Interactions of Pseudomonas aeruginosa and Staphylococcus epidermidis in adhesion to a hydrogel

Bacterial strains with known capability to bind to hydrogel lenses were examined for their relative capacities to attach irreversibly to a hydrogel contact lens in pure and mixed cultures.

Time course studies of adhesion through adenosine triphosphate (ATP) or radiolabel analyses indicated that primary adhesion by Pseudomonas aeruginosa to a 37% water-content hydrogel lens was more dense and rapid than that of Staphylococcus epidermidis. Primary adhesion of P. aeruginosa was similar after 5 min and 2 hr, whereas S. epidermidis showed an incremental increase in adhesion over the first 30 min. Sequential challenge of lenses with P. aeruginosa followed by S. epidermidis gave levels of primary adhesion for each species similar to those obtained with single pure cultures. When lenses were challenged with S. epidermidis first, primary adhesion of P. aeruginosa was significantly diminished. Exposures of multiple sets of lenses (n = 4) to a standard inoculum of P. aeruginosa resulted in levels of primary adhesion per lens after 1 hr equivalent to that found for a single lens in 5 min or in 2 hr.

These data further support that normal biota may be protective for the eye. The data also suggest that under conditions of the primary adhesion-screening test, a limited number of cells of GSU no. 3 (selected phenotype) are involved in adhesion to the hydrogel.