Antibacterial potential of Manuka honey against three oral bacteria in vitro.

Honey is an ancient natural remedy for the treatment of infected wounds. It has regained attention in the medical profession, as it has recently been reported to have a broad-spectrum inhibitory effect against bacteria. Data concerning Manuka honey of New Zealand origin, which is claimed to provide additional non-peroxide antimicrobial activity (so-called standard NPA) against oral pathogens, is still scarce. Therefore, this study aimed to screen for the antibacterial efficacy of different Manuka honey products against S. mutans (OMZ 918), P. gingivalis (OMZ 925) and A. actinomycetemcomitans (OMZ 299). Chlorhexidine and saline served as positive and negative controls, respectively, whereas a Swiss multifloral honey served as control honey without intrinsic non-peroxide activity. Chlorhexidine showed the highest inhibiting potential against all specimens tested. Manuka honey below an NPA value of 15 showed the least bacterial growth-inhibiting potential, even less – although not significantly so – than multifloral Swiss honey. Manuka honey above an NPA value of 15 showed a significantly higher antibacterial effect compared to the other honeys tested. All Manuka honey preparations were more effective in inhibiting the growth of P. gingivalis and A. actinomycetemcomitans, rather than S. mutans. In conclusion, the study showed an NPA dose-dependent antibacterial efficacy of Manuka honey. Further investigations of this natural product are now open for scrutiny.