A cluster of hypersensitivity pneumonitis associated with exposure to metalworking fluids

Surfactant additives in water-based metalworking fluids lead to strong biophysical inhibition of pulmonary surfactant film

As a class of very common and important industrial liquid materials, metalworking fluids (MWFs) are easy to be vaporized into the air and cause pulmonary toxic effects. The inhaled MWF aerosols should first interact with the pulmonary surfactant (PS) film that plays an essential role in maintaining the normal respiratory mechanics and pulmonary immunology in a human body. Here, to probe any potential adverse impacts of airborne MWFs on the biophysical and physiological functions of PS film that may help achieve a deep and comprehensive understanding of the pulmonary toxicology of MWFs, a systematic study on the interaction between an animal-derived natural PS (i.e., Calsurf) film and the aerosols of water-based MWFs and their different constituents is conducted using constrained drop surfactometry (CDS) capable of closely simulating normal tidal breathing and lung-related physiological conditions in vitro. It was found that the airborne MWFs can induce strong PS inhibitions once their accumulated amount in the environment attains 0.2 mg/cm3. And their inhibitory effects are demonstrated to mainly originate from the surfactant additives such as polyethylene glycol monooleate (PEGMO) that can desorb PS film from the air/water interface via competitive interfacial adsorption, although it has normally been regarded as an eco-friendly commercial reagent.

Prevalence of occupational hypersensitivity pneumonitis: a systematic review and meta-analysis

In this meta-analysis, we aimed to evaluate the prevalence of occupational hypersensitivity pneumonitis (OHP) among different occupations globally. Our search was conducted on MEDLINE via PubMed, Scopus, Web of Science, and Cochrane CENTRAL from inception to September 2023. Eligible studies were observational in nature and focused on several specific occupations. A total of 46 articles were included (n = 2,826,420 participants). The overall prevalence of OHP was found to be 4.2% (95% CI: 2.1% to 8.0%), but this varied significantly based on occupation and geographic location. Printers had the highest OHP prevalence at 57.14%, followed by tobacco workers (26.32%), and water-related workers (24.10%). South America showed the highest prevalence of 16.71%, compared to Asia (15.19%), and North America (8.52%). Significant variations in OHP prevalence by occupation and region were found, with the highest rates in printers and tobacco workers. Age and smoking were identified as contributing factors to the prevalence variability.

Differential Immunogenicity and Lung Disease-Inducing Potential of Mycobacterium immunogenum Genotypes and Impact of Co-Exposure with Pseudomonas: Optimizing a Mouse Model of Chronic Hypersensitivity Pneumonitis

Mycobacterium immunogenum (MI) colonizing metalworking fluids (MWFs) has been associated with chronic hypersensitivity pneumonitis (HP) in machinists. However, it is etiologically unclear why only certain mycobacteria-contaminated fluids induce this interstitial lung disease. We hypothesized that this may be due to differential immunogenicity and the HP-inducing potential of MI strains/genotypes as well as the confounding effect of co-inhaled endotoxin-producers. To test this hypothesis, we optimized a chronic HP mouse model in terms of MI antigen dose, timepoint of sacrifice, and form of antigen (cell lysates vs. live cells) and compared six different field-isolated MI strains. Overall, MJY10 was identified as the most immunogenic and MJY4 (or MJY13) as the least immunogenic genotype based on lung pathoimmunological changes as well as Th1 cellular response (IFN-γ release). Infection with MI live cells induced a more severe phenotype than MI cell lysate. Co-exposure with Pseudomonas fluorescens caused a greater degree of lung innate immune response and granuloma formation but a diminished adaptive (Th1) immune response (IFN-γ) in the lung and spleen. In summary, this study led to the first demonstration of differential immunogenicity and the disease-inducing potential of field strains of MI and an interfering effect of the co-contaminating Pseudomonas. The improved chronic MI-HP mouse model and the identified polar pair of MI strains will facilitate future diagnostic and therapeutic research on this poorly understood environmental lung disease.

Microbial Community Establishment, Succession, and Temporal Dynamics in an Industrial Semi-Synthetic Metalworking Fluid Operation: A 50-Week Real-Time Tracking

Microorganisms colonizing modern water-based metalworking fluids (MWFs) have been implicated in various occupational respiratory health hazards to machinists. An understanding of the exposure risks from specific microbial groups/genera/species (pathogenic or allergenic) and their endotoxins and the need for strategies for effective, timely fluid management warrant real-time extended tracking of the establishment of microbial diversity and the prevailing fluid-related factors. In the current study, the microbial community composition, succession, and dynamics of a freshly recharged industrial semi-synthetic MWF operation was tracked in real-time over a period of 50 weeks, using a combination of microbiological and molecular approaches. Substantial initial bacterial count (both viable and non-viable) even in the freshly recharged MWF pointed to the inefficiency of the dumping, cleaning, and recharge (DCR) process. Subsequent temporal analysis using optimized targeted genus/group-specific qPCR confirmed the presence of Pseudomonads, Enterics, Legionellae, Mycobacteria (M. immunogenum), Actinomycetes, and Fungi. In contrast, selective culturing using commercial culture media yielded non-specific isolates and collectively revealed Gram-negative (13 genera representing 19 isolates) and Gram-positive (2 genera representing 6 isolates) bacteria and fungi but not mycobacteria. Citrobacter sp. and Bacillus cereus represented the most frequent Gram-negative and Gram-positive isolates, respectively, across different media and Nectria haematococca isolation as the first evidence of this fungal pathogen colonizing semi-synthetic MWF. Unbiased PCR-DGGE analysis revealed a more diverse whole community composition revealing 22 bacterial phylotypes and their succession. Surges in the endotoxin level coincided with the spikes in Gram-negative bacterial population and biocide additions. Taken together, the results showed that semi-synthetic MWF is conducive for the growth of a highly diverse microbial community including potential bacterial and fungal pathogens, the current DCR practices are inefficient in combating microbial reestablishment, and the practice of periodic biocide additions facilitates the build-up of endotoxins and non-viable bacterial population.

Machine operator's lung outbreak due to Eikenella corrodens

BACKGROUND

Outbreaks of hypersensitivity pneumonitis (HP) are not uncommon in workplaces where metalworking fluids (MWFs) are used. The recirculation of MWFs leads to microbiological contamination, which is responsible for outbreaks. Most outbreak reports come from USA and the UK; however, no similar reports have been published from Central Europe.

AIMS

To describe an outbreak of MWF-associated HP in workers from a compressor assembly manufacturing facility in Slovak Republic and to identify the potential antigens responsible for the outbreak.

METHODS

We investigated the history of worker's symptoms, physical examinations, lung function tests, radiographic scans and lung biopsies. The MWF samples were analysed for different strains of bacteria and fungi. Antigen extracts were produced from the microorganisms isolated from MWFs, and positive precipitin reactions were evaluated.

RESULTS

MWF-associated HP was diagnosed in 21 men and 6 women. All workers had work-related dyspnoea and cough with abnormal pulmonary diffusing capacity. Twenty-four cases had evidence of interstitial lung disease. Four cases were classified as having fibrotic HP. Nineteen microbial isolates (12 bacteria and 7 fungi) were cultured from the MWFs. Twenty-five cases had a positive response to at least one isolate. Eikenella corrodens and Bacillus subtilis were the most frequently reacting antigens (in 15 and 12 workers, respectively).

CONCLUSIONS

Despite decreasing reports of MWF-associated HP outbreaks over the past several decades, we describe one of the largest outbreaks in Europe. While the bacterium E. corrodens was found in the MWF samples, its relationship to the disease should be further investigated.