Low pH nasal rinse solution enhances mupirocin antimicrobial efficacy.

Area of Science:

• Microbiology
• Pharmacology
• Otolaryngology

Background:

• Chronic rhinosinusitis (CRS) significantly impairs quality of life, with bacterial biofilms implicated in its persistent nature.
• Conventional antibiotic therapies struggle to eradicate these biofilms, necessitating alternative treatment strategies.
• Topical antibiotic delivery via nasal rinse offers localized high concentrations with reduced systemic side effects.

Purpose of the Study:

• To investigate the efficacy of mupirocin, an antibiotic, when dissolved in commonly used Australian sinus rinse solutions.
• To assess the impact of different sinus rinse formulations and pH levels on mupirocin's antimicrobial activity against Staphylococcus aureus.
• To determine the optimal conditions for topical mupirocin delivery in managing CRS.

Main Methods:

• Planktonic and biofilm cultures of Staphylococcus aureus, including methicillin-resistant (MRSA) and susceptible strains, were treated with mupirocin in three sinus rinses.
• Experiments evaluated mupirocin's efficacy in FloCRS at both its natural pH (5.64) and an elevated pH (7.7).
• Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), biofilm biomass (crystal violet assay), and metabolic activity (alamarBlue assay) were measured.

Main Results:

• Mupirocin combined with the low pH (5.64) FloCRS demonstrated the highest efficacy against both planktonic and biofilm Staphylococcus aureus.
• Significantly greater reductions in biofilm biomass and metabolic activity were observed with mupirocin in low pH FloCRS compared to other rinse solutions or higher pH FloCRS.
• The pH of the sinus rinse solution was a critical factor influencing mupirocin's antimicrobial effectiveness.

Conclusions:

• The choice of irrigant solution is crucial for the antimicrobial efficacy of topical mupirocin.
• Low pH FloCRS provides an effective vehicle for delivering mupirocin to combat Staphylococcus aureus biofilms in chronic rhinosinusitis.
• This targeted delivery method holds promise for eradicating S. aureus biofilms on sinus mucosa in CRS patients.