Outer membrane protein expression during in vivo cultivation of Vibrio salmonicida

Vibrio sabmonicida cultures held in dialysis tubing containers were implanted in the peritoneal cavity of rainbow trout (Oncorhynchus mykiss) for periods of between 2 and 8 days. Implants were inoculated with 1 x 10(9) cfu. Bacteria within the implants were found to replicate rapidly during the initial implantation period (1.05 x 10(10) cfu after 4 days), stabilise in number, then decrease (minimum 4.8 x 10(7) cfu after 8 days). Escaping bacteria resulted in septicaemic conditions in those fish implanted for 7 days or longer. Bacterial outer membrane protein expression was compared before and after implantation using SDS-PAGE. Expression of three proteins of approximately 99, 90 and 78 kDa, was up-regulated under in vivo conditions by V. salmonicida. Ultrastructural studies using transmission electron microscopy and ruthinium red containing fixatives suggest that V. salmonicida does not produce a capsule in vivo. The results are discussed in relation to vaccine development. (C) 1998 Academic Press.