The Antimicrobial Activity of Multipurpose Disinfecting Solutions in the Presence of Different Organic Soils

OBJECTIVE: During use, contact lens disinfecting solutions are exposed to tears and clinical microbial isolates. The current study was designed to test the performance of several disinfecting solution in the presence of organic soils or clinical isolates. METHODS: Standard and clinical isolates were exposed to the disinfecting solutions in the presence or absence of different organic soils. The number of microbial cells killed during disinfection was established by growing cells after disinfection on agar plates. RESULTS: The disinfecting activity of the povidone-iodine or hydrogen peroxide solutions was not affected by the organic soils or clinical isolates. The presence of yeast organic soil did not affect the performance of the disinfecting solutions when tested with standard microbial strains, but the addition of a model tear organic soil significantly reduced the disinfecting activity of the solutions containing various combinations of polyhexamethylene biguanide, polyquaternium-1, alexidine, and myristamindopropyl dimethylamine especially when tested against the standard fungal strains (reducing the effectiveness by between 0.5-4 log10) or the clinical bacterial isolates (reducing the effectiveness by between 0.5-3.5 log10). One disinfecting solution that contained polyquaternium-1 and myristamindopropyl dimethylamine had very poor activity against the clinical bacterial isolates in the absence or presence of either organic soil. CONCLUSIONS: Povidone-iodine or hydrogen peroxide disinfecting solutions are not affected by organic soils and are very active against clinical bacterial isolates. Disinfecting solutions containing combinations of polyhexamethylene biguanide, polyquaternium-1, alexidine, and myristamindopropyl dimethylamine are affected by model tear organic soil and may have poor activity against clinical isolates.