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Polish Journal of Microbiology 2013A total of 71 Aeromonas strains were isolated in the south of Jiangsu Province China in order to analyze the difference ofAeromonas spp. distribution between diseased... (Comparative Study)
Comparative Study
A total of 71 Aeromonas strains were isolated in the south of Jiangsu Province China in order to analyze the difference ofAeromonas spp. distribution between diseased fish and water environment. The sequence of 16S rDNA and gyrB demonstrated that the 71 Aeromonas isolates could be divided into 4 species, including A. veronii (55), A. hydrophila (11), A. salmonicida (3) and A. media (2). A. veronii was the most common species isolated from fish and water environment. All Aeromonas isolates were screened for three putative virulence genes, aer, hly and alt. hly was the most common gene among three virulence genes.
Topics: Aeromonas; Animals; Bacterial Proteins; Carps; Fish Diseases; Fresh Water; Gram-Negative Bacterial Infections; Virulence Factors
PubMed: 24459836
DOI: No ID Found -
MBio Nov 2014Prokaryotic taxonomy is the underpinning of microbiology, as it provides a framework for the proper identification and naming of organisms. The "gold standard" of...
UNLABELLED
Prokaryotic taxonomy is the underpinning of microbiology, as it provides a framework for the proper identification and naming of organisms. The "gold standard" of bacterial species delineation is the overall genome similarity determined by DNA-DNA hybridization (DDH), a technically rigorous yet sometimes variable method that may produce inconsistent results. Improvements in next-generation sequencing have resulted in an upsurge of bacterial genome sequences and bioinformatic tools that compare genomic data, such as average nucleotide identity (ANI), correlation of tetranucleotide frequencies, and the genome-to-genome distance calculator, or in silico DDH (isDDH). Here, we evaluate ANI and isDDH in combination with phylogenetic studies using Aeromonas, a taxonomically challenging genus with many described species and several strains that were reassigned to different species as a test case. We generated improved, high-quality draft genome sequences for 33 Aeromonas strains and combined them with 23 publicly available genomes. ANI and isDDH distances were determined and compared to phylogenies from multilocus sequence analysis of housekeeping genes, ribosomal proteins, and expanded core genes. The expanded core phylogenetic analysis suggested relationships between distant Aeromonas clades that were inconsistent with studies using fewer genes. ANI values of ≥ 96% and isDDH values of ≥ 70% consistently grouped genomes originating from strains of the same species together. Our study confirmed known misidentifications, validated the recent revisions in the nomenclature, and revealed that a number of genomes deposited in GenBank are misnamed. In addition, two strains were identified that may represent novel Aeromonas species.
IMPORTANCE
Improvements in DNA sequencing technologies have resulted in the ability to generate large numbers of high-quality draft genomes and led to a dramatic increase in the number of publically available genomes. This has allowed researchers to characterize microorganisms using genome data. Advantages of genome sequence-based classification include data and computing programs that can be readily shared, facilitating the standardization of taxonomic methodology and resolving conflicting identifications by providing greater uniformity in an overall analysis. Using Aeromonas as a test case, we compared and validated different approaches. Based on our analyses, we recommend cutoff values for distance measures for identifying species. Accurate species classification is critical not only to obviate the perpetuation of errors in public databases but also to ensure the validity of inferences made on the relationships among species within a genus and proper identification in clinical and veterinary diagnostic laboratories.
Topics: Aeromonas; Computational Biology; DNA, Bacterial; Genome, Bacterial; Phylogeny; Sequence Analysis, DNA
PubMed: 25406383
DOI: 10.1128/mBio.02136-14 -
Applied and Environmental Microbiology Apr 2010A total of 227 isolates of Aeromonas obtained from different geographical locations in the United States and different parts of the world, including 28 reference...
Distribution of virulence factors and molecular fingerprinting of Aeromonas species isolates from water and clinical samples: suggestive evidence of water-to-human transmission.
A total of 227 isolates of Aeromonas obtained from different geographical locations in the United States and different parts of the world, including 28 reference strains, were analyzed to determine the presence of various virulence factors. These isolates were also fingerprinted using biochemical identification and pulse-field gel electrophoresis (PFGE). Of these 227 isolates, 199 that were collected from water and clinical samples belonged to three major groups or complexes, namely, the A. hydrophila group, the A. caviae-A. media group, and the A. veronii-A. sobria group, based on biochemical profiles, and they had various pulsotypes. When virulence factor activities were examined, Aeromonas isolates obtained from clinical sources had higher cytotoxic activities than isolates obtained from water sources for all three Aeromonas species groups. Likewise, the production of quorum-sensing signaling molecules, such as N-acyl homoserine lactone, was greater in clinical isolates than in isolates from water for the A. caviae-A. media and A. hydrophila groups. Based on colony blot DNA hybridization, the heat-labile cytotonic enterotoxin gene and the DNA adenosine methyltransferase gene were more prevalent in clinical isolates than in water isolates for all three Aeromonas groups. Using colony blot DNA hybridization and PFGE, we obtained three sets of water and clinical isolates that had the same virulence signature and had indistinguishable PFGE patterns. In addition, all of these isolates belonged to the A. caviae-A. media group. The findings of the present study provide the first suggestive evidence of successful colonization and infection by particular strains of certain Aeromonas species after transmission from water to humans.
