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PubMed1999

Antimicrobial susceptibility patterns of Aeromonas jandaei, A. schubertii, A. trota, and A. veronii biotype veronii.

Fifty-six isolates of four Aeromonas species, which have been documented as causative agents of human infections or isolated from human clinical specimens, were subjected to antimicrobial susceptibility testing using a MicroScan WalkAway conventional (overnight incubation) gram-negative panel. The four species tested and the number of isolates of each were as follows: Aeromonas jandaei, 17; A. schubertii, 12; A. trota, 15; and A. veronii biotype veronii, 12. All isolates of A. trota were susceptible to all antimicrobial agents tested, except cefazolin (20% of isolates were resistant) and cefoxitin (13% of isolates were resistant). All isolates of A. schubertii and A. veronii biotype veronii, as well as 88% of A. jandaei isolates, were resistant to ampicillin. Resistance to ampicillin-sulbactam ranged from 25% of A. schubertii strains to 100% of A. veronii biotype veronii strains. Cefazolin resistance ranged from 17% of A. veronii biotype veronii isolates to 59% of A. jandaei isolates. Imipenem resistance was detected in 65% of A. jandaei strains and 67% of A. veronii biotype veronii strains. A. jandaei displayed resistance to piperacillin and ticarcillin in 53 and 71% of the isolates, respectively. A. veronii biotype veronii strains were 100% susceptible to piperacillin and 100% resistant to ticarcillin. These antibiogram data may be useful in establishing the identification of these four species when members of the genus Aeromonas are isolated from human clinical sources.

Aeromonas↗
PubMed2003

The genus Aeromonas: biochemical characteristics, atypical reactions, and phenotypic identification schemes.

A total of 193 strains representing 14 different Aeromonas genomospecies were evaluated for 63 phenotypic properties to create useful tables for the reference identification of mesophilic aeromonads. Only 9 of 62 biochemical tests (14%) yielded uniform results, and the fermentation of certain carbohydrates was found to be linked to specific species. A number of unusual or aberrant properties for the genus Aeromonas were also detected in the collection of 428 strains (193 in the phenotypic study, 235 in a retrospective review). These tests included susceptibility to the vibriostatic agent, fermentation of m-inositol and D-xylose, hydrolysis of urea, and the lack of cytochrome oxidase activity. Fermentation of melibiose was linked to raffinose fermentation in all Aeromonas species except A. jandaei. Keys are provided for clinical laboratories choosing to identify aeromonads to species level based upon initial Møeller decarboxylase and dihydrolase reactions. In addition, several new tests were identified that help to separate members of the A. caviae complex (A. caviae, A. media, and A. eucreonophila).

Aeromonas↗
PubMed2004

Typing of clinical and environmental Aeromonas sp. strains by random amplified polymorphic DNA PCR, repetitive extragenic palindromic PCR, and enterobacterial repetitive intergenic consensus sequence PCR.

A collection of 120 strains isolated from stool specimens collected from humans suffering from gastroenteritis and from environmental samples were analyzed by random amplified polymorphic DNA PCR (RAPD), repetitive extragenic palindromic PCR (REP-PCR), and enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). Species of Aeromonoas hydrophila, A. bestiarum, A. salmonicida, A. caviae, A. media, and A. veronii revealed clonal structure. There was no dominant clone causing gastroenteritis in humans. Moreover, there was no genetic similarity between clinical and environmental strains of Aeromonas sp. isolated from different geographical areas as well as from the same geographical area. Some clones colonized specific ecosystems, e.g., drinking water distribution systems. RAPD and ERIC-PCR methods had the same discriminatory power and proved to be useful for epidemiological investigation and population genetic analysis of Aeromonas spp., whereas REP-PCR was less effective for differentiating the isolates of Aeromonas spp.

Aeromonas↗
PubMed1972

Isolation of Aeromonas species from clinical sources.

In a period of one year, in a general hospital, Aeromonas hydrophila was isolated from 13 patients and Aeromonas shigelloides from one patient. Eight of the patients had superficial infections, two had urinary tract infections, and four had bacteriaemia. The association of Aeromonas bacteriaemia with cirrhosis of the liver and malignant disease, which has been previously reported, was observed in three of the four bacteriaemic patients. The key to laboratory diagnosis of this genus is the routine performance of the oxidase test in bacteriological procedures for the identification of Gram-negative bacilli.

Adolescent↗
PubMed1992

Phenotypic methods for speciating clinical Aeromonas isolates.

AIMS: To establish the suitability of currently available phenotypic methods for speciation of clinical Aeromonas isolates in diagnostic microbiology laboratories. METHODS: Using 62 Aeromonas spp, three schemes based on biochemical reactions were compared: a series of conventional tests; a system based on the suicide phenomenon, comprising two tubes in total; and a commercially available test, API 20 NE, augmented with a plate assay for beta haemolysin production. The whole cell and outer membrane protein (OMP) profiles of strains were examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS PAGE), according to the results of the above schemes, to determine the intra-species homogeneity. RESULTS: Ninety per cent of strains were identified satisfactorily according to conventional criteria. For these strains, agreement was obtained using the suicide phenomenon and API schemes in 93% and 88% of cases, respectively. The three schemes concurred for 82% of strains. Whole cell protein profiles were unsuitable for comparing strains within a species. However, OMP patterns were similar for 89% of A caviae and 63% of A hydrophila. CONCLUSION: Phenospeciation of clinical Aeromonas isolates by the scheme based on the suicide phenomenon is simple to perform and accurate, and suitable for use in the diagnostic laboratory. OMP profiles are potentially useful for confirming the identity of A caviae and most A hydrophila, but not A sobria.

Aeromonas↗
PubMed1994

Assessment of a chemiluminescent universal probe for taxonomical and epidemiological investigations of Aeromonas sp isolates.

AIMS: To assess a chemiluminescent universal probe for taxonomical and epidemiological investigations of Aeromonas sp isolates. METHODS: Total DNA was extracted from 69 well characterised Aeromonas sp strains and digested with the restriction endonucleases Sma I or Pst I. Following electrophoresis, the resulting fragments were transferred to a nylon membrane where they were hybridised to a commercially available universal probe of 16S + 23S rRNA. The banding patterns (ribotypes) were made visible by enhanced chemiluminescence. RESULTS: Both restriction endonucleases produced heterogeneous ribotypes so that no allocation could be made to any of the control genospecies tested. For A hydrophila and A caviae, however, groups of strains (mostly from the same patient) could be identified by indistinguishable banding patterns. A relatively high proportion (36%) of A sobria strains were non-typable. CONCLUSIONS: Although this universal chemiluminescent probe is user friendly, it is unsuitable for taxonomical investigations of Aeromonas sp. It is useful in epidemiological studies of A hydrophila and A caviae, but is of less value for A sobria.

Adult↗
PubMed1975

Aeromonas proteolytica--a halophilic aeromonad?

Aeromonas proteolytica, a halophilic bacterium originally isolated from the intestine of a marine isopod, was compared with 93 strains of Aeromonas hydrophila and representative strains of five similar genera in a computer and serological analysis. Aeromonas proteolytica was peritrichate and non-reactive with six A. hydrohila antisera, and possessed a percentage guanine + cytosine ratio (49.5) outside the range for other aeromonads (55-62%). Moreover, in the computer analysis it shared a lower level of similarity with other aeromonads than with both strains of Vibrio anguillarum tested.

Aeromonas↗
PubMed1977

Isolation of enterotoxigenic Aeromonas from fish.

This paper reports two different enterotoxigenic classes of the genus Aeromonas isolated from fishes. Strains of A. sobria were isolated from healthy fishes only wheras strains of A. hydrophila were isolated from both healthy and moribund fishes. Aeromonas sobria and hydrophilia strains produced a cytotoxic factor and were highly proteolytic. Seventy-five percent (75%) of the A. sobria strains produced only one type of hemolysis on 5% blood agar, but 92% of the A. hydrophilia produced two types of hemolysis. Enterotoxigenicity of all strains was tested by the rabbit gut loop technique and the suckling mouse test. Most of those Aeromonads were enterotoxigenic. Enterotoxigenic strains appeared to produce two different enterotoxins which were antigenically related, but they seemed to have different mechanisms of action. Enterotoxins of Aeromonas were shown to be antigenically different from those of E. coli.

