Adhesion of Stenotrophomonas maltophilia, Delftia acidovorans and Achromobacter xylosoxidans to contact lenses

Abstract

Purpose: Contact lens cases become contaminated with microbes during use with certain MPDS containing Polyquaternium/Aldox associated with high levels of Gram-negatives in cases, and the degree of contamination is dependent on the type of multipurpose disinfecting solution (MPDS) that is used. Furthermore, the MPDS solution that has high levels of case contamination is also associated with higher levels of infiltrates during lens wear. Thus, we wished to establish whether microbes isolated from these MPDS/lens cases were able to adhere to contact lenses, as this is hypothesized to be the likely mechanism for transfer to the eye leading to the production of infiltrates.

Methods: Strains of D. acidovorans, S. maltophilia, A. xylosoxidans and P. aeruginosa isolated from contact lens cases (or contact lenses at time of infiltrative response, P. aeruginosa only) were used. Initially S. maltophilia was grown on agar plate overnight, cells collected and washed once in PBS and re-suspended in 1:100 TSB:PBS at 1.0 x 10⁵ to 1.0 x 10⁹ cfu/ml and allowed to adhere to lenses (senofilcon A or etafilcon A) for 24 hours. Subsequently, all strains of bacteria were allowed to adhere to lenses for 24 hours at starting inoculum of 1.0 x 10⁷ cfu/ml. The numbers of bacteria adherent to each lens type was estimated by culture.

Results: The adhesion of S.maltophilia to lenses was not affected by initial inoculum size, with adhesion reaching 6.3 ± 0.2 log₁₀cfu/lens after 24 hours. Using initial inocula of 1.0 x 10⁷cfu/ml, adhesion to etafilcon A ranged from 5.0 ± 0.1 log₁₀cfu/lens for A. xylosoxidans to 6.2 ± 0.0 log₁₀cfu/lens for S.maltophilia. Adhesion to senofilcon A ranged from 5.1 ± 0.3 log₁₀cfu/lens for D. acidovorans to 6.2 ± 0.3 log₁₀cfu/lens for P. aeruginosa. Adhesion to etafilcon A was significantly higher (p<0.05) for P. aeruginosa and S. maltophilia compared to D. acidovorans or A. xylosoxidans; adhesion to senofilcon A was significantly higher (p<0.05) for P.aeruginosa only.

Conclusions: This study has found that bacteria that are commonly found in contact lens cases of Polyquaternium/Aldox care systems can adhere to contact lenses in relatively high numbers. This may facilitate their transfer into the eye and the production of corneal infiltrates.

Keywords: 477 contact lens • 480 cornea: basic science • 433 bacterial disease