Characterization of Vibrio anguillarum and closely related species isolated from farmed fish in Norway

Abstract

A total of 264 bacterial strains tentatively or definitely classified as Vibrio anguillarum were examined. The strains were isolated from diseased or healthy Norwegian fish after routine autopsy. With the exception of five isolates from wild saithe (Pollachius virens), the strains originated from nine different species of farmed fish. The bacteria were subjected to morphological, physiological, and biochemical studies, numerical taxonomical analyses, serotyping by slide agglutination and enzyme-linked immunosorbent assay, DNA-plasmid profiling, and in vitro antimicrobial drug susceptibility testing. The results of the microbiological studies were correlated to anamnestic information. The bacterial strains were identified as V. anguillarum serovar 01 (n = 132), serovar 02 (n = 89), serovar 04 (n = 2), serovar 08 (n = 1), and not typeable (n = 1) as well as Vibrio spkndidus biovar I (n = 36) and biovar II (n = 1), Vibrio tubiashii (n = 1), and Vibrio fischerii (n = 1). V. anguillarum serovar 01 or 02 was isolated in 176 out of 179 cases of clinical vibriosis in Atlantic salmon (Salmo salar). V. anguillarum serovar 01 was the only serovar isolated from salmonid fish species other than Atlantic salmon, while V. anguillarum serovar 02 was isolated from all marine fish suffering from vibriosis. A 48-Mda plasmid was isolated from all V. anguillarum serovar 01 isolates examined. Serovar 02 isolates did not harbor any plasmids. Resistance against commonly used antibiotic compounds was not demonstrated among V. anguillarum isolates. Neither V. splendidus biovar I nor other V. anguillarum-related species appeared to be of clinical importance among salmonid fish. However, such bacteria were isolated from diseased turbot (Scopthalmus maximus) and sea bass (Dicentrarchus labrax). The precise role of these bacteria as fish pathogens has to be elucidated. Cell and culture morphology, cell motility, hemolysis patterns, and especially alginate-degrading ability were found to be suitable characteristics for the differentiation of V. splendidus biovar I within the arginine decarboxylase-positive group of Vibrio species. Luminescence could not be demonstrated among V. splendidus isolates. Vibriosis due to Vibrio anguillarum is one of the most important bacterial infections in fish throughout the world (1, 19). The disease has great importance, particularly for marine fish farming (4, 15, 55). Infections have been reported also among farmed bivalve mollusks and crustaceans (11, 12). V. anguillarum and closely related bacterial species are commonly found in estuarine and coastal marine habitats and can readily be isolated from different environmental sources (31-34, 52, 65, 67). These bacteria constitute part of the normal microflora of healthy marine fish (34, 41, 45). On the basis of biochemical and serological differences, two distinct biotypes of V. anguillarum were described (6, 8, 19). Biotype 2 was later differentiated as a new species, Vibrio ordalii (54). A total of 10 different 0 serovars (01 to 010) and additional 0 subgroup...

Haemorrhagic areas in the mouth of farmed turbot, Scophthalmus maximus (L.)

“…External clinical signs of moribund turbot were similar to an epizootic produced by V. anguillarum reported by Horne, Richards, Roberts & Smith (1977), The start of the present epizootic in turbot was associated with a sudden rise in water temperature. This increase in temperature could favour the invasion of the Vibrio strain in turbot previously debilitated by this stress situation, as reported by several authors (Wedemeyer 1970;Devesa et al 1989;Lupiani et al 1989;Myhr et al 1991;Fouz et al 1992), II turbot and rainbow trotit with ( >tic was V. splendidus biotype I. ink Dr Ju; stela, for tli…”

Vibrio spp. isolated from salmonids with shallow skin lesions and reared at low temperature

“…This finding indicates that these heterogenous bacteria are a normal microbiota of fish and sea water, contaminating the samples rather than acting as opportunistic pathogens. Myhr, Larsen, Lillehaug, Gudding, Heum & Håstein (1991) found V. splendidus biovar I in samples from healthy salmonid fish and incidentally in low numbers from mixed cultures from the kidneys of salmonid fish suffering another major bacterial or viral disease. In the same study, V. splendidus was found in diseased turbot and sea bass in Norway.…”

An aerolysin‐like enterotoxin from Vibrio splendidus may be involved in intestinal tract damage and mortalities in turbot, Scophthalmus maximus (L.), and cod, Gadus morhua L., larvae

“…Several studies have reported that V. splendidus is involved in infections in turbot (Myhr, Larsen, Lillehaug, Gudding, Heum & Håstein 1991;Pazos, Santos, Magariños, Bandin, Núñez & Toranzo 1993;Angulo, Lopez, Vicente & Saborido 1994;Gatesoupe et al 1999;Thomson 2001;Thomson et al 2005) and oysters (Gay, Renault, Pons & Le Roux 2004;Le Roux et al 2007). In isolates from moribund turbot, Gatesoupe et al (1999) and Thomson et al (2005) were only able to distinguish between pathogenic and non-pathogenic isolates of V. splendidus by their effects on larval turbot and not from physiological and biochemical properties.…”