Endophthalmitis caused by gram-positive bacteria resistant to vancomycin: Clinical settings, causative organisms, antimicrobial susceptibilities, and treatment outcomes

Abstract

Purpose: To report the clinical settings, causative organisms, antimicrobial susceptibilities, and treatment outcomes of patients with endophthalmitis caused by gram-positive bacteria resistant to vancomycin. Methods: Retrospective case series of all patients with culture-proven endophthalmitis caused by gram-positive bacteria resistant to vancomycin between January 2010 and December 2016 in LV Prasad Eye Institute, Visakhapatnam, India. Results: The current study included 14 patients. The clinical settings were post-cataract surgery in 8/14 (57.1%) and open globe injury in 6/14 (42.8%). Primary intervention for all patients included tap and intravitreal antibiotic injection. During subsequent follow-up, pars plana vitrectomy was performed in 6 patients and one patient underwent penetrating keratoplasty. Mean number of intravitreal antibiotic injections performed were 3.4 per patient. The most common organisms isolated were coagulase-negative Staphylococci in 6/14 (42.8%), Staphylococcus aureus in 5/14 (35.7%), Streptococcus sp in 2/14 (14.2%) and Bacillus sp in 1/14 (7.14%). In addition to vancomycin, resistance to multiple drugs (three or more groups of antibiotics) was found in all 14 cases. Antimicrobial susceptibility results showed susceptibility to amikacin in 7/14 (50.0%), gatifloxacin in 6/14 (42.8%), moxifloxacin in 3/13 (23.0%), cefazoline in 5/14 (35.7%), cefuroxime in 3/14 (21.4%), ciprofloxacin in 2/14 (14.2%) and linezolid in 5/5 (100%). The mean duration of follow-up was 30.7 weeks (6 weeks–90 weeks). At last follow-up, visual acuity (VA) of 20/200 or better was recorded in 7/14 (50%) and VA < 5/200 occurred in 7/14 (50%). Conclusion and importance: Antimicrobial susceptibility testing may help in selection of suitable antimicrobial agents for repeat intravitreal injection. Inspite of retreatment with intravitreal antibiotics, these patients generally had poor VA outcomes. Keywords: Coagulase-negative Staphylococci, Endophthalmitis, Linezolid, Vancomycin