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PubMed1993

The growth and expression of virulence factors at refrigeration temperature by Aeromonas strains isolated from foods.

A potentially significant subset (10%, 6/61) of Aeromonas strains isolated from food (milk, lamb, chicken, seafood), all A. veronii biotype sobria, were able to produce two or more exotoxins (haemolysin, enterotoxin, and cytotoxin) at 37 degrees C, and grow well at 43 degrees C. Although mesophilic organisms, they grew at 5 degrees C. In addition, they could adhere to HEp-2 cells when grown at 37 degrees C, or at 5 degrees C, and expressed flexible pili (possible colonization factors) in greater numbers at the lower temperature. These strains, as well as other exotoxin-producing strains (A. veronii biotype sobria and A. hydrophila) (33%, 20/61) lacking adhesive ability, were able to produce cytotoxins in broth cultures over a seven to 10-day period at 5 degrees C. One strain in particular, an A. hydrophila isolated from goats' milk, grew rapidly at low temperature. This psychrotrophic strain produced all three exotoxins within 3 days in broth cultures at 5 degrees C. The properties of the above strains suggest they could be of public health significance in food products that have an extended shelf-life at refrigeration temperature.

Aeromonas↗
PubMed1993

Occurrence of Aeromonas spp. in samples of ground meat and chicken.

Aeromonas spp. was commonly isolated from ground meat and chicken samples at the retail level. The dominant species in ground meat were A. hydrophila and A. caviae. In chicken, A. sobria was common while A. caviae was isolated infrequently. Although A. hydrophila was isolated from 75% of ground meat samples and 62% of chicken samples, DL-lactate-positive A. hydrophila (genospecies 1) was isolated from only 25 or 37% or respective samples. Sorbitol-positive A. hydrophila (genospecies 3) was common in both ground meat and chicken.

Aeromonas↗
PubMed1994

Presence of Aeromonas hydrophila in slaughtered animals.

The fate of Aeromonas hydrophila after a bacteriaemia in four healthy pigs intravenously inoculated with 10(9) and 10(15) cells of the bacterium was investigated. In two pigs slaughtered 30 min after inoculation the bacteria were found in blood (8 x 10(2)/ml and 4.2 x 10(2)/ml), meat and fatty tissues (1-10/g), but not in liver, spleen and superficial inguinal lymph nodes. A. hydrophila was not found in blood, meat, fatty tissue, liver, spleen, kidneys and superficial inguinal lymph nodes of other two pigs slaughtered 5.5 h postinoculation, with exception of one superficial inguinal lymph node of one pig.

Abattoirs↗
PubMed1994

An example of the stages in the development of a predictive mathematical model for microbial growth: the effects of NaCl, pH and temperature on the growth of Aeromonas hydrophila.

The stages involved in developing a predictive model are illustrated using data describing the effects of temperature (3-20 degrees C), NaCl concentration (0.5-4.5% w/v) and pH (4.6-7.0) on the aerobic growth of Aeromonas hydrophila (cocktail of 6 strains). Optical density measurements using micro-titre plates were used as an initial screen, to determine the appropriate sampling times for viable counts to be made and to determine the approximate boundaries for growth. Growth curves were generated from viable counts and fitted using a modified Gompertz equation. Quadratic response surface equations were fitted to the log of lag and generation times, in response to the variables of temperature, NaCl and pH (in terms of hydrogen ion concentration). The effects of various combinations of these controlling factors are described. Comparisons between predicted growth rates and lag times from our response surface equations and other models for growth of A. hydrophila, developed with viable count data and optical density measurements, are made, together with comparisons with data from the literature on the growth of this bacterium in foods.

Aeromonas hydrophila↗
PubMed1984

Aeromonas hydrophila: an outbreak of hospital infection.

Aeromonas hydrophila is a Gram-negative water-borne organism widely distributed in the environment. This organism is a recognized cause of diarrhoea and an opportunist pathogen in immunosuppressed patients. An outbreak of hospital-acquired infection which included three cases of pneumonia is reported. The organism was isolated from 19 patients.

Aeromonas↗
PubMed1988

Aeromonas hydrophilia infection in burn patients.

Aeromonas hydrophilia rarely infects burn wounds. Three cases of early A. hydrophilia burn wound infection, with one death, are reported. A history of extinguishing the fire with dirty water or by rolling in dirt should alert the physician to consider A. hydrophilia as a possible infection organism.

Adolescent↗
PubMed1989

The quantitative relationship of lethality between extracellular protease and extracellular haemolysin of Aeromonas salmonicida in Atlantic salmon (Salmo salar L.).

