Anterior chamber and vitreous concordance in endophthalmitis: Implications for prophylaxis

Objective: To examine the relationship between anterior chamber (AC) sterilization and vitreous positivity rate in cases of endophthalmitis. Design: Retrospective case-control study. A review of all consecutive cases of endophthalmitis (N=758) between January 1, 1999, and December 31, 2008, identified 229 matched AC and vitreous samples. Matched samples were evaluated for sensitivity and specificity, positive and negative predictive values, and positive and negative likelihood ratios. The main outcome measures were sensitivity and specificity of AC and vitreous samples in cases of endophthalmitis. Antibiotic resistance profiles from culture-positive endophthalmitis cases are given. Results: Gram-positive organisms accounted for 124 of 154 (80.5%) culture-positive endophthalmitis isolates (146 of 229 [63.8%]). The sensitivity (0.36%) and specificity (0.71%) of AC culture results were poor predictors of positive vitreous culture. Positive and negative predictive values were less than 60%. Positive likelihood ratio (1.24) and negative likelihood (0.91) of AC culture results did not aid in predicting vitreous findings. Grampositive isolates demonstrated in vitro resistance to moxifloxacin (47.1%), ciprofloxacin (43.4%), gatifloxacin (36.8%), levofloxacin (29.0%), gentamicin (19.2%), and ceftazidime (16.7%). Conclusions: The AC lacks concordance with vitreous findings in cases of endophthalmitis. Use of broadspectrum antibiotics to sterilize the ocular surface and provide therapeutic levels in the AC may not prevent endophthalmitis. In this study, the finding of a sterile AC did not rule out vitreous infection. These results may have implications for the routine use of broad-spectrum antibiotics as a means of vitreous protection and endophthalmitis prophylaxis.