| The flagellin gene (flaA) of Yersinia ruckeri serovar 1 strain RS7 was inactivated to explore the role of flagella in virulence. The flaA gene was PCR-amplified using primers designed from the flagellin gene (fleA) of Yersinia enterocolitica, and flaA was then replaced with a gentamicin resistance cassette (aacC1) by homologous recombination. The aflagellar, non-motile strain, WK4 was used in infection challenges of rainbow trout, Oncorhynchus mykiss. The parental strain was recovered from organs at a higher level (CFU/g tissue) than WK4 in the first 3 days post-infection, indicating flagella conferred a slight advantage during the initial stages of infection. However, WK4 reached the same level of infection as RS7 by day 6 post-infection (P > 0.1), and after 42-days, no significant difference was detected between the strains. When naive rainbow trout were held in tanks with fish co-infected with RS7 and WK4, only RS7 transmitted to new hosts. |
