Edwardsiella ictaluri, Flavobacterium columnare
and Aeromonas hydrophila are 3 major bacterial
pathogens of fish that cause diseases with significant
economic impact on the aquaculture industry.
E. ictaluri, the primary cause of enteric septicemia in
channel catfish (Ictalurus punctatus Rafinesque), has
also been frequently associated with disease in other
food fish (Plumb & Sanchez 1983). Flavobacterium
columnare, the cause of columnaris disease, is comprised
of 4 distinct genogroups (Arias et al. 2004) and
has a broad host range, with known infections in over
36 species of fish throughout the world (Anderson &
Conroy 1969). A. hydrophila infects many species of
fish and other terrestrial animals (Colwell et al. 1986),
including humans (Janda & Duffey 1988). Particular
importance is attached to A. hydrophila from a public
health perspective due to its involvement in foodborne
gastroenteritis and various opportunistic infections
in immunocompromised human patients (Altwegg
& Geiss 1989, Janda & Abbott 1998, Ullmann et
al. 2005).
Enteric septicemia of catfish (ESC), reported by
67% of operations within 1 yr, and columnaris disease,
reported by 50% of operations within 1 yr, are the 2