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Bandarage Mahesh Kithsiri Bandara, Rani S Bandara, Hua Zhu, Mark D P Willcox, Percy Lazon De La Jara, Brien A Holden; Disinfection efficacy of hexamidine against ocular pathogens. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6045.
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Hexamidine has demonstrated broad spectrum antimicrobial activity. The purpose of this study was to evaluate the antimicrobial activity of hexamidine in combination with polyhexamethylene biguanide (PHMB) against ocular pathogens.
Antimicrobial activity of solutions containing 50, 75, 100 and 125 ppm of hexamidine in combination with or without 1 ppm PHMB were evaluated according to the stand-alone test described by ISO 14729 (2001). ATCC strains of Serratia marcescens 13880, Staphylococcus aureus 6538, Pseudomonas aeruginosa 9027, Fusarium solani 36031, Candida albicans 10231, and clinically resistant strains of Staphylococcus aureus, Stenotrophomonas maltophilia, Delftia acidovorans, Serratia marcescens and Candida albicans were used to challenge the test solutions. After incubation 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 castellani 044, and the number of survivors were determined following 7 days at 32°C. Phosphate buffered saline was used as a control. Cytotoxicity of the solutions was also examined using direct contact assay according to ISO 10993-5 standards.
The tested lowest concentration of hexamidine (50 ppm) in combination with 1 ppm PHMB demonstrated complete kill of S. marcescens, S. aureus, and P. aeruginosa ( > 6 logs) after 6 hours of disinfection. Further, the same concentrations of PHMB and hexamidine also displayed > 1 log reductions against C. albicans, F. solani and trophozoites of A. castellanii and displayed >3.0 log reductions against clinical strains of S. maltophilia, and C. albicans and D. acidovorans. This activity of hexamidine increased in a dose dependent manner. The direct contact assay showed no cytotoxic effect of the tested solutions.
The results have demonstrated that the combination of hexamidine and PHMB was effective against all tested micoorganisms. This non toxic combination might be useful in development of a safe and effective disinfection solution for soft contact lenses.
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