Mycobacterium immunogenum is a species of the phylum actinobacteria (Gram-positive bacteria with high guanine and cytosine content, one of the dominant phyla of all bacteria), belonging to the genus mycobacterium. These non-tuberculous mycobacteria are sometimes found in fouling water-based cutting fluids, often causing hypersensitivity pneumonitis to the machinists in the affected grinding plants.