Saccharopolyspora rectivirgula from Quebec dairy barns: application of simplified criteria for the identification of an agent responsible for farmer's lung disease

Saccharopolyspora rectivirgula (Micropolyspora faeni) is one of the major a gents responsible for farmer's lung disease, a form of hypersensitivity pne umonitis. It is frequently isolated from the air of contaminated barns. The identification of this actinomycete is difficult because most of its pheno typic characteristics are variable and classical tests are not easy to perf orm on actinomycetes, Fatty acid analysis is very useful for the identifica tion of these strains, but is not available except in some research or refe rence laboratories. Morphological (microscopic and macroscopic observations ), physiological and biochemical tests (growth properties; macromolecules d egraded; citrate utilisation and acid production from carbohydrates; resist ance to antibiotics, lysozyme and heat), cell wall and fatty acid analyses and IgG analyses with serum from patients with farmer's lung were performed on 12 environmental isolates presumed to be S. rectivirgula and two contro l strains of S, rectivirgula. From this, a simple and rapid scheme for the identification of this actinomycete is proposed: optimal growth temperature (55 degrees C); colony appearance based on morphology (filamentous) and co lour (beige to orange-brown); microscopic morphology (chains of spores on b oth aerial and substrate mycelium); growth on NaCl 10%; cell-wall analysis (type IV); and the verification of antibody response with serum from a pati ent with farmer's lung. This last criterion is important to confirm the imm unogenicity of the strains identified as S, rectivirgula, This scheme provi des an accurate and efficient way of identifying S, rectivirgula strains an d evaluating exposure to this bacterium, The study shows the limited value and the lack of reproducibility of some classical biochemical tests.