Aeromonas↗
PubMed1979

Deoxyribonucleic acid relationships among members of the genus Aeromonas.

Polynucleotide sequences among 24 motile and 11 non-motile aeromonads were studied by analysis of deoxyribonucleic acid - deoxyribonucleic acid (DNA-DNA) duplexes with endonuclease S1. In addition, DNA base composition (mole % guanine and cytosine (G + C)) and relative genome sizes were determined for selected strains. Large variations in genome size were found and % GC ranged from 57.1 to 62.9%. On the basis of the strains examined, the Genus Aeromonas consists of two genotypically legitimate groups: a diverse group of motile aeromonads, and the genetically more homogeneous non-motile aeromonads, comprising the species Aeromonas salmonicida. Internal homology groups could not be demonstrated within the motile aeromonads, and significant divergence in related sequences was indicated. This diverse motile group forms the single species Aeromonas hydrophila.

Aeromonas↗
PubMed1989

Purification and partial characterization of a cytotonic enterotoxin produced by Aeromonas hydrophila.

This report describes the purification and partial characterization of a cytotonic enterotoxin produced by a human diarrheal isolate (SSU) of Aeromonas hydrophila. The extracellular enterotoxin was purified by (NH4)2SO4 precipitation, hydrophobic column chromatography, and chromatofocusing. The highly purified enterotoxin exhibited a molecular mass of 44 kDa and an isoelectric point in the range of 4.3 - 5.5 as determined by chromatofocusing. Western blot analysis using Aeromonas anti-enterotoxin revealed a single band at 44 kDa; however, cholera antitoxin failed to detect the enterotoxin antigen. This non-cholera toxin cross-reactive (non-CTC) enterotoxin was biologically active in vivo as determined by rabbit ligated ileal loop and rabbit skin vascular permeability assays. Biological activity also was in vitro by this toxin as measured by the elongation of Chinese hamster ovary (CHO) cells. The enterotoxic activity associated with this molecule was neutralized completely by homologous antibodies but not by cholera antitoxin. The purified toxin preparation was free of hemolytic and cytotoxic activities as determined by its inability to lyse rabbit red blood cells or damage CHO cells, respectively. Furthermore, this toxin induced the elevation of cAMP in CHO cells suggesting thereby that the mechanism of action of Aeromonas non-CTC enterotoxin may be similar to heat-labile enterotoxins of Escherichia coli and Vibrio cholerae.

Aeromonas↗
PubMed1993

Cloning, expression, and sequence analysis of a cytolytic enterotoxin gene from Aeromonas hydrophila.

The structural gene and regulatory element for a cytolytic enterotoxin of a diarrheal isolate, SSU, of Aeromonas hydrophila was cloned and its DNA sequence was determined. A complementary, mixed synthetic oligonucleotide based on the first 10 NH2-terminal amino acid residues of the Aeromonas cytolytic enterotoxin was used as a probe to screen a genomic library constructed in bacteriophage EMBL3. Cell lysates of Escherichia coli (lambda CH4), containing the cytolytic enterotoxin gene, lysed rabbit red blood cells and destroyed Chinese hamster ovary cells, caused fluid secretion in rat ileal loops, and were lethal to mice when injected intravenously. All biological activities associated with the cytolytic enterotoxin were neutralized by rabbit homologous polyclonal antibodies. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and subsequent Western blot analysis of the cell lysate of E. coli (lambda CH4) revealed a protein band of approximately 52 kDa, using antisera to the cytolytic enterotoxin or antibodies generated against a synthetic peptide to the toxin. DNA sequence analysis of a 2.8-kb SalI-BamHI fragment revealed the presence of one large open reading frame (1479 bp) that would encode a protein of 54.5 kDa, a precursor form of the cytolytic enterotoxin, with a 23 amino acid leader peptide. Despite a significant amount of homology at the DNA and amino acid levels between our cytolytic enterotoxin and two aerolysins of Aeromonas species, variation in the restriction maps of these three toxin genes was prominent. Likewise, considerable divergence in DNA sequence was observed upstream of the structural genes for the reported aerolysins and our cytolytic enterotoxin, suggesting that these structurally similar toxin molecules may be regulated differently. Finally, our data showed that the cytolytic enterotoxin from a diarrheal isolate, SSU, of A. hydrophila exhibited characteristics that were unique compared with those of the reported aerolysins.

