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PubMed1996

Enzyme kinetics and biochemical analysis of ImiS, the metallo-beta-lactamase from Aeromonas sobria 163a.

The metallo-beta-lactamase from Aeromonas sobria 163a, ImiS, was isolated in a two stage purification procedure using protein affinity columns. Enzyme kinetics show that ImiS hydrolyses the carbapenems but displays poor activity against other beta-lactams. ImiS possesses the narrowest spectrum of activity of the Group 3 enzymes that have been analysed. Sequencing of the 40 N-terminal amino acids show this region to be identical to that of the CphA metallo-beta-lactamase from Aeromonas hydrophila (Massidda, Rossolini & Satta, 1991). Light scattering analysis indicates that ImiS is functionally active as a monomer.

Aeromonas↗
PubMed2000

Aeromonas hydrophila AmpH and CepH beta-lactamases: derepressed expression in mutants of Escherichia coli lacking creB.

The class 1 cephalosporinase (CepH) and class 2d oxacillinase (AmpH) from an Aeromonas hydrophila clinical isolate, strain T429125, have been cloned and sequenced. Both enzymes are typical of their equivalents in other species of Aeromonas Both cloned beta-lactamase genes were expressed at a low level in a standard laboratory Escherichia coli strain, but when cloned into a cre deletion E. coli mutant, they were expressed at significantly higher levels. Specific disruption of the creB gene resulted in similar increased levels of beta-lactamase expression, so it was concluded that CreB represses the transcription of ampH and cepH in a cre(+) E. coli strain. The expression of cepH was four times that of ampH in the deltacre mutant because of an additional factor encoded on the cloned T429125 chromosomal fragment containing cepH. This factor was able to trans-activate expression of co-resident ampH in the deltacre mutant such that expression of the two genes was approximately equal. The entire cepH-containing fragment was sequenced, but it contained no genes that were obviously related to any known class of DNA-binding protein.

Aeromonas hydrophila↗
PubMed1993

Prolyl endopeptidase from Aeromonas hydrophila: cloning, sequencing, and expression of the enzyme gene, and characterization of the expressed enzyme.

A strain of Aeromonas hydrophila was found to show prolyl endopeptidase activity. The enzyme gene was cloned and expressed in Escherichia coli JM83. A 12 kbp EcoRI fragment containing the enzyme gene was subcloned at the HincII site of pUC19 to construct plasmid pAPEP-3 with a 3.5 kbp insert. E. coli JM83 transformed with this plasmid showed about 100-fold higher activity than the parent Aeromonas. Analysis of the nucleotide sequence of the insert revealed that the mature enzyme-encoding sequence starts just after the ATG initiation codon of the open reading frame. The enzyme was a single polypeptide composed of 689 amino acid residues with a molecular weight of 76,383. It showed properties very similar to those of Flavobacterium prolyl endopeptidase, except that the isoelectric point was 5.5. The amino acid sequence was 56 and 41% homologous to those of Flavobacterium and porcine brain prolyl endopeptidases, respectively. From a survey of sequence homology with other members of the prolyl endopeptidase family, the amino acid residues involved in the catalytic triad were deduced to be Ser-537, His-656, and Asp-512 (or Asp-621).

Aeromonas hydrophila↗
PubMed1994

Isolation and characterization of the prolyl aminopeptidase gene (pap) from Aeromonas sobria: comparison with the Bacillus coagulans enzyme.

The Aeromonas sobria pap gene encoding prolyl aminopeptidase (PAP) was cloned. It consists of 425 codons and encodes a homotetrameric enzyme of 205 kDa. The purified enzyme showed an almost absolute specificity for amino-terminal proline. Proline and hydroxyproline residues from many peptide and amide substrates could be easily removed, while no activity was detected for substrates having other amino terminals. The enzyme was very similar to that from Bacillus coagulans in many aspects, such as the strong inhibition caused by PCMB and the weak or no inhibition caused by DFP and chelators, respectively. However, these enzymes show only 15% identity in their amino acid sequences. Differences were also observed in their molecular weight, stability and activity toward some peptide substrates. When aligning the deduced amino acid sequence with known sequences from other microorganisms, conserved sequences were found at the amino-terminal region; the significance of these conserved regions is discussed. Based on the results of this work, and on the studies available to date, the occurrence of at least two types of PAPs is postulated. One group would be formed by the Bacillus, Neisseria, and Lactobacillus enzymes, and the other by enzymes such as the Aeromonas PAP.

Aeromonas↗
PubMed1988

Cefotaxime-sensitive Aeromonas hydrophila infection in a revascularized foot.

