Typing of Histoplasma capsulatum strains by fatty acid profile analysis

Abstract

The performance of fatty acid profiling for strain differentiation ofHistoplasma capsulatumwas assessed. Total fatty acids were isolated from the yeast-phase cells of seven stock and two previously unreported clinical strains ofH. capsulatumvar.capsulatum, as well as from one unreported clinical strain and one stock strain ofH. capsulatumvar.duboisii, and one strain of each of three other dimorphic zoopathogenic fungal species,Blastomyces dermatitidis,Paracoccidioides brasiliensisandSporothrix schenckii. Different colony morphology and pigmentation types of theH. capsulatumstrains were also included. The most frequently occurring fatty acids were oleic, palmitic, stearic and linoleic acids. There were variations in the relative percentage fatty acid contents ofH. capsulatumstrains that could be used for strain identification and discrimination. Differentiation betweenH. capsulatumstrains was achieved by the comparison of detected fatty acids accompanied by principal component analysis using calculated Varimax-rotated principal component loadings. Statistical analysis yielded three major principal components that explained over 94 % of total variance in the data. All the strains ofH. capsulatumvar.capsulatumRFLP classes II and III were grouped into two distinct clusters: the heterogenic RFLP class I formed a large, but also well-defined group, whereas the outgroup strains ofH. capsulatumvar.duboisii,B. dermatitidis,P. brasiliensisandS. schenckiiwere shifted away. These data suggest that fatty acid profiling can be used inH. capsulatumstrain classification and epidemiological studies that require strain differentiation at the intraspecies level.