Differences in bacteriologic treatment failures in acute otitis externa between ciprofloxacin/dexamethasone and neomycin/polymyxin B/hydrocortisone: Results of a combined analysis

Objective: To compare treatment failure rates for the two major acute otitis externa (AOE) pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, by topical therapy with ciprofloxacin 0.3%/dexamethasone 0.1% (CDex) or neomycin 0.35%/polymyxin B 10 000 IU/mL/hydrocortisone 1% (Cort) based on clinical and microbiological failure in patients positive for these pathogens at baseline. Research design and methods: A combined analysis was conducted from two similar, but non-identical clinical trials involving CDex vs. Cort. Outcomes of the combined efficacy analysis were treatment failure rates and antibiotic susceptibility values for P. aeruginosa and S. aureus. The raw data for the treatment failure rates from the two studies were combined to calculate the overall treatment failure rates of each treatment group. Chi-square tests of independence were conducted to assess differences in treatment failure rates between treatment groups. Results: Of the 789 patients with culture-positive ears prior to the initiation of therapy, 61.0% (n=481) were positive for P. aeruginosa and 8.9% (n=70) were positive for S. aureus. While treatment failure rates for S. aureus were similar for the two therapies, CDex had a significantly lower treatment failure rate than Cort (5.1 vs. 13.0%; p=0.0044) for P. aeruginosa. All of the persisting P. aeruginosa and S. aureus isolates were susceptible to fluoroquinolones and neomycin/polymyxin B. Limitations: The analysis strength is dependent on pooled data from similar studies. Conclusions: Ototopical ciprofloxacin 0.3%/dexamethasone 0.1% more effectively eradicates P. aeruginosa compared to Cort. Eradication of S. aureus by either drug was similar. These results favor CDex as a better first-line choice in the treatment of AOE compared to Cort.