The aim of this study was to investigate the presence of multidrug resistant yeasts in the faeces of synanthropic wild birds from the Bangsar suburb of Kuala Lumpur.
The biodiversity and the killer activity of yeasts isolated from various types of fermented food in Malaysia were investigated in this study. Of 252 yeasts isolated from 48 fermented food samples in this study, 19 yeast species were identified based on sequence analysis of the ITS1-5.8S-ITS2 partial fragments of the yeasts. A total of 29 (11.5%) of the yeast isolates demonstrated killer activity to at least one Candida species tested in this study; including 22 isolates of Trichosporon asahii, 4 isolates of Pichia anomala, and one isolate each of Pichia norvegensis, Pichia fermentans and Issatchenkia orientalis, respectively. The presence of killer yeasts reflects antagonism that occurs during microbial interaction in the fermented food, whereby certain yeasts produce killer toxins and possibly other toxic substances in competition for limited nutrients and space. The anti-Candida activity demonstrated by killer yeasts in this study should be further explored for development of alternative therapy against candidiasis.
This study describes the killer phenotypes of tropical environmental yeasts and the inhibition effects of the culture filtrates on the biofilm of Candida albicans. A total of 26 (10.5%) of 258 yeast isolates obtained from an environmental sampling study demonstrated killer activity to Candida species. The killer yeasts were identified as species belonging to the genus Aureobasidium, Pseudozyma, Ustilago and Candida based on sequence analysis of the ITS1-5.8S-ITS2 region of the yeasts. Pseudozyma showed the broadest killing effects against sensitive strains of Candida. New species of Ustilago and Pseudozyma demonstrating killer phenotypes were identified in this study. Interestingly, more than 50% reduction in the metabolic activity of Candida albicans biofilm was noted after exposure to the culture filtrates of the nine killer yeasts. Purification and characterization of toxin and metabolites are essential for understanding the yeast killing effects.
The yeast species composition of 12 cocoa bean fermentations carried out in Brazil, Ecuador, Ivory Coast and Malaysia was investigated culture-independently. Denaturing gradient gel electrophoresis of 26S rRNA gene fragments, obtained through polymerase chain reaction with universal eukaryotic primers, was carried out with two different commercial apparatus (the DCode and CBS systems). In general, this molecular method allowed a rapid monitoring of the yeast species prevailing during fermentation. Under similar and optimal denaturing gradient gel electrophoresis conditions, the CBS system allowed a better separated band pattern than the DCode system and an unambiguous detection of the prevailing species present in the fermentation samples. The most frequent yeast species were Hanseniaspora sp., followed by Pichia kudriavzevii and Saccharomyces cerevisiae, independent of the origin of the cocoa. This indicates a restricted yeast species composition of the cocoa bean fermentation process. Exceptionally, the Ivorian cocoa bean box fermentation samples showed a wider yeast species composition, with Hyphopichia burtonii and Meyerozyma caribbica among the main representatives. Yeasts were not detected in the samples when the temperature inside the fermenting cocoa pulp-bean mass reached values higher than 45 °C or under early acetic acid production conditions.