To determine whether intravitreal dexa methasone administration can alter the elimination of intravitreal vancomycin hydrochloride in rabbit eyes with experimental Streptococcus pneumoniae endophthalmitis. Methods: Albino rabbits were infected with an intravitreal inoculum of S pneumoniae (2 ϫ 10 3 colony-forming units) and randomized after 24 hours to treatment with intravitreal vancomycin hydrochloride (1 mg), alone or in combination with intravitreal dexamethasone (400 µg). For comparison, uninfected eyes were similarly treated. All eyes were enucleated 24, 48, or 72 hours after treatment, and vitreous levels of vancomycin were quantitated using a fluorescence polarizing immunoassay. Results: The half-life of intravitreal vancomycin in infected eyes was prolonged from 48 to 84 hours when eyes were treated with dexamethasone. Conversely, such treatment shortened the half-life in uninfected eyes from 56 to 42 hours. Conclusions: Intravitreal dexamethasone administration reduces the elimination of intravitreal vancomycin in rabbit eyes with pneumococcal endophthalmitis, whereas an opposite effect is noted in uninfected eyes.

Little is known about the mucosal microflora of the colon and rectum at the time of elective surgery. Our objective was to determine the concentrations of anaerobic and aerobic bacteria associated with the mucosa of the mechanically prepared large bowel. Ten patients were studied after a standard polyethylene glycol-electrolyte lavage preparation. No patient had taken antibiotics in the preceding four weeks. Sterile wire brushes passed through the colonoscope during advancement were used to culture the rectal, transverse colon, and cecal mucosa. Total anaerobic, aerobic, Gram-positive, and enteric bacterial counts were determined along with specific cultures for Bacteroides fragilis, Clostridium difficile, Escherichia coli, Pseudomonas aeruginosa, enterococcus, and staphylococcus species. The results showed that there was a significant increase (P < 0.01) in aerobes, anaerobes, enterics, Gram positives, B. fragilis, and E. coli mucosal counts with proximal progression. Aerobes showed a steady gradient, while anaerobes demonstrated an increase from the rectum to the transverse colon but no change between the transverse colon and cecum. We conclude that, in the prepared bowel, there is an increase in the mucosal bacterial counts in the more proximal portions of the bowel. The results may serve as a baseline for future studies on the mucosal-associated bacteria of the large intestine.

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