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Outbreaks of hypersensitivity pneumonitis (HP) among industrial metal-grinding machinists working with water-based metalworking fluids (MWF) have frequently been associated with high levels of mycobacteria in the MWF, but little is known about these organisms. We collected 107 MWF isolates of mycobacteria from multiple industrial sites where HP had been diagnosed and identified them to the species level by a molecular method (PCR restriction enzyme analysis [PRA]). Their genomic DNA restriction fragment length polymorphism (RFLP) patterns, as determined by pulsed-field gel electrophoresis (PFGE), were compared to those of 15 clinical (patient) isolates of the recently described rapidly growing mycobacterial species Mycobacterium immunogenum. A total of 102 of 107 (95%) MWF isolates (from 10 industrial sites within the United States and Canada) were identified as M. immunogenum and gave PRA patterns identical to those of the clinical isolates. Using genomic DNA, PFGE was performed on 80 of these isolates. According to RFLP analysis using the restriction enzymes DraI and XbaI, 78 of 80 (98%) of the MWF isolates represented a single clone. In contrast, none of the 15 clinical isolates had genetic patterns the same as or closely related to those of any of the others. Given the genomic heterogeneity of clinical isolates of M. immunogenum, the finding that a single genotype was present at all industrial sites is remarkable. This suggests that this genotype possesses unusual features that may relate to its virulence and its potential etiologic role in HP and/or to its resistance to biocides frequently used in MWF.The recognition of the presence of mycobacterial contamination in used water-based metalworking fluids (MWF) used in industrial (primarily automotive) metal grinding is quite recent. The timing of this finding coincided with the emergence of occupational asthma and of hypersensitivity pneumonitis (HP) in industrial machinists, suggesting that the two events may be related (4). Other key features which may play roles in both of these developments are the aggressive use of formaldehyde condensate biocides used to control growth of gramnegative bacilli, the dominant population in MWF, and changes in the bacterial flora related to the use of these biocides which facilitated the presence of the mycobacteria. Microbial growth is considered important in the degradation of MWF and water-based hydraulic fluids (12, 13). (1) reported additional cases of HP associated with the use of semisynthetic MWF, a disorder he referred to as "machine operator's lung." Although AFB were not identified in the MWF, AFB were recovered on culture of the sputum from one of the six affected patients. By 1997, eight clusters of HP involving almost 100 workers had been described, prompting investigation of the characteristics of the MWF that might be responsible (8).A review of the microbiology of these outbreaks revealed that used water-based MWF supported a complex population of microbial flora, with numbers that frequently exceeded 10 7 ...

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Staphylococcal L forms revealed characteristics not observed previously. The ability to produce coagulase was retained by the variant. In the presence of blood, many L forms were found within red cells, comparable with the intraerythrocytic stages reported for streptococci. Agar lysis was a unique characteristic of the mature L form.Inhibitors were not required to initiate the L stage and the variant and classical form grew commensally on enriched media. As nutrition was simplified, the L stage was supported, whereas the classical form did not reproduce. A small inoculum resulted in exclusive growth of L forms even in media containing special growth factors. The relative ease with which the L forms are produced experimentally suggests that this phase of growth may occur in vivo.

A previously healthy woman developed hypersensitivity pneumonitis of such severity that she required chronic systemic corticosteroid therapy for symptom control. Detailed investigation of her workplace and home environments revealed fungi in her typical suburban home, to which she had specific serum precipitating antibodies. Efforts to remove mold from the home were unsuccessful in relieving symptoms, and moving to another residence was the only intervention that allowed her to be withdrawn from corticosteroid therapy. Hypersensitivity pneumonitis is commonly associated with occupational or avocational exposures, such as moldy hay in farmers or bird antigen in bird breeders. We propose that hypersensitivity pneumonitis may occur in North America, as it does in Japan, from domestic exposures alone.