Material-Dependent Adhesion and Biofilm Formation of Pseudomonas aeruginosa and Candida albicans on Six Commercial Soft Contact Lens Materials: An In Vitro Comparison

Contact lens-related microbial keratitis remains a major cause of ocular morbidity, and microbial adhesion and biofilm development on lens surfaces may contribute to its pathogenesis. This study compared adhesion and biofilm formation by Pseudomonas aeruginosa and Candida albicans on six commercially available soft contact lens materials (five silicone hydrogels and one conventional hydrogel). Comfilcon A, Senofilcon A, Lotrafilcon A, Lotrafilcon B, Delefilcon A, and Nelfilcon A were evaluated in a 24 h in vitro model using three selected reference strains (P. aeruginosa ATCC 27853, P. aeruginosa ATCC 10145, and C. albicans ATCC 10231). Adherent biomass was quantified by crystal violet staining (OD570), while viable adherent cells were enumerated by colony-forming unit counts on three parallel lenses per material. Adherent biomass differed significantly among lens materials for all strains (p ≤ 0.01; partial η2 = 0.69–0.97), with 3.4- to 4.3-fold differences between the materials showing the highest and lowest biomass values. Lotrafilcon A and Lotrafilcon B generally supported the highest biomass values, whereas the lowest values were observed on Senofilcon A, Nelfilcon A or Delefilcon A, depending on the strain; the materials with the highest biomass were therefore the same for both species, whereas those with the lowest biomass differed between species and strains. Biomass varied several-fold among the five silicone hydrogel materials. In material-level analyses (n = 6), no statistically significant association was detected between adherent biomass and either water content or replacement modality. Under the static in vitro conditions used, microbial adhesion and biofilm formation differed markedly among individual commercial lens materials. Because each material combines several characteristics and only one conventional hydrogel was included, the design does not allow these differences to be attributed to polymer class, water content, or any individual surface feature.