California-Nevada Fish Health Center
Pacific Southwest Region


Bacteria is one of the primary causes of disease in fish. The detection, prevention, and control of infectious diseases for fish remains one of the most important considerations for their successful culture. Worldwide, approximately 35 species of bacteria have been isolated from or associated with diseased fish. Of these, 12 species of bacteria are considered major pathogens of fish, and five are considered obligate pathogens (only causes disease in fish).

Growth and isolation of bacteria on appropriate media is the standard method used for diagnostic screening, monitoring of stocks, and fish health inspections for bacterial pathogens. Initial isolation and biochemical tests are preformed to identify the bacteria. The bacterial culture can also be tested against various antibiotics for effective treatment of some diseases. Bacteriological testing, from collection to positive identification, usually takes 3-4 days to complete.

Last updated: May 19, 2011