Evidence of unique genetic diversity in Aspergillus fumigatus isolates from Cameroon

Aspergillus fumigatus is a saprophytic fungus that can cause lethal invasive aspergillosis in immunocompromised patients. Recent studies have shown that Eurasian and North American populations of A. fumigatus often consist of genetically diverse strains. However, very little is known about African populations of A. fumigatus. Here, we characterise the genetic diversity and triazole susceptibility of A. fumigatus in Cameroon, West Africa. A total of 495 soil samples were obtained from nine collection sites in three Cameroonian regions. Nine microsatellite markers were used to genotype all 51 identified A. fumigatus isolates. In vitro susceptibility to itraconazole and voriconazole was tested using micro broth dilution. The 51 Cameroonian A. fumigatus isolates belonged to 45 genotypes. Consistent with recombination, 32 of 36 possible pairwise loci combinations are phylogenetically incompatible. Interestingly, evidence for geographic sub-structuring was found within Cameroon and the sub-population with the most evidence of recombination was also the least susceptible sub-population to the triazole antifungals tested. Furthermore, the Cameroonian sample was significantly differentiated from those in Eurasia and North America. Overall, our results indicate the genetic uniqueness of Cameroonian A. fumigatus populations and that additional novel genetic diversity likely exist in other parts of Africa.