Broad Spectrum of Antibacterial Activity of a New Multipurpose Disinfecting Solution

Purpose. Contact lens–related corneal infection and inflammation have been associated with microbial contamination of the contact lens or contact lens storage case. Antimicrobial performance of contact lens disinfection systems is an important factor in reducing contamination. The purpose of this study was to evaluate the antimicrobial efficacy of a new multipurpose disinfecting solution (MPDS), preserved with 0.001% polyquaternium-1 and 0.0005% myristamidopropyl dimethylamine, against a range of bacteria and fungi. Methods. The MPDS was challenged with a broad range of clinical and environmental isolates, including 10 gram-positive and eight gram-negative bacterial strains and three strains of fungi. The panel of reference microorganisms recommended by the International Organization for Standardization standards was also included. Samples were removed for analysis after 4 hours, 6 hours, or 24 hours of exposure to the MPDS. The number of survivors was determined by plate counts. Results. The new MPDS showed antimicrobial activity against the five reference microorganisms in excess of that recommended by International Organization for Standardization standards. The solution showed a broad spectrum of antibacterial activity, showing more than a 3 log reduction (mean, 4.2 ± 1.4) in 8 of 10 gram-positive bacteria and more than a 4 log reduction (mean, 5.3 ± 0.5) in all eight gram-negative bacteria at the 6-hour disinfection time. The efficacy of the solution was increased with longer exposure times (P<0.01). Some differences in activity between clinical and the reference bacterial strains were observed. The solution exceeded the 1 log unit reduction for all fungal species tested. Conclusions. The new MPDS produced a significant reduction in the growth of various clinical and environmental bacteria and fungi.