• Cornea/External Disease

    This study found that corneal ulcers caused by invasive strains of Pseudomonas aeruginosa were associated with better visual acuity at presentation but less improvement in visual acuity after three months than those caused by cytotoxic strains. Furthermore, P. aeruginosa subtype appeared to affect how the ulcers responded to steroid therapy.

    The authors analyzed Pseudomonas aeruginosa isolates from the Steroids for Corneal Ulcers Trial, a National Eye Institute-funded, randomized, placebo-controlled trial investigating the effect of topical corticosteroids as adjunctive treatment with antibiotics for bacterial keratitis.

    Of 101 confirmed P aeruginosa isolates, 74 had a classically cytotoxic or invasive genotype. Corneal ulcers caused by invasive strains were associated at presentation with significantly better visual acuity than corneal ulcers caused by cytotoxic strains after adjusting for the effect of ulcer location. However, at three months, invasive ulcers had improved significantly less than cytotoxic ulcers.

    Compared with topical moxifloxacin alone, adjunctive treatment with topical corticosteroids was associated with significantly more improvement in visual acuity in the invasive subgroup (P = .04) but was associated with less improvement in visual acuity in the cytotoxic subgroup (P = .07).

    The authors conclude that these results suggest the potential to use virulence determinants to guide management decisions in corticosteroid treatment. Additionally, they illustrate the concept that not all infections caused by pathogens of a single species present or respond to treatment similarly. Further studies to elucidate differences in clinical presentation and therapeutic response based on specific virulence determinants for other pathogens may be warranted.