Abstract

Objective: To investigate the antifungal activity of crude cultures of putative strains of lactic acid bacteria (LAB) from a selection of Zimbabwean traditional and commercial food/ medicinal products against yeasts (strains of environmental isolates of Candida albicans and Rhodotorula spp.). Methods: Cultures of putative LAB from our selection of fermented products were enriched in de Man, Rogosa and Sharpe and isolated on de Man, Rogosa and Sharpe agar. Results: The crude microbial cultures from the products that showed high antifungal activities (zone of inhibition, mm) were as follows: supernatant-free microbial pellet (SFMP) from an extract of Melia azedarach leaves [(27.0 ± 2.5) mm] > cell-free culture supernatants (CFCS) from Maaz Dairy sour milk and Mnandi sour milk [approximately (26.0 ± 1.8/2.5) mm] > CFCS and SFMP from Amansi hodzeko [(25.0 ± 1.5) mm] > CFCS from Parinari curatellifolia fruit [(24.0 ± 1.5) mm], SFMP from Parinari curatellifolia fruit [(24.0 ± 1.4) mm] and SFMP from mahewu [(20.0 ± 1.5) mm]. These cultures also showed high tolerance to acidic conditions (pH 4.0 and pH 5.0). However, culture from WAYA LGG (shown elsewhere to harbour antimicrobial activities) showed no antifungal activity. The LAB could have inhibited yeasts by either competitive exclusion or the release of antimicrobial metabolites. Conclusions: Our cultures of LAB from a selection of Zimbabwean fermented products, especially Ziziphus mauritiana and fermented milk products have great potential for use as antifungal probiotics against yeast infections. Studies are ongoing to determine the exact mechanisms that are employed by the putative LAB to inhibit Candida albicans.

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