D-067. Contact Lens-Associated Keratitis Involving Pseudomonas aeruginosa Biofilms In Vivo

K. P. C. Tam¹, J. J. Mun¹, I. Alarcon², D. Kowbel¹, D. J. Evans^1,3, S. M. J. Fleiszig^1,2;
¹Sch. of Optometry, Univ. of California, Berkeley, CA, ²Univ. of California, Berkeley, CA, ³Coll. of Pharmacy, Touro Univ. California, Vallejo, CA.

Background: Contact lens wear predisposes to P. aeruginosa keratitis, yet the normal ocular surface is constantly exposed to microbes (including P. aeruginosa) without infection. We aimed to determine how lens wear enables susceptibility to infection. Methods: The left corneas of Lewis rats were tissue-paper blotted to disrupt epithelial barrier function (to fluorescein), inoculated with 10⁹ cfu of P. aeruginosa (strain PAO1), then fitted with custom made soft contact lenses pre-soaked in P. aeruginosa (10¹¹ cfu/ml) for 2 h without prior rinsing to remove non-adherent bacteria. Corneas were monitored daily for evidence of disease (opacity). Lenses were removed 1 to 7 days after disease was first detected and the underlying ocular surface was immediately washed with PBS to collect non-adherent bacteria. Viable counts were performed on both contact lens homogenates and ocular surface washes. In other experiments, the ability of the non-lens wearing eye to clear bacteria was determined by inoculating healthy rat and mouse eyes (10⁹ cfu PAO1) prior to washing to collect viable bacteria at various time points post-inoculation (PI). Susceptibility of tissue-paper blotted eyes to bacterial infection (10⁹ cfu PAO1) was assessed in mice. Results: Inoculated lens-wearing rats began to develop disease 5-14 days PI. At sacrifice (6-21 days PI), significant numbers of bacteria were recovered from both the ocular surface (~10⁵ cfu) and the contact lens (~10⁷ cfu). Without a lens, the inoculum was rapidly cleared (99.9999% removed within 3 h), and did not enable infection of mouse corneas even after the tissue-paper blotting procedure that disrupts epithelial barrier function. Conclusions: While rapidly cleared from the normal ocular surface, P. aeruginosa can persist on and under a contact lens in the eye for extended periods of time eventually leading to keratitis within 1-2 weeks. The data suggest involvement of biofilm formation on the contact lens in persistence and virulence in this model. The respective involvement of bacterial adaptation versus bacterial/lens-mediated changes to ocular defenses against infection is to be determined.