Three days following revascularization of a foot injured in a boating accident, Aeromonas hydrophila cellulitis developed in the victim's foot and leg. The infection resolved with debridement and 10 days of cefotaxime therapy. A. hydrophila infection has not previously been reported in a revascularized extremity. Clinical response of an A. hydrophila cellulitis to cefotaxime is likewise undescribed. Our findings of a cefotaxime-sensitive Aeromonas infection and its successful treatment suggests that the organism should undergo further evaluation of cefotaxime sensitivity and that cefotaxime and other third-generation cephalosporins may have a role as broad-spectrum antibiotic agents in fresh-water trauma.

Adult↗
PubMed2004

A secreted metallo protease from Aeromonas hydrophila exhibits prothrombin activator activity.

Detection, purification, and partial characterization of a protease from Aeromonas hydrophila capable of cleaving prothrombin into active thrombin is described. The protease has been characterized with respect to enzymatic characteristics such as optimum reaction conditions for prothrombin activation, usage of additional substrates, as well as sensitivity against inhibitors. The protease activity can reversibly be inhibited by Me2+ chelating agents like ethylenediamine tetraacetic acid. The enzyme exhibits a pI value of 4.4 and can withstand temperatures up to 55 degrees C without loss of activity. With respect to prothrombin the enzyme exhibits a K(M) value of 1.47 micromol/l and a vmax value of 1.66 mol/min per mol enzyme. Amino terminal sequence analysis as well as mass spectrometry of fragments obtained by trypsin digest showed identity to a recently described elastase type protease from the same organism and homology to known proteases from other procaryotes (e.g. Aeromonas caviae, Vibrio proteolytica, Pseudomonas aeruginosa).

Aeromonas hydrophila↗
PubMed1980

Fulminant wound infection with Aeromonas hydrophila.

Aeromonas hydrophila was isolated from a water-soaked traumatic wound of a previously healthy 16-year-old boy. A progressive necrotizing infection developed despite administration of antibiotics. Aeromonas should be considered in wound infections which are water-related.

Adolescent↗
PubMed1988

Pneumonia due to Aeromonas hydrophila-complex: epidemiologic, clinical, and microbiologic features.

Review of published data examining the various types of infections produced by strains of the Aeromonas hydrophila-complex demonstrates a paucity of information on lower respiratory tract infections due to this organism. Although it is rarely cited as a cause of pneumonitis, we have been able to collect epidemiologic, clinical, and microbiologic data on eight patients who have had evidence of Aeromonas pneumonia. Interestingly, seven of the eight patients were male, and the average age for the group was 54.3 years. In contrast to reports showing a prevalence of other types of A hydrophila infections during the summer months, five of the pneumonitis cases occurred during late fall and early winter. Infections were both community-acquired and nosocomial. A proven or suspected history of aspiration was present in six patients. Preexisting medical conditions were noted in all patients, the majority having multiple predisposing factors, which included alcohol abuse and alcoholic liver disease, cardiovascular and cerebrovascular disease, and chronic lung disease. Three patients died of their acute pulmonary infection. Based on in vitro antimicrobial susceptibility testing, aminoglycoside therapy would seem appropriate in the treatment of these infections.

Adult↗
PubMed1992

rRNA gene restriction patterns as taxonomic tools for the genus Aeromonas.

In the genus Aeromonas there are at least 13 DNA hybridization groups, which are difficult to differentiate biochemically. We investigated the usefulness of rRNA gene restriction patterns for characterization and identification of the various groups. Genomic DNA was digested with restriction endonuclease SmaI, transferred to a nylon membrane, and hybridized with biotinylated plasmid pKK3535 containing the rrnB operon of Escherichia coli. The SmaI bands at 0.8 to 4 kb but not those at positions corresponding to sizes larger than 4 kb showed a good correlation with hybridization groups, allowing identification of strains to the level of genetic species. We demonstrated that the 567-bp fragment localized between positions 80 and 647 of the 16S ribosomal gene of E. coli was essential for hybridization to the low-molecular-weight fragments, whereas the remainder of the operon did not hybridize to these fragments. On the basis of these results, we concluded that the Aeromonas chromosome contains multiple rRNA operons which may be used for species identification.

Aeromonas↗
PubMed1988

DNA:DNA reassociation analysis of Aeromonas salmonicida.

