Hypersensitivity pneumonitis and metalworking fluids contaminated by mycobacteria

Area of Science:

• Occupational Health
• Immunology
• Environmental Microbiology

Background:

• Metalworking fluids (MWF) are a known cause of hypersensitivity pneumonitis (HP) in exposed workers.
• Identifying the specific antigen responsible for MWF-associated HP is crucial for accurate diagnosis and prevention.
• Optimizing serological diagnostic methods is needed to differentiate between affected patients and asymptomatic exposed individuals.

Purpose of the Study:

• To identify the specific antigen responsible for hypersensitivity pneumonitis (HP) linked to metalworking fluids (MWF).
• To establish reliable thresholds for serological diagnostic tests to distinguish HP patients from asymptomatic exposed workers.

Main Methods:

• Microbial analysis of 83 used MWFs to identify causative agents.
• Serological testing (electrosyneresis and ELISA) of sera from HP patients, asymptomatic exposed workers, and healthy controls against identified antigens.
• Immunological response assessment to three antigens, including Mycobacterium immunogenum.

Main Results:

• Mycobacterium immunogenum was identified in 40% of used MWFs via culture and DNA sequencing.
• Electrosyneresis showed a threshold of five arcs of precipitation differentiating patients from controls (77% sensitivity, 92% specificity).
• ELISA methods using M. immunogenum protein extract established a threshold of 1.6 AU, achieving 92% sensitivity and 100% specificity.

Conclusions:

• High levels of specific antibodies against Mycobacterium immunogenum antigens in patient sera strongly suggest its role in MWF-associated HP.
• The study proposes specific thresholds for electrosyneresis (five arcs) and ELISA (1.6 AU) for accurate discrimination between MWF-associated HP patients and asymptomatic exposed workers.