Serotyping of Vibrio anguillarum.

A serotyping scheme based on the detection of O antigens by slide agglutination in fish-pathogenic strains of Vibrio anguillarum is presented. Over a period of 5 years 270 Vibrio strains from feral and cultured fish, 189 strains from the environment, and 36 strains from invertebrates were collected. The strains were divided into 10 distinct serotypes (O1 through O10). More than 90% of the fish-pathogenic strains, but only 40% of the environmental strains, were typable; 71% of the strains isolated from cultured rainbow trout were serotype O1, whereas 78% of the strains isolated from feral fish were serotype O2. No dominating environmental serotype was found. A serotyping system for V. anguillarum is proposed. A total of 90 strains received from culture collections and laboratories in different countries were typed according to the present system.     

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

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 O1 (n = 132), serovar O2 (n = 89), serovar O4 (n = 2), serovar O8 (n = 1), and not typeable (n = 1) as well as Vibrio splendidus biovar I (n = 36) and biovar II (n = 1), Vibrio tubiashii (n = 1), and Vibrio fischerii (n = 1). V. anguillarum serovar O1 or O2 was isolated in 176 out of 179 cases of clinical vibriosis in Atlantic salmon (Salmo salar). V. anguillarum serovar O1 was the only serovar isolated from salmonid fish species other than Atlantic salmon, while V. anguillarum serovar O2 was isolated from all marine fish suffering from vibriosis. A 48-Mda plasmid was isolated from all V. anguillarum serovar O1 isolates examined. Serovar O2 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.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monoclonal antibodies against Vibrio anguillarum O2 and Vibrio ordalii identify antigenic differences in lipopolysaccharide O-antigens

Abstract Monoclonal antibodies (mAbs) that recognize distinct species-specific antigenic epitopes in O-antigens from Vibrio anguillarum O2, O2a and certain O2b strains (mAb 7B4) and from Vibrio ordalii strains (mAbs A16 and 7D11) were generated. Western immunoblot analysis using these mAbs revealed that vibrio strains grown in the presence of fresh rainbow trout blood expressed lipopolysaccharide (LPS) with longer (high molecular mass) O-antigens and extracellular capsular layers when compared to strains grown without rainbow trout blood. We also generated mAbs that react with O-antigens from V. anguillarum serotype O1 (mAbs 7B8, 7B5 and 1C3) and serotype O3 (mAbs 13A1 and 14C5) strains. These mAbs provide rapid and accurate diagnostic reagents for serological differentiation of V. ordalii from serotype O2 strains of V. anguillarum , and for serotyping of these pathogenic vibrios.     

Characterization and Relatedness of Marine Vibrios Pathogenic to Fish: Physiology, Serology, and Epidemiology

Cultural characteristics and serological relationships of pathogenic marine vibrios isolated from fish in the Pacific Northwest were studied. These organisms were compared with cultures of Vibrio anguillarum, a known fish pathogen. On the basis of morphological and cultural characteristics, the Pacific Northwest strains of Vibrio were found to be closely related to V. anguillarum. Serological analyses of thermostable antigens served to distinguish three serotypes among the vibrios. Serotype 1 was composed of organisms isolated from Northwest salmonids; serotype 2 of strains of V. anguillarum from European waters; and serotype 3 of organisms isolated from Pacific herring. The epidemiology of vibrio disease among populations of fish in the Pacific Northwest is discussed.     

Vibrio anguillarum serogroup O3 and V. anguillarum-like serogroup O3 cross-reactive species--comparison and characterization

Forty-five Vibrio anguillarum-like isolates reacting with V. anguillarum serogroup O3 antiserum were examined in 30 characters to clarify their phenotypical properties, while their genotype was examined by ribotyping. The strains were isolated from diseased and dead fish or from environmental sources such as water, sediment, plankton, and faeces and gills of healthy fish. Phenotypically, the similarity of all the strains was more than 90%. However, significant differences between the fish-associated and environmental strains were detected. Biochemically, deviations were found in the Voges-Proskauer test and lysine decarboxylase reaction. Clustering analysis of the ribotypes showed two distinct clusters with a similarity of only 32%. Two strains representing each of these groups were used in a LD50 study, which showed some difference also in the pathogenicity between environmental and fish strains. It is suggested that the environmental strains belong to another species than V. anguillarum, but serologically cross-reacting with the V. anguillarum serogroup O3. The ribotyping as well as biochemical results indicated that the environmental strains possibly belong to Vibrio aestuarianus. The bona fide V. anguillarum serogroup O3 strains proved to be very homogeneous both phenotypically and genotypically, and the similarity of ribotypes was more than 96%. The V. anguillarum-like, serogroup O3-reactive strains from the environment were more heterogeneous in their biochemical behaviour, and showed an approximately 70% similarity in ribotypes.     

