Fluoroquinolones have gained widespread use for treating ocular infections.1,2 We report a case of scleral buckle infection with Pseudomonas aeruginosa resistant to ciprofloxacin.
A 35-year-old man was seen by his ophthalmologist in Ecuador with a 1-day history of irritation, redness, and chemosis of the left eye. Eighteen months earlier, he had undergone successful repair of rhegmatogenous retinal detachment in the left eye. A diagnosis of scleral buckle infection was made and therapy was begun with topical norfloxacin and 1% prednisone acetate every 2 hours along with ciprofloxacin, 500 mg twice a day by mouth. No improvement was noted after 1 week and the patient was seen at our institution. Visual acuity was 20/20 OD and 20/80 OS. Left eye showed severe erythema and chemosis of the bulbar conjunctiva. Fundus examination revealed attached retina with good buckle support.
The patient underwent removal of the infected buckle and the scleral bed was irrigated with gentamicin solution. Postoperatively, the patient was initially treated with ofloxacin every 2 hours and ciprofloxacin capsules, 750 mg twice a day by mouth. On postoperative day 2, the patient started experiencing increasing pain and discharge and was noted to have conjunctival pseudomembranes along with inferior symblephron. Forty-eight-hour culture results from the buckle grew P aeruginosa resistant to ofloxacin and ciprofloxacin, resistance being defined as minimum inhibitory concentration of 4 µg/mL3 or higher. The sensitivities were tested using the automated Vitek test system (bioMerieux Vitek Inc, St Louis, Mo) and confirmed using the conventional disc diffusion method and the "E" test (AB Biodisk, Solna, Sweden). The organism was sensitive to aminoglycosides, ceftazidime, imipenem, mezlocillin, pipericillin, and ticarcillin. Therapy was switched to 1.4% fortified tobramycin (14 mg/mL) every hour. Within 48 hours, the pain subsided. At 2 weeks, visual acuity was 20/25 OS with mild conjuntival erythema. Tobramycin was switched to 0.3% solution, 4 times a day, and the patient returned to Ecuador.
Animal studies and clinical trials have shown that ciprofloxacin is an effective agent for most ocular infections.1,2 There are reports of ciprofloxacin-resistant systemic isolates including Staphylococcus aureus, coagulase-negative Staphylococcus species, and P aeruginosa.3 The possible mechanisms for acquired resistance include a decrease in the susceptibility of DNA gyrase to the drug-mediated inhibition and a decrease in the amount of drug accumulation within the bacteria.4
In the ophthalmic literature, there are multiple reports of ciprofloxacin-resistant ocular isolates including coagulase-negative Staphylococcus, S aureus, Streptococcus viridans, Corynebacterium pseudodiphtheriticum, Xanthomonas maltophila, and Mycobacterium chelonae .1,2,4,5 To our knowledge, this is the first reported case of an ocular infection from ciprofloxacin-resistant P aeruginosa. There are published cases of Pseudomonas species bacterial keratitis unresponsive to ciprofloxacin therapy, but all those isolates showed in vitro susceptibility to the antibiotic.1 In vitro resistance to a given antibiotic does not mean that the ocular infection will not respond to the antibiotic. The in vitro susceptibilities are based on minimum inhibitory concentration values for serum concentration of antibiotics and do not always equate with in vivo susceptibilities for the treatment of ocular infections. Much higher concentrations of antibiotics may be obtained and host factors also come into play in this setting. However, in our case, clinical failure of treatment correlated with the in vitro results.
In general, mild scleral buckle infection is treated with topical broad-spectrum antibiotics (aminoglycosides or fluoroquinolones).5 In resistant or severe cases, removal of the infected buckle with topical and periocular broad-spectrum antibiotics is usually recommended. The antibiotic is later adjusted according to culture sensitivities from the buckle. In some cases, mere removal of the infected buckle may result in resolution of persistent buckle infection even when the same preoperative antibiotic is used postoperatively. This was the rationale for the postoperative use of fluoroquinolones in our case.
Knauff et al6 showed a statistically significant increase in ciprofloxacin-resistant systemic isolates from 1988 to 1993. All these systemic isolates are also common ocular pathogens. If the present trend continues, widespread ciprofloxacin resistance among the common ocular isolates may occur in the near future.
Reprints not available from the authors.
Chaudhry NA, Tabandeh H, Rosenfeld PJ, Miller D, Davis J. Scleral Buckle Infection With Ciprofloxacin-Resistant Pseudomonas aeruginosa. Arch Ophthalmol. 1998;116(9):1251. doi: