Use of PCR-restriction fragment length polymorphism for the identification of zoonotic mycobacteriosis in zebrafish caused by Mycobacterium abscessus and Mycobacterium chelonae

Skin ulcers, scoliosis, and dropsy-like scale edema were observed in laboratory-maintained zebrafish. Affected fish had multifocal granulomas not only in internal organs such as the liver, intestine, genital organs, kidney, muscle, and spleen but also in the fin, epithelium, gills, and sclera of the eyes. Large numbers of acid-fast-rod-shaped bacteria were observed within the necrotic centers of well-demarcated, multifocal granulomas with Gram's stain and Ziehl–Neelson's stain. The size of the Mycobacterium spp. was 1–2 μm × 2–3 μm with a double-layered cell wall, based upon electron-microscopical features. Definitive diagnosis of these outbreaks was obtained by culture on selective media followed by PCR-restriction fragment length polymorphism analysis (PRA) of the rpoB gene for species identification. The amplified 360-bp products of the rpoB gene of mycobacteria isolated from zebrafish were digested with MspI restriction enzyme, which revealed unique band patterns matching those of Mycobacterium abscessus and Mycobacterium chelonae which are responsible for skin and soft tissue infection caused by rapidly growing mycobacteria in humans. This is the first documentation of the precise identification of zoonotic non-tuberculous mycobacteria isolated from laboratory-maintained zebrafish by the PRA of the rpoB gene; this study thus provides a great deal of useful epidemiological information and reduces the likelihood that epizootics will occur.This work was supported in part by a grant from the Korea Institute of Environmental Science and Technology, a grant from the Brain Korea 21 Project (J.H.P), a grant from the Korea Health 21 R&D Project (01-PJ10-PG6-01GM03-0002), and Ministry of Health & Welfare and Brain Korea 21 project to Medical Sciences (S.N.C). Additional support was also provided by Korea Research Foundation grants (KRF-005-E00076 and KRF-005-E00077) as well as Research Institute of Veterinary Science, College of Veterinary Medicine, Seoul National University