Patent ID: 6951618

Claim:
A method for suppressing growth of mycobacteria including Mycobacterium immunogenum associated with hypersensitivity pneumonitis in an industrial metalworking fluid which comprises: (a) providing a composition comprising a copper complex comprising disodium monocopper (II) citrate and an isothiazolone mixture comprising 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, wherein the copper complex provides copper ion to the used metalworking fluid in an amount which maintains biocidal activity of the isothiazolone mixture; (b) adding the copper complex and isothiazolone to the metalworking fluid which contains components from use of the fluid which interfere with the antimicrobial activity of isothiazoline mixture in an amount which is sufficient to suppress the growth of the mycobacteria in the metalworking fluid for at least 48 hours; and (c) monitoring the metalworking fluid containing the composition for the mycobacteria to determine that the mycobacteria have been suppressed.