(~1.3 × 105 CFU ml–1 of each organism); Group 5, E.
ictaluri + A. hydrophila (~ 1.4 × 105 CFU ml–1 of each
organism); Group 6, F. columnare + E. ictaluri + A.
hydrophila (~1 × 105 CFU ml–1 of each organism). An
uninfected group (Group 7) of 7 fish were maintained
as controls. Fish were monitored following infection
and dead or moribund fish were promptly removed for
sample collection. Blood was collected into 1 ml hypodermic
syringes by direct cardiac puncture, and the
kidney and gill tissues were surgically removed.
Duplicate sample sets were collected to provide for
nucleic acid extraction and for bacteriological culture.
In addition to samples from infected fish, tissues (gills,
kidney and blood) obtained from euthanized (using
200 mg l–1 tricaine methanesulfonate; Western Chemical)
naïve fish were spiked with F. columnare, E.