Quantifying Pseudomonas aeruginosa adhesion to contact lenses

Pseudomonal keratitis can occur in soft contact lens wearers following compromise of the corneal epithelium and exposure to pathogens. This study was initiated to determine if Pseudomonas aeruginosa has the ability to adhere preferentially to unused contact lenses made from different FDA group polymers.

Pseudomonas aeruginosa (strain PA01) was grown to its early stationary phase and diluted into phosphate-buffered saline to a concentration of 12000 to 16000 cells/mL. Samples from each of the four FDA-designated polymer classes used for the manufacture of soft lenses were incubated in pseudomonal inoculant for 4 hours. The lenses were removed and the number of bacteria bound was quantified using electrical impedance particle counting.

A lens constructed from a group I polymer (nonionic polymer with <50% water) bound the fewest bacteria (7.2% of total cells +/- 1.0 SD) whereas a lens made from group II polymers (nonionic polymer with >50% water) showed the highest level of bacterial binding (42% of total cells +/- 4.5 SD). Lenses constructed from group III and IV polymers showed intermediate levels of bacterial binding (28.4% +/- 1.8 SD and 29.3% +/- 1.7 SD, respectively).

The polymer type used to construct the contact lens may influence subsequent bacterial adhesion events. Contact lenses made from nonionic polymers with high water content may carry higher risks of bacterial contamination.