Attachment of Pseudomonas to human-worn, disposable etafilcon A contact lenses

After 7 days of continuous wear, Acuvue (Vistakon, Jacksonville, FL, U.S.A.; etafilcon A) lenses were soaked in a Pseudomonas aeruginosa suspension (1.4 x 10(8) cfu/ml). New Acuvue lenses served as controls. A single strain of P aeruginosa harvested from a human corneal ulcer was used throughout the experiment. Lenses were examined by culture and scanning electron microscopy (SEM). We found significantly greater (p less than 0.05) bacterial attachment to new Acuvue lenses [culture, 3.1 x 10(4) (+/- 0.82 x 10(4)) cfu/mm2; SEM, 2.6 x 10(4) (+/- 0.47 x 10(4)) bacteria/mm2] compared with those previously worn [culture, 1.0 x 10(4) (+/- 0.17 x 10(4)) cfu/mm2; SEM, 0.73 x 10(4) (+/- 0.21 x 10(4)) bacteria/mm2]. No statistical difference was found among the individuals. Our findings demonstrate that the biological coating resulting from 1 week of continuous contact lens wear restricts P. aeruginosa attachment to the Acuvue lens when comparing new and used lenses.