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MK Rhee, RP Kowalski, EG Romanowski, LM Karanchak, FS Mah, DC Ritterband, YJ Gordon; How Shall We Treat Ciprofloxacin-Resistant Pseudomonas aeruginosa Ocular Infections? . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1586.
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Purpose: The emergence of ciprofloxacin-resistant Pseudomonas aeruginosa (CRPA) has created a new therapeutic challenge for ophthalmology. We evaluated ophthalmic antibiotics with in vitro and in vivo studies to determine possible effective therapy. Methods: In the in vitro studies, the susceptibilities of 12 CRPA were determined for amikacin, ceftazidime, tobramycin, polymyxin, gentamicin, ticarcillin, and 2nd, 3rd, 4th generation fluoroquinolones using E-tests and NCCLS standards. In the in vivo studies, we used a rabbit keratitis model to test the topical efficacy of polymyxin B (10,000 units/ml), tobramycin (14 mg/ml), ceftazidime (50 mg/ml), ciprofloxacin (3 mg/ml), and PBS control for treating an isolate of CRPA. The in vivo data were analyzed non-parametrically (Kruskal-Wallis ANOVA) with Duncan's multiple comparisons. Results: In vitro antibiotic testing revealed susceptibilities and median potencies (µg/ml) as follows: amikacin, 92%, 14.0; ceftazidime, 75%, 4.0; tobramycin, 67%, 1.75; polymyxin, 42%, 7.0; gentamicin, 17%, 7.0; ticarcillin and 2nd, 3rd, 4th generation fluoroquinolones, 0%, ≷≷32.0. In vivo antibiotic testing determined that there was no significant difference between the four antibiotics and control phosphate buffered solution. Conclusion: In vitro data indicate that tobramycin and ceftazidime, and perhaps, amikacin may be the preferred antibiotics for CRPA. However, in vivo testing revealed no difference among the miscellaneous drugs; in fact, no antibiotic was efficacious in the time frame of the model. This highlights the necessity of introducing another medication for the treatment of CRPA. Other antibiotics have shown encouraging reports of efficacy in multi-drug resistant strains of respiratory Pseudomonas aeruginosa, commonly seen in patients with cystic fibrosis. Perhaps, we should look to the treatment of CRPA in other disease processes for new therapeutic options.
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