THE ROLE OF PILI IN THE ATTACHMENT OF PSEUDOMONAS-AERUGINOSA TO UNWORN HYDROGEL CONTACT-LENSES

Contamination of contact lenses is thought to increase the risk of inf ectious keratitis, yet factors promoting attachment of bacteria to con tact lenses are not fully understood. It has been suggested that strai ns of Pseudomonas aeruginosa attach to mucosal surfaces via pill which are appendages found on some strains. This study investigated the rol e of pill and the effect of incubation time on the attachment of P. ae ruginosa to 20 unworn hydrogel lenses representative of each of the fo ur FDA categories. Ten lenses were incubated for 15 minutes and anothe r ten for 180 minutes. Lenses were incubated with either PAK+ P. aerug inosa which possessed pill or its isogenic mutant pair, PAK-, which wa s genetically similar except for the absence of pill. Bacteria were qu antified, following homogenization of the contact lens, by viable coun ts. Non-piliated bacteria were significantly more likely to adhere to the lenses (p < 0.001). A significant interaction between lens type an d incubation time was observed (p < 0.05); thus it is difficult to gen eralize about either of these effects in isolation. These results show that surface characteristics may confer an attachment advantage to ba cteria.