Bacteria isolated from an outbreak with moderate mortalities in farmed sole, Solea senegalensis (Kaup), in the south of Spain were identified as Vibrio harveyi and V. parahaemolyticus. Only bacterial strains showing swarming were virulent in sole and caused mortalities in experimentally inoculated fish. However, the signs of the disease were only reproduced with V. harveyi. The intramuscular inoculation of the extracellular products (ECPs) of both species produced mortalities in inoculated fish and the appearance of surface ulcers in the case of V. harveyi. However, the inoculation of sublethal doses of ECPs to fish showed a protective effect against V. harveyi.

No abstract

No abstract

Several characteristics, including biochemical, serological, drug resistance and plasmid profiles, of strains isolated from clams in southwestern Spain affected with brown ring disease have been comparatively studied. On the basis of 36 standard physiological and biochemical tests, all strains isolated were included in the genus Vibno and further divided into 6 groups. The groups were differentiated on the basis of only 8 phenotypic traits: growth at 35 "C, arginine dihydrolase, gelatinase production, Voges-Proskauer and ONPG tests, and acid production from sucrose, amygdalin and mannitol. Applying these characteristics, the strains resembled Vibno pelagius and V. splendidus species. However, the isolates of each group showed no cross-reactions with the antisera raised against several reference strains of different species of Vibrio, including V. angu~llarum, V. tubiashii, V. damsela, V. pelagius, V. splendidus and the unclassified Vibno PI. Although only 57.7 % of the strains tested harbored one or more plasmids, the majority of the plasmid-containing strains (93.3 %) carried a large plasmid band of 34.4 MDa. A high number of isolates, regardless of their taxonomic group, were resistant to ampicillin and erythromycin. However, all the Vibrio strains were sensitive to chloramphenicol, tetracycline, gentamicin, nitrofurantoin, nalidixic acid and trimethoprim sulphamethoxazole. No correlation between plasmid content and drug resistance was observed.

ResumenSeveral virulence factors involved in the potential pathogenic capacity of Vibrio Pl, the causative agent of brown ring disease (BRD) affecting cultured Manila clam adults (Ruditupes philippinarum), have been evaluated in comparison with other strains of several Vibrio species isolated from diseased clams. The importance of bacterial ceIl surface associated properties as virulence factors has been studied considering both non-specific and specific bacterial adhesion to clams. Vihrio Pl showed moderate hydrophobicity, but high affinity to bind to Congo Red dye and the presence of appendages, characterized as fimbriae or pili. Al1 the strains of Vibrio P l secreted haemolysis and cytotoxins, and were also strong exotoxin producers. The presence of a large 49.2-MDa plasmid in al1 the strains of Vibrio P l may be used as an epidemiological marker, but its involvement in pathogenic mechanisms has not yet been established. Although in some Vibrio strains, iron-acquisition systems play an essential role in their pathogenicity, they do not seem tu be an important factor in Vihrin Pl, since this pathogen lacks siderophore-mediated iron transport mechanisms.