Effect of nutrient limitation on adhesion characteristics of Pseudomonas aeruginosa

Pseudomonas aeruginosa causes a variety of diseases in humans including lun g and ocular infections. Infections of the cornea are usually associated wi th wearing contact lenses and can result in loss of vision. This study aime d to determine the effect of carbon or nitrogen limitation on the adhesion to contact lenses of a strain of Ps. aeruginosa isolated from contact lens- related corneal inflammation. Cells were grown in a continuous culture appa ratus in varying levels of glucose or ammonia to effect nutrient limitation . Adhesion to contact lenses was measured as total counts and viable counts . The cell surface hydrophobicity and charge were measured using adhesion t o surface-modified Sepharose. Changes in lipopolysaccharide were determined using 1D SDS-PAGE and changes in cell-surface proteins were measured using 2D gel electrophoresis. The more the cultures were nitrogen limited, the g reater the increase in adhesion to unworn hydrogel contact lenses 0.3 x 10( 3)-2.2 x 10(3) cells/mm(2) on Etafilon A lenses. Cells that were carbon lim ited showed a greater increase in adhesion to contact lenses when the lense s had been coated in artificial tears. It appeared that lipopolysccharide m ay have been involved in the constitutive adhesion to unworn lenses that oc curred during C-limitation, whereas changes in the outer membrane proteins contributed to the increased adhesion under nitrogen limitation, or the cha nge in adhesion that occurred to carbon-limited cells using contact lenses coated in artificial tears. Nine cell-surface proteins appeared during nitr ogen limitation with kDa/pI of 75/4.8, 4.9, 5.0; 62/5.6; 89/6.5; 38/6.4; 28 /1.5; 18/6.4; 12/4.5. Any or all of these may hare been involved in the inc reased adhesion and further experiments are underway to examine this possib ility.