Purpose To report the clinical settings, antibiotic susceptibilities, and outcomes of endophthalmitis caused by Streptococcus species. Design Retrospective, observational case series. Methods Single-center study evaluating all patients with culture-positive endophthalmitis caused by Streptococcus species between January 1, 2000, and December 31, 2011. Results Study criteria were met by 63 patients. The most common clinical settings were bleb associated (n = 17; 27%), after intravitreal injection (n = 16; 25%), and after cataract surgery (n = 13; 21%). The isolates were Streptococcus viridans (n = 47; 71%), Streptococcus pneumoniae (n = 13; 21%), and β-hemolytic Streptococci (n = 5; 8%). Sixty (95%) of 63 isolates were susceptible to vancomycin, 47 (98%) of 48 isolates were susceptible to ceftriaxone (third-generation cephalosporin), and 57 (93%) of 61 isolates were susceptible to levofloxacin (third-generation fluoroquinolone). Between the first and second half of the study, the minimal inhibitory concentration of antibiotics required to inhibit 90% of isolates increased by 1.5-fold for ceftriaxone and 2-fold for levofloxacin and remained the same for vancomycin. Initial treatment was vitreous tap (49; 78%) or pars plana vitrectomy (14; 22%); all received intravitreal antibiotics. Visual acuity outcomes were variable: best-corrected visual acuity was 20/400 or better in 16 (25%) patients and worse than 20/400 in 47 (75%) patients. Evisceration or enucleation was performed in 16 (25%) patients. Conclusions Streptococcus isolates generally had high susceptibility rates to commonly used antibiotics. Higher antibiotic minimal inhibitory concentrations were required to inhibit 90% of isolates in vitro in the second half of the study period compared with the first half. Despite prompt treatment, most patients had poor outcomes.
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