Abstract

As mycobacteriosis is an important disease of freshwater, brackish, and marine fishes, as well as a potential zoonotic risk to human, significant reduction or elimination of this bacterial pathogen from an aquarium or aquaculture facility is important. Disinfection is the process that eliminates many or all pathogenic microorganisms from inanimate objects. Disinfection methods available for aquaculture usage include chemical disinfection, UV irradiation and ozonation. The most commonly recommended chemicals for mycobacterial disinfection (phenolics, glutaraldehyde) are toxic to animals, including both fish and humans. In addition, there are only a few chemical disinfectants registered by the U.S. Environmental Protection Agency for use with foodfish aquaculture, and none of these is specifically labeled for mycobacteria.

Various disinfectants have been evaluated in our laboratory for their ability to disinfect the water, aquatic surfaces and equipment of an aquarium or aquaculture facility. An effective disinfectant is defined as one whose use results in a 3-log reduction of bacterial growth within 10 minutes of contact time. PVP iodine (100 ppm, 50 ppm), ethyl alcohol (70% and 50%), benzyl-4-chlorophenol/phenylphenol (Lysol®) and sodium chlorite (Clidox-S®) were the most effective disinfectants, each reducing the number of detectable M. marinum to zero within one min of contact time. Sodium hypochlorite (Clorox®) was moderately effective, but required at least 10 min of contact time to reduce bacterial counts and 20 min of contact time to eliminate the organism. Formalin (250 ppm), Chloramine-T (15mg/L), potassium peroxymonosulfate/sodium chloride (1%, Virkon-S®), and two formulations of N-alkyl dimethyl benzyl ammonium chloride (1:256, Roccal-D Plus®, 1:256, Micronex®) were not effective against M. marinum.

Additionally, it is recommended that a thorough cleaning and/or longer contact time may be required in actual aquatic situations, since the organic loads commonly present in aquaculture tanks or aquariums, or the ability of Mycobacterium organisms to be incorporated into aquatic biofilms are generally not taken into account.