Topics: Aeromonas; Bacterial Proteins; Bacterial Toxins; Bacterial Typing Techniques; Cluster Analysis; DNA Fingerprinting; DNA Modification Methylases; Electrophoresis, Gel, Pulsed-Field; Enterotoxins; Genotype; Gram-Negative Bacterial Infections; Humans; Nucleic Acid Hybridization; United States; Virulence Factors; Water Microbiology
PubMed: 20154106
DOI: 10.1128/AEM.02535-09 -
Infection and Immunity Dec 1988The biological activities in vivo and in vitro of 59 motile Aeromonas spp. isolated from fish and water tanks were simultaneously analyzed in poikilothermic and...
The biological activities in vivo and in vitro of 59 motile Aeromonas spp. isolated from fish and water tanks were simultaneously analyzed in poikilothermic and homoiothermic systems. A total of 64.3% of the isolates tested were pathogenic for fish, and 62% of Aeromonas hydrophila and A. sobria isolates either virulent or nonvirulent for fish were enterotoxigenic. Although the majority of the strains were proteolytic and amylolytic and produced DNase, other activities, such as elastase and staphylolysis, were only present in A. hydrophila. Most of the strains (96%) produced hemolysins, and 68% had agglutinating capacity, but neither isolates pathogenic for fish nor enterotoxigenic isolates showed specificity for trout or human erythrocytes, respectively. The production of siderophores, agglutination in acriflavine, and precipitation after boiling were found not to be useful tests for screening virulent strains. Although statistical analysis revealed a significant relationship between virulence for fish and positive results for arabinose and sucrose fermentations, elastase, and hemolysis of human erythrocytes, only lysine decarboxylase showed a significant positive relationship with enterotoxigenicity. Using extracellular products from representative Aeromonas strains with different virulence markers and belonging to distinct O serogroups, we demonstrated a lack of correlation between cytotoxicity for fish and homoiothermic cell lines and pathogenicity. The extracellular products from selected pathogenic A. hydrophila strains were lethal for rainbow trout and displayed proteolytic, hemolytic, and cytotoxic activities which were simultaneously lost after heat treatment. The findings reported here indicate that it is not possible to establish a common and single mechanism involved in the invasion of Aeromonas spp. in poikilothermic and homoiothermic hosts.
Topics: Aeromonas; Animals; Bacterial Adhesion; Cell Line; Cell Survival; Enterotoxins; Hemagglutinins; Hemolysin Proteins; Iron Chelating Agents; Phenotype; Salmonidae; Serotyping; Siderophores; Trout
PubMed: 2972627
DOI: 10.1128/iai.56.12.3285-3293.1988 -
MBio Apr 2013Aeromonas hydrophila has increasingly been implicated as a virulent and antibiotic-resistant etiologic agent in various human diseases. In a previously published case... (Comparative Study)
Comparative Study
UNLABELLED
Aeromonas hydrophila has increasingly been implicated as a virulent and antibiotic-resistant etiologic agent in various human diseases. In a previously published case report, we described a subject with a polymicrobial wound infection that included a persistent and aggressive strain of A. hydrophila (E1), as well as a more antibiotic-resistant strain of A. hydrophila (E2). To better understand the differences between pathogenic and environmental strains of A. hydrophila, we conducted comparative genomic and functional analyses of virulence-associated genes of these two wound isolates (E1 and E2), the environmental type strain A. hydrophila ATCC 7966(T), and four other isolates belonging to A. aquariorum, A. veronii, A. salmonicida, and A. caviae. Full-genome sequencing of strains E1 and E2 revealed extensive differences between the two and strain ATCC 7966(T). The more persistent wound infection strain, E1, harbored coding sequences for a cytotoxic enterotoxin (Act), a type 3 secretion system (T3SS), flagella, hemolysins, and a homolog of exotoxin A found in Pseudomonas aeruginosa. Corresponding phenotypic analyses with A. hydrophila ATCC 7966(T) and SSU as reference strains demonstrated the functionality of these virulence genes, with strain E1 displaying enhanced swimming and swarming motility, lateral flagella on electron microscopy, the presence of T3SS effector AexU, and enhanced lethality in a mouse model of Aeromonas infection. By combining sequence-based analysis and functional assays, we characterized an A. hydrophila pathotype, exemplified by strain E1, that exhibited increased virulence in a mouse model of infection, likely because of encapsulation, enhanced motility, toxin secretion, and cellular toxicity.
