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PubMed1994

Mutagenesis of the paracrystalline surface protein array of Aeromonas salmonicida by endogenous insertion elements.

The tetragonal paracrystalline surface protein array (A-layer) of the fish pathogenic bacterium Aeromonas salmonicida is a virulence factor and bacteria which are unable to produce A-layer are attenuated in their ability to kill fish. Ten independent mutants of Aeromonas salmonicida which were unable to produce A-layer were isolated by growth at 30 degrees C. These mutants displayed either reduced synthesis of the A-layer subunit, synthesis of a truncated subunit, or complete loss of the ability to produce the subunit protein. Restriction mapping and analysis by polymerase chain reaction showed that the mutations had resulted from insertion of two different insertion sequence (IS) elements into different sites in the A-layer subunit gene (vapA) and its promoter. Sequence comparisons indicated that ISAS1 is unique among reported IS elements. It is 1223 bp long with imperfect terminal inverted repeats of 22 bp and insertion resulted in a duplicated 8 bp target sequence in vapA. ISAS1 expressed a 42,000 molecular weight (M(r)) protein in mini-cells. ISAS2 was 1084 bp long, expressed proteins of M(r) 38,000 and 39,000 in vitro, had imperfect 29 bp terminal inverted repeats and had duplicated a 3 bp target sequence. Sequence comparisons indicated that ISAS2 was also unique to A. salmonicida; however, the proteins encoded by ISAS2 showed strong homology to the putative transposases encoded by the IS30 family of IS elements. Southern analyses showed that both ISAS1 and ISAS2 were restricted to A. salmonicida strains A449 and A450 where they were present in low copy number. The ability of these two IS elements to mutate the ability of A. salmonicida to produce its paracrystalline surface array provides a novel method for the attenuation of virulence.

Aeromonas↗
PubMed1999

Catecholamine enhancement of Aeromonas hydrophila growth.

Several species of bacteria have been shown to respond to the administration of norepinephrine and other catecholamines with increased growth (in culture) and virulence. In this study, we examined the effects of catecholamines on the growth of cultures of Aeromonas hydrophila, a Gram-negative bacillus found in brackish water. Bacterial cultures were maintained in tryptic soy both, then washed free of medium and transferred to a bovine serum-supplemented minimal salts medium. Treatment of A. hydrophila cultures with 10(-3)to 10(-5)M norepinephrine resulted in dramatic increases in growth at 24 h and longer, as assessed by spot plate analysis on tryptic soy agar plates. Norepinephrine-treated cultures had 4.5 log greater bacterial numbers than control cultures. Epinephrine, dopamine and isoproterenol were shown to be similarly effective in enhancing growth of A. hydrophila, over narrower concentration ranges. Acetylcholine supplementation of cultures did not alter the growth of A. hydrophila. Serotonin slightly enhanced Aeromonas growth when administered at very high concentrations (10(-3)M). The increased growth observed after catecholamine administration may alter the capacity to infect an animal under stressful conditions, and is another potential mechanism by which a stress response can affect susceptibility to disease.

Acetylcholine↗
PubMed1980

Salmonella, arizona, Shigella and Aeromonas isolated from the snail Achatina achatina in Nigeria.

The Salmonella, Arizona, Shigella and Aeromonas contents of 39 snails (Achatina achatina) were investigated. Serotyping of the Salmonella isolates revealed the presence of S. manhattan, S. ndolo, S. reading, S. uppsala, and S. typhimurium. Six of 18 Shigella isolates were identified as Sh. sonnei while all the Aeromonas proved to be A. hydrophila. Fifty eight percent of these A. hydrophila isolates were enterotoxigenic, and their toxin was shown to be heat labile. All the A. hydrophila strains were both protease positive and haemolytic: 66.7% being both alpha and beta haemolytic while 33.3% showed only alpha haemolysis.

Aeromonas↗
PubMed1989

Bombesin: an activator of specific Aeromonas antibody secretion in rat intestine.

