Effectiveness of Honey on S.aureus and P.aeruginosa Biofilms

Abstract

Problem Biofilms formed by Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) have been shown to be an important factor in the pathophysiology of chronic rhinosinusitis (CRS). Growth in biofilms increases bacterial resistance to antibiotics, which may explain why CRS responds poorly to antibiotic therapy. Honey has been used as an effective topical antimicrobial agent in the treatment of antibiotic-resistant bacterial wound infections. To our knowledge, no research has studied the effect of honey on biofilms. Methods We used a previously established biofilm model to assess antibacterial activity of Manuka honey from New Zealand and Sidr honey from Yemen. These were tested at a 1 in 2 dilution against 11 isolates of methicillin-susceptible SA (MSSA), 11 methicillin-resistant SA (MRSA), and 11 PA isolates. Honeys were tested against both planktonic (broth) and biofilm-grown bacteria. Results Both honeys were effective in killing 100% of the isolates in the planktonic form. Biofilm-grown bacteria were less susceptible to the honeys, but honey still had significant bactericidal activity. The bactericidal rate for the Sidr and Manuka honeys against MSSA MRSA and PA were 63%, 73%, 91% and 82%, 63% and 91%, respectively. These rates were significantly higher (p<0.001) than those seen with single antibiotics commonly used against MSSA and MRSA (e.g. cloxacillin and vancomycin) in a previous study done on the same bacterial isolates. Conclusion Honey, which is a natural, non-toxic and inexpensive product, is effective in killing SA and PA bacterial biofilms. Significance This intriguing observation may have important clinical implications and could lead to a new approach for treating refractory CRS.