Isolation, Identification, and Characterization of a New Highly Pathogenic Field Isolate of Mycobacterium avium spp. avium

Avian tuberculosis is a chronic, contagious zoonotic disease affecting birds, mammals, and humans. The disease is most often caused by Mycobacterium avium spp. avium (MM). Strain resources are important for research on avian tuberculosis and vaccine development. However, there has been little reported about the newly identified MM strain in recent years in China. In this study, a new strain was isolated from a fowl with symptoms of avian tuberculosis by bacterial culture. The isolated strain was identified to be MM by culture, staining, and biochemical and genetic analysis, except for different colony morphology. The isolated strain was Ziehl-Zeelsen staining positive, resistant to p-nitrobenzoic acid, and negative for niacin production, Tween-80 hydrolysis, heat stable catalase and nitrate production. The strain had the DnaJ gene, IS1245, and IS901, as well. Serum agglutination indicated that the MM strain was of serotype 1. The MM strain showed strong virulence via mortality in rabbits and chickens. The prepared tuberculin of the MM strain had similar potency compared to the MM reference strain and standard tuberculin via a tuberculin skin test. Our studies suggested that this MM strain tends to be a novel subtype, which might enrich the strain resource of avian tuberculosis.