The development of a new three-step protocol to determine the efficacy of disinfectant wipes on surfaces contaminated with Staphylococcus aureus.

We developed a three-step protocol to quantify the efficacy of disinfectant wipes, their ability to remove and prevent microbial transfer from surfaces and their overall antimicrobial activity. Meticillin-resistant (MRSA) or -susceptible (MSSA) Staphylococcus aureus (6-7 log(10)cfu) were inoculated onto stainless steel discs with or without organic load and dried. Grapefruit extract-containing test wipes and unmedicated control wipes were used. In step 1, wipes were mechanically rotated against surfaces for 10s at 60rpm, exerting a weight of 100+/-5g. Bacterial removal was assessed by transferring the steel discs to neutraliser, resuspending and counting remaining bacteria. In step 2, bacterial transfer from wipes was assessed by eight consecutive mechanical adpression transfers to agar/neutraliser plates. Step 3 was the measurement of antimicrobial activity by direct inoculation of the wipes for 10s followed by neutralisation and enumeration. Test wipes achieved a significantly higher bacterial cell removal than control wipes on all surfaces (P<0.05). The low bactericidal activity of the wipes (<1 log(10) reduction when directly inoculated) and the subsequent survival of bacteria on the wipes, however, led to repeated microbial transfer when initially high contamination levels were present. There were no differences between MRSA and MSSA in removal, transfer or antimicrobial activity. The three-step method is a useful tool for developing future guidelines to assess the ability of wipes to disinfect surfaces.