The disease attacks the trout’s colorful body, causing ulcers. Fish infected with Coldwater Disease develop lesions on the skin and fins. Fins may appear dark, torn, split, ragged, frayed and may even be lost completely. Affected fish become lethargic and stop feeding. The infection can then spread systemically. The infection is often fatal and it causes havoc through hatcheries. The disease is triggered by the aquatic bacterium Flavobacterium psychrophilum. As well as trout, the disease can infect Coho salmon.
The reason for the research is due to the considerable economic loss that depleted trout populations. Although antibiotic treatments are available, these are not particularly effective and data suggests that the infectious organism is becoming resistant to commonly used antibiotics. Moreover, the use of antibiotics is not necessarily good for the environment.
The study found that the probiotics function by secreting a toxic protein. The protein does not harm the trout, but can kill the Coldwater Disease bacterium. The probiotic selected is a strain of Enterobacter species called C6-6. This was discovered through a review of hundreds of species detected in the intestinal tract of the rainbow trout.
The probiotic produces a toxic protein called an entericidin. The probiotic has now been patented and the plan is to market it commercially.
The study was a collaborative effort between researchers based at University of Idaho and Washington State University. The probiotic research has been published in the journal Applied and Environmental Microbiology. The research paper is headed “Entericidin Is Required for a Probiotic Treatment (Enterobacter sp. Strain C6-6) To Protect Trout from Cold-Water Disease Challenge.”
