Sporicidal activity in liquid chemical products to sterilize or high-level disinfect medical and dental instruments

Background Various liquid chemical products are commercially available in Mexico under sporicidal label claims. Frequently, information provided on their labels conflicts with published data on active ingredients, use concentrations, or exposure times. Objective To evaluate sporicidal activity in 8 chemical products sold for the sterilization or high-level disinfection of medical and dental instruments. Methods Bacillus atrophaeus ATCC 9372 spores were suspended (106 spores in 50 mL) in each of 4 glutaraldehyde solutions: a super oxidized solution, a hydrogen peroxide formulation, a quaternary ammonium compound, and an ortho-phthalaldehyde solution. After up to a 10-hour exposure, the solutions were passed through 0.22-μm filters, which were then rinsed with 1% sodium bisulfite, washed, and incubated on tryptic soy agar for 5 days at 37°C. Results At the use concentrations stipulated on their labels, only 2 of 6 products registered as sterilants showed sporicidal activity when challenged with 6 log10: a 2% glutaraldehyde in 10 hours and the hydrogen peroxide solution in 6 hours. Of 2 products registered as high-level disinfectants, only the ortho-phthalaldehyde showed noticeable sporicidal activity after 10-hour exposure. Conclusion The results show that some chemical products, commercially available in Mexico as “Liquid Chemical Sterilants/High-Level Disinfectants” cannot be used reliably to process instruments between patients.