[A clinical bacteriological efficacy study on a fosfomycin otic solution]

Fosfomycin (FOM) otic solution was administered to 587 patients with suppurative otitis media infections including 190 patients in the dose-establishment test, 126 patients in the open clinical trial and 271 patients in the double blind test. Various bacteria were detected in the 549 cases in which bacteriological investigation was possible. Main bacteria detected from the above cases were S. aureus (261 strains, 47.5%), P. aeruginosa (93 strains, 16.9%), coagulase negative Staphylococci (CNS) (89 strains, 16.2%), Providencia spp. (35 strains, 6.4%) and Proteus spp. (28 strains, 5.1%). Twenty-seven strains of anaerobic bacteria (4.9%) were also detected. The MIC of FOM, and the reference drug, chloramphenicol (CP), fradiomycin (FRM), cefmenoxime (CMX) and cephalexin (CEX), were determined up to a concentration of 800 micrograms/ml with inoculum sizes of 10(6) and 10(8) CFU/ml. About 30% of S. aureus was multi-drug resistant, including methicillin and cephems, but FOM showed excellent antibacterial activity against it. The FOM had superior antibacterial activity against P. aeruginosa to CP, FRM and CMX, and was also active against other bacteria. The antibacterial activity of FOM was inferior to other drugs against CNS, Enterobacter spp., P. putida and P. cepacia. The detection rate of these bacteria, however, was low and since their role as causative organisms is not well defined, the inferior activity of FOM has no effect on the bacteriological evaluation of FOM. Since the concentration in the tympanic cavity about 1 hour after the administration of 3% FOM solution was estimated to be 2,000 to 3,000 micrograms/ml, it could be presumed that bacteria inhibited by 800 micrograms/ml of FOM at an inoculum size of 10(8) CFU/ml would be eradicable. The low ototoxicity of FOM is likely due to its characteristic as an inhibitor of bacterial cell wall synthesis. From these results, 3% FOM otic solution may be considered as a remarkably useful topical preparation for the treatment of suppurative otitis media.