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E. W. Fitz, M. Shah, R. C. Gentile, R. B. Rosen; Interaction of Silicone Oil and Perfluorocarbon Liquid With Antibiotics in Endopthalmitis. Invest. Ophthalmol. Vis. Sci. 2007;48(13):692.
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This study examines the interaction of antibiotics, silicone oil and perfluorocarbon liquids in vitro.
Initially, a vancomycin sensitive Bacillus Cereus strain from a case of endophthalmitis was recovered. In a first experiment, a disk of vancomycin (BD BBLTM Sensi-DiscTM Susceptibility Test Discs) was sequestered at the bottom of a tube of thioglycollate medium (BD BBLTM Fluid Thioglycollate Medium). The disk was covered by 2 mLs of perfluorocarbon liquid (FC- 104: 3M corporation), and then 8 mLs of medium into which 1 drop of a solution containing a 105 concentration of B. Cereus was placed. In a subsequent set of experiments, a design involving four tubes of thioglycollate medium was used: tube #1 was a positive control which contained thioglycollate medium and an inoculum of B. Cereus; tube #2 was a negative control which contained liquid vancomycin (1mg/0.1 mL concentration) and an inoculum of B.Cereus; in tube #3, liquid vancomycin was placed under 2 mL of perflourocarbon liquid and then topped with B. Cereus containing thioglycollate medium; finally, in tube #4, liquid vancomycin was placed on top of 2 mLs of 1, 000 centistoke polydimethylsiloxane (Silikon 1000:Alcon Labs) which had been placed over B. Cereus containing thioglycollate medium. Multiple ratios of vancomycin dose to B. Cereus concentration were tried: 300ug of vancomycin with 0.05cc of 105 pathogen, 1mg with 0.05cc of 105, and 1.5mg with 0.05cc of 102.
The growth of the B. Cereus was brisk in the perflourocarbon liquid containing tube despite the presence of a vancomycin disk. In the four tube setup, a dose of 1 mg of vancomycin was unable to inhibit the growth of B. Cereus in any tube. The silicone oil and the perfluorocarbon liquid were recovered from tubes in which the infection was active and subsequently cultured. There was growth of pathogen from both liquids. In contrast, 1.5 mg of liquid vancomycin was able to inhibit the growth of 1/20th of a cc of a 102 concentration B. Cereus in the negative control tube and when placed under perflourocarbon liquid( tube #3). Growth in the positive control was brisk. Faint growth was seen in the culture media of the silicone oil containing tube at 48 hours. Curiously, small bubbles were seen in the silicone oil for the first 24 hours that may have represented antibiotic liquid moving slowly through the oil.
Both silicone oil and pefluorocarbon liquids could sequester antibiotic away from active infection. Careful consideration should be given when considering intraocular tamponade after vitrectomy for endophthalmitis.
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