Determining the Efficacy of Chemicals for the Inactivation of Liquid Waste Containing Gram-Positive Bacteria of Risk Group 2

Background: Inactivation of infectious liquid waste can be performed by different means, including autoclaving or chemical inactivation. Autoclaving is most widely used, but cannot always be implemented, so that chemical inactivation is a possible alternative. However, its efficacy has to be proven by in-house validation. Here, we provide an easy-to-implement validation process adapted from existing standards.Methods: The bactericidal activity of two commercially available disinfectants, containing glucoprotamine or peracetic acid, was tested on two gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae (SP). Quantitative suspension tests were adapted from the European standard EN 13727. Membrane filtration was used to remove any trace of the active antiseptic. The stability of working solutions and the effect of different organic loads were also assessed. Further, the aquatic toxicity of glucoprotamine was tested on the viability and behavior of zebrafish larvae.Results: Peracetic acid was highly efficient against both strains, even at a working concentration of 0.25% for 1 minute S. pneumoniae was also highly sensitive to glucoprotamine, whereas MRSA required either higher concentrations (1%) or longer exposure times (30 min) at lower concentrations. Further, the lethal dosis that kills 50% of the embryos (LD50) for glucoprotamine was 3-3.5 mg/L using the zebrafish Embryo Acute Toxicity Test.Conclusion: We could confirm the very high efficacy of glucoprotamine- and peracetic-based disinfectants to inactivate liquid waste containing gram-positive bacteria. Also considering aquatic toxicity, this methodology could help laboratories to establish validated procedures for chemical inactivation of infectious liquid wastes relevant to their institution, balancing efficacy, and environmental issues.