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

Abstract

Hypersensitivity pneumonitis, also known as "machine operator's lung" (MOL), has been related to microorganisms growing in metalworking fluids (MWFs), especially Mycobacterium immunogenum. We aimed to (i) describe the microbiological contamination of MWFs and (ii) look for chemical, physical, and environmental parameters associated with variations in microbiological profiles. We microbiologically analyzed 180 MWF samples from nonautomotive plants (e.g., screw-machining or metalcutting plants) in the Franche-Comté region in eastern France and 165 samples from three French automotive plants in which cases of MOL had been proven. Our results revealed two types of microbial biomes: the first was from the nonautomotive industry, showed predominantly Gram-negative rods (GNR), and was associated with a low risk of MOL, and the second came from the automotive industry that was affected by cases of MOL and showed predominantly Gram-positive rods (GPR). Traces of M. immunogenum were sporadically detected in the first type, while it was highly prevalent in the automotive sector, with up to 38% of samples testing positive. The use of chromium, nickel, or iron was associated with growth of Gram-negative rods; conversely, growth of Gram-positive rods was associated with the absence of these metals. Synthetic MWFs were more frequently sterile than emulsions. Vegetable oil-based emulsions were associated with GNR, while mineral ones were associated with GPR. Our results suggest that metal types and the nature of MWF play a part in MWF contamination, and this work shall be followed by further in vitro simulation experiments on the kinetics of microbial populations, focusing on the phenomena of inhibition and synergy.

Biological and chemical hazards in water-mix metalworking fluids and mists

“…P.pseudoalcaligenes was the most frequently detected 16S rRNA sequence in these used MWF samples, which may support the view that it is more successful at inhabiting 126 MWF due to its ability to degrade hydrocarbons and stability in alkaline pH (Murat et al, 2012). According to the HSE guidance (Senior et al, 2015) whilst there have been no reports of ill health as a result of using bio-concept MWF, concerns remain about using this type of fluid because: A study by Mattsby-Baltzer et al (1989), set out to determine whether individuals exposed to high levels of P.pseudoalcaligenes endotoxins would present with serum antibodies for P.pseudoalcaligenes lipopolysaccharides (LPS/ endotoxins).…”

“…A large number of studies investigating the cause of respiratory allergy in machinists have relied on traditional culture based methods for quantifying bacteria present in MWF (Khan and Yadav, 2004;Saha et al, 2011). It is now understood that most microbes present in MWF may not grow readily in these standard culture conditions, and this is consistent with many microorganisms recovered from the general environment (Murat et al, 2012). The use of these traditional methods can lead to a significant under-representation of many types of microorganisms in MWF depending on their ability to grown under the experimental conditions used (Veillette et al, 2004).…”

“…These involve culturing bacteria in nutrient selective media and different substratum. It is now understood that bacteria present within MWF adapt to the carbon source provided by the oil (Murat et al, 2012). Therefore, they may not grow in standard microbiology culture conditions.…”

“…This can be attributed to physiological factors. When the bacteria are isolated from the MWF they have adapted to grow, and then are placed in a standardised growth media with different physiological conditions (gas concentrations, temperature and pH) (Murat et al, 2012).…”

“…Mycobacteria are more resistant to biocides than other bacteria and therefore this may account for the reason why Group C contains the organism. Levels of other bacteria are likely to be reduced due to the levels of biocide, and therefore the slow growing and robust mycobacteria were able to continue to grow with less competition (Murat et al, 2012). However, the inoculation of mycobacteria into the machine may also be attributed to other factors.…”