In vitro efficacy of Otic Domeboro against Pseudomonas aeruginosa

The in vitro activity of prophylactic ear drops (Otic Domeboro) which are widely used by saturation divers against external otitis has been assessed. Four strains of Pseudomonas aeruginosa, 1 reference strain and 3 clinical isolates from cases of external otitis were employed. Two of the clinical isolates were from saturation divers who were using Otic Domeboro. Otic Domeboro solution was bactericidal even when diluted 1:2 in serum or broth. There were no significant differences between strains. There was no measurable inoculum effect. Survival kinetic analysis showed 60% killing at 5 min and 99.9% killing at about 2 h. Otic Domeboro is an effective anti-P. aeruginosa agent. There was no evidence of increased resistance among strains isolated from divers. The rate of killing in relation to usual prophylactic recommendations suggests that frequent dripping may be more effective. The therapeutic use of Otic Domeboro in saturation diving should be evaluated to avoid unnecessary use of antibiotic drops.