Biocidal Activity of Formaldehyde and Nonformaldehyde Biocides toward Mycobacterium immunogenum and Pseudomonas fluorescens in Pure and Mixed Suspensions in Synthetic Metalworking Fluid and Saline

Abstract

The microbicidal activity of four different biocides was studied in synthetic metalworking fluid (MWF) against Mycobacterium immunogenum, a suspected causative agent for hypersensitivity pneumonitis, and Pseudomonas fluorescens, a representative for the predominant gram-negative bacterial contaminants of MWF. The results indicated that M. immunogenum is more resistant than P. fluorescens to the tested formaldehyde-releasing biocides (Grotan and Bioban), isothiazolone (Kathon), and phenolic biocide (Preventol). Kathon was effective against mycobacteria at lower concentrations than the other three test biocides in MWF. In general, there was a marked increase in biocidal resistance of both the test organisms when present in MWF matrix compared to saline. Increased resistance of the two test organisms to biocides was observed when they were in a mixed suspension (1:1 ratio). The results indicate the protective effect of the MWF matrix against the action of commonly used biocides on the MWF-colonizing microbial species of occupational health significance, including mycobacteria.Metalworking fluid (MWF) is used as lubricant, coolant, and/or metal removing agent in machining operations. The modern synthetic metalworking fluids, which contain organic and inorganic salts, hydrocarbons, organic esters, and lubricating fluids, are excellent sources of nutrition for microorganisms (5). Microbial contamination of MWF has been frequently associated with occupational health problems, such as hypersensitivity pneumonitis due to inhalation of aerosolized MWF bacteria (9, 10) and dermatitis due to MWF microflora exposure (1), that occur in metalworkers. The occurrence of mycobacteria in MWF and their potential occupational health significance has been highlighted (8,10,18). Mycobacterium immunogenum, a nontuberculous Mycobacterium species, has been reported in MWF and implicated as possible causative agent of hypersensitivity pneumonitis in machine workers who have been exposed to it (21,23,24). Among other MWF microbial communities, pseudomonads often constitute the major fraction of gram-negative organisms responsible for endotoxin release and accumulation in the fluids, resulting in occupational health hazards in metalworkers (2). In modern machine industries, the most commonly used method to control microbial contamination is the use of chemical biocides. However, little information is available on evaluation of relative efficacy of commercial biocides against microbial genera or species associated with metalworking fluids. Our aim here was to investigate the potential effectiveness of the commonly used commercial formaldehyde (HCHO) and nonformaldehyde (non-HCHO) biocides in metalworking fluids against two widely recognized bacterial genera of occupational health concern: Mycobacterium and Pseudomonas. To our knowledge, this is the first report to investigate the effect of any biocide against the MWF-associated Mycobacterium species alone and in the presence of common microbial cocontaminant Pseudomonas.Microorganisms and cu...

Microorganisms in metalworking fluids: Current issues in research and management

“…The presence of both mycobacteria and pseudomonads in mixed suspension enhances tolerance of M. immunogenum to both formaldehyde-releasing and non-formaldehyde biocides [45,46]. Multiple genotypes of M. immunogenum isolated from distinct MWFs showed different susceptibility to formaldehyde-releasing biocide Grotan and the izothiazole biocide Kathon, and these isolates were more tolerant to biocides than a reference, laboratory strain [47].…”

Factors Influencing the Microbial Composition of Metalworking Fluids and Potential Implications for Machine Operator's Lung

“…However, the use of biocides is not necessarily a confounding factor, since it is assumed to be one of the factors leading to alteration of the microbial biome through the selection of resistant bacteria. Indeed, adding biocide can result in an increase in bacterial load, with maintenance of pathogenic, highly resistant bacteria (Enterobacteriaceae, Moraxella spp., and P. aeruginosa) (10), while mycobacteria, including M. immunogenum, were shown to exhibit reduced susceptibility to some biocides (35,49), possibly due to biofilms (11).…”

Development of a Rapid ATP Bioluminescence Assay for Biocidal Susceptibility Testing of Rapidly Growing Mycobacteria

“…For instance, Cidexplus (3.4% alkaline glutaraldehyde) is used for mycobacterial and other disinfection capabilities for a wide range of contaminated hospital materials and medical instruments (3,8,29). Isothiazolone-based formulations, such as Kathon, are among the common biocides used for control of mycobacterial colonization of metalworking fluids (31,32).…”