Biofilm formation of Clostridium difficile and susceptibility to Manuka Honey

BACKGROUND: Biofilm bacteria are relatively more resistant to antibiotics. The escalating trend of antibiotic resistance higlights the need for evaluating alternative potential therapeutic agents with antibacterial properties. The use of honey for treating microbial infections dates back to ancient times, though antimicrobial properties of Manuka honey was discovered recently. The aim of this study was to demonstrate biofilm formation of specific Clostridium difficile strains and evaluate susceptibility of the biofilm to Manuka honey. METHODS: Three C. difficile strains were used in the study including the ATCC 9689 strain, a ribotype 027 strain and a ribotype 106 strain. Each test strain was grown in sterile microtitre plates and incubated at 37°C for 24 and 48 hours in an anaerobic cabinet to allow formation of adherent growth (biofilm) on the walls of the wells. The effect of Manuka honey on the biofilms formed was investigated at varying concentrations of 1-50% (w/v) of Manuka honey. RESULTS: The three C. difficile strains tested formed biofilms after 24 hours with the ribotype 027 strain producing the most extensive growth. There was no significant difference (p > 0.05) found between the amount of biofilms formed after 24 and 48 hours of incubation for each of the three C. difficile strains. A dose–response relationship between concentration of Manuka honey and biofilm formation was observed for all the test strains, and the optimum Manuka honey activity occurred at 40-50% (v/v). CONCLUSION: Manuka honey has antibacterial properties capable of inhibiting in vitro biofilm formed by C. difficile.