Background Pseudomonas aeruginosa (PA) and Staphylococcus aureus (SA) biofilms are associated with poor chronic rhinosinusitis (CRS) disease control following surgery. Manuka honey (MH) has been shown to be both an effective in vitro treatment agent for SA and PA biofilms and nontoxic to sinonasal respiratory mucosa. Methylglyoxal (MGO) has been reported to be the major antibacterial agent in MH. The effect of this agent against SA and PA biofilms has yet to be reported. Our objective was to determine the in vitro effect of MGO against biofilms of SA and PA, via in vitro testing of MGO against bacterial biofilms.

Methods An established biofilm model was used to determine the effective concentration (EC) of MGO against 10 isolates of methicillin‐resistant SA (MRSA) and PA. The EC of MGO was also determined against planktonic (free‐swimming) MRSA and PA.

Results For MRSA, the EC against planktonic organisms was a concentration of 0.08 mg/mL to 0.3 mg/mL whereas against the biofilm MRSA isolates, the EC ranged from 0.5 mg/mL to 3.6 mg/mL. For PA, the EC against planktonic organisms was a concentration of 0.15 mg/mL to 1.2 mg/mL for planktonic organisms whereas against the biofilm PA isolates, the EC ranged from 1.8 mg/mL to 7.3 mg/mL.