[Bacteriological evaluation of ofloxacin otic solution]

Clinical trials of ofloxacin (OFLX) otic solution, such as an early phase II study, a dose-finding study, a phase III double-blind comparative study and open studies, were conducted in the period from February 1988 to October 1989. In these studies, organisms were isolated from secretions of middle ear in patients with chronic otitis media and acute exacerbation of chronic otitis media, and from secretions of external ear in patients with external otitis. These organisms were subjected to identification, followed by determination of susceptibilities to OFLX and the other antibacterials. Results obtained are summarized as follows: 1. In total, 746 organisms were defined as the presumable causative organisms in 439 patients with otitis media and 80 with external otitis. Among the isolates, aerobic Gram-positive organisms were most prevalent, with an isolation rate of 66.9%, followed by aerobic Gram-negative organisms (32.4%), and obligate anaerobes (0.7%). Staphylococcus aureus and Pseudomonas aeruginosa were the organisms isolated most frequently among aerobic Gram-positive and Gram-negative bacteria, respectively. 2. The MIC90 of OFLX against the above 746 strains was 6.25 micrograms/ml. At this level, OFLX was 8 times more potent than cefmenoxime (CMX), and 32 times more potent than fosfomycin (FOM) and fradiomycin (FRM). It was postulated that OFLX retained higher local level than the MIC90 of the drug at 2 hours after topical adaptation of the otic solution, and had enough "above the MIC" and "time above MIC". 3. The MIC90 of OFLX against glucose-nonfermentative Gram-negative rods (GNF-GNR) including P. aeruginosa, which were isolated in 32.6% of the 519 patients, was superior to those of CMX, FOM, and FRM. The well-balanced antibacterial activity of OFLX was thought to be one of the properties of OFLX otic solution. 4. Previously-reported post antibiotic effect of OFLX was thought to be another property of OFLX otic solution. In conclusion, OFLX otic solution appeared to be clinically useful, because it possessed advantageous properties beyond other clinically-available otic solutions.