2.5. Detection of putative virulence genes
Amplification of the six virulence genes of E. ictaluri,including the type III secretion system (T3SS), ersC , putative
T3SS effector eseI and its chaperone, escD , type IV
secretion system (T4SS), virD4 , type VI secretion system (T6SS),evpC , and ureA-C genes of the urease operon, were performed on
all 26 isolates using specific primers and protocols outlined by Rogge
et al. (2013) (Table 2). Nuclease-free water was used as a no-template
control. Thermal conditions were used for each of the respective primer
sets as described previously (Rogge et al., 2013) with 1 cycle of 98 °C
for 30 s, 35 cycles of 98 °C for 10 s, 56 °C for 30 s, and 72 °C for 2
min, followed by a final extension at 72 °C for 5 min. The PCR products
were stained and visualized as described above.