Study of Vibrio anguillarum strains from different sources with emphasis on ecological and pathobiological properties.

A total of 317 Vibrio anguillarum strains were isolated from water, sediment, and diseased as well as healthy rainbow trout at a Danish mariculture farm and from feral fish caught close to the farm. All strains were examined serologically. Ten sera permitted determination of the O group in 66.7% of the strains from diseased rainbow trout. Furthermore, the O group could be determined in 45.1 to 65.4% of the strains from mucus, gills, and intestinal contents of healthy rainbow trout, while only 22.2 to 28.8% of the isolates from water, sediment, and gills or mucus of feral fish were groupable. Serogroup O1 and to some extent O2 appeared to be associated with trout. Strains from these serogroups were selected for analyses of hemagglutinating activity and surface hydrophobicity. Serogroup O1 comprised hemagglutinating as well as nonhemagglutinating strains; from cases of vibriosis, all O1 strains were nonhemagglutinating. The strains belonging to serogroup O2 were generally hemagglutinating. Examinations of surface hydrophobicity by salt aggregation and hydrophobic interaction chromatography suggested that the O1 strains were more hydrophobic than the O2 strains. In pathogenicity tests, O1 strains isolated from gills and mucus of healthy rainbow trout killed all trout in the test groups. A strain from the intestinal contents of healthy rainbow trout did not produce significant mortality. This strain could, however, be frequently reisolated from the pronephros of fish in the test group concerned. After challenge with strains from eel mucus and seawater, mortality was not produced, and furthermore, these strains could not be reisolated from the pronephros.     

Study of Vibrio anguillarum strains from different sources with emphasis on ecological and pathobiological properties

A total of 317 Vibrio anguillarum strains were isolated from water, sediment, and diseased as well as healthy rainbow trout at a Danish mariculture farm and from feral fish caught close to the farm. All strains were examined serologically. Ten sera permitted determination of the O group in 66.7% of the strains from diseased rainbow trout. Furthermore, the O group could be determined in 45.1 to 65.4% of the strains from mucus, gills, and intestinal contents of healthy rainbow trout, while only 22.2 to 28.8% of the isolates from water, sediment, and gills or mucus of feral fish were groupable. Serogroup O1 and to some extent O2 appeared to be associated with trout. Strains from these serogroups were selected for analyses of hemagglutinating activity and surface hydrophobicity. Serogroup O1 comprised hemagglutinating as well as nonhemagglutinating strains; from cases of vibriosis, all O1 strains were nonhemagglutinating. The strains belonging to serogroup O2 were generally hemagglutinating. Examinations of surface hydrophobicity by salt aggregation and hydrophobic interaction chromatography suggested that the O1 strains were more hydrophobic than the O2 strains. In pathogenicity tests, O1 strains isolated from gills and mucus of healthy rainbow trout killed all trout in the test groups. A strain from the intestinal contents of healthy rainbow trout did not produce significant mortality. This strain could, however, be frequently reisolated from the pronephros of fish in the test group concerned. After challenge with strains from eel mucus and seawater, mortality was not produced, and furthermore, these strains could not be reisolated from the pronephros.     

Seasonal incidence of autochthonous antagonistic Roseobacter spp. and Vibrionaceae strains in a turbot larva (Scophthalmus maximus) rearing system

Bacteria inhibitory to fish larval pathogenic bacteria were isolated from two turbot larva rearing farms over a 1-year period. Samples were taken from the rearing site, e.g., tank walls, water, and feed for larvae, and bacteria with antagonistic activity against Vibrio anguillarum were isolated using a replica plating assay. Approximately 19,000 colonies were replica plated from marine agar plates, and 341 strains were isolated from colonies causing clearing zones in a layer of V. anguillarum. When tested in a well diffusion agar assay, 173 strains retained the antibacterial activity against V. anguillarum and Vibrio splendidus. Biochemical tests identified 132 strains as Roseobacter spp. and 31 as Vibrionaceae strains. Partial sequencing of the 16S rRNA gene of three strains confirmed the identification as Roseobacter gallaeciensis. Roseobacter spp. were especially isolated in the spring and early summer months. Subtyping of the 132 Roseobacter spp. strains by randomly amplified polymorphic DNA with two primers revealed that the strains formed a very homogeneous group. Hence, it appears that the same subtype was present at both fish farms and persisted during the 1-year survey. This indicates either a common, regular source of the subtype or the possibility that a particular subtype has established itself in some areas of the fish farm. Thirty-one antagonists were identified as Vibrio spp., and 18 of these were V. anguillarum but not serotype O1 or O2. Roseobacter spp. strains were, in particular, isolated from the larval tank walls, and it may be possible to establish an antagonistic, beneficial microflora in the rearing environment of turbot larvae and thereby limit survival of pathogenic bacteria.     

Distribution of plasmid- and chromosome-mediated iron uptake systems in Vibrio anguillarum strains of different origins

We investigated the incidence of plasmid-mediated and chromosome-mediated iron uptake systems in strains of Vibrio anguillarum that belong to serotypes O1 and O2 and were isolated from different fish species and in different geographic areas. All of the strains gave positive reactions in CAS agar medium and in the Arnow test, which indicated that catechol types of siderophores were produced. The majority of V. anguillarum serotype O1 strains harbored a 65-kb plasmid similar to plasmid pJM1 from strain 775, which encodes the siderophore anguibactin and its outer membrane receptor, protein OM2. All of the isolates harboring this plasmid promoted the growth of an anguibactin-deficient receptor-proficient mutant derived from strain 775, but none of these isolates promoted the growth of mutants lacking receptor OM2. Furthermore, under iron-limiting conditions all of these strains induced outer membrane proteins that were identical in size to protein OM2 of strain 775. In contrast, none of the serotype O2 strains contained a high-molecular-weight plasmid, but all of them induced the growth of mutants defective in the anguibactin-mediated system regardless of the presence or absence of receptor OM2. The serotype O2 strains, but not the plasmid-bearing serotype O1 strains, also induced the growth of Salmonella typhimurium enb-1 which utilizes only enterobactin as a siderophore.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of plasmid- and chromosome-mediated iron uptake systems in Vibrio anguillarum strains of different origins.

We investigated the incidence of plasmid-mediated and chromosome-mediated iron uptake systems in strains of Vibrio anguillarum that belong to serotypes O1 and O2 and were isolated from different fish species and in different geographic areas. All of the strains gave positive reactions in CAS agar medium and in the Arnow test, which indicated that catechol types of siderophores were produced. The majority of V. anguillarum serotype O1 strains harbored a 65-kb plasmid similar to plasmid pJM1 from strain 775, which encodes the siderophore anguibactin and its outer membrane receptor, protein OM2. All of the isolates harboring this plasmid promoted the growth of an anguibactin-deficient receptor-proficient mutant derived from strain 775, but none of these isolates promoted the growth of mutants lacking receptor OM2. Furthermore, under iron-limiting conditions all of these strains induced outer membrane proteins that were identical in size to protein OM2 of strain 775. In contrast, none of the serotype O2 strains contained a high-molecular-weight plasmid, but all of them induced the growth of mutants defective in the anguibactin-mediated system regardless of the presence or absence of receptor OM2. The serotype O2 strains, but not the plasmid-bearing serotype O1 strains, also induced the growth of Salmonella typhimurium enb-1 which utilizes only enterobactin as a siderophore.(ABSTRACT TRUNCATED AT 250 WORDS)     

Production of acylated homoserine lactones by different serotypes of Vibrio anguillarum both in culture and during infection of rainbow trout