An additive relationship of lethality between purified protease and haemolysin of the extracellular products (ECP) of Aeromonas salmonicida was demonstrated by i.p. injection in Atlantic salmon (Salmo salar L.). The lethal toxicity of the combinations of protease and haemolysin follow a linear regression line y = -54.54x + 2400. The LD50 of protease and haemolysin when injected separately was 2400 ng/g fish and 44 ng protein/g fish, respectively.

Aeromonas↗
PubMed1989

Characterization of a pilus produced by Aeromonas hydrophila.

A pilus produced by Aeromonas hydrophila was purified and partially characterized. The pilin monomers had an apparent molecular weight of 17,000. Agglutination studies indicated serological cross-reactivity in the pili of A. hydrophila strains. Presence of pili did not correlate with hydrophobicity or haemagglutinating ability of the bacteria.

Aeromonas↗
PubMed1990

Direct selection of monoclonal antibodies neutralising the cytotoxic activity of Aeromonas sobria.

Monoclonal antibodies directed against the cytotoxic activity of Aeromonas sobria were raised by immunising mice with a culture supernatant concentrated by ammonium sulphate precipitation. Neutralising antibodies were specifically selected for by exposing hybridomas to cytotoxic levels of the immunising preparation. Cultures free from cytopathic effects after three hours were selected for further investigation. Ten cytotoxin resistant hybridomas were isolated but only two of these produced detectable neutralising activity in Vero and rabbit red blood cell assays. Different polypeptide binding patterns were observed for the neutralising antibodies compared with the other antibodies in immunoblotting studies. One of the neutralising antibodies was shown to act at an early stage in the development of cytotoxicity, probably by inhibiting binding.

Aeromonas↗
PubMed1990

Cross resistance between oxytetracycline and oxolinic acid in Aeromonas salmonicida associated with alterations in outer membrane proteins.

Oxytetracycline resistant mutants of Aeromonas salmonicida isolated from mutation frequency experiments showed decreased susceptibility to oxolinic acid. Outer membrane preparations of these resistant mutant strains revealed a major protein, with a molecular mass of approximately 37 kDa, which was not present in significant quantities in the parent strain.

Aeromonas↗
PubMed1991

Genetic variation in related cytolytic toxins produced by different species of Aeromonas.

Comparative analyses were performed at the immunological, biological, and genetic level to establish the degree of relatedness of a group of four cytotoxic enterotoxins and aerolysins produced by different isolates of Aeromonas: SSU [16], Ah1 [13], Ah2 [18], and Ah65 [21]. Results obtained from Western blot analysis, neutralization studies, and Southern blot analysis indicated that although the members of this group of toxins displayed structural similarities they also differed from each other at the immunological, biological and genetic level.

Aeromonas↗
PubMed1991

Multilocus genetic relationships between clinical and environmental Aeromonas strains.

Allelic variations in the chromosomal genome of 120 isolates of motile Aeromonas (A. hydrophila, A. sobria and A. caviae) and eight reference strains with one Plesiomonas shigelloides were assessed by analysis of electrophoretically demonstrable polymorphism in 16 genes encoding metabolic enzymes. The strains were collected from humans (n = 59) and from the aquatic environment (n = 61) in canton Tessin, Switzerland. Clustering of the electrophoretic types (ET) from a matrix of pairwise genetic distances, based on the 16 enzyme loci, confirmed the genetic distinctness of the three species. Furthermore, A. hydrophila and A. sobria were divided in three and two groups respectively. For each species clinical strains were well differentiated from those collected in the environment.

Aeromonas↗
PubMed1991

Specific binding of lactoferrin to Aeromonas hydrophila.

The interaction of lactoferrin (Lf) with Aeromonas hydrophila (n = 28) was tested in a 125I-labeled protein-binding assay. The mean per cent binding values for human Lf (HLf) and bovine Lf (BLf) were 13.4 +/- 2.0 (SEM), and 17.5 +/- 2.7 (SEM), respectively. The Lf binding was characterized in type strain A. hydrophila subsp. hydrophila CCUG 14551. The HLf and BLf binding reached a complete saturation within 2 h. Unlabeled HLf and BLf displaced 125I-HLf binding in a dose-dependent manner, and more effectively by the heterologous (1 microgram for 50% inhibition) than the homologous (10 micrograms for 50% inhibition) ligand. Apo- and holo-forms of HLf and BLf both inhibited more than 80%, while mucin caused approx. 50% inhibition of the HLf binding. Various other proteins (including transferrin) or carbohydrates did not block the binding. Two HLf-binding proteins with an estimated molecular masses of 40 kDa and 30 kDa were identified in a boiled-cell-envelope preparation, while the unboiled cell envelope demonstrated a short-ladder pattern at the top of the separating gel and a second band at approx. 60 kDa position. These data establish a specific interaction of Lf and the Lf-binding proteins seem to be porins in A. hydrophila.

