Adhesion of Stenotrophomonas maltophilia, Delftia acidovorans and Achromobacter xylosoxidans to contact lenses in the presence of organic soil

Abstract

Purpose: Contact lens cases become contaminated with microbes during use, and the degree of contamination is dependent on the type of multipurpose disinfecting solution (MPDS) that is used, with certain MPDS containing Polyquad/Aldox associated with high levels of Gram-negatives in cases. We wished to compare adhesion of microbes isolated from these MPDS/lens cases to contact lenses with and without organic soil.

Methods: Strains of D. acidovorans (D.aci 001), S. maltophilia (S.mal 002 & S.mal 006), A. xylosoxidans (A.xyl 001) isolated from contact lens cases (test strains) and P. aeruginosa (P.aer 001) isolated from contact lenses at time of infiltrative response (control strain) were used. Bacteria were grown on agar plates overnight, cells collected and washed once in phosphate buffered saline (PBS) and re-suspended in PBS or 10% organic soil (heat killed S.cerevisiae re-suspended in complement inactivated bovine serum). Two silicone hydrogel lenses (senofilcon A & comfilcon A) were used. Bacteria (1.0 x10⁶ and 1.0 x10⁸ cfu/ml) were allowed to adhere to lenses for 24 hours and the numbers of bacteria adherent to each lens type (with and without organic soil) was estimated by culture.

Results: In general, bacteria adhered in higher numbers to both senofilcon A (0.9 log CFU; p<0.01) and comfilcon A (0.5 log CFU;p<0.05) in the presence of organic soil. Regardless of the lens type, D. aci 001 (0.6 log CFU;p<0.05), S.mal 002 (1.3 log CFU;p<0.05), S.mal 006 (0.7 log CFU;p<0.05) and A.xyl 001 (0.6 log CFU;p<0.05) adhered in higher numbers in the presence of organic soil. However, the presence of organic soil did not have an effect on the adhesion of P.aer 001 (0.2 log CFU;p>0.05).

Conclusions: This study has found that bacteria that are commonly found in contact lens cases can adhere to contact lenses in relatively high numbers in the presence of organic soil. This may indicate that a similar phenomenon could occur in the presence of tears. This may facilitate their transfer from the lens to the cornea and the production of corneal infiltrates.

Keywords: 477 contact lens • 573 keratitis • 594 microbial pathogenesis: experimental studies