Pseudomonas aeruginosa 122, Serratia marcescens ATCC 13880, and Staphylococcus aureus ATCC 6538 were selected as the challenge bacteria. These strains were chosen because they demonstrated the ability to form adequate biofilms on lens storage cases in a pilot study. The strains of S. marcescens and S. aureus were standard strains, whereas P. aeruginosa 122 was isolated from a case of microbial keratitis. Each strain was obtained from a bacterial stock stored at −80°C and streaked on a chocolate agar plate (Oxoid Australia, Sydney, NSW, Australia). Plates were incubated in O2 at 37°C for 24 hours. After 24 hours, colonies were harvested and suspended in PBS with 1% Luria broth (PBS-LB;10.0 g/L tryptone, 5.0 g/L yeast extract, and 5.0 g/L NaCl) and adjusted spectrophotometrically to achieve an optical density (OD) reading of 0.1 (approx. 108 CFU/mL) at 660 nm wavelength. Subsequently, the concentration of each inoculum was adjusted to approximately 106 per mL using serial dilution in PBS-LB.