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PubMed1990

Electrophoretic analysis of the surface components of autoagglutinating surface array protein-positive and surface array protein-negative Aeromonas hydrophila and Aeromonas sobria.

The protein and lipopolysaccharide (LPS) compositions of 10 autoagglutinating Aeromonas hydrophila and Aeromonas sobria strains were studied; one group consisted of five serogroup O:11 strains that contained an S layer, while a second group was composed of diverse serogroups that were S layer negative by transmission electron microscopy. All serogroup O:11 strains were found to contain a predominant 52,000- to 54,000-molecular-weight protein that was present on both whole-cell and outer membrane protein profiles; this protein was found to be glycine extractable under low-pH (pH 4) conditions and was identified as the surface array protein. LPS analysis revealed that all O:11 strains exhibited homogeneous-length O-polysaccharide side chains characterized primarily by two or three major bands. In contrast, S-layer-negative autoagglutinating strains of other serogroups lacked this predominant surface array protein, and silver stain analysis of LPS indicated that such profiles mainly consisted of core antigens and were deficient in or devoid of O-polysaccharide side chains. These collective results offer potential explanations for observed differences between these two groups in virulence, disease spectrum, and pathogenic properties.

Aeromonas↗
PubMed1980

Relationships between selected strains of typical and atypical Aeromonas salmonicida, Aeromonas hydrophila, and Haemophilus piscium.

Serological analyses of typical and atypical Aeromonas salmonicida divided the representative strains into two distinguishable groups based on their antigenic composition. However, the serological groupings do not coincide with divisions constructed on the basis of physiological reactions. All of the A. salmonicida strains and the two A. hydrophila strains examined share at least one antigen and are sensitive to A. salmonicida bacteriophage 40 RR2.8t. These data reinforce the reasons for placing these two species in the genus Aeromonas. Haemophilus piscium, the causative agent of ulcer disease, was serologically indistinguishable from A. salmonicida and sensitive to A. salmonicida bacteriophages. This information, in addition to published H. piscium DNA studies, suggests this organism is actually an atypical A. salmonicida; more H. piscium isolates should be characterized to confirm this identification.

Aeromonas↗
PubMed2001

Is Aeromonas hydrophila the dominant motile Aeromonas species that causes disease outbreaks in aquaculture production in the Zhejiang Province of China?

The significance of Aeromonas hydrophila in association with disease outbreaks in aquaculture production in the Zhejiang province of China was investigated. Bacteriological examination of moribund fish and crabs resulted in 95 bacterial isolates: 88 bacterial isolates from fish and 7 isolates from crabs. PCR and traditional biochemical methods were used for identification of A. hydrophila. Out of 69 motile aeromonads, 35 isolates were identified as A. hydrophila by biochemical tests. However, 6 of those were not identified as A. hydrophila by a species specific PCR method. Serotyping revealed 2 dominant serotypes (O9 and O97) among A. hydrophila isolates. The data presented show that approximately 42% of the motile aeromonads isolated from disease outbreaks among various fish species were A. hydrophila. It is noteworthy that A. hydrophila accounted for more than 50% of the isolated aeromonands isolated from crucian carp Carassius carassius and Wuchang bream Megalobrama amblycephala with haemorrhagic septicaemia. Although this species was the most frequently isolated organism from internal organs of diseased fish and crabs in the present study, other motile Aeromonas spp. were also found. The PCR assay was useful in preventing misidentification of A. hydrophila, which may occur when only phenotypic tests are employed.

Aeromonas hydrophila↗
PubMed1996

Production of haemolysin and enterotoxin by Aeromonas jandaei and Aeromonas trota strains after animal passage.

Five Aeromonas jandaei and 12 Aeromonas trota isolates were tested for the production of haemolysin and enterotoxin, and the correlation between these two properties. The majority (10 isolates) of the strains produced beta-haemolysis. The titres of haemolytic activity for both species were 8-64 HU/mL. In the initial ileal loop test, only two (A. trota) of the 17 isolates produced enterotoxin. One each of these 2 A. trota strains was beta-haemolytic and non-haemolytic. The remaining isolates of A. trota and A. jandaei included alpha-, beta- and non-haemolytic strains, and failed to cause any fluid accumulation in the initial tests, but did so after one-to-five sequential passages through the rabbit ileal loops. Three alpha- and 4 non-haemolytic strains switched over to the production of beta-haemolysis when they showed the positive ileal loop reaction. However, on repeated subcultures or on storage in the laboratory, all of them reverted back to their original alpha- or non-haemolytic character and no longer produced enterotoxin.

Aeromonas↗
PubMed1995

RAPD analysis of Aeromonas salmonicida and Aeromonas hydrophila.

The randomly amplified polymorphic DNA (RAPD) technique was used to analyse the genetic differentiation of 13 strains of Aeromonas salmonicida subsp. salmonicida, and seven strains of Aer. hydrophila. Reproducible profiles of genomic DNA fingerprints were generated by polymerase chain reaction (PCR) using a single randomly designed primer. The RAPD profiles of all the non-motile aeromonads, Aer. salmonicida subsp. salmonicida were identical. However, profiles of the motile aeromonads, Aer. hydrophila differed between isolates. These findings reveal genomic homogeneity in Aer. salmonicida subsp. salmonicida and genetic variety in Aer. hydrophila strains.

