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Ajay Kumar Vijay, Hua Zhu, Mark Willcox, Fiona Stapleton, Roya N. Borazjani; Contact Lens Storage Case Hygiene Practice and Case Contamination. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6480.
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Persistent microbial contamination of contact lens (CL) storage cases is common and is associated with microbial keratitis and corneal infiltrates. This study investigated the ability of storage case care and cleaning regimens to remove robust microbial biofilms.
Test storage cases were inoculated with 2mL of 106 CFU/mL of ocular isolates of either P.aeruginosa or S.aureus and incubated for 48 hours. Cases were subsequently treated with either a 10 second rinse (hot water or test multipurpose solution (MPS, containing polyhexamethyl biguanide and polyquad), soaking (MPS or 3% hydrogen peroxide), followed by air-drying for 6 hours or tissue wiping. The number of survivors were enumerated using standard techniques.
Challenge biofilms comprised 8.3±0.2 log CFU (P.aeruginosa) and 6.5±0.2 log CFU (S.aureus). Rinsing with MPS or hot water and air-drying cases had no significant effect on S.aureus biofilms and partially removed P.aeruginosa biofilms (3.2-6.8 log CFU survivors). Soaking in MPS for 4 hours caused no reduction of biofilm whereas hydrogen peroxide partially removed biofilms (6.1±0.7 log CFU survivors P.aeruginosa; 1.2±2.1 log CFU S.aureus). Rinsing or soaking cases with MPS, tissue wiping and air-drying showed the greatest reduction in biofilm (0.9±0.2 log CFU survivors P.aeruginosa; 3.4±1.2 log CFU S.aureus).
Biofilms formed by the S.aureus isolate were more resistant to hygiene procedures than those of the P.aeruginosa isolate. Rinsing (with MPS or hot water) followed by 6 hours of air-drying is insufficient to remove heavy biofilm. Soaking in the test MPS followed by tissue wiping or a long drying period was effective for both strains.
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