title: Effects of biocides and other metal removal fluid constituents on Mycobacterium immunogenum.
abstract: Cells of Mycobacterium immunogenum are significantly more resistant to biocides and antimicrobial compounds used for disinfection of metal removal fluids (MRFs) than cells of the gram-negative bacterium Pseudomonas pseudoalcaligenes. To ensure accurate measurement of M. immunogenum susceptibility, a biocide inactivation step must be included to prevent an overestimation of killing for short-term exposures. Cell suspensions in 5% MRF for 30 min rather than direct plating following biocide exposure increased the killing of M. immunogenum cells, suggesting a heretofore undiscovered interaction between MRF components and biocides. Biocide killing was reduced at high M. immunogenum cell densities (>10(6)/ml). Among the chemicals tested, only Synergex Premier, Preventol CMK, and dicyclohexylamine killed greater than 90% of M. immunogenum cells in 6 h. M. immunogenum cells adhered to and grew rapidly on glass, copper, and galvanized surfaces, forming biofilms of 10(6) cells/cm(2) within 2 weeks and suggesting it is likely that the majority of M. immunogenum cells in MRF systems are on surfaces. M. immunogenum cells grown on surfaces in biofilms were three- to 100-fold more resistant to the biocides Synergex Premier and Preventol CMK than cells grown in suspension, compounding the problem of eradication of M. immunogenum cells from MRF systems.
authors.affiliation: Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0406, USA.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Falkinham
mesh_terms: D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D008670:Metals / Q000378:metabolism*; D050296:Microbial Viability; D009161:Mycobacterium / Q000187:drug effects*; D013997:Time Factors
chemical_list: D004202:Disinfectants; D008670:Metals