The effect of bombesin (BBS) in modulating the secretion of specific Aeromonas antibodies in rat intestine was determined. Rats were immunized with the culture supernatant of Aeromonas hydrophila, isolate SSU. This culture supernatant contained a number of toxins that may be considered virulence factors. After 24 days of immunization, rats were anesthetized and a 10-cm intestinal segment was perfused with phosphate-buffered saline. The effluents were collected for measurement of IgA and IgG by the enzyme-linked immunosorbent assay. When compared with the effect of intravenous administration of normal saline in the control group, intravenous injection of BBS (20 micrograms/kg) in the experimental group caused a significant increase in rat intestinal IgA and IgG in perfusates. The stimulatory effects of BBS on the presence of IgA and IgG were depressed partially by proglumide, a receptor antagonist of cholecystokinin (CCK) and gastrin. Treatment with pentagastrin (250 micrograms/kg) accelerated intestinal secretion of IgA, but failed to stimulate intestinal IgG secretion. In addition, intravenous injection of CCK-8 (120 ng/kg) evoked the intestinal secretion of either IgA or IgG. These findings demonstrated that BBS, gastrin, and CCK can stimulate antibody secretion in rat intestine and the stimulatory effect of BBS may be mediated partially via release of CCK and gastrin. These results suggest that neuropeptides such as BBS and gastrointestinal hormones, eg, CCK and gastrin, may participate in the regulation of intestinal secretion of IgA and IgG antibodies, respectively, in rats.

Aeromonas↗
PubMedDate not supplied

Aeromonas and plesiomonas as possible causes of diarrhoea.

The number of reports on the isolation of Aeromonas from patients with diarrhoeal disease is now large and suggests an etiological role of the bacterium. It is well established that strains of Aeromonas produce an enterotoxin. This enterotoxin is cytotonic, i.e. it does not damage the membrane, and it does not cross-react immunologically with cholera toxin and Escherichia coli heat-labile (LT) toxin. Most enterotoxigenic strains also produce a cytotoxic protein (hemolysin), the role of which is probably limited in diarrhoea but potentially toxic in humans in other kinds of infections. Strains of Plesiomonas shigelloides also seem to be able to cause diarrhoea in some cases. The pathogenesis of Plesiomonas-induced diarrhoea remains to be elucidated, but a heat-stable enterotoxin may be involved.

Aeromonas↗
PubMed1983

Investigation of Aeromonas isolated from water; a serological study using Ouchterlony and immunoelectrophoresis techniques.

We have shown that immunoelectrophoresis and the Ouchterlony double diffusion technique are valuable assays for the identification of Aeromonas species. Serological correlations have been found between the antigenic extracts originated from a collection reference strains of Aeromonas hydrophila subsp. hydrophila and those originated from wild type water isolated.

Aeromonas↗
PubMed1987

Isolation frequency of Aeromonas species in relation to patient age.

Over a period of 18 months Aeromonas spp. were isolated from stool specimens of 116 patients (total isolation frequency 1.6%). Isolation rates in children up to ten years of age were significantly higher only for Aeromonas caviae as compared to other age groups. Additional data are needed to assess the clinical significance to these findings.

Adolescent↗
PubMed1975

Antibiotic sensitivity of two Aeromonas and nine Pseudomonas species.

An agar dilution method was used to determine the in vitro sensitivity of different Pseudomonas and Aeromonas species to sulphonamide, tetracycline, colistin, gentamicin, tobramycin, amplicillin, carbenicillin, and cephalothin. P. aeruginosa was generally sensitive to carbenicillin, colistin, tobramycin, and gentamicin. P. putida and P. fluorescens were generally resistant to beta-lactam antibodies but sensitive to gentamicin and tobramycin. P. cepacia and P. maltophilia were mostly resistant to colistin, gentamicin and tobramycin. Other Pseudomonas species were usually more sensitive to the antibodies tested. Strains of Aeromonas hydrophila were mostly resistant to beta-lactam antibiotics but sensitive to other antibiotics, while strains of A. shigelloides were very sensitive to all antibiotics tested.

Aeromonas↗
PubMed1995

Cell-surface charge and cell-surface hydrophobicity of collagen-binding Aeromonas and Vibrio strains.

Partitioning in aqueous polymer two-phase systems of polyethylene glycol and dextran was used to detect and compare cell-surface charge and cell-surface hydrophobicity of Aeromonas hydrophila, A. caviae, A. sobria, Vibrio cholerae, and V. anguillarum strains. These strains have cell-surface components that bound either native or thermally denatured type I collagen (i.e., a mixture of the alpha1+alpha2 chains) and gelatin immobilized on latex beads. Our goals were: (1) to compare the possible relationship between the cell-surface charge/hydrophobicity and binding to collagen and (2) to evaluate the influence of the culture media on the expression of surface properties. There was no apparent relationship between cell-surface charge, cell-surface hydrophobicity, and binding to collagen. The expression of surface properties was dependent on the culture media. There was no relationship between binding to immobilized collagen and binding to soluble 125I-labeled collagen. Particle-agglutination reactivity differed when using various collagen-coated microbead preparations. There were general differences in the particle-agglutination reactivity when collagen-coated latex beads were prepared using different coating procedures. The negative charge and hydrophobicity of the various collagen-coated microbead preparations were also studied by partitioning in the two-phase system of polyethylene glycol and dextran. Under these conditions, the alpha1+alpha2 collagen-chain mixture covalently immobilized on carboxy-modified latex beads was less hydrophobic and negatively charged than gelatin and native collagen immobilized on the same kind of latex beads. For latex beads passively coated with collagen preparations, the alpha1+alpha2 collagen-chain mixture was more hydrophobic than gelatin and native collagen. We suggest that for screening collagen-binding among Vibrio and Aeromonas strains, a reliable and sensitive particle-agglutination assay should consider the collagen preparation and the coating procedure for the immobilization of collagen onto the latex beads. In this regard, carboxy-modified latex beads coated with an alpha1+alpha2 collagen-chain mixture gave the best results.

