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C. Lakkis, S. Lakkola, S. Conaglen; The Effect of Organic Soil on Contact Lens Disinfection Efficacy Against Serratia Marcescens With Extended Storage. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5375.
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© ARVO (1962-2015); The Authors (2016-present)
Organic material, such as tear film components, may affect the antimicrobial efficacy of chemical contact lens (CL) disinfectants. We have shown that organic soil increases Serratia marcescens (S. marcescens) resistance to some CL disinfectants when tested over 6 hours (h). The aim of this study was to investigate the effect of organic soil on disinfection of S. marcescens strains over extended storage periods of 1 week (W).
Disinfection susceptibility of five S. marcescens isolates (ATCC 13880 and four clinical ocular isolates) was investigated with and without the addition of organic soil (ISO 14729 organic soil model). Six disinfectants (A-F) were assessed; A and D preserved with polyquaternium-1 0.001% and myristamidopropyl dimethylamine 0.0005%, B, C and E preserved with polyhexamethylene biguanide (PHMB) 0.0001% and F preserved with alexidine 0.00045%. 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 W) post-inoculation.
At 1 W, resistance to disinfection varied significantly between the strains for solutions A, B, D & E, with poorer efficacy observed with the addition of organic soil compared to unsoiled samples for at least one isolate (p<0.05). Three isolates in solutions B & E and two isolates in solution D showed significant increases (1.3 to 2.1 logs) after 1 W of storage with organic soil (p<0.05), despite log reductions at earlier time points. Susceptibility to solutions C and F did not vary significantly between the strains in the presence or absence of organic soil. The lab strain ATCC 13880 was more susceptible to all disinfectants than the clinical isolates (p<0.05).
S. marcescens isolates varied in susceptibility to four out of six CL disinfectants in the presence of organic soil, despite extended storage time of 1 W. The majority of isolates showed greater resistance when tested with organic soil. Clinical isolates should be included in regulatory testing of CL disinfectants, as activity against one laboratory strain does not ensure efficacy against clinical isolates. Minimizing the presence of organic material within the CL case may decrease bacterial resistance to disinfection and reduce contamination of CLs and CL care systems.
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