ASTM Symposium on the Recovery and Enumeration of Mycobacteria from the Metalworking Fluid Environment

Abstract Since 1994, when the first documented hypersensitivity pneumonitis cluster was reported at a metalworking plant, there have been approximately 200 diagnosed cases of hypersensitivity pneumonitis within the metalworking industry. Although there are a variety of bacterial and fungal etiologic agents associated with hypersensitivity pneumonitis, metalworking industry stakeholders have focused their attention on a hypothesis that links Mycobacterium immunogenum exposure to the disease. A number of barriers confound attempts to test this hypothesis. Today's symposium opens a dialogue on two significant barriers. There is no consensus practice for sampling and recovering Mycobacterium immunogenum from either bulk metalworking fluids or metalworking fluid aerosols. There is no consensus method for quantifying mycobacteria that may be present in either bulk fluid or aerosol samples. This paper provides a context for the symposium's other presentations. After offering a brief overview of the history of hypersensitivity pneumonitis in the metalworking environment, the author will address the current state of knowledge regarding Mycobacterium immunogenum distribution in metalworking fluids. Finally, the author will summarize the three primary strategies for enumerating mycobacteria: microscopic examination of acid-fast stained preparations, viable counts, and non-conventional methods.