Strategies to Mitigate a Mycobacterium marinum Outbreak in a Zebrafish Research Facility

Abstract

In 2011, the zebrafish research facility at the University of Oregon experienced an outbreak of Mycobacterium marinum that affected both research fish and facility staff. A thorough review of risks to personnel, the zebrafish veterinary care program, and zebrafish husbandry procedures at the research facility followed. In the years since 2011, changes have been implemented throughout the research facility to protect the personnel, the fish colony, and ultimately the continued success of the zebrafish model research program. In this study, we present the history of the outbreak, the changes we implemented, and recommendations to mitigate pathogen outbreaks in zebrafish research facilities.

FIG. 1.

Comparison of fluorescent Mycobacterium marinum (5.95 × 10⁸ CFU/mL) after exposure to 1 part per thousand (ppt) PVPI for 2 min (A) and 30 ppm sodium hypochlorite solution for 10 min (B). Numerals represent exposure time in seconds (A) and minutes (B). Cultures grown on Middlebrook 7H11 media; circles indicate where bacteria were spotted onto the plate for testing. Sodium hypochlorite essentially eradicated M. marinum after 10 min, whereas PVPI had almost no effect. PVPI, povidone–iodine.

FIG. 2.

Without surface disinfection, GFP-expressing M. marinum were observed on the embryo chorion (A) after 24 h and in the larval zebrafish gut (arrowhead in C) after 6 days. GFP-expressing mycobacteria were present on the chorion (B) after 24 h, but absent in the larval zebrafish gut (D) after 6 days when the chorion was surface disinfected using 30 ppm sodium hypochlorite for 10 min. Larvae are positioned anterior to the left, dorsal up. GFP, green fluorescent protein. Color images available online at www.liebertpub.com/zeb

FIG. 3.

Rotifers (Brachionus plicatilis) readily consume GFP-expressing M. marinum. Color images available online at www.liebertpub.com/zeb

FIG. 4.

Severe mycobacterial infection in a single adult zebrafish. Arrows pointed to acid-fast bacilli that are observed in the coelomic cavity, including ovary (A) and kidney (B), but are also observed in the brain (C) and choroid (D). Color images available online at www.liebertpub.com/zeb