Increased resistance of contact lens-related bacterial biofilms to antimicrobial activity of soft contact lens care solutions.

PURPOSE: To determine if clinical and reference strains of Pseudomonas aeruginosa, Serratia marcescens, and Staphylococcus aureus form biofilms on silicone hydrogel contact lenses and ascertain antimicrobial activities of contact lens care solutions.
METHODS: Clinical and American Type Culture Collection reference strains of P. aeruginosa, S. marcescens, and S. aureus were incubated with lotrafilcon A lenses under conditions that facilitate biofilm formation. Biofilms were quantified by quantitative culturing (colony-forming units, CFUs), and gross morphology and architecture were evaluated using scanning electron microscopy and confocal microscopy. Susceptibilities of the planktonic and biofilm growth phases of the bacteria to 5 common multipurpose contact lens care solutions and 1 hydrogen peroxide care solution were assessed.
RESULTS: Pseudomonas aeruginosa, S. marcescens, and S. aureus reference and clinical strains formed biofilms on lotrafilcon A silicone hydrogel contact lenses, as dense networks of cells arranged in multiple layers with visible extracellular matrix. The biofilms were resistant to commonly used biguanide-preserved multipurpose care solutions. Pseudomonas aeruginosa and S. aureus biofilms were susceptible to a hydrogen peroxide and a polyquaternium-preserved care solution, whereas S. marcescens biofilm was resistant to a polyquaternium-preserved care solution but susceptible to hydrogen peroxide disinfection. In contrast, the planktonic forms were always susceptible.
CONCLUSION: Pseudomonas aeruginosa, S. marcescens, and S. aureus form biofilms on lotrafilcon A contact lenses, which in contrast to planktonic cells are resistant to the antimicrobial activity of several soft contact lens care products.