| Abstract | Emerging evidence suggests that the immune system is vulnerable to disruption in response to a wide variety of chemical contaminants; thus, there is a need to test chemicals for immunotoxicity. To understand how chemicals impact the ability of the immune system to ward off infection, the Jeffries Lab uses fathead minnows (FHM, a common toxicological model) infected with Yersinia ruckeri (a bacteria) as a model system. To determine the effect of chemicals on immune function using the model system, pathogen resistance challenges are run which infect chemically exposed and unexposed fish with pathogen and measure their ability to fight off the pathogen and survive infection. The use of Y. ruckeri is not favorable in the model system, however, because fish must be injected with the bacteria to develop an infection and this process is a time-consuming non-natural route of exposure so introduces many sources of human error. Thus, the goal of this project was to develop a new host-pathogen system for FHMs by identifying a pathogen that induces infection via immersion while also evaluating its growth characteristics. To do this, the growth characteristics of Flavobacterium columnare were analyzed by raising bacteria in its growth media and measuring time, optical density, and colony forming units every hour. Following this, the ability of Flavobacterium columnare to infect FHMs via immersion was evaluated by running fin-clipped and non-fin-clipped immersion challenge trials. Results of this study revealed F. columnare was capable of surviving in water and grew best in MAT broth, and that it could induce an infection via immersion in FHMs. Infection was most successful following a fin-clip procedure, in which a small portion of the caudal fin is removed, resulting in all male FHMs dying and females showing signs of infection. Overall, this result successfully establishes the potential for an FHM-Flavobacterium columnare model system for future use in immunotoxicity testing, replacing the currently used Yersinia ruckeri. |
