The controlled in vitro susceptibility of gastrointestinal pathogens to the antibacterial effect of manuka honey

S. M. Lin, P. C. Molan, R. T. Cursons

The susceptibility of common gastrointestinal bacteria against manuka honey with median level non-peroxide antibacterial activity (equivalent to that of 16.5% phenol) was investigated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using a standardized manuka honey with the broth microdilution method. The measured sensitivity of bacteria showed that manuka honey is significantly more effective than artificial honey (a mixture of sugars as in honey), indicating that osmolarity is not the only factor that is responsible for the antibacterial activity of the honey. Most tested gastrointestinal pathogens have MIC and MBC values in the range of 5-10% of honey, other than Enterobacter spp. which was in the range of 10-17%. The difference in efficacy between the honey with and without hydrogen peroxide removed was also studied, and it was found that both hydrogen peroxide and the non-peroxide components contribute to the bacteriostatic and bactericidal activity of the honey. It was also found that treatment against multi-antibiotic resistant microorganisms such as Salmonella typhimurium DT104 and ESBL-producing organisms with manuka honey may be promising.