Evaluation of the antimicrobial efficacy and skin safety of a novel color additive in combination with chlorine disinfectants

OBJECTIVE: A novel color additive colorizes chlorine disinfectants blue to improve visibility and enhance spray surface coverage, and it fades to colorless to indicate elapsed contact time. We investigated its interactions with 3 chlorine disinfectants to determine if the additive would adversely affect the disinfectants' antimicrobial efficacy or skin safety. METHODS: We tested 0.5% sodium hypochlorite, 0.2% calcium hypochlorite, and 0.5% sodium dichloroisocyanurate (NaDCC) alone versus with color additive. An independent laboratory tested efficacy against Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholerae, and human coronavirus 229E. An independent laboratory also tested direct skin irritation. RESULTS: Chlorine disinfectants with and without color additive achieved equal levels of efficacy against the tested pathogens. Against S. aureus, 0.5% sodium hypochlorite with and without color additive met Environmental Protection Agency criteria for disinfection success. Against human coronavirus 229E, 0.5% sodium hypochlorite alone failed disinfection success criteria, whereas 0.5% sodium hypochlorite with color additive achieved full viral inactivation (≥4.50 log(10) reduction). Against V. cholerae, 0.2% calcium hypochlorite alone and with color additive achieved 5.99 log(10) and >6.03 log(10) reductions, respectively. Against S. aureus and P. aeruginosa, 0.5% NaDCC with and without color additive achieved >4.9 log(10) and >3.54 log(10) reductions, respectively. All 3 chlorine disinfectants with color additive tested as negligible skin irritants. CONCLUSIONS: This color additive can be combined with chlorine disinfectants without adversely affecting antimicrobial efficacy or skin safety.