Aeromonas hydrophila↗
PubMed1997

A 4-year study of the diversity and persistence of coliforms and Aeromonas in the water of a Swedish drinking water well.

Coliforms and Aeromonas, isolated over a sampling period of 4 years from a Swedish drinking water well, were analysed for their phenotypical diversity and for their ability to persist in the well water. From each of the 40 water samples collected from the well, 32 bacterial isolates were subjected to typing by the PhenePlate (PhP) biochemical fingerprinting system. Strains able to persist in the well water were further characterized using the API 20E system, gas-liquid chromatographic cellular fatty acid analysis, and the DNA fingerprinting technique AFLP. Using the PhP system, a total of 170 different phenotypes were identified among 1143 studied isolates. Most phenotypes were only represented by a few isolates and (or) were restricted to one or two sampling occasions. However, one particular phenotype (RV-C01), identified as Aeromonas hydrophila using the API 20E system and fatty acid analysis, reoccurred in 28 samples distributed over the whole study period and often dominated the bacterial population in the well water. AFLP analysis revealed that the RV-C01 isolates displayed basically identical fingerprints. Our results thus suggest that a genetically stable Aeromonas clone resided in the well water over the whole 4-year study, whereas other bacterial strains studied were only transient inhabitants of the well.

Aeromonas↗
PubMed2005

Production of acylated homoserine lactones by Aeromonas and Pseudomonas strains isolated from municipal activated sludge.

Up to now, the production and role of N-acyl homoserine lactones (AHLs) in activated sludge have been poorly understood. In this study, cross-feeding assays with the reporter strains Agrobacterium tumefaciens NTL4 and Chromobacterium violaceum CV026 were used to investigate AHL signal production by municipal activated sludge samples. AHL signal production was consistently detected from municipal activated sludge when different samples were incubated on nutrient media. From one municipal activated sludge sample, 10 strains producing AHL-like auto inducers were isolated by an overlay technique. 16S rDNA-based phylogenetic analysis showed that eight of the isolates belonged to Aeromonas spp. and two to Pseudomonas spp. Box-PCR indicated that six of these Aeromonas isolates were different strains and the two Pseudomonas strains were identical. The production of AHL or AHL-like compounds by these strains was confirmed by thin layer chromatography and biosensor overlays. The six different Aeromonas strains were found to produce the same set of AHLs, including N-hexanoyl-L-homoserine lactone. These results may indicate the possible presence of AHLs in municipal activated sludge. The potential roles of AHL in this eco system are briefly discussed.

4-Butyrolactone↗
PubMed2004

Aeromonas spp associated with children's diarrhoea in Tehran: a case-control study.

The study sought a possible pathogenic role for Aeromonas spp in Tehranian children presenting with diarrhoea. During a 10-month period (February to October 2001), 310 children <10 years of age with diarrhoea and a group of 310 age- and sex-matched controls were selected. Both groups were investigated for diarrhoeal pathogens. Of 310 children who presented with acute diarrhoea, Aeromonas spp was isolated from 14 (4.5%) (A. veronii biovar sobria 8, A. caviae 5 and A. hydrophila 1). The isolation rate was significantly higher than in the controls (p<0.001). Other enteropathogens were also more commonly isolated in children with diarrhoea: 57 (18.4%) Shigella spp (p<0.0001), 8 (2.6%) Salmonella spp (p<0.01), 7 (2.3%) enteropathogenic E. coli (p<0.05) and 8 (2.6%) Giardia lamblia (p<0.01). No enteropathogens were isolated in the control group. Dysentery was the dominant clinical feature in children positive for Aeromonas spp.

Acute Disease↗
PubMed1990

Aeromonas, acclimation, and penicillin as complications when leeches are applied to skin flaps in rabbits.