DNA from 26 Aeromonas salmonicida strains, namely 11 'typical' and 15 so-called 'atypical' strains, was used to assess the taxonomic relatedness within the species. The genomes were characterized by determination of DNA base composition, DNA:DNA reassociation, calculation of sequence divergence following reassociation, and by genome size estimations. By comparison with DNA obtained from controls and the Aeromonas hydrophila group, A. salmonicida strains were determined to be correctly placed with respect to genus and species. A. salmonicida subspecies salmonicida (the 'typical' group) was an extremely homogeneous taxon. The 'atypical' strains were more diverse, but distinct biotypes were recognizable. The first biotype included several geographically diverse isolates from goldfish. The second recognizable biotype included strains isolated from European carp. Other 'atypical' isolates could not be grouped but showed enough internal homology to be retained within the species. The A. salmonicida subspecies achromogenes and masoucida were found to be closely related to the motile aeromonads. It is considered that the present classification of A. salmonicida is unsuitable and should be restructured to include A. salmonicida subspecies salmonicida, subspecies achromogenes (to include the present subspecies masoucida), and the reintroduced subspecies nova.

Aeromonas↗
PubMed1991

Acquisition of iron from host sources by mesophilic Aeromonas species.

The mesophilic Aeromonas species are opportunistic pathogens that produce either of the siderophores amonabactin or enterobactin. Acquisition of iron for growth from Fe-transferrin in serum was dependent on the siderophore amonabactin; 50 of 54 amonabactin-producing isolates grew in heat-inactivated serum, whereas none of 30 enterobactin-producing strains were able to grow. Most isolates (regardless of siderophore produced) used haem as a sole source of iron for growth; all of 33 isolates grew with either haematin or haemoglobin and 30 of these used haemoglobin when complexed to human haptoglobin. Mutants unable to synthesize a siderophore used iron from haem, suggesting that this capacity was unrelated to siderophore production. Some members of the mesophilic Aeromonas species have evolved both siderophore-dependent and -independent mechanisms for acquisition of iron from a host.

Aeromonas↗
PubMed1994

The susceptibility of S-layer-positive and S-layer-negative Aeromonas strains to complement-mediated lysis.

Forty strains of Aeromonas hydrophila and Aeromonas veronii recovered from invasive and non-invasive infections were tested for their susceptibility to complement-mediated lysis by 65% pooled human serum (PHS). Based upon the results of this assay, two major populations could be defined. The first group (n = 20) consisted of serogroup O:11 strains, all of which possessed a paracrystalline surface layer (S layer); all of these strains were refractory to the bactericidal activity of 65% PHS with the exception of A. hydrophila strain AH-121, which was composed of mixed subpopulations of serum-susceptible and serum-resistant clones. A second collection of isolates (n = 20), all of which were S-layer-negative, contained a subgroup of strains (n = 7) that were highly susceptible to complement-mediated lysis, showing a greater than 100-fold reduction of viable progeny within 30 min of exposure to 65% PHS. Serum-resistant strains from both groups could not be lysed by exposure of bacterial cells to polyclonal somatic or whole cell antisera or to 30 micrograms ml-1 of polymyxin B nonapeptide prior to challenge with 65% PHS. Analysis of selected serum-resistant and serum-susceptible strains from both groups showed that all isolates activated the complement pathway and most bound C3b to the cell surface, indicating that the inability of complement to lyse serum-resistant strains was related to a defect in the terminal portions of the complement pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Aeromonas↗
PubMed2001

Occurrence of two superoxide dismutases in Aeromonas hydrophila: molecular cloning and differential expression of the sodA and sodB genes.

Aeromonas spp., considered as emerging opportunistic pathogens, belong to the family Vibrionaceae. Among the criteria currently used for their classification is the presence of a single FeSOD (iron-containing superoxide dismutase), which distinguishes them from Enterobacteriacea. In this paper the cloning of the sodA and sodB genes encoding two different SODs in Aeromonas hydrophila ATCC 7966 is reported. The sodB gene encoded an FeSOD (196 amino acids, 21.5 kDa), was constitutively expressed and showed 75% homology with the E. coli FeSOD. The sodA gene encoded a protein of 206 amino acids (22.5 kDa) with MnSOD (manganese-containing SOD) activity and showed 55% homology with the Escherichia coli MnSOD. The MnSOD of A. hydrophila was detected only during the stationary phase of growth under high aeration or when induced by lack of iron. Nevertheless, paraquat had no detectable effect on its production. The amino-terminal part of the Mn-containing protein contained a putative signal sequence which could permit a periplasmic localization.

Aeromonas↗
PubMed1981

Detection of enterotoxins of Aeromonas hydrophila by a suckling-mouse test.

The suckling-mouse assay was reliable for detecting enterotoxigenic strains of Aeromonas hydrophila when standard conditions for growth and toxin testing were used. Enterotoxins were produced by bacteria grown in tryptone soya broth supplemented with yeast extract and aerated by shaking in an environmental incubator or water bath. When culture supernates together with dye were administered intragastrically to mice less than 6 days old, the presence of enterotoxin was assessed on the basis of a scoring system that incorporated the ratio intestinal weight: remaining body weight, and production of diarrhoea. This method should facilitate the detection of enterotoxigenic strains of Aeromonas in epidemiological studies.