Onehundred and forty-eight out of onehundred and fifty strains of Vibrio anguillarum isolated from vibriosis in Danish marine aquaculture produced bacterial communication signals, acylated homoserine lactones, eliciting a response in the Agrobacterium tumefaciens (pZLR4) monitoring system. One strain, a serotype O4, induced a strong response in the Chromobacterium violaceum (CV026) monitoring system. Profiles of AHLs determined by TLC separation revealed the presence of at least four AHLs and a compound similar to N-3-oxo-decanoyl homoserine lactone (3-oxo-C10-HSL) was present in all strains. The production rate of the presumed 3-oxo-C10-HSL followed the growth rate of V. anguillarum whereas the production rate of a small AHL (Rf value of 0.74) increased faster than the growth rate of V. anguillarum indicating autoinduction. AHLs were produced by all serotypes (O1 to O10) and by non-typable strains. During infection with V. anguillarum, AHLs could be extracted from liver, kidney and muscle of rainbow trout and AHLs were detected both in vitro and in vivo when cell numbers reached 10(7) per ml or gram. Preliminary investigations of interactions between AHLs and the fish immune system were carried out determining oxidative burst of fish macrophages exposed to 3-oxo-C10-HSL. No activation or suppression of the superoxide anion production in the head kidney macrophages was seen when treated with the AHL compound in concentrations of 1 nM-10 microM. Our data show that AHLs are produced by almost all V. anguillarum strains and that no clear pattern relating AHL production to disease or virulence appear.     

Relationships between plasmids and phenotypes of presumptive strains of Vibrio anguillarum isolated from different fish species

On the basis of plasmid composition as well as serological and biochemical properties, 26 strains identified as Vibrio anguillarum isolated from diseased fish could be assigned to two different groups. Except for three reference strains, these++ strains were isolated from Norwegian fish. The four strains isolated from rainbow trout (Salmo gairdneri), the only strain isolated from char (Salvelinus alpinus), and three of six strains isolated from Atlantic salmon (Salmo salar) harbored a plasmid of 47 megadaltons (MDa). Restriction endonuclease analysis showed that this plasmid and the virulence plasmid pJM1, carried by V. anguillarum strain 775, were very similar but not identical. Strains harboring the 47-MDa plasmid had nearly identical biochemical properties and were serotype O1. Strains isolated from reared coastal cod (Gadus morhua), turbot (Scophthalmus maximus), halibut (Hippoglossus hippoglossus), free-living saithe (Pollachius virens), and partly from reared Atlantic salmon differed from strains harboring the 47-MDa virulence plasmid by not containing this plasmid, by having different biochemical traits, and by being serotype O2. Rainbow trout which were experimentally infected with a strain isolated from cod suffering from vibriosis developed clinical symptoms similar to those in cod but quite different from those usually seen in rainbow trout.     

Relationships between plasmids and phenotypes of presumptive strains of Vibrio anguillarum isolated from different fish species.

On the basis of plasmid composition as well as serological and biochemical properties, 26 strains identified as Vibrio anguillarum isolated from diseased fish could be assigned to two different groups. Except for three reference strains, these++ strains were isolated from Norwegian fish. The four strains isolated from rainbow trout (Salmo gairdneri), the only strain isolated from char (Salvelinus alpinus), and three of six strains isolated from Atlantic salmon (Salmo salar) harbored a plasmid of 47 megadaltons (MDa). Restriction endonuclease analysis showed that this plasmid and the virulence plasmid pJM1, carried by V. anguillarum strain 775, were very similar but not identical. Strains harboring the 47-MDa plasmid had nearly identical biochemical properties and were serotype O1. Strains isolated from reared coastal cod (Gadus morhua), turbot (Scophthalmus maximus), halibut (Hippoglossus hippoglossus), free-living saithe (Pollachius virens), and partly from reared Atlantic salmon differed from strains harboring the 47-MDa virulence plasmid by not containing this plasmid, by having different biochemical traits, and by being serotype O2. Rainbow trout which were experimentally infected with a strain isolated from cod suffering from vibriosis developed clinical symptoms similar to those in cod but quite different from those usually seen in rainbow trout.     

Analysis of antigens present in the extracellular products and cell surface of Vibrio anguillarum serotypes O1, O2, and O3.

Antigens present in the extracellular products (ECP) and cell walls of strains of Vibrio anguillarum of serotypes O1, O2, and O3 isolated from different fish species in distinct geographic areas were characterized. The usefulness of slide agglutination, dot blot assay, and quantitative agglutination for subtyping V. anguillarum serovars was also evaluated. The three serological assays used to establish the serogroups within V. anguillarum isolates demonstrated that serotype O1 constitutes a homogeneous group, whereas within serotypes O2 and O3, two different patterns of serological reactions were detected. Among the three serological methods used, only dot blot and quantitative agglutination assays differentiated subgroups within serotypes O2 and O3 with unabsorbed sera. Electrophoretic analysis and immunoblot assays of cell envelope and ECP components showed that strains belonging to serotype O1 possessed immunologically related lipopolysaccharide (LPS) and proteins, while V. anguillarum isolates grouped in serotypes O2 and O3 exhibited internal heterogeneity in their LPS and protein banding patterns. On the other hand, although the LPS present in the ECP and those obtained from cell envelopes of V. anguillarum strains showed apparently different gel patterns, a strong relationship between both types of LPS was seen by immunoblot assay. From these results, it can be concluded that V. anguillarum strains representative of each of the antigenic groups (O1, O2 alpha, O2 beta, O3A, and O3B) and their ECPs should be included in the formulation of vaccines against vibriosis in areas where the three serotypes coexist.     

辽宁省食源性副溶血性弧菌毒力基因、血清分型及耐药性分析

研究辽宁省2017-2020年市售水产品及其制品中分离的158株副溶血性弧菌的毒力基因、血清分型和耐药性, 为食源性疾病的暴发和散发进行评估和预警。

采用多重荧光定量PCR技术对毒力基因tlh、tdh和trh进行检测, 同时检测血清分型; 采用肉汤稀释法测定副溶血性弧菌MIC值并分析其耐药性。

158株副溶血性弧菌中均携带tlh基因, 携带tdh基因的菌株2株, 携带trh基因的菌株2株, 同时携带tdh基因和trh基因的菌株1株; 158株中67株血清型为O2(含K不分型), 39株为O3(含K不分型), 携带tdh和trh毒力基因的菌株血清型均为O3;副溶血性弧菌122株(77.22%)对头孢唑啉耐药, 36株(22.78%)对头孢西丁耐药, 30株(18.99%)对氨苄西林耐药, 18株菌呈现耐受2类及以上的多重耐药性。携带毒力基因的5株副溶血性弧菌对头孢唑啉均耐药。

大多数食源性副溶血性弧菌不携带毒力基因, O2血清型(42.41%)是辽宁省食源性副溶血性弧菌的主要血清型, 其次为O3(24.68%); 副溶血性弧菌对头孢唑啉显著耐药, 少数菌表现出多重耐药, 提示应继续加强水产品及其生食制品中副溶血性弧菌的致病性和耐药性监测。

     

Ribotypes and plasmid contents of Vibrio anguillarum strains in relation to serovar.

Eighty-six strains of the 10 major agglutination types of Vibrio anguillarum (serovars O1 to O10) and 6 nontypeable strains of V. anguillarum have been characterized by ribotyping with a probe complementary to 16S and 23S rRNA of Escherichia coli and by plasmid profile analysis. Forty-four different ribotypes were observed with the restriction enzyme HindIII. Ribotype similarity was compared by using the Dice coefficient (Sd), and three significantly different levels of homogeneity within the V. anguillarum serovars were observed (serovars O1, O3A, O7, and O9, Sds of > 90%; serovars O2B, O4, and O10, Sds of 80 to 90%; serovars O2A, O3B, O5, and O8, Sds between 46 and 70%). None of the ribotype patterns of V. anguillarum strains were observed among 20 other Vibrio strains typed for comparison. By cluster analysis, the V. anguillarum strains were divided into a main cluster containing 83 strains, while all strains of serovar O3B, one strain (each) of serovars O2A, O5, and O8, and a nontypeable strain were separated from this cluster by at least 15% difference in similarity coefficients. Plasmids were demonstrated in only six strains other than serovar O1. In serovar O1, a 67- to 70-kilobase-pair (kb) plasmid molecule was present in 17 of 19 strains tested; of the two remaining strains, one strain harbored two plasmids (45 and 6.5 kb) and one strain had no plasmids.     

Rapid detection and identification of Vibrio anguillarum by using a specific oligonucleotide probe complementary to 16S rRNA.

Partial 16S rDNA from Vibrio collection type strains and recent isolates of Vibrio-related strains were sequenced and compared with previously published sequences. A 24-base DNA oligonucleotide (VaV3) was designed and used as a specific probe for detection and identification of Vibrio anguillarum. Its specificity was tested against collection type strains and environmental isolates and no cross-reaction was found. The probe detected 8 of the 10 V. anguillarum serovars. It was applied to screen different Vibrio-related strains isolated from marine hatcheries and fish farms. The detection limit in DNA-DNA slot blot hybridization was 150 pg.     

Isolation and characterization of turbot (Scophtalmus maximus)-associated bacteria with inhibitory effects against Vibrio anguillarum.

More than 400 isolates from the intestine and the external surface of farmed Scophtalmus maximus as well as from fish food and hatchery water were screened for inhibitory effects against the fish pathogen Vibrio anguillarum HI 11345 and seven other fish pathogens. The bacteria with inhibitory effects were then characterized with regard to their sites of colonization, especially the intestinal regions and sites within each region. Of the total number of bacterial isolates from the intestine, 28% were inhibitory against V. anguillarum HI 11345. A marine biochemical assay was used to order the inhibitory strains into different phena. Most inhibitory bacteria were found in the rinse and mucus fractions of the gastrointestinal tract. No correlations among the different phena, site of colonization, and inhibitory effect could be found; however, a biochemical diversity was noted in the strains with an inhibitory effect. Of the isolates with an inhibitory effect against V. anguillarum HI 11345, 60% had an inhibitory effect on five other fish-pathogenic serotypes of V. anguillarum. Inhibitory effects of the isolates were also shown against Aeromonas salmonicida and Aeromonas hydrophila.     

Identification of Vibrio anguillarum in fish by using partial 16S rRNA sequences and a specific 16S rRNA oligonucleotide probe.

16S rRNA from seven different Vibrio anguillarum strains was partially sequenced and compared. From this sequence information we could design a 25-base-long oligonucleotide and use it as a specific probe for identification of V. anguillarum. This was determined by RNA-DNA colony hybridization and slot-blot hybridization. Strong, specific hybridization to the probe was observed for all V. anguillarum strains tested. Furthermore, no cross-hybridization could be seen against five other bacterial species. The detection limit was 5 x 10(3) bacteria per ml. It was even possible to detect V. anguillarum, by slot-blot hybridization, directly in a homogenized kidney from a fish that had died of vibriosis. The partial sequence information revealed small but significant differences between strains of the same species. These sequence differences are sufficiently significant to allow serotyping on the RNA level. Comparing strains of different serotypes revealed a 10-base and an 11-base difference in V. anguillarum serotypes O8 and O9, respectively, in a 122-base partial sequence.     

Isolation and characterization of turbot (Scophtalmus maximus)-associated bacteria with inhibitory effects against Vibrio anguillarum.

More than 400 isolates from the intestine and the external surface of farmed Scophtalmus maximus as well as from fish food and hatchery water were screened for inhibitory effects against the fish pathogen Vibrio anguillarum HI 11345 and seven other fish pathogens. The bacteria with inhibitory effects were then characterized with regard to their sites of colonization, especially the intestinal regions and sites within each region. Of the total number of bacterial isolates from the intestine, 28% were inhibitory against V. anguillarum HI 11345. A marine biochemical assay was used to order the inhibitory strains into different phena. Most inhibitory bacteria were found in the rinse and mucus fractions of the gastrointestinal tract. No correlations among the different phena, site of colonization, and inhibitory effect could be found; however, a biochemical diversity was noted in the strains with an inhibitory effect. Of the isolates with an inhibitory effect against V. anguillarum HI 11345, 60% had an inhibitory effect on five other fish-pathogenic serotypes of V. anguillarum. Inhibitory effects of the isolates were also shown against Aeromonas salmonicida and Aeromonas hydrophila.