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C. Lakkis, S. Lakkola, F. Anastasopoulos; The Effect of Organic Soil on Hydrogen Peroxide Disinfection Efficacy During Extended Storage. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3410.
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Organic material, such as tear film components, may affect the antimicrobial efficacy of contact lens (CL) disinfectants. We have previously shown that organic soil increases S. marcescens resistance to many multipurpose solutions at the minimum recommended disinfection time and with extended storage. The aim of this study was to investigate the effect of organic soil on hydrogen peroxide disinfection of S. marcescens strains over extended storage periods of 1 week.
Disinfection susceptibility of 5 S. marcescens isolates (ATCC 13880 and 4 clinical ocular isolates) was investigated with and without the addition of organic soil (ISO 14729 organic soil model). Three lots of disinfectant (3% hydrogen peroxide with Pluronic 17R4) were assessed with each strain. Testing was carried out in CL cases at room temperature using an initial inoculum of 106 CFU/ml. The number of bacterial survivors was determined at 4, 6, 24, 48 and 168 h (1 week) post-inoculation.
At 4, 6 and 24 h, there were no significant differences between soiled and unsoiled samples (p>0.05) with log reductions of 5.6 ± 0.8 to 6.1 ± 0.3 logs achieved. However, at 48 h and 1 week, significantly poorer efficacy was observed in the presence of organic soil compared to unsoiled samples (p<0.05), due to regrowth of bacteria within the solution. Four out of five isolates, including ATCC 13880, showed significant increases (1.3 to 2.4 logs compared to baseline) after 1 week of storage with organic soil (p<0.05), despite significant log reductions at earlier time points.
Organic soil significantly decreased hydrogen peroxide efficacy against S. marcescens over extended storage times. The majority of isolates showed greater resistance when tested with organic soil. Minimizing organic material within the CL case may decrease bacterial resistance to disinfection and reduce contamination of care systems. Hydrogen peroxide users should be encouraged to change their disinfection solution every 24 h and avoid extended storage times.
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