Genetic Diversity Of Pathogenic Yeasts

Human fungal diseases, including yeast infections, pose a significant concern to public health, affecting over one billion people worldwide and causing one million deaths per annum. Yeasts do not form a separate taxonomic group; instead, they are placed in two separate phyla: Ascomycota and Basidiomycota. Yeasts occur in a variety of environmental niches; many are part of the human normal microbiota but become pathogenic in immunocompromised individuals, thus acting as opportunistic pathogens. Since the number of people presenting immune system dysfunctions is increasing, yeast pathogens are becoming much more prevalent in systemic infections. Pathogenic yeasts include species of Cryptococcus, Candida, Paracoccidioides, Histoplasma, Sporothrix, Blastomyces and Pneumocystis. These yeasts cause a significant challenge for clinical microbiologists and physicians. Advances in medical research, made during the last few decades, have improved the diagnostic and therapeutic capabilities for a variety of infections. The availability of refined molecular data has increased the understanding of genetic and environmental diversity of pathogenic yeasts, as well as of the evolution of virulence attributes. This chapter reviews the genetic diversity and geographical distribution of the aforementioned pathogenic yeasts as assessed by specific loci targeting techniques.