Samples were taken 24 h after challenge to measure adhesion of bacteria
to gills using q PCR analysis. Eight fish were collected from each
treatment. As described by Beck et al. (2012), a section of the left second
gill arch (approximately 50mg)was taken from each fish. Samples were
stored at 80 °C until DNA extraction. All DNA extractions were performed
according to the manufacturer's directions using a DN easy
Blood and Tissue Kit (Qiagen, Valencia, California). The extracted template
DNA (composed of catfish genomic and bacterial DNA) was used
for pathogen detection, identity confirmation, and quantification using
the primers of Panangala et al. (2007) which were FcFp [50-CCTGTA
CCTAATTGGGGAAAAGAGG-30], FcRp [50-CGGTTATGGCCTTGTTTATC
ATAGA-30] and FAM labeled probe [50-ACAACAATGATTTTGCAGGAGG
AGTATCTGATGGG-30]. This primer and fluorescent probe-set targets a
region of the chondroitin AC lyase gene of F. columnare. Primers and
FAMlabeled probewere obtained fromApplied Biosystems Incorporated
(Foster City, California).