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Secretory Phospholipase A₂ Deposition on Contact Lenses and Its Effect on Bacterial Adhesion

From the Vision Cooperative Research Centre, The University of New South Wales, Sydney, New South Wales, Australia.

PURPOSE. Secretory phospholipase A₂ (sPLA₂) is a potent antibacterial enzyme in tears and has been found to kill Staphylococcus aureus rapidly in vitro. The purpose was to determine whether sPLA₂ deposition is associated with contact lens (CL) type, if sPLA₂ remains active on CLs, and if this has an effect on bacterial adhesion.

METHODS. Ionic (etafilcon A) and nonionic (Polymacon) high-water, soft CLs were used. CLs were worn for 6 hours (daily wear, n = 39) or 6 nights on an extended-wear schedule (n = 25). Tears were collected from patients and worn contact lenses were removed and protein and active enzymes extracted for estimation of their levels. The number of S. aureus adhering to sPLA₂-soaked CLs in vitro was also quantified.

RESULTS. There was no significant difference in the concentration of sPLA₂ in tears between groups of daily CL wearers. Significantly less sPLA₂ was recovered from Polymacon CLs for both daily and extended wear compared with etafilcon A CLs (daily wear: 3 vs. 5 ng/lens; extended wear: 3 vs. 6 ng/lens; P < 0.05). sPLA₂ activity correlated with protein amounts from lenses. Relatively less active sPLA₂ was recovered from Polymacon contact lenses. sPLA₂ reduced adhesion of Staphylococcus to contact lenses in vitro.

CONCLUSIONS. Etafilcon A CLs absorb more active sPLA₂ than Polymacon CLs, which increases with length of CL wear. The sequestering of sPLA₂ onto CLs did not affect amounts of the enzyme in tears. sPLA₂ adsorbed to a CL can reduce the viable Staphylococcus adhering to the CL, which may protect the eye from colonization by this pathogen.