Aeromonas↗
PubMedDate not supplied

Isolation of Aeromonas spp. from canal water.

Aeromonas sobria was identified from soil and canal water at the East End of London. There was a correlation between water and faecal isolates from children attending the nearby Children's Hospital. In view of the potential risk of enteric and non-enteric infections due to Aeromonas spp, efforts are needed to ensure that canals, rivers, natural water sources and domestic water supply are free of these organisms.

Aeromonas↗
PubMed1996

Application of a colorimetric DNA-DNA hybridization method for identification of Aeromonas genomic species, isolated from diarrheal stools.

The colorimetric DNA-DNA hybridization method for the identification of 18 strains of Aeromonas spp. isolated from human stools was used. Bacterial isolates were also examined by phenotypic characteristics. On the basis of biochemical tests 13 strains were included in phenogroup A. caviae and 5 strains in A. sobria. Identification to the species level was obtained by colorimetric hybridization method. DNA-DNA similarity values showed that isolates of A. caviae group belong to hybridization group (HG) 4 whereas isolates of A. sobria belong to HG 8/10. DNA relatedness results obtained by the colorimetric method showed good agreement with values detected by the spectrophotometric method. The background in the colorimetric method is lower than in the spectrophotometric one. Results of this study indicate the usefulness of the colorimetric DNA-DNA hybridization in microplates method for the identification of Aeromonas genomic species, isolated from human diarrheal stools.

Adult↗
PubMed2005

Production of N-acetyl-beta-D-glucosamine from chitin by Aeromonas sp. GJ-18 crude enzyme.

A bacterium, GJ-18, having strong chitinolytic activity was isolated from coastal soil. The isolated strain was identified as Aeromonas sp. by morphological and biochemical properties along with 16S rRNA gene sequence. The crude chitinolytic activity of culture supernatants was maximal on the 5th day of culture. Below 45 degrees C, chitin was effectively hydrolyzed to N-acetyl-beta-D-glucosamine (GlcNAc) by Aeromonas sp. GJ-18 crude enzymes, but hydrolysis decreased markedly above 50 degrees C. The optimum pH for enzyme activity was 5.0. TLC and HPLC analysis revealed that, below 45 degrees C, the major reaction product was GlcNAc with a small amount of (GlcNAc)(2) and (GlcNAc)(3), whereas above 50 degrees C the major product was (GlcNAc)(2). When swollen chitin (100 mg) was incubated with crude enzyme preparations (10 U) at 40 degrees C, chitin was hydrolyzed to 83.0 and 94.9% yield of GlcNAc within 5 and 9 days, respectively.

Acetylglucosamine↗
PubMed2000

Bacteraemia caused by non-glucose-fermenting gram-negative bacilli and Aeromonas species in patients with haematological malignancies and solid tumours.

The clinical characteristics and outcome of bacteraemia caused by non-glucose-fermenting gram-negative bacilli and Aeromonas spp. were examined in 115 adults with haematological malignancies or solid tumours. The most aggressive pathogens were Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Aeromonas spp., Acinetobacter spp. and Burkholderia cepacia, all of which caused either septic syndrome or pneumonia in more than 40% of cases. Pseudomonas aeruginosa was involved less often in catheter-related bacteraemia than other species. Polymicrobial bacteraemia (n=28) was more often catheter-related than monomicrobial bacteraemia and more often required catheter removal for definitive cure. The most important predictors of catheter-related bacteraemia and its outcome were polymicrobial infection, the presence of pneumonia or septic syndrome and the species involved.

Adolescent↗
PubMed1988

Molecular cloning of a phospholipid-cholesterol acyltransferase from Aeromonas hydrophila. Sequence homologies with lecithin-cholesterol acyltransferase and other lipases.