IMPORTANCE
Aeromonas hydrophila is a common aquatic bacterium that has increasingly been implicated in serious human infections. While many determinants of virulence have been identified in Aeromonas, rapid identification of pathogenic versus nonpathogenic strains remains a challenge for this genus, as it is for other opportunistic pathogens. This paper demonstrates, by using whole-genome sequencing of clinical Aeromonas strains, followed by corresponding virulence assays, that comparative genomics can be used to identify a virulent subtype of A. hydrophila that is aggressive during human infection and more lethal in a mouse model of infection. This aggressive pathotype contained genes for toxin production, toxin secretion, and bacterial motility that likely enabled its pathogenicity. Our results highlight the potential of whole-genome sequencing to transform microbial diagnostics; with further advances in rapid sequencing and annotation, genomic analysis will be able to provide timely information on the identities and virulence potential of clinically isolated microorganisms.
Topics: Aeromonas hydrophila; Animals; Disease Models, Animal; Female; Flagella; Genome, Bacterial; Genotype; Gram-Negative Bacterial Infections; Humans; Locomotion; Mice; Microscopy, Electron; Molecular Sequence Data; Sequence Analysis, DNA; Virulence Factors; Wound Infection
PubMed: 23611906
DOI: 10.1128/mBio.00064-13 -
Journal of Applied Microbiology 2002To study the phenotypic characteristics of Aeromonas spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy.
AIMS
To study the phenotypic characteristics of Aeromonas spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy.
METHODS AND RESULTS
A collection of 202 Aeromonas strains isolated from bivalve molluscs, water and clinical samples was tested for 64 phenotypic properties; 91% of these isolates were identified at species level. Aeromonas caviae was predominant in bivalve molluscs and Aerom. bestiarum in freshwater samples. Cluster analyses revealed eight different phena: three containing more than one DNA-DNA hybridization group but including strains that belong to the same phenospecies complex (Aerom. hydrophila, Aerom. sobria and Aerom. caviae), Aerom. encheleia, Aerom. trota and three containing unidentified Aeromonas strains isolated from bivalve molluscs.
CONCLUSIONS
Aeromonas spp. are widely distributed in environmental and clinical sources. A selection of 16 of the phenotypical tests chosen allowed the identification of most isolates (91%), although some strains remain unidentified, mainly isolates from bivalve molluscs, suggesting the presence of new Aeromonas species. Numerical taxonomy was not in total concordance with the identification of the studied strains.
SIGNIFICANCE AND IMPACT OF THE STUDY
Numerical taxonomy of Aeromonas strains isolated from different sources revealed the presence of potentially pathogenic Aeromonas spp., especially in bivalve molluscs, and phena with unidentified strains that suggest new Aeromonas species.
Topics: Aeromonas; Animals; Bacterial Typing Techniques; Classification; Fresh Water; Gram-Negative Bacterial Infections; Guinea Pigs; Humans; Mollusca; Nucleic Acid Hybridization; Phenotype; Reproducibility of Results; Spain
PubMed: 12174040
DOI: 10.1046/j.1365-2672.2002.01711.x -
Applied and Environmental Microbiology Jul 2011The genus Aeromonas has been described as comprising several species associated with the aquatic environment, which represents their principal reservoir. Aeromonas spp....
The genus Aeromonas has been described as comprising several species associated with the aquatic environment, which represents their principal reservoir. Aeromonas spp. are commonly isolated from diseased and healthy fish, but the involvement of such bacteria in human infection and gastroenteritis has frequently been reported. The primary challenge in establishing an unequivocal link between the Aeromonas genus and pathogenesis in humans is the extremely complicated taxonomy. With the aim of clarifying taxonomic relationships among the strains and phenotypes, a multilocus sequencing approach was developed and applied to characterize 23 type and reference strains of Aeromonas spp. and a collection of 77 field strains isolated from fish, crustaceans, and mollusks. All strains were also screened for putative determinants of virulence by PCR (ast, ahh1, act, asa1, eno, ascV, and aexT) and the production of acylated homoserine lactones (AHLs). In addition, the phenotypic fingerprinting obtained from 29 biochemical tests was submitted to the nonparametric combination (NPC) test methodology to define the statistical differences among the identified genetic clusters. Multilocus sequence typing (MLST) achieved precise strain genotyping, and the phylogenetic analysis of concatenated sequences delineated the relationship among the taxa belonging to the genus Aeromonas, providing a powerful tool for outbreak traceability, host range diffusion, and ecological studies. The NPC test showed the feasibility of phenotypic differentiation among the majority of the MLST clusters by using a selection of tests or the entire biochemical fingerprinting. A Web-based MLST sequence database (http://pubmlst.org/aeromonas) specific for the Aeromonas genus was developed and implemented with all the results.
