Comparison of acridine orange and Gram stains in bacterial keratitis.

We assessed the comparative sensitivities of acridine orange and Gram stains in the examination of corneal scrapings using an experimental model of Pseudomonas aeruginosa keratitis. Acridine orange was more sensitive than Gram stain, requiring concentrations of about 10(4) colony-forming units/mg of corneal tissue compared to approximately 10(5) colony-forming units/mg. Our clinical experience with 21 consecutive cases of suspected microbial keratitis showed a similar diagnostic accuracy of acridine orange and Gram stain. Acridine orange accurately predicted culture results in 15 of 21 specimens (71%) compared to a diagnostic accuracy of 62% (13 of 21 specimens) for Gram stain.