We have determined the nucleotide sequence of a gene encoding Aeromonas hydrophila phospholipid-cholesterol acyltransferase, an enzyme which shares many properties with mammalian lecithin:cholesterol acyltransferase. The derived amino acid sequence of the protein contains two regions which are homologous to the proposed active sites and binding sites of the plasma acyltransferase and to similar sequences in other interfacially acting lipolytic enzymes. The amino terminus is preceded by a typical 18 amino acid signal sequence. The protein, which is released into the culture supernatant by Aeromonas hydrophila, is confined to the periplasm of Escherichia coli.

Acyltransferases↗
PubMed1983

ES complexes of Aeromonas aminopeptidase: direct observation by stopped-flow fluorescence.

Intermediates of Aeromonas aminopeptidase are monitored through fluorescence generated by radiationless energy transfer (RET) between enzyme tryptophans and the dansyl group of the bound substrate. Upon binding of the substrate enzyme tryptophan fluorescence is quenched and substrate dansyl fluorescence enhanced. These processes are reversed upon hydrolysis of the Leu-Ala bond and release of Ala-DED from the enzyme. Stopped-flow RET kinetic analysis yields values of kcat = 36 sec-1 and Km = 3.7 microM at pH 7.5 and 20 degrees C. These values represent the highest kcat/Km ratio, 1 X 10(7) M-1 sec-1, of any substrate for Aeromonas aminopeptidase. The excellent binding properties of the peptide permit direct visualization of ES complexes even at enzyme concentrations of 10(-7) M.

Aeromonas↗
PubMed1985

A transition-state-analog inhibitor influences zinc-binding by Aeromonas aminopeptidase.

The transition-state-analog inhibitor, 1-butaneboronic acid, markedly enhances the uptake of one g-atom of Zn2+ ions from a metal ion buffer system by Zn-depleted Aeromonas aminopeptidase. In contrast, a substrate-analog inhibitor, n-valeramide, does not perturb the equilibrium between Zn2+ ions and the enzyme in a metal ion buffer system. These results establish a role for metal ions in the binding of 1-butaneboronic acid to Aeromonas amino-peptidase and strongly imply that a bound Zn2+ ion interacts directly with substrate during catalysis but not during initial binding of substrate.

Aeromonas↗
PubMed1988

Antibiotic sensitivities of Aeromonas hydrophila cultured from medicinal leeches.

Increased use of medicinal leeches (Hirudo medicinalis) for the treatment of venous congestion in flaps and replanted parts has coincided with reports of soft tissue infections following leech application. We cultured the gullets of 20 medicinal leeches to re-examine the antibiotic sensitivities of Aeromonas hydrophila, the leech enteric organism associated with reported infections. These isolates reflected reported resistance to penicillin and first generation cephalosporins as well as sensitivity to gentamicin, tetracycline and chloramphenicol. Additionally, the cultures were sensitive to cefamandol, cefoxitin and two third generation cephalosporins (cefoperazone and cefotaxime). These findings suggest that cefamandol, cefoxitin and some third generation cephalosporins may have a role as perioperative antibiotics in replantation and flap surgery. These antibiotics might provide prophylaxis against Aeromonas hydrophila infection when leech use is required.

Aeromonas↗
PubMed1983

Characterization of immunoglobulins from the brown bullhead (Ictalurus nebulosus) produced against a naturally occurring bacterial pathogen, Aeromonas hydrophila.

The primary immune response in the brown bullhead (Ictalurus nebulosus) to intramuscularly injected, chloroform-killed Aeromonas hydrophila reached an agglutination titer of 128 in 3 wk, and the response to the bacteria plus adjuvant reached a titer of 512 in 5 wk. Anti-Aeromonas hydrophila antibodies from brown bullheads were excluded from Sephadex G-200 and had an immunoelectrophoretic migration pattern toward the cathode. Cleavage of the macromolecule by 2-ME reduction and iodoacetamide alkylation yielded subunits that were resumptively heavy chains of about 50,500 daltons and light chains of about 22,500 daltons. Bullhead antibodies were assumed to be tetrameric in configuration and therefore to have an approximate molecular weight of 600,000 daltons assuming a J chain is present in both early (6 wk) and late (20 wk) immune sera. The agglutinating activity of the antibody was completely eliminated by exposure to 65 degrees C for 30 min. Immunoelectrophoresis showed a single antibody component that moved toward the cathode. The structure and molecular weight of bullhead antibodies appears similar to that observed in channel catfish and other closely related teleost fish.

Aeromonas↗