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PubMed1998

Analysis of the interaction of Aeromonas caviae, A. hydrophila and A. sobria with mucins.

Aeromonas species are known to be involved in human gastrointestinal diseases. These organisms colonize the gastrointestinal tract. Aeromonas hydrophila, A. caviae, and A. sobria have been demonstrated microscopically to adhere to animal cell lines that express mucous receptors, but quantitative studies of adherence to mucosal components such as mucin have not been published to date. Purified bovine submaxillary gland, hog gastric mucin, and fish skin mucin were used as a model to study mucin-binding activity among A. caviae, A. hydrophila, and A. sobria strains. Our findings revealed that binding of radiolabeled and enzyme-conjugated mucins to Aeromonas cells varied depending on the labeling procedure. The highest binding was observed when the three mucin preparations were labeled with horseradish peroxidase. Binding of the various horseradish peroxidase-labeled mucins by A. caviae, A. hydrophila, and A. sobria cells is a common property among Aeromonas species isolated from human infections, diseased fish, and from environmental sources. The proportion of Aeromonas strains which bind the various horseradish peroxidase-labeled mucins was significantly higher for A. hydrophila than for A. caviae and A. sobria. Bacterial cell-surface extracts containing active mucin-binding components recognized the horseradish peroxidase-labeled mucins. The molecular masses of the mucin-binding proteins were estimated by SDS-PAGE and Western blot as follows: A. caviae strain A4812 (95 and 44 kDa); A. hydrophila strain 48748 (97, 45, 33 and 22 kDa); and A. sobria strain 48739 (95 and 43 kDa). Mucin interaction with Aeromonas cells was also studied in terms of growth in mucin-rich media. The culture conditions greatly influence the expression of A. hydrophila mucin-binding activity.

Aeromonas↗
PubMedDate not supplied

Interaction of cefotetan and the metallo-beta-lactamases produced in Aeromonas spp. and in vitro activity.

Aeromonas spp. are increasingly being recognized as human pathogens. The presence of metallo-beta-lactamases in these organisms represents a potential problem in antimicrobial therapy. Mechanism-based inactivators of beta-lactamases are used to overcome the resistance of clinical pathogens to beta-lactam antibiotics, but no clinical useful inhibitors of the metallo-beta-lactamases are presently known. Studying the interaction between cefotetan and Aeromonas spp. producing metallo-beta-lactamase activity, we observed that cefotetan behaved as a transient inactivator for both the crude extracts of Aeromonas strains and the purified enzymes from Aeromonas hydrophila AE036 and Aeromonas schubertii MNSA20. The direct hydrolysis of cefotetan showed that it was a poor substrate for both purified enzymes. In view of the minimum inhibitory concentrations, cefotetan shows to be a useful antimicrobial agent against Aeromonas spp.

Aeromonas↗
PubMed1996

Characterization of a type IV bundle-forming pilus (SFP) from a gastroenteritis-associated strain of Aeromonas veronii biovar sobria.

The colonization mechanisms of enteropathogenic Aeromonas strains are poorly characterized, but recent studies indicate that some filamentous structures are intestinal adhesins. This study describes the purification and characterization of a long, flexible pilus from a gastroenteritis-associated strain of Aeromonas veronii biovar sobria. SDS-PAGE analysis (various conditions) of pili preparations yielded a pilin protein band of approximately 21 kDa. Its N-terminal amino acid sequence was unambiguous and homologous with those of type IV pilins. Immunogold electron microscopy with rabbit antisera produced against this pilin protein (SFP) decorated single pili and rope-like bundles of pili on the bacterial surface. These were seen more frequently on strains grown at 22 degrees C compared with 37 degrees C and in liquid rather than on solid medium. SFP was not detected on any of 104 strains of Aeromonas (different species and sources) from our culture collection, although morphologically similar structures were seen on a number of these strains. This finding and differences among other published amino acid sequences show that Aeromonas type IV pili are antigenically diverse. Bundle-forming type IV 'class B' pili are important in the virulence of other enteropathogenic bacteria. The N-terminal amino acid sequence of the Aeromonas SFP, however, showed closer homology to the type IV 'class A' pilins. Studies are in progress to investigate the role of SFP in Aeromonas virulence.

