Abstract
Purpose: :
To determine the antimicrobial activity of Vancomycin–supplemented Optisol–GS (Bausch & Lomb) (Optisol–GSV) against ocular pathogens in a clinical corneal storage model.
Methods: :
Four ocular isolates, methicillin resistant Staphylococcus aureus (MRSA), Enterococcus faecalis (vancomycin susceptible), alpha hemolytic streptococcus, and Streptococcus pneumoniae, each at a concentration of 105 CFU/ ml were inoculated both into stock Optisol–GS and Optisol–GS freshly supplemented with Vancomycin (100 µg/ml). The bottles were stored at a refrigerated temperature of 4oC for 72 hours and then at room temperature in an effort to mimic established clinical practice. Time–kill kinetics were determined for each group. The experiment was repeated with Optisol–GSV supplemented 3 months before use, utilizing the time–kill kinetics for comparison of anti–microbial activity.
Results: :
Optisol–GSV did not have an additive effect in Streptococcus pneumoniae and did not reach bactericidal activity after 24 hours of room temperature storage with alpha hemolytic streptococcus. It exhibited a detrimental effect with MRSA, delaying the bactericidal activity for 24 hours over non–supplemented media. An additive effect was seen with Enterococcus faecalis, achieving bactericidal activity after 8 hours of room temperature storage.
Conclusions: :
The rate of keratoplasty–related endophthalmitis remains demonstrably higher than the rate seen in cataract surgery and is an often devastating complication. Proportionately, gram positive pathogens are increasingly responsible and are, as confirmed by this in vitro study, not addressed by current stock antibiotic supplementation. The study confirms that refrigeration temperature reduces the efficacy of supplemental antibiotics, but that Vancomycin supplementation does not comprehensively address the current deficiencies of gram positive coverage.
Keywords: cornea: storage • antibiotics/antifungals/antiparasitics • endophthalmitis