Copper and zinc exposure of zebrafish, Brachydanio rerio (Hamilton-Buchaman): effects in experimental Listeria infection.

To investigate the effects of heavy metals on susceptibility of fish to Listeriosis, normal zebrafish, Brachydanio rerio (Hamilton-Buchanan), were exposed to varying concentrations of zinc (0.05, 0.15, and 0.25 mg/liter) and copper (0.05, 0.10, and 0.15 mg/liter). During copper exposure, this heavy metal did not accumulate in zebrafish kidney. Unlike copper, a small amount of zinc accumulated in kidneys of fish exposed at 0.25 mg/liter. To estimate the effects of this heavy metal on listerial infection, the mortality of fish and the number of viable bacteria in fish kidney were determined at various times (1, 4, 7, and 10 days) after ip challenge with Listeria monocytogenes (strain 31386, serotype 4b). The results indicate that the number of colony-forming units in zinc-exposed fish decreased at 4, 7, and 10 days after challenge with 0.2 x LD50 of viable bacteria. In contrast, copper-exposed fish indicated both decreases and increases in the number of colony-forming units depending on the concentration of L. monocytogenes used.