Antibiofilm efficacy of honey and bee-derived defensin-1 on multispecies wound biofilm

Many clinically relevant biofilms are polymicrobial. Examining the effect of antimicrobials in a multispecies biofilm consortium is of great clinical importance. The goal of this study was to investigate the effect of different honey types against bacterial wound pathogens grown in multispecies biofilm and to test the antibiofilm activity of honey defensin-1 (Def-1) in its recombinant form. A modified Lubbock chronic wound biofilm formed by four bacterial species (Staphylococcus aureus, Streptococcus agalactiae, Pseudomonas aeruginosa and Enterococcus faecalis) was used for evaluation of honey and recombinant bee -derived Def-1 antibiofilm efficacy. Recombinant Def-1 was prepared by heterologous expression in Escherichia coli. We showed that different types of honey (manuka and honeydew) were able to significantly reduce the cell viability of wound pathogens (Staphylococcus aureus, Streptococcus agalactiae and Pseudomonas aeruginosa) in mature polymicrobial biofilm. None of the tested honeys showed the ability to eradicate Enterococcus faecalis in biofilm. In addition, recombinant Def-1 successfully reduced the viability of Staphylococcus aureus and Pseudomonas aeruginosa cells within established polymicrobial biofilm after 24 and 48 h of treatment. Interestingly, recombinant Def-1 did not affect the viability of Streptococcus agalactiae cells within the biofilm, whereas both natural honeys significantly reduced the viable bacteria. Although Enterococcus faecalis was highly resistant to Def-1, Def-1 significantly affected the biofilm formation of Enterococcus faecalis and Streptococcus agalactiae after 24 h of treatment, most likely by inhibiting its extracellular polymeric substances production. In conclusion, our study revealed that honey and Def-1 are effective against established multispecies biofilm; however, Enterococcus faecalis grown in multispecies biofilm was resistant to both antimicrobials.