Effects of mupirocin at subinhibitory concentrations on biofilm formation in Pseudomonas aeruginosa

BACKGROUND: Subinhibitory concentrations of mupirocin can suppress flagellar formation in Pseudomonas aeruginosa. In this study, we evaluated the effect of mupirocin on biofilm formation in P. aeruginosa. METHODS: P. aeruginosa PAO-1 (MIC, >1,024 microg/ml for mupirocin) was used. Viable bacteria adhering or forming biofilm on a Cell Desk were counted and observed by scanning electron microscopy. RESULTS: With or without continuous exposure to 256 microg/ml of mupirocin, counts of adherent and/or biofilm-forming bacteria showed no difference until day 10. Whereas biofilm formation with glycocalyx was observed on day 6-10 without mupirocin, mupirocin reduced biofilm formation and glycocalyx production for 10 days. CONCLUSIONS: Subinhibitory concentrations of mupirocin can reduce biofilm formation in vitro in P. aeruginosa.