An additional layer, exterior to the outer membrane cellwall
layer, was found on Aeromonas salmonicida cells from aggregating
strains. Nonaggregating strains were found to lack this layer.
The nonaggregating strains were all avirulent (LD₅₀
greater than
1 X 10
⁸ CFU/fish) while the majority of the aggregating strains
were virulent...