those previously described [ 25 ].…”

Analyses of the Global Multilocus Genotypes of the Human Pathogenic Yeast Candida tropicalis

“…Over the past three decades, several molecular methods have been used to identify genotypes and examine the relationships among strains and populations of human pathogenic yeasts (Xu, 2005; Lachance et al, 2011; Zuza-Alves et al, 2017). These included multilocus isozyme electrophoresis (e.g., Brandt et al, 1993), electrophoretic karyotyping (e.g., Fries et al, 1996), PCR fingerprinting (e.g., Xu et al, 2000a), amplified fragment length polymorphisms (e.g., Duarte-Escalante et al, 2013), simple sequence repeats (e.g., Field et al, 1996), and multilocus sequence typing (MLST) (e.g., Xu et al, 2000b; Tavanti et al, 2005; Afsarian et al, 2015). For C. tropicalis , the emerging consensus since 2005 for strain typing is MLST, based on the single nucleotide polymorphisms (SNPs) at six gene fragments (Tavanti et al, 2005).…”

Selection of Specific Peptides for Coccidioides spp. Obtained from Antigenic Fractions through SDS-PAGE and Western Blot Methods by the Recognition of Sera from Patients with Coccidioidomycosis

“…were used, consisting of nine isolates from Mexico and two isolates from Argentina. The clinical isolates were identified at the species level according to Duarte-Escalante et al [46], using the method of Bialek et al [47]. The isolates were preserved at 4 °C in vials with sterile water and in tubes with mycobiotic agar (Bioxón, México, MX), with and without mineral oil.…”