Strain Typing Mycobacterium marinum from Outbreaks at Zebrafish Research Facilities

Zebrafish (Danio rerio) are used as model organisms for biological research due to their rapid and transparent development and high fecundity amongst other reasons. Research has expanded beyond embryonic studies, with adult fish used for longer-term studies such as human disease and senescence. Zebrafish are often housed at high density in large colonies. As with any similar husbandry situation, diseases can occur, with impacts that range from morbidity to premature mortality costing researchers time and money. Understanding the impact of underlying diseases in zebrafish is crucial, particularly for long-term studies where chronic infections may confound results. One such disease problem is mycobacteriosis, caused by numerous Mycobacterium species. Mycobacteria likely spread when fish are exchanged between facilities with no precautions for biosecurity. Bacteria can also persist in the water and live on surface biofilms, making control more difficult. Mycobacterium marinum is one species that is of interest because it is highly virulent, contributing to serious outbreaks. It is also a concern for occupational health because it can cause skin infections in humans. To better understand the spread of mycobacteriosis caused specifically by M. marinum, strain typing was conducted to categorize isolates from seven different zebrafish facilities throughout the United States. For strain typing a variable number of tandem repeat assay was used. This technique was adapted using fluorescently labeled primers followed by fragment analysis in order to increase throughput and repeatability. These results were then used to determine if any epidemiological linkages exist between facilities experiencing outbreaks