We used a rabbit model of bacterial keratitis to assess in vivo efficacy of topical imipenem, a highly potent β-lactam antibiotic with an unusually broad spectrum of activity, including aminoglycoside-resistant Pseudomonas aeruginosa. Albino rabbits received intrastromal injections of 5 x 102 organisms of an aminoglycoside-resistant strain of P. aeruginosa. At five hours postinoculation, imipenem (5 mg/ml) therapy was initiated using one drop per 30 minutes for 12 hours. Corneal tissue was then excised for colony forming unit counts. Imipenem was highly effective in reducing colony forming unit counts to zero in comparison to 4.1 x 105 organisms for untreated controls. A second regimen beginning 24 hours postinoculation of one drop per hour for 24 hours was also successful in significantly reducing colony forming units vs controls (P < .05). These data suggest that topical imipenem may have clinical applicability in the treatment of P. aeruginosa keratitis.
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