Stenotrophomonas maltophilia induced post-cataract-surgery endophthalmitis: Outbreak investigation and clinical courses of 26 patients.

BACKGROUND: Stenotrophomonas maltophilia, a microorganism which colonizes plastic material, is a rare causative agent of iatrogenic endophthalmitis. PATIENTS AND METHODS: A cluster of 26 cases of acute post-cataract-surgery endophthalmitis (PE) was identified. An outbreak investigation was performed. Information was abstracted from patients' charts and questionnaires sent to patients and their general practitioners. Vision was examined before, during, as well as one and six months after acute PE. Bacterial isolates were subjected to molecular typing.
RESULTS: All patients initially received empiric systemic antibiotic treatment. The source of the infections was identified to be the rinsing solution used during cataract surgery, which was contaminated with two strains of S. maltophilia. Antibiotic therapy was subsequently changed to trimethoprim/sulfamethoxazol and ciprofloxacin for 30 days, complemented with iv fluocortolone and topical treatment with prednisolone, ciprofloxacin, and chloramphenicol. Twenty-one patients (81%) received pars plana vitrectomy and were additionally treated with intravitreal injections of vancomycin, amikacin and dexamethasone, or imipenem and dexamethasone, respectively. In addition, oxacillin, mezlocillin, and prednisolone were applied subconjunctivally after vitrectomy. Six months after acute infection, a final visual acuity of > or = 0.2 was achieved by 21/26 patients (80%), a visual acuity of > or = 0.5 by 14/26 patients (54%). Twenty of 26 patients (77%, 17 of whom had undergone vitrectomy) achieved a higher visual acuity than before surgery. Patients from the vitrectomy group had a median final visual acuity of 0.5 compared to 0.4 in the 5 patients without vitrectomy. There was 1 retinal ablation, 2 intra-retinal bleedings, and relapse of infection in 2/26 patients (8%), with isolation of S. maltophilia in one of the relapsing infection cases.
CONCLUSIONS: Empiric antibiotic treatment of PE may not adequately treat rare pathogens such as S. maltophilia. Administration of an effective systemic or intravitreal antibiotic treatment after identification of S. maltophilia may have contributed to the favorable clinical course and relatively low relapse frequency in our patients. Despite the known problem of persistence of S. maltophilia, visual acuity outcome after treatment is comparable to PE induced by other Gram-positive or Gram-negative bacteria.