Metalworking fluids biodiversity characterization.

Area of Science:

• Environmental microbiology
• Occupational health
• Industrial hygiene

Background:

• Hypersensitivity pneumonitis in machinists has been linked to Mycobacterium immunogenum in metalworking fluids (MWF).
• The microbial ecology of MWF, particularly concerning organisms like Pseudomonas, is not well understood despite continuous exposure.
• Quantifying and characterizing the microbial load in in-use MWF is crucial for assessing occupational health risks.

Purpose of the Study:

• To quantify and characterize the microbial load in 44 in-use metalworking fluid samples.
• To assess the biodiversity of microorganisms present in these fluids.
• To identify dominant bacterial species and compare microbial loads determined by different methods.

Main Methods:

• Utilized cultural methods, quantitative PCR (qPCR), and denaturing gradient gel electrophoresis (DGGE) to assess microbial biodiversity.
• Measured total bacteria concentrations using 16S rRNA gene copies per milliliter.
• Identified predominant bacterial species, including Mycobacterium immunogenum, Pseudomonas pseudoalcaligenes, and Ochrobactrum anthropi.

Main Results:

• Bacterial concentrations in MWF ranged from undetectable to 10^9 gene copies/mL, with qPCR revealing significantly higher loads than culture methods.
• Two samples showed high concentrations of Mycobacterium immunogenum.
• Low overall biodiversity was observed, with Pseudomonas pseudoalcaligenes (33/44 samples) and Ochrobactrum anthropi (32/44 samples) being the most prevalent bacteria.

Conclusions:

• In-use MWF harbor very high bacterial concentrations and limited biodiversity.
• Pseudomonas pseudoalcaligenes and Ochrobactrum anthropi were the dominant microorganisms found.
• Further investigation is required to confirm the role of these prevalent microorganisms in occupational respiratory disorders.