Aeromonas hydrophila↗
PubMed1992

Stimulation of neutrophil leukocyte chemotaxis by a cloned cytolytic enterotoxin of Aeromonas hydrophila.

A cytolytic enterotoxin produced by Aeromonas hydrophila, isolate SSU, has been cloned in our laboratory. This enterotoxin lysed rabbit red blood cells, destroyed Chinese hamster ovary cells, caused fluid secretion in rat ligated ileal loops, inhibited the phagocytic function of mouse phagocytes, and was lethal to mice when injected intravenously. In this study, the effect of this cytolytic enterotoxin on the chemotaxis of human leukocytes (cell line RPMI 1788) was examined. This toxin, at concentrations from 92.5 to 370 ng/ml, significantly stimulated the chemotactic activity of human leukocytes in a dose-dependent fashion. The stimulation of leukocyte chemotaxis elicited by cytolytic enterotoxin was abolished when the toxin was neutralized, heated, or exposed to low pH values. This stimulatory effect also was inhibited by various concentrations of pertussis toxin. These results demonstrated that cytolytic enterotoxin may stimulate increased chemotaxis of human leukocytes, and suggest that human leukocytes may possess cytolytic enterotoxin receptors which may be coupled to pertussis toxin-sensitive G-protein.

Aeromonas hydrophila↗
PubMed1992

The cloning and nucleotide sequence of the serine protease gene (aspA) of Aeromonas salmonicida ssp. salmonicida.

The gene for Aeromonas salmonicida serine protease has been cloned into phagemid pTZ18R in two restriction fragments, 2.0-kb PstI and 2.3-kb KpnI, of genomic DNA. The nucleotide sequences of the two fragments have been determined, in both directions, after subcloning, by double-stranded sequencing of nested deletions. An open reading frame of 1863 bp translated into a sequence of 621 amino acids, a 24-amino acid signal peptide and a 597-amino acid mature enzyme of molecular mass 64,173 Da. The consensus sequence, NGTS, of a serine protease substrate primary binding site was identified and a putative ribosome-binding site GGAG occurred 6 bp upstream of the ATG initiation codon.

Aeromonas↗
PubMed1992

Occurrence of a capsule in Aeromonas salmonicida.

Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides. The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1. The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1. The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.

Aeromonas↗
PubMed1992

Cloning and expression in Escherichia coli of the gene encoding an extracellular deoxyribonuclease (DNase) from Aeromonas hydrophila.

The gene encoding an extracellular DNase from Aeromonas hydrophila CHC-1 has been cloned and sequenced. Following expression of the dns in Escherichia coli, it was revealed that some of the cloned enzyme was present in the cell-free extracellular supernatant fluid, and there was no cell lysis and concurrent release of cytoplasmic or periplasmic proteins. Therefore, results suggest that E. coli cells were capable of secreting the DNase extracellularly, albeit very inefficiently. The dns is transcribed from its own promoter in E. coli, and expressed as a 25-kDa product, as determined by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis of the culture supernatant preparations followed by a DNA-hydrolysis assay. Nucleotide sequence analysis predicted a single open reading frame of 690 bp encoding a 230-amino acid (aa) polypeptide, with a potential 20-aa signal peptide located at the N terminus of the predicted protein. The deduced aa sequence of the entire protein is highly homologous with that of the DNase of Vibrio cholerae.

Aeromonas hydrophila↗
PubMed1995

The periplasmic endonuclease I of Escherichia coli has amino-acid sequence homology to the extracellular DNases of Vibrio cholerae and Aeromonas hydrophila.

The gene endA, encoding the periplasmic endonuclease I (EndoI) of Escherichia coli, was identified on a cloned chromosomal 1.5-kb HindIII fragment. The nucleotide sequence of the fragment revealed an open reading frame (ORF) coding for a polypeptide of 235 amino acids (aa). The ORF preceeded by a region with two possible promoter sites displays promoter activity when cloned into an expression vector. On the C-terminal side, two sequences with putative transcription termination function are present. The predicted aa sequence suggests the presence of a signal peptide of 22 aa and a signal peptide cleavage site. A cold-shock supernatant from cells harbouring a multicopy endA+ plasmid contained an approx. tenfold higher amount than wild-type cells of the DNA double-strand- and single-strand-cleavage activities characteristic of EndoI. The growth rate and viability of the cells was not affected. The predicted aa sequence of the ORF is 60 and 54% identical to the sequence of extracellular DNases from Vibrio cholerae and Aeromonas hydrophila, respectively.

Aeromonas hydrophila↗