Abstract
Purpose:
To determine the antimicrobial susceptibility profile of viridans group streptococci (VGS) isolated from endophthalmitis.
Methods:
27 consecutive, non-duplicate isolates of VGS recovered from patients with clinically diagnosed endophthalmitis seen at the Visual Sciences and Ophthalmology Department of Escola Paulista de Medicina, Federal University of Sao Paulo in the last 11 years were included. Isolates were identified on the basis of biochemical tests regularly used to differentiate alpha-hemolytic streptococci including optochin susceptibility test and bile solubility test. Minimum inhibitory concentration (MIC) was determined for a panel of 19 antibiotics using standard MIC plates (Sensititre Trek).
Results:
All the isolates were susceptible (100%) to vancomycin, linezolid, and cephalosporins: cefuroxime, cefotaxime, ceftriaxone and cefepime. It was observed high susceptibility rates to the fluoroquinolones levofloxacin (100%) and moxifloxacin (96.4%) and to carbapenem: ertapenem and meropenem (both 96.4%) and daptomycin (96.4%). The isolates were 53.6% susceptible to sulfamethoxazole-trimethoprim. Resistance rate to penicillin was low (14.3%). Erythromycin and azithromycin demonstrated high resistance rates, 50% and 39.3%, respectively.
Conclusions:
Although the correlation between the phenotypic tests and the initial identification found in this study, the biochemical characteristics currently used to classify the alpha-hemolytic Streptococcus are not reliable. Further investigation using molecular tests, like multilocus sequence analysis (MLSA) will be performed in order to determine the species and evaluate trends in antimicrobial susceptibility. The isolates were susceptible to antibiotics commonly used for treatment and prevention of endophthalmitis including vancomycin, cephalosporins and fluoroquinolones.
Keywords: 513 endophthalmitis •
422 antibiotics/antifungals/antiparasitics