Comparison of the Efficacy of Disinfectants used in Dental Clinic

Objective: We would like to investigate the efficacy and verify the shelf life of disinfectants commercially used in dental clinic against three standard bacterial strains. Method:  Staphylococus aureus (ATCC 25923), Salmonella typhimurium (ATCC 14028) and Bacillus subtilis (ATCC 6633) were chosen to test against seven disinfectants: alcohol, sodium hypochlorite (NaOCl), glutaraldehyde (CIDEX^®), iodophore (POSE^®), modern combination of QAC and alcylamines (Alpro^® BIB FORTE), chlorhexidine gluconate (Chx), combination of isopropryl alcohol and dual-QAC (Umonium^®). Micro-dilution assay was used to determine the minimum inhibitory concentration (MIC) of each disinfectant. Minimum bactericidal concentration (MBC) was determined by the spread plating method. Potency of various shelf lives of the disinfectants was also tested. Result: All of the disinfectants tested, except alcohol, were effective against all three bacterial strains at working concentration (WC). MIC and MBC of Umonium^®, Alpro^®, CIDEX^®, and Chx were less than 1/8WC. Whereas POSE^® and NaOCl were less effective against S. typhimurium and B. subtilis. Surprisingly, alcohol was not effective at all concentrations against B. subtilis. After prepared to WC, all of the disinfectants retained their potency up to 4 weeks against S. typhimurium and S. aureus. Whatever the shelf life is, alcohol was not at all effective against B. subtilis. Conclusion: Iodophore and sodium hypochlorite, an oxidizing compound, were not effective when use in diluted form. Alcohol was not effective at all against B. subtilis, a spore forming bacteria. All of the disinfectants except alcohol, if keep in close container, retained its potency up to 4 weeks after prepared to WC.