Izothiazolone based biocides: efficiency evaluation on Staphylococcus warneri isolated from e-coat process rinse water

The e-coat process is the first step in automotive painting and consists of immersing the part in a conductive water-based paint bath, followed by several rinse tanks and preceded by a rinse tank with demineralized water after pre-treatment. In this process, microbiological contamination is common, which is prevented or eliminated by adding isothiazolone based biocides combined with other active components. The objective of this study was to evaluate the efficiency of two commercial biocides containing the active components, 5-Chloro-2-methyl-2H-isothiazol-3-one (CIT) and 2-Methyl-2H-isothiazol-3-one (MIT), in the inactivation of two Staphylococcus warneri strains, isolated from contaminated water from tanks of an e-coat paint applicator company. The Minimum Inhibitory Concentration (MIC) was 5 mg/L and the Minimum Bactericide Concentration (MBC) was 10 mg/L for both biocides. Survival curves were obtained and the Weibull model was adjusted. The models obtained indicated lower resistance of S. warneri strain isolated from the demineralized water tank and higher inactivation rate of the biocide containing the association of isothiazolinone and ethylenedioxy (dimethanol).