Endophthalmitis Caused by Staphylococcus epidermidis: Clinical Outcomes and in vitro Antibiotic Susceptibilities

Abstract

Abstract: : Purpose: To analyze the clinical outcomes, treatment patterns, and in vitro antibiotic susceptibility patterns of vitreous isolates from patients with endophthalmitis caused by methicillin–sensitive Staphylococcus epidermidis (MSSE) versus methicillin–resistant Staphylococcus epidermidis (MRSE). Methods: Consecutive case series of 85 patients with Staphylococcus epidermidis endophthalmitis at the Bascom Palmer Eye Institute from January 1, 1996 through July 1, 2004. The in vitro study involved the E test and disc diffusion methods to determine antibiotic susceptibility of the vitreous isolates. Visual outcomes after treatment were recorded from the corresponding medical record. Results: Staphylococcus epidermidis endophthalmitis was identified in 85 patients. The etiologic categories were the following: cataract surgery (59), glaucoma surgery (11), trauma (11), and penetrating keratoplasty (4). There were 51 MRSE and 34 MSSE isolates. There was a greater prevalence of MRSE (43/59) in cataract cases compared to other surgeries (8/26, p = 0.001). All study eyes received intravitreal antibiotics. Initial management consisted of two approaches: vitreous aspiration in 66.7% and pars plana vitrectomy in 33.3%. There was no statistical difference in the visual acuity outcomes between the MRSE and MSSE groups. The percentage of patients with visual acuity better than or equal to 20/200 at each time is as follows: Initial, 9.4%; 3 months, 66.7%; 6 months, 58.1%; 1 year, 75%. The MRSE group had a significantly higher incidence of secondary pars plana vitrectomy and intraocular antibiotics (9/51) compared to the MSSE group (0/34, p = 0.009 Logrank test). Using in vitro antibiotic susceptibility testing, all MSSE and MRSE isolates were susceptible to vancomycin. There was a significant difference (MSSE vs. MRSE) in the susceptibility pattern for the following antibiotics: ciprofloxacin 75% vs. 49%; gentamicin 93.9% vs. 65.4%; clindamicin 93.5% vs. 65.3%; cephalothin 97.2% vs. 0%; imipenem 100% vs. 0%; levofloxacin 83.3% vs. 52.9%; gatifloxacin 100% vs. 66.7%. Conclusions: In the current study, there were no significant differences in visual acuity outcomes of MSSE versus MRSE endophthalmitis. MRSE isolates are more likely to be resistant to a variety of antibiotics including third and fourth generation fluoroquinolones, although all isolates were sensitive to vancomycin.

Keywords: endophthalmitis