The Value of Cellular Fatty Acid Analysis in the Identification of Oral Yeasts

Antifungal susceptibility of South African oral yeast isolates from HIV/AIDS patients and healthy individuals

The in vitro antifungal susceptibility profile of 589 oral yeast isolates from HIV/AIDS patients and healthy South Africans was determined against amphotericin B, nystatin, 5-fluorocytosine (5-FC), clotrimazole, miconazole, ketoconazole, itraconazole and fluconazole. The broth microdilution method of the National Committee on Clinical Laboratory Standards was used and MIC(50) and MIC(90) determined. A 100% susceptibility to fluconazole was observed among the 466 isolates of Candida albicans. Among C. krusei, the second most common isolate, only 2.6% of isolates were susceptible to fluconazole and itraconazole. Despite the lack of previous exposure to antifungal agents, very little difference was observed in the antifungal profile between the South African isolates and isolates from the United States (U.S.), Canada and South America. South Africa has a particularly high incidence of HIV-infection and oral candidiasis is the most common oral complication in these patients. This study provides important baseline data as the isolates were collected prior to fluconazole being made freely available to HIV/AIDS patients attending government health clinics.

Phospholipid molecular species distribution of some medically important Candida species analysed by fast atom bombardment mass spectroscopy

The aim of this study was to obtain detailed information on phospholipids (PL) of the medically important Candida species and to determine their possible chemotaxonomic significance. Lipids were extracted from 22 strains representing 8 Candida species and their PL molecular species distributions were determined by Fast Atom Bombardment Mass Spectroscopy (FAB MS) in negative ion mode. Fifteen major lower mass peaks (m/z 221 to 289) were attributable to the expected presence of carboxylate anions and 24 major higher mass peaks (m/z 557 to 837) were attributable to phospholipid anions. Major carboxylate peaks were of the following m/z and identities : 253, C16:1; 255, C16:0; 277, C18:3; 279, C18:2; 281, C18:1; and 283, C18:0. The most abundant peaks consistent with the presence of phospholipid molecular species anions include those of m/z 673, 743, 833, 834 and 836 tentatively identified as phosphatidic acid (PA) (34:1), phosphatidylglycerol (PG) (34:3), phosphtidylinositol (PI) (34:2) and two unknown molecular species. This profile is diagnostic for the genus Candida. Quantitative differences were observed between different Candida species. Thus, polar lipid molecular species distribution in Candida spp. has chemotaxonomic significance, especially so in the case of carboxylate anions.