Aeromonas↗
PubMed1985

Methods for the detection of haemagglutinins in Aeromonas.

When grown in specified conditions and tested by a rocked-tile method, 40 of 41 isolates of two species of Aeromonas formed simultaneously at least two haemagglutinins among which were: (i) a mannose-sensitive haemagglutinins with strongest activity for guinea-pig or fowl red cells, formed by all of 31 isolates of A. hydrophila and 9 of 10 isolates of A. punctata ss. caviae; (ii) a haemagglutinin, sensitive to L-fucose or D-mannose, that reacted with human red cells and which was formed by all 41 isolates; and (iii) a mannose-resistant 'tanned red cell' haemagglutinin formed by 29 isolates of A. hydrophila and one isolate of A. punctata ss. caviae. Results emphasise that for the fullest possible identification of haemagglutinins produced by Aeromonas spp., strains should be cultured in a variety of conditions and tested with a wide range of red-cell species.

Aeromonas↗
PubMed1986

Pathophysiology of experimental Aeromonas hydrophila infection in mice.

A virulent fish strain of Aeromonas hydrophila was inoculated intramuscularly into laboratory mice (B10.G strain). Histological, biochemical and haematological changes during the first 36 h of the infection were measured. Inoculation led to septicaemia, tissue damage, endotoxic shock and death. Histological examination revealed: (1) severe muscle necrosis at the injection site; (2) oedema, haemorrhage and neutrophil infiltration of the lung; and (3) focal parenchymal necrosis in the liver. Significant increases in aspartate aminotransferase, alanine aminotransferase, intestinal bilirubin and blood urea nitrogen were noted in blood and intestinal samples; decreased plasma glucose and haematological changes were also recorded. Ketones, increased protein, glucose, bilirubin and blood were detected in the urine. Endotoxaemia was demonstrated as early as 2 h after inoculation and persisted for more than 36 h. The changes resembled those described for certain other experimental infections in laboratory animals. Our results suggest that endotoxin contributed to the pathogenesis of aeromonas infection in mice.

Aeromonas↗
PubMed1986

Partial characterisation of a soluble haemagglutinin from human diarrhoeal isolates of Aeromonas.

A soluble haemagglutinin has been identified in cell-free culture supernates of human diarrhoeal isolates of Aeromonas sobria, A. hydrophila and A. caviae. It was oligomeric; a major peak of haemagglutinating activity had an apparent mol. wt of 780,000 but there was haemagglutinating activity throughout the mol. wt range less than 40,000- greater than 10(6). Human group O, A and B, horse, rabbit, chicken and rat erythrocytes, but not those of sheep and cow, were agglutinated by the soluble haemagglutinin, in contrast to the cell-bound agglutinin. Agglutination was inhibited by fetuin, a complex glycoprotein, but not by simple sugars. The haemagglutinating activity was not affected by 0.5 M NaCl, dithiothreitol or the presence or absence of Ca++. It was unrelated to the haemolytic, enterotoxigenic and proteolytic activities present in cell-free extracts of A. sobria. All A. sobria, 73% of A. hydrophila and 68% of A. caviae strains tested produced this soluble haemagglutinin. A. caviae does not appear to be an enteric pathogen, therefore this soluble haemagglutinin alone is unlikely to be a virulence factor in Aeromonas spp.

Adult↗
PubMed1986

Biochemical characteristics, enterotoxigenicity and susceptibility to antimicrobial agents of clinical isolates of Aeromonas species encountered in the western region of Saudi Arabia.

The biochemical characteristics, enterotoxigenicity and susceptibility to antibiotics are reported for 22 strains of Aeromonas species isolated from clinical specimens in the Western Region of Saudi Arabia. Aeromonas caviae was the species most frequently observed; a high proportion of these strains fermented lactose, whereas lactose fermentation was not observed in strains of A. hydrophila and A. sobria. Enterotoxigenicity, as judged by cytotoxicity in tissue culture was observed in three of four A. hydrophila strains and six of seven A. sobria strains, but in only one of 11 A. caviae strains. Two schemes for the biochemical assessment of enterotoxigenicity were found to be in 91% and 86% agreement respectively with cytotoxicity studies and in 95% agreement with each other. No single biochemical test correlated fully with enterotoxigenicity, but 86% of strains that oxidized gluconate produced a cytotoxin. Most strains were inhibited by concentrations of gentamicin, amikacin, chloramphenicol and tetracycline achievable in plasma. Most strains were resistant to broad-spectrum penicillins and many were also resistant to cefuroxime and cefoxitin.

Aeromonas↗