A comparison of the sensitivity of four Staphylococcus aureus isolates to two chlorine-based disinfectants and an eco-friendly commercially available cleaning agent.

The aim of this study was to determine the effect of household bleach, a sodium dichloroisocyanurate (NaDCC)-based disinfectant and an eco-friendly cleaning agent (EFCA) on four Staphylococcus aureus strains, including two isolated from community infections. The products were assessed using the suspension (EN 1276) and surface (EN 13697) tests, while biofilm activity was determined using the 96-well plate method. Bleach and NaDCC caused > 5 log reduction in viable counts within 5 min in suspension, whilst on surfaces the reduction was < 3 log. Bleach at 5000 ppm free available chlorine completely eradicated MSSA NCTC 13297 and PVL CA MSSA biofilms within 10 min, but not at 500 and 50 ppm, NaDCC was less effective against biofilms. The EFCA demonstrated no antimicrobial activity. It is of concern that at the recommended "use" dilution, bleach did not eradicate biofilms. Although increasing contact time and/or concentration should improve the activity, this may not be acceptable to the user.