Anti-biofilm effects of honey against wound pathogens Proteus mirabilis and Enterobacter cloacae

Biofilm growth and its persistence within wounds have recently been suggested as contributing factors to impaired healing. The goal of this study was to investigate the anti-biofilm effects of several honey samples of different botanical origin, including manuka honey against Proteus mirabilis and Enterobacter cloacae wound isolates. Quantification of biofilm formation was carried out using a microtiter plate assay. All honeys at a sub-inhibitory concentration of 10% (w/v) significantly reduced the biofilm development of both isolates. Similarly, at a concentration of 50% (w/v), each of the honeys caused significant partial detachment of Pr. mirabilis biofilm after 24 h. On the other hand, no honey was able to significantly detach Ent. cloacae biofilm. In addition, treatment of Ent. cloacae and Pr. mirabilis biofilms with all honeys resulted in a significant decrease in colony-forming units per well values in a range of 0.35-1.16 and 1.2-7.5 log units, respectively. Of the tested honeys, manuka honey possessed the most potent anti-biofilm properties. Furthermore, methylglyoxal, an antibacterial compound of manuka honey, was shown to be responsible for killing biofilm-embedded wound bacteria. These findings suggest that manuka honey could be used as a potential therapy for the treatment of wounds containing Pr. mirabilis or Ent. cloacae.