O-SEROGROUPING AND SURFACE COMPONENTS OF AEROMONAS-HYDROPHILA AND AEROMONAS-JANDAEI PATHOGENIC FOR EELS

The relationship between virulence, O-serogroup, and some cell-surface features (self-pelleting [SP] and precipitation after boiling [PAB], profile of lipopolysaccharides [LPSs] and outer membrane proteins [OMPs]) was investigated in strains of the pathogenic species Aeromonas hydrophila and A. jandaei isolated from eels. Virulent strains of A, hydrophila reacted mostly with O:19 antiserum, and those of A, jandaei reacted with O:4, O:11, O:15 and O:29 antisera (Guinee and Jansen system). Regarding the PAB and LPS profiles two groups could be distinguished; (i) five PAB(+) strains of serotype O:19 that possessed a homogeneous O polysaccharide side chain and (ii) thirteen PAB(-) strains antigenically diverse that either exhibited a heterogeneous side chain or were side chain deficient. A major 50 kDa protein was only found in the PAB(+) strains, whereas major OMPs detected in PAB(-) strains ranged from 33 to 45 kDa irrespective of the species. Epizootic eel isolates of A, hydrophila belong to serotype O:19 and share cell-surface features with the Aeromonas highly virulent for other hosts. In contrast, epizootic A. jandaei isolates were antigenically diverse. These findings reinforce the importance of an O-serotype as an epidemiological marker in motile Aeromonas strains pathogenic for eels.