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Bandarage M. Bandara, Rani S. Bandara, Duojia Wu, Hua Zhu, Sylvie Franz, Mark D. Willcox; Evaluation of Antimicrobial Activity and Cytotoxicity of Diamidine as a Disinfectant. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6088.
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Aromatic diamidines have been demonstrated to be active against different pathogens, such as bacteria, fungi and protozoa. The purpose of this study was to evaluate the antimicrobial activity and cytotoxicity of diamidine in combination with polyhexamethylene biguanide (PHMB).
Antimicrobial activity of a solution containing diamidine and PHMB was evaluated according to the stand-alone test for contact lens disinfection products described by ISO 14729 (2001). ATCC strains of Serratia marcescens 13880, Staphylococcus aureus 6538, Pseudomonas aeruginosa 9027, F. solani 36031 and Candida albicans 10231 were used to challenge the test solutions. Phosphate buffered saline was used as a control. After disinfection at 25°C for 6 hours, the numbers of viable microorganisms in the samples were determined and the average log reductions in test samples for each strain were calculated. The solutions were also challenged with trophozoites of Acanthamoeba polyphaga ROS and Acanthamoeba castellani 044, and the number of survivors were determined following 7 days of incubation at 32º C. Cytotoxicity of the solutions were examined using agar overlay and acute ocular irritation assays according to ISO 10993-5 and 10993-10 standards respectively.
Diamidine in combination with PHMB demonstrated complete kill of S. marcescens, S. aureus, and P. aeruginosa (i.e. > 7 logs), and displayed 5.1 ± 0.5 or 2.4 ± 0.8 log reductions against C. albicans or F. solani respectively after 6 hours of disinfection. Further, the combination of diamidine and PHMB also displayed 3.0 and 2.6 log reductions against trophozoites of A. polyphaga and A. castellanii respectively after 6 hours of disinfection. Both agar overlay and acute ocular irritation assays showed no toxic effect of the combination of diamidine and PHMB.
The results have demonstrated that a combination of diamidine and PHMB is effective against various microorganisms. The combination was not toxic. This combination may be useful in development of safe and effective disinfection solutions for soft contact lenses.
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