Attenuated Mycobacterium marinum protects zebrafish against mycobacteriosis

Fish mycobacteriosis is a common bacterial disease in many species of freshwater and marine fish (Decostere, Hermans & Haesebrouck 2004). Infections are common in wild fish, aquaculture and ornamental fish (Jacobs, Stine, Baya & Kent 2009). This chronic progressive disease is commonly caused by aquatic Mycobacterium spp. such as M. marinum, M. fortuitum and M. chelonae (Decostere et al. 2004), although some previously recognized human mycobacteria such as M. haemophilum and M. peregrinum have also been found in zebrafish during mycobacteriosis outbreaks (Kent, Whipps, Matthews, Florio, Watral, Bishop-Stewart, Poort & Bermudez 2004). Fish mycobacteriosis usually leads to systemic infections, which have reportedly caused massive mortalities among fish grown in intensive aquaculture systems (Bruno, Griffiths, Mitchell, Wood, Fletcher, Drobniewski & Hastings 1998; Diamant, Banet, Ucko, Colorni, Knibb & Kvitt 2000). With the remarkable increase in fin fish culture, there has been a concurrent increased concern about mycobacteriosis in cultured species (Ostland, Watral, Whipps, Austin, St-Hilaire, Westerman & Kent 2008). In addition to acute mortalities, chronic mycobacterium infections may result not only in low level mortality but also in reduced growth or marketability of fish due to macroscopic lesions. In addition, Mycobacterium spp. infecting fish are all potentially zoonotic (Tchornobay, Claudy, Perrot, Levigne & Denis 1992; Vazquez & Sobel 1992; Parent, Salam, Appelbaum & Dossett 1995; Lehane & Rawlin 2000). There are a few reports of treatment of infections with antibiotics (Santacana, Conroy, Mujica, Marin & Lopez 1982; Lawhavinit, Hatai, Kubota, Toda & Suzuki 1988; Conroy & Conroy 1999), but these have been limited and mostly at the experimental level. Presently, there are no effective drugs for treating food fish on a commercial scale.