The medicinal leech, Hirudo medicinalis, has been recognized by plastic surgeons for its ability to reduce congestion and improve blood flow in grafted skin flaps by withdrawing excess blood. The leech's ability to digest blood is due to the presence of Aeromonas hydrophila in the gut of the leech. In this report we describe the occurrence of Aeromonas hydrophila septicaemia in rabbits used in a study to evaluate the efficacy of the medicinal leech on abdominal skin flap survival. In New Zealand White rabbits, twin 5 x 10 cm abdominal skin flaps were prepared and the epigastric vein was ligated to produce a model of venous congested skin. After 12 hours, a leech was applied to one of the congested abdominal flaps and skin survivability was assessed and compared with the unleeched flap. Five rabbits died acutely approximately 24 hours post-operatively. Gross necropsy, bacteriology and histopathology findings indicated that A. hydrophila was the causative agent of the septicaemia-toxaemia syndrome with an associated pneumonia and typhlitis. Review of the management and the experimental surgery protocol suggested that the two major disposing factors of Aeromonas septicaemia in these rabbits were stress and excessive prophylactic administration of penicillin.

Aeromonas↗
PubMed2006

Detection of conjugation related type four secretion machinery in Aeromonas culicicola.

BACKGROUND: Aeromonas sp. can now be considered relatively common enteropathogens due to the increase of diseases in humans. Aeromonas culicicola is a gram negative rod-shaped bacterium isolated for the first time from the mosquito mid-gut, but subsequently detected in other insects and waters also. Our previous study discovered that A. culicicola harbors three plasmids, which we designated as pAc3249A, pAc3249B and pAc3249C. We investigated and report here the existence and genetic organization of a Conjugal Type IV Secretion System (TFSS) in pAc3249A. METHODOLOGY/PRINCIPLE FINDING: The complete operon is 11,061 bp in length and has G+C content of 47.20% code for 12 ORFs. The gene order and orientation were similar to those found in other bacteria with some differences. We have designated this system as AcTra for Aeromonas culicicola transfer system. BLAST results of ORFs and phylogenetic analysis showed significant similarity towards the respective proteins of the IncI2 plasmid R721 of E. coli. Other bioinformatics studies have been performed to predict conserved motifs/domains, signal peptides, transmembrane helices, etc. of the ORFs. CONCLUSIONS/SIGNIFICANCE: BLAST results of ORFs and phylogenetic analysis showed significant similarity towards the respective proteins of the IncI2 plasmid R721 of E. coli.

Aeromonas↗
PubMed2006

Aeromonas spp. isolated from oysters (Crassostrea rhizophorea) from a natural oyster bed, Ceará, Brazil.

Between April and October 2002, thirty fortnightly collections of oysters (Crassostrea rhizophorea) from a natural oyster bed at the Cocó River estuary in the Sabiaguaba region (Fortaleza, Ceará, Brazil) were carried out, aiming to isolate Aeromonas spp. strains. Oyster samples were submitted to the direct plating (DP) and the presence/absence (P/A) methods. Aeromonas were identified in 15 (50%) samples analyzed by the DP method and in 13 (43%) analyzed by the P/A method. A. caviae, A. eucrenophila, A. media, A. sobria, A. trota, A. veronii bv. sobria, A. veronii bv. veronii and Aeromonas sp. were isolated. The predominant species was A. veronii (both biovars), which was identified in 13 (43%) samples, followed by A. media in 11 (37%) and A. caviae in seven (23%). From the 59 strains identified, 28 (48%) presented resistance to at least one of the eight antibiotics tested.

Aeromonas↗
PubMedDate not supplied

[The prevalence of Aeromonas spp. in the diarrheal feces of children under the age of 5 years in the city of Goiânia, Goiás in the 1995-1996 biennium].

From 1995 through 1996, 163 fecal specimens of children aged under 5 years were analysed, 91 being from diarrhea feces and 72 without diarrhea. The material was collected in transport medium and submitted to the enrichment procedure at 4 degrees C for 7 days. For the primary isolation starch ampicillin agar was used and incubated at 35 degrees C for 18 to 24 hours. Twenty (20.9%) from the following specimens were isolated: Aeromonas (A.) caviae (7.7%), A. salmonicida salmonicida (6.6%), A. sobria (4.3%), A. hydrophila (2.2%) and Salmonicida achromogenes (1.1%). No Aeromonas spp. was isolated from the 72 control subjects. The Aeromonas spp. susceptibility to antimicrobial was greater with ciprofloxacin, being this susceptibility gradually diminished with chloranphenicol, gentamicin, ampicillin and erythromycin.

Aeromonas↗