M. T. Horne

The potency of adjuvanted injected vaccines in rainbow trout (Salmo gairdneri Richardson) and bath vaccines in Atlantic salmon (Salmo salar L.) against furunculosis

Abstract The efficacy of adjuvanted vaccine (administered IP) was evaluated in rainbow trout, Salmo gairdneri Richardson. In general, simple mineral oil-based adjuvants resulted in protection against furunculosis, vibriosis and enteric red mouth (ERM). The addition of whole cell bacterin to the adjuvant doubled protection to about 40 relative percentage protection (RPP). Increasing the administration volume also improved protection. The efficacy of bath vaccine was also evaluated in Atlantic salmon, Salmo salar. Booster vaccinations using Aeromonas salmonicida whole cells were effective against furunculosis (48.5 RPP), when given 4 weeks after the primary vaccination. A single vaccination using whole cells extracted with the non-ionic detergent Triton X-100 resulted in protection against furunculosis (29.9 RPP), while bacteria treated with EDTA gave little or no protection. Untreated whole cells gave 9.9 RPP. Extracellular products (ECP) from Aeromonas salmonicida were effective in protection when presented in particularised form, by binding ECP to polystyrene beads (35.6 RPP). Soluble ECP vaccine provided no protection at all.

Detection of A-protein in Aeromonas salmonicida and some effects of temperature on A-layer assembly

Abstract Coomassie Brilliant Blue solid medium is shown to be a rapid and reliable indicator of the presence of surface protein, ‘A-layer’ array of A. salmonicida . This allows the dynamics of A and A variants to be studied in mixed cultures. Considerable variability between strains is found for the stability of the A-layer at different temperatures.

The association between virulence and cell surface characteristics of Aeromonas salmonicida

Abstract Two virulent strains of Aeromonas salmonicida were shown to lose their capacity for causing furunculosis in rainbow trout ( Salmo gairdneri Richardson) following serial subculture on agar. Strain MT004 (A-layer negative, non-autogglutinating, protease positive) ceased to produce extracellular products (ECP) soon after subculturing, while the other strain, 184 86 (A-layer positive, autoagglutinating, protease negative), retained the A-layer, but the synthesis of another protein in the outer membrane, termed the P0 protein, appeared to be inhibited. Strains 184 86 , MT004 (both virulent) and five other strains (all avirulent) were characterised with regard to their surface properties. All autoagglutinating strains ( 184 86 , B85016 and P-480) were A-layer positive (using a monoclonal antibody probe), while all non-agglutinating strains (B85016, P + 480, 1102 and MT004) were A-layer negative. Strain 8060, previously characterised by other workers as A-layer negative but autoagglutinating was found to be A-layer positive. These results illustrate that the virulence mechanism of Aeromonas salmonicida is complex and appears to vary between strains.

Autoaggregation and extracellular A-layer protein in Aeromonas salmonicida

Abstract Fifteen strains of Aeromonas salmonicida were examined for the presence of an extracellular protein A-layer. The presence of an A-layer has been associated with the property of bacterial autoaggregation. However, three of the ten autoaggregating strains examined in this study showed no detectable A-layer subunit protein.