In vitro, acidic, non-proteinaceous antifungal activities of lactic acid bacteria isolated from salad vegetables against human pathogenic Candida albicans

Abstract

Background: The antagonistic abilities of lactic acid bacteria (LAB) against clinical isolates of Candida albicans are not quite widely reported and such are even scarce in Nigeria. This study therefore investigated inhibitory potentials of LAB isolated from locally grown cabbage, cucumber and lettuce against four (4) clinical isolates of C. albicans.

Methods: The cell free supernatants (CFS) generated from LAB culture filtrate was evaluated for anti-candida activity using agar well diffusion method, and the CFS-LAB pH was measured and neutralized using standard methods. The proteinaceous inhibitory metabolites were assayed for using sodium dodecylsulphate polyacrilamide gel electrophoresis (SDS-PAGE) technique. The LAB strains used were previously isolated and identified by 16S rRNA partial sequencing and their data submitted to GenBank for accessioning.

Results: The CFS of six (6) LAB strains showed varying degrees of anti-candida activity. Pediococcus pentosaceus BTA 51 from cucumber showed the widest inhibition zone of 14 mm while at neutral pH, it was 12 mm diameter. Weissella confusa BTA 20, BTA 40 isolated from cabbage and lettuce produced 10 mm and 12 mm zones of inhibition at acidic and neutral pH respectively. Lactobacillus plantarum BTA 07 from lettuce showed inhibition zone of 12 mm while L. fermentum BTA 47 and BTA 62 from cucumber showed zones of 14 mm each in acidic pH only. The SDS-PAGE did not detect any proteinaceous substances.

Conclusion: In conclusion, LAB isolated from cabbage, cucumber and lettuce produced organic acids, non proteinaceous metabolites at neutral pH, exhibiting invitro inhibitory abilities against clinical isolates of C. albicans.

Keywords: In vitro, Lactic acid bacteria, 16S rRNA, antifungal, SDS-PAGE, salad vegetables