Fungal contamination of the respiratory tract and associated respiratory impairment among sawmill workers in India

Wood processing workers are exposed to wood-associated microbiological contaminants, including fungi. Our aim was to study the potential association between sputum fungus and adverse respiratory effects in such workers. In a group of sawmill workers, we administered a respiratory questionnaire, performed lung function testing and quantified the proportions of leukocytes in spontaneously expectorated sputum samples. We identified fungal species by DNA sequencing. Of 54 sawmill workers, 19 yielded fungal positive sputum samples (mean age 42.5±10.4 years) and 35 were negative for fungus (mean age 36.9±5.2 years). The fungus was identified as Candida sp. in all samples. Those with fungal-positive sputum, compared to others, reported more cough (26% versus 63%) and haemoptysis (6% versus 37%) (both p<0.05), manifested reduced forced midexpiratory flow rates (FEF25-75%) (82.3±4.5 versus 69.2±9.9% predicted, p<0.001), and had higher sputum eosinophil counts (median 9.25 versus 3.25%, p<0.01). Reduction of FEF25-75% was associated both with fungus detection in sputum (-12.7%, 95% CI-8.5- -16.9%) and sputum eosinophils (-2.1% per 1% increase in eosinophils, 95% CI -1.5- -2.8%) (both p<0.001). In sawmill workers, Candida sp. detectable in sputum was associated with respiratory symptoms, sputum eosinophilia and reduced FEF25-75%.