Extended contact lens wear enhances Pseudomonas aeruginosa adherence to human corneal epithelium.

Extended wear of soft contact lenses is associated with an increased risk of Pseudomonas aeruginosa infection of the cornea. To assess the role of bacterial adherence in the pathogenesis of these infections, superficial corneal epithelial cells and leukocytes from ten patients who use extended-wear soft lenses and ten control eyes were compared for their propensity to attach P. aeruginosa in vitro. Cells were washed from the cornea by saline irrigation, incubated with a 10-ml solution containing 10(7) colony-forming units/ml of bacteria at 35 degrees C for 30 min, collected on a filter, and prepared using a modified acridine orange staining method. Fluorescence microscopy showed bacterial adherence to corneal epithelial cells, leukocytes, and ocular mucus. The mean number of bacteria adhering to epithelial cells was 2.6 for control eyes and 6.6 for the lens-wearing eyes (P = 0.002). The percentage of epithelial cells attaching greater than or equal to four bacteria was higher for lens-wearing eyes than control eyes (57.4% versus 26.0%, P = 0.0005). There was no significant difference between contact lens-wearing eyes and control eyes in the number of leukocytes collected or in the number of bacteria attached to these cells. These results show that P. aeruginosa adherence to epithelial cells is enhanced in those who use extended-wear soft contact lenses, and this may contribute to the increased incidence of P. aeruginosa keratitis for this population.