Posttraumatic Endophthalmitis: Responsible Microorganisms and Rate of Resistance

Purpose: To identify the microorganisms responsible for the posttraumatic endophthalmitis and evaluate their resistance to seven antibiotics. Patients and Methods: Aqueous and vitreous samples were obtained from 49 patients who underwent vitrectomy for posttraumatic endophthalmitis and were inoculated into blood agar, chocolate agar, and Sabouraud agar media. Susceptibility testing was performed using the Kirby-Bauer disk diffusion method for seven antibiotics (vancomycin, ceftazidime, ciprofloxacin, oxacillin, azithromycin, imipenem, and rifampin). Results: Twenty patients (40.8 %) had intraocular foreign bodies. The cultures were positive in 19 patients (38.8 %). In all patients (except for one case), one species was isolated. The most frequent isolated microorganism was staphylococcus epidermidis in 9 patients (47.4 %), followed by staphylococcus aureus, bacillus species, streptococcus viridans, streptococcus pneumonia, enterococcus, diphtheroid species, and pseudomonas aeruginosa. No case with fungal growth was found. Microorganisms showed higher sensitivity to different antibiotics. All gram-positive cocci were sensitive to vancomycin and 71.4 % were sensitive to ceftazidime or rifampin. All gram-positive bacilli were sensitive to vancomycin, ciprofloxacin and azithromycin. The gram-negative bacillus (pseudomonas) was sensitive to ceftazidime, ciprofloxacin, imipenem, and rifampin. Conclusion: No single antibiotic was effective against all groups of bacteria present in patients undergoing vitrectomy for posttraumatic endophthalmitis. The conventional intravitreal regimen (vancomycin + ceftazidime) seems to be still valuable in treatment of bacterial endophthalmitis among this group of patients.