Clinical and Epidemiological Advantages of Culturing Bacterial Keratitis

PURPOSETo examine how the corneal culture result is associated with the antibacterial treatment response rate of ulcerative keratitis in a prospective cohort study and to determine whether culture confirmation affects the relative treatment effect in randomized clinical trials of bacterial keratitis. METHODSThe influence of a positive bacterial culture on the rates of antibacterial improvement and cure was estimated by proportional hazards regression among 608 patients with ulcerative keratitis treated with topical ciprofloxacin monotherapy. The interaction of culture confirmation on the relative cure rates of 735 patients enrolled in 4 clinical trials comparing fluoroquinolone monotherapy to combined cephalosporin and aminoglycoside therapy was evaluated by metaregression. RESULTSIn a prospective cohort study, bacterial keratitis that was culture positive and longer than 4 mm had a 37% (95% confidence interval, 20%, 51%) slower improvement rate and a 56% (95% confidence interval, 41%, 67%) slower cure rate during ciprofloxacin therapy. Among randomized clinical trials, the culture result did not modify the relative effect of treatments having similar 1-week cure rates. CONCLUSIONSCulture confirmation affects the antibacterial therapeutic response rate of ulcerative keratitis and, while not modifying the comparative effect of equivalent antibacterial treatments, facilitates generalizability of clinical trials of bacterial keratitis.