Topics: Acyl-Butyrolactones; Aeromonas; Bacterial Typing Techniques; Base Sequence; Biodiversity; DNA, Bacterial; Genotype; Molecular Sequence Data; Multilocus Sequence Typing; Nucleotide Mapping; Phenotype; Phylogeny; Polymerase Chain Reaction; Sequence Analysis, DNA; Virulence Factors
PubMed: 21642403
DOI: 10.1128/AEM.00708-11 -
The Tohoku Journal of Experimental... Oct 2011The genus Aeromonas comprises flagellated gram-negative rods widely distributed in freshwater, estuarine and marine environments. Aeromonas species may cause a variety...
The genus Aeromonas comprises flagellated gram-negative rods widely distributed in freshwater, estuarine and marine environments. Aeromonas species may cause a variety of illnesses in humans, such as enterocolitis and septicemia, especially in warmer tropical or subtropical environments. To recognize the characteristics of Aeromonas septicemia in Japan, we reviewed laboratory data and medical records in our hospital. During 11 years (from 2000 to 2010), Aeromonas septicemia was observed in seven patients involving six female subjects. Six patients were observed in summer or fall. The incidence of Aeromonas septicemia was about 0.07 per 1000 admissions, and two out of the seven patients died. All patients had underlying diseases such as malignancy (six patients) and choledocholithiasis (one patient). Two patients developed septicemia within two days after ingesting raw seafood. Five patients developed Aeromonas septicemia > 48 h after admission. Fever was present in all patients, and four out of the seven patients developed septic shock. All patients developed monomicrobial septicemia. A. hydrophila was isolated from five patients, and A. caviae and A. veronii biovar sobria were isolated from one patient each. Most antimicrobial agents had high activity against the isolated strains. However, a carbapenem-resistant strain appeared in one patient during treatment and led to death. Aeromonas septicemia is uncommon in temperate areas but can occur particularly in warm seasons. Immunocompromised conditions and recent ingestion of raw fish or shellfish are important characteristics of developing Aeromonas septicemia.
Topics: Adolescent; Adult; Aeromonas; Aged; Aged, 80 and over; Anti-Infective Agents; Female; Gram-Negative Bacterial Infections; Hospitals; Humans; Japan; Male; Sepsis
PubMed: 21892001
DOI: 10.1620/tjem.225.81 -
Journal of Applied Microbiology 2002To evaluate the public health significance of representative strains of two Aeromonas spp., mainly from freshwater fish, on the basis of production of...
AIMS
To evaluate the public health significance of representative strains of two Aeromonas spp., mainly from freshwater fish, on the basis of production of virulence-associated factors and presence of the haemolytic genes aerA and hlyA.
METHODS AND RESULTS
Eleven strains of Aer. hydrophila, three strains of Aer. veronii biovar sobria (all from freshwater fish) and one strain of Aer. hydrophila from human diarrhoea were tested for potential virulence traits and for the presence of the haemolytic genes aerA and hlyA. Ten Aer. hydrophila isolates were aerA(+)hlyA(+) and two aerA(+)hlyA(-). Aeromonas veronii biovar sobria isolates were aerA(-)hlyA(-). Strains from the three genotypes showed enterotoxic activity in the suckling mouse assay. At 28 degrees C, four Aer. hydrophila fish strains could be considered as potentially virulent (possessing at least two of these characteristics: haemolytic, cytotoxic and enterotoxic). One Aer. veronii biovar sobria strain and the clinical isolate were cytotoxic on Vero cells. When grown at 4 degrees C, these six isolates fulfilled virulence criterion, but at 37 degrees C, only one fish strain, an Aer. hydrophila, did.
CONCLUSIONS
The potential health risk derived from the presence of Aer. hydrophila and Aer. veronii biovar sobria in ice-stored freshwater fish should not be underestimated.
SIGNIFICANCE AND IMPACT OF THE STUDY
Expression of virulence factors is affected by temperature incubation and not always related to the presence of haemolytic genes.
Topics: Aeromonas; Aeromonas hydrophila; Animals; Animals, Suckling; Bacterial Proteins; Bacterial Toxins; Chlorocebus aethiops; Diarrhea; Esocidae; Fish Diseases; Fresh Water