Aeromonas↗
PubMed1986

Incidence and virulence of Aeromonas species in feces of children with diarrhea.

Aeromonas spp. occurring in feces of children with diarrhea were studied. Forty-eight strains were isolated from 2,025 specimens during a one year period. Only 11 of 44 strains tested yielded virulence factors (cytotoxin, hemolysin and hemagglutinin). Six strains were identified as Aeromonas sobria and five as Aeromonas hydrophila. The other strains isolated were identified as Aeromonas caviae. The biochemical characteristics associated with virulence factors were a positive Voges-Proskauer reaction, production of gas from glucose, fermentation of mannose, and absence of beta-lactosidase. Beta-D-glucosidase and esculin hydrolysis were the main characteristics used to differentiate Aeromonas sobria from the other two species. The incidence of Aeromonas spp. with virulence factors in feces of children with diarrhea would seem to vary widely from one area to another.

Adolescent↗
PubMed1996

Diarrheal and environmental isolates of Aeromonas spp. produce a toxin similar to Shiga-like toxin 1.

Diarrheal and environmental isolates of 39 strains of Aeromonas spp. were studied for detection of virulence factors. Although these 39 strains did not produce either heat-labile or heat-stable enterotoxins, culture filtrates of 31 strains produced cytopathic effects on Vero cells. Among these, culture filtrates of three strains of Aeromonas hydrophila and one strain of Aeromonas caviae could be neutralized by Escherichia coli O157:H7 Shiga-like toxin 1 antiserum. A single band of plasmid DNA of 2.14 kbp was isolated from these strains of Aeromonas spp. and E. coli O157:H7, which could be amplified by the polymerase chain reaction (PCR), employing oligonucleotide primers from the Shiga-like toxin 1 (SLT1) gene of E. coli O157:H7. E. coli HB 101 cells when transformed with the same plasmid showed cytopathic effects on Vero cells, which indicates that the SLT 1 homolog gene(s) of Aeromonas spp. is plasmid encoded. These results suggest that Aeromonas spp. may also produce Shiga-like toxin 1, or at least a cytotoxin with some homology with the Shiga-like toxin 1 of E. coli O157:H7.

Aeromonas↗
PubMed2005

Adaptational changes in cellular fatty acid branching and unsaturation of Aeromonas species as a response to growth temperature and salinity.

The effects of growth temperature and salinity on the cellular fatty acids were investigated on Aeromonas caviae, Aeromonas hydrophila and Aeromonas sobria. Under optimal growth conditions, fatty acids patterns were dominated by even-numbered chains C(16:0), C(16:1cis9), C(18:1cis11), C(12:0) and C(14:0). Growth temperature modifications induced, in the three Aeromonas species, important changes in fatty acid (i) unsaturation, (ii) branching and (iii) chain length. An important decrease in the C(18:1cis11) fatty acid content was observed for the three species below 15 degrees C and above 25 degrees C. The evolution of C(18:1cis11) and C(16:0) showed a mirror image for the three Aeromonas species. Low NaCl concentrations did not elicit significant changes in the fatty acids content of the three Aeromonas species. However, for high NaCl concentration in the medium, the growth ability was related to an important decrease of the unsaturated to saturated fatty acids ratio indicating a membrane rigidification. Thermal and salinity adaptations were branched fatty acid-dependent for A. caviae, whereas this phenomenon was less significant for A. hydrophila and A. sobria.

Adaptation, Physiological↗
PubMed2005

Comparison of ELISA and PCR vis-à-vis cultural methods for detecting Aeromonas spp. in foods of animal origin.

The present study was conducted to assess the best method of the most commonly used methods for detection of aeromonads in foods of animal origin. With this objective an OMP based indirect plate ELISA and a duplex-PCR using primers targeting aerolysin gene and 16S rRNA gene and yielding amplicons of 252 bp and 599 bp, respectively, were standardized. The standardized protocols and the conventional cultural method were then compared for their respective sensitivities and specificities for detecting aeromonads from chicken and milk samples. Both the standardized assays were found to be highly specific for Aeromonas. The efficiency of the standardized indirect-ELISA and duplex-PCR protocols was assessed by artificial inoculation studies with varying concentrations of Aeromonas cells inoculated in chicken and milk samples followed by enrichment in Alkaline Peptone Water supplemented with 10 mg/ml cephalothin (APW-C) for 12 h. The results revealed that indirect-ELISA was able to detect a minimum of 10(3) cells/ml or g of Aeromonas cells in spiked milk and chicken samples, respectively. Whereas, duplex-PCR and cultural method were able to detect as low as 1 cell/ml or g of Aeromonas cells in spiked milk and chicken samples. The developed assays were also tested for their efficiency to detect Aeromonas spp. in naturally contaminated milk and chicken samples. Out of a total 50 milk samples screened for presence of Aeromonas by the three methods viz., indirect-ELISA, duplex-PCR and cultural method only 1 (2%) turned out to be positive showing positive results by all three methods. Similarly, 50 samples of chicken were tested by all three methods. Three samples (6%) turned out to be positive and here again by all the three methods.

Aeromonas↗
PubMed2000

Modification of the bile salts-Irgasan-brilliant green agar for enumeration of Aeromonas species from food.

The present study evaluated the productivity of BIBG medium for the isolation of Aeromonas spp. from food and describes a modification of the BIBG medium (mBIBG) (increased pH (8.7), replacement of xylose by soluble starch as a carbon source, decreased concentration of bile salts) to increase its selectivity and electivity. Using the mBIBG medium, growth of the majority of the Enterobacteriaceae (9/10) was suppressed except for Citrobacter freundii. The mBIBG medium supported growth of Pseudomonas species but a clear distinction between Aeromonas and Pseudomonas colonies could be made. Interpretation of the mBIBG medium should be performed after 24 h of incubation. It was noted that three of the 27 Aeromonas strains tested did not develop on the mBIBG medium. The ability or inability to grow on a selective medium is strain-dependent. Enumeration of Aeromonas species (A. hydrophila LMG 3771, A. caviae LMG 3775, A. veronii biovar veronii LMG 9075, A. veronii biovar sobria LMG 13071) from artificially contaminated foods (shrimp, minced meat (beef/pork), precut leek, and shredded carrots) confirmed that the mBIBG medium is suitable for quantitative recovery of aeromonads (ca. 10(2)-10(7) cfu/g) in the presence of a high background flora (10(5)-10(6) cfu/g). Screening of naturally contaminated foods (vegetables, seafood, meat) for the presence of Aeromonas resulted in three out of 14 food samples showing presumptive Aeromonas colonies on mBIBG.

Aeromonas↗
PubMed2004

Faecal contamination indicators, Salmonella, Vibrio and Aeromonas in water used for the irrigation of agricultural products.

The faecal contamination indicators (total coliforms, faecal coliforms, Escherichia coli, enterococci) and the genera Salmonella, Vibrio, Aeromonas were investigated in water samples used for irrigation. During 4 months, 52 samples were taken. The methods used were: multiple tube fermentation method for faecal contamination indicators and membrane filtration techniques for salmonella, aeromonas and vibrio. Two samples were positive for Salmonella spp., fourteen for Aeromonas spp. and no samples for Vibrio spp. No correlation was found between aeromonas and the indicators of faecal contamination. Regarding Aeromonas spp., 21.6% of the strains were adhesive and 12.6% cytotoxic: this confirms the possible role of aeromonas in human pathologies. These results are important to determine the quality of irrigation water in relation to human health. In fact, the spray or sprinkler irrigation produces bioaerosol, which can contaminate the crops that are likely to be eaten uncooked. In addition, the flood or furrow irrigation represents a risk to field workers.

Aeromonas↗
PubMed2001

The occurrence of aerolysin-positive Aeromonas spp. and their cytotoxicity in Norwegian water sources.

AIMS: The aim of the study was to investigate the occurrence of Aeromonas spp. and their aerolysin status in Norwegian natural water sources. METHODS AND RESULTS: Seventy-one samples from 33 Norwegian water sources were examined for the presence of Aeromonas spp. From most of the sample sites, the strains were isolated on blood-ampicillin-agar and Difco Aeromonas agar simultaneously. The majority of the samples (73/77) contained Aeromonas spp., with an average of 35-100 cfu 100 ml(-1). The highest counts were found in faecally-contaminated water. Using PCR, 445 isolates were screened for the presence of aerolysin, and 79% of them were found to be carriers of the aerolysin gene. A selection of the isolated strains was tested on Vero cell cultures and 83% of them showed cytotoxicity. CONCLUSION: There is widespread occurrence of aerolysin-positive cytotoxic Aeromonas spp. in many different Norwegian natural waters, including drinking water sources. SIGNIFICANCE AND IMPACT OF THE STUDY: The widespread occurrence of potentially-pathogenic Aeromonas spp. in the environment demands that these bacteria should not be ignored in drinking water supplies and in the food industry.

Aeromonas↗
PubMed2000

Incidence and identification of mesophilic Aeromonas spp. from retail foods.

Sixty-eight food samples were examined for the presence of mesophilic Aeromonas species both qualitatively and quantitatively. Aeromonads were isolated from 26% of the vegetable samples, 70% of the meat and poultry samples and 72% of the fish and shrimps. Numbers of motile aeromonads present in the food samples varied from <10(2) cfu g(-1) to >10(5) cfu g(-1). GLC analysis of FAMEs was used to identify a selection of presumptive Aeromonas colonies to fenospecies or genomic species level. Aeromonas strains belonging to the Aer. caviae complex, which also includes the potentially pathogenic genospecies HG4, were mostly isolated from vegetables but were also found in meat, poultry and fish. In addition, three strains of the virulent taxon Aer. veronii biovar sobria HG8 were isolated from poultry and minced meat. All members of the Aer. hydrophila complex, predominant in the fish, meat and poultry samples, were classified in the non-virulent taxon HG3. Although the significance of Aeromonas in foods remains undefined, the isolation of Aeromonas HG4 and HG8 strains from a variety of retail foods may indicate that these products can act as possible vehicles for the dissemination of food-borne Aeromonas gastroenteritis.

Aeromonas↗
PubMed2003

Induced colistin resistance as an identifying marker for Aeromonas phenospecies groups.

AIMS: To investigate the taxonomic interest of colistin resistance as an identifying marker for Aeromonas phenospecies groups. METHODS AND RESULTS: Colistin resistance was investigated in 387 Aeromonas isolates identified at species level using a 14-test format protocol with miniaturized tests combined with determination of urocanic acid utilization whenever necessary. Colistin resistance, determined by the disc diffusion method, was unreliable when compared with minimum inhibitory concentration (MIC) determination. In some strains, the MIC values and resistance rates of colistin could be increased after overnight induction with a 50- microg colistin disc in 20 ml of Mueller-Hinton broth (2.5 mg l(-1)). Colistin-induced resistance level was raised to 85.8% in the Aeromonas hydrophila complex, 2.1% in the A. caviae complex and 2.5% in the A. veronii complex except for A. jandaei (100% colistin resistant). This new marker allowed the identification of 96.2 and 93.6% of Aeromonas isolates to phenospecies and species level, respectively. CONCLUSIONS: Colistin-induced colistin resistance is a new phenotypic marker for Aeromonas isolates. SIGNIFICANCE AND IMPACT OF THE STUDY: With the present protocol, colistin resistance determination may improve the identification of Aeromonas isolates to phenogroup level, when results obtained by conventional biochemical methods are ambiguous.

Aeromonas↗
PubMed2000

Aeromonas infection in acute suppurative cholangitis: review of 30 cases.

OBJECTIVES: Aeromonads, though not common pathogens in biliary sepsis, caused substantial mortality in patients with impaired hepatobiliary function. Our aim was to study the pathogenic role of Aeromonas in acute suppurative cholangitis. METHODS: Between 1996 and 1998, the medical records of patients with a diagnosis of biliary sepsis were reviewed. Those who fulfilled the diagnostic criteria for acute suppurative cholangitis and had positive bile or blood cultures for Aeromonas species were studied. RESULTS: One thousand and forty-five patients were confirmed to have acute suppurative cholangitis. Of these, 30 patients (2.9%) had Aeromonas species isolated from bile; four were complicated by aeromonas septicaemia with simultaneous recovery of the bacteria from blood. All except two isolates were A. hydrophila. Twenty-four patients (80%) had bile duct stones, four (13%) had cholangiocarcinoma and two (7%) pancreatic cancer. Twenty-five cases (83%) had previous exploration of the biliary tract. There was substantial resistance to piperacillin (58%), ceftazidime (30%) and imipenem (15%). Most patients improved after biliary decompression. Only three patients (10%) died, two had terminal malignancy and one had end-stage liver failure. No excess mortality was attributable to Aeromonas infection in biliary sepsis. CONCLUSIONS: Previous instrumentation facilitated ascending Aeromonas infection of the biliary tract from the gastrointestinal tract. Unlike early reports, our results showed that aeromonads did not adversely affect the clinical outcome of acute suppurative cholangitis with successful drainage of biliary obstruction.

Acute Disease↗
PubMed1995

Aeromonas bacteremia: review of 59 episodes.

Fifty-nine episodes of bacteremia due to Aeromonas species occurred within a 5-year period in one medical center in southern Taiwan. Underlying diseases in the 58 patients included hepatic cirrhosis (36%) and cancer (24%). Patients with aeromonas bacteremia more often had underlying hepatic cirrhosis than did those with bacteremia due to other gram-negative bacilli. Males (67%) outnumbered females. The cases appeared to cluster in the summer and fall months. Thirty-two percent were polymicrobial infections; often the Aeromonas pathogens were accompanied by other gram-negative bacilli. Aeromonas hydrophila was the most common species isolated (69%). In addition to fever, hypotension and jaundice were the common clinical manifestations of aeromonas sepsis. In cirrhotic patients, spontaneous bacterial peritonitis, altered mental status, and jaundice were most common, and aeromonas bacteremia in such patients was monomicrobial and community-acquired more often than in noncirrhotic patients. In vitro aeromonads were generally susceptible to aminoglycosides, cefuroxime, the third-generation cephalosporins, and quinolones. The overall crude fatality rate was 36%. Predictors of fatal outcome for cirrhotic patients included spontaneous bacterial peritonitis, hypotension on admission, diabetes mellitus, and high Pugh scores.

Adolescent↗
PubMed2000

Aeromonas salmonicida subsp. pectinolytica subsp. nov., a new pectinase-positive subspecies isolated from a heavily polluted river.

Aeromonas strains which phenotypically and genetically belong to the Aeromonas salmonicida species but that according to their phenotypic properties constitute a new subspecies have been isolated from the water of a heavily polluted river, the Matanza river, situated near the central district of Buenos Aires city. These strains were ascribed to the A. salmonicida species by using 65 biochemical tests and by DNA-DNA hybridization. They produce acid from -sorbitol, an unusual biochemical property found in a few members of the A. salmonicida species. They also utilize urocanic acid and do not ferment L-rhamnose or utilize LD-lactate, and are elastase- and gluconate-negative. The DNA relatedness was over 70%, the current limit accepted for the phylogenetic definition of a species, to the described A. salmonicida subspecies and nearly 100% within the new group of Aeromonas strains. Phenotypic differentiation from other A. salmonicida subspecies was readily achieved using the following characteristics: growth at 37 degrees C, melanin production, indole and Voges-Proskauer assays, growth on KCN broth, mannitol and sucrose fermentation and gas from glucose. A remarkable property of the strains of the new group was their ability to degrade polypectate, an unusual feature among Aeromonas species in general. The complete 16S rRNA gene of one strain of the new group was sequenced. Comparison with rDNA sequences of Aeromonas members available in databases revealed a close relationship between this strain and strains belonging to A. salmonicida subsp. salmonicida, masoucida and achromogenes, in agreement with the biochemical data. Since the new A. salmonicida strains constitute a tight genomic group that can be identified by phenotypic properties it was concluded that they represent a new subspecies for which the name Aeromonas salmonicida subsp. pectinolytica is proposed. The type strain of A. salmonicida subsp. pectinolytica is 34melT (= DSM 12609T).

Aeromonas↗
PubMed1995

Association of Aeromonas spp. with travellers' diarrhoea in Finland.

The association of Aeromonas spp. with travellers' diarrhoea was studied among 978 Finnish tourists travelling to Morocco in winter (n = 398) and autumn (n = 580) in 1989. Fifty-five isolates from diarrhoeal patients with (n = 16) or without (n = 39) a recent travelling history in a developing country were also included. In Morocco, Aeromonas spp. were isolated from 8.7% of patients with diarrhoea and from 1.4% of non-diarrhoeal tourists (p < 0.001). Aeromonas spp. were found as the sole pathogen in 5.5% of patients (p < 0.001). Diarrhoea with multiple pathogens, including Aeromonas spp., was found in 3.1% of patients. Species identification by phenotypic and genotypic methods indicated that A. veronii biotype sobria (hybridisation group HG 8/10) and A. caviae (HG 4) were the most common Aeromonas spp. associated with travellers' diarrhoea. A. hydrophila (HG 1) and A. caviae (HG 4) were common in patients acquiring diarrhoea in Finland. Ribotyping of strains within a species showed that all strains had different ribotypes although the tourists were infected during the same trip. This study suggested that only certain Aeromonas spp. were commonly found in travellers' diarrhoea. However, the causative role of those species is unclear.

Aeromonas↗
PubMed2003

Aeromonas veronii biovar veronii septicaemia and acute suppurative cholangitis in a patient with hepatitis B.

Gram-negative bacilli of the genus Aeromonas are widespread in aquatic environments and can be responsible for human infections. Although Aeromonas extraintestinal and systemic infections have been reported with growing frequency in recent years, Aeromonas septicaemia remains an uncommon finding, often associated with serious underlying disease and predominantly related to the species Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae. Here, a case of A. veronii biovar veronii septicaemia and acute suppurative cholangitis is reported in a patient with chronic hepatitis B.

Aeromonas↗
PubMed2006

Prevalence of environmental Aeromonas in South East Queensland, Australia: a study of their interactions with human monolayer Caco-2 cells.

AIMS: To investigate the prevalence of Aeromonas in a major waterway in South East Queensland, Australia, and their interactions with a gut epithelial model using Caco-2 cells. METHODS AND RESULTS: A total of 81 Aeromonas isolates, collected from a major waterway in South East Queensland, Australia, were typed using a metabolic fingerprinting method, and tested for their adhesion to HEp-2 and Caco-2 cells and for cytotoxin production on Vero cells and Caco-2 cells. Aeromonas hydrophila had the highest (43%) and Aeromonas veronii biovar sobria had the lowest (25%) prevalence. Four patterns of adhesion were observed on both HEp-2 and Caco-2 cell lines. Representative isolates having different phenopathotypes (nine strains) together with two clinical isolates were tested for their translocation ability and for the presence of virulence genes associated with pathogenic Escherichia coli. The rate and degree of translocation across Caco-2 monolayers varied among strains and was more pronounced with LogA pattern. Translocation was associated with the adherence of strains to Caco-2 cells microvilli, followed by internalization into Caco-2 cells. Two Aer. veronii biovar sobria strains were positive for the presence of heat-labile toxin genes, with one strain also positive for Shiga-like toxin gene. CONCLUSIONS: Pathogenic strains of Aeromonas carrying one or more virulence characteristics are highly prevalent in the waterways studied and are capable of translocating across a human enterocyte cell model. SIGNIFICANCE AND IMPACT OF THE STUDY: This study indicates that Aeromonas strains carrying one or more virulence properties are prevalent in local waterways and are capable of translocating in a human enterocyte cell culture model. However, their importance in human gastrointestinal disease has yet to be verified under competitive conditions of the gut.

Aeromonas↗