Aeromonas↗
PubMed2005

Phenotypic, genotypic, and phylogenetic discrepancies to differentiate Aeromonas salmonicida from Aeromonas bestiarum.

The taxonomy of the "Aeromonas hydrophila" complex (comprising the species A. hydrophila, A. bestiarum, A. salmonicida, and A. popoffii) has been controversial, particularly the relationship between the two relevant fish pathogens A. salmonicida and A. bestiarum. In fact, none of the biochemical tests evaluated in the present study were able to separate these two species. One hundred and sixteen strains belonging to the four species of this complex were identified by 16S rDNA restriction fragment length polymorphism (RFLP). Sequencing of the 16S rDNA and cluster analysis of the 16S-23S intergenic spacer region (ISR)-RFLP in selected strains of A. salmonicida and A. bestiarum indicated that the two species may share extremely conserved ribosomal operons and demonstrated that, due to an extremely high degree of sequence conservation, 16S rDNA cannot be used to differentiate these two closely related species. Moreover, DNA-DNA hybridization similarity between the type strains of A. salmonicida subsp. salmonicida and A. bestiarum was 75.6 %, suggesting that they may represent a single taxon. However, a clear phylogenetic divergence between A. salmonicida and A. bestiarum was ascertained from an analysis based on gyrB and rpoD gene sequences, which provided evidence of a lack of congruence of the results obtained from 16S rDNA, 16S-23S ISR-RFLP, DNA-DNA pairing, and biochemical profiles.

Aeromonas↗
PubMed1989

[Studies on motile-Aeromonas infection: incidence of motile-Aeromonas in river mud, river water and fresh-water fish].

During the period from October 1982 to July 1984, a total of 1,157 specimens that consisted of 132 river and lake water, 514 river and lake muds, and 511 fresh-water fish caught in both Tama River and Sagami River were examined the presence of the organisms. Of them, 132 (100%) river and lake waters, 304 (59.1%) river and lake muds, and 462 (90.4%) intestinal contents of fresh-water fish were found to have harbor a mean concentration of 1.3 x 10(3)/l, 1.6 x 10(6)/g, and 1.1 x 10(6)/g of motile-Aeromonas respectively. However, nonseasonal variation was observed in the incidence of the organisms throughout the period of investigation. When attempts were made to classify the isolates by the method described Popoff et al., 17 (14.2%) of 120 water-isolates were typed as A. hydrophila, 33 (27.5%) as A. sobria and 35 (29.2%) as A. caviae respectively. And the rest of the 35 (29.2%) remained untypable. As for the 176 mud-isolates, 38 (21.6%) were typed as A. hydrophila 23 (13.1%) as A. sobria and 41 (23.3%) as A. caviae respectively. And the rest of 74 (42.0%) remained untypable. Some efforts were made on the 1,056 strains obtained from fresh-water fish, and 182 (17.2%) were typed as A. hydrophila, 332 (31.4%) as A. sobria and 206 (19.5%) as A. caviae respectively. And the rest of the 336 (31.8%) remained untypable.

Aeromonas↗
PubMed1987

Plasmids and resistance to antimicrobial agents in Aeromonas sobria and Aeromonas hydrophila clinical isolates.

The antimicrobial susceptibilities of 75 Aeromonas isolates were determined by agar dilution. Differences in resistance patterns were observed between strains isolated from different geographic locations and between A. sobria and A. hydrophila isolates. Multiple resistance was common; however, only one conjugative plasmid was detected. This 110-megadalton plasmid mediated resistance to eight antibiotics.

Aeromonas↗
PubMed2003

A colonization factor (production of lateral flagella) of mesophilic Aeromonas spp. is inactive in Aeromonas salmonicida strains.

The nine laf (lateral flagellum) genes of mesophilic aeromonads are in the Aeromonas salmonicida genome. The laf genes are functional, except for lafA (flagellin gene), which was inactivated by transposase 8 (IS3 family). A pathogenic characteristic of mesophilic aeromonads (lateral flagella) is abolished in this specialized pathogen with a narrow host range.

Aeromonas↗
PubMed1981

A toxigenic profile of Aeromonas hydrophila and Aeromonas sobria isolated from fish.

Forty strains of motile Aeromonas were isolated from healthy and diseased fish. These strains were identified as A. hydrophila or a A. sobria. It was found that only strains of A. hydrophila produced a dermonecrotic factor and two zones of hemolysis on blood agar. All the strains of A. sobria tested and 72% of the A. hydrophila were enterotoxigenic. Finally, we observed that only A. hydrophila strains could regularly produce hemolysin at 10 degrees C.

Aeromonas↗
PubMed1983

Distribution of IMVC biogroups of Aeromonas hydrophila and Aeromonas sobria isolated from human, fish and water.

Aeromonas sobria and A.hydrophila were isolated from infected fish in ratio of 3.5:1 during the outbreak of fish infections from December 1982 to February 1983, while isolates from human diarrheic stool was 1 :2. On the basis of IMVC reactions 138 isolates of motile aeromonads could be divided into 11 biogroups, with biogroup 4 showing statistically significant association with infections. Nine biogroups of aeromonads which were isolated from infected fish reflected that the outbreak was not caused by a single type of bacteria. There may have been some common factors which acted as predisposing causes. The possibility of zoonosis spreading of this epidemic infection of fish was low, because the majority of the infective agents in man and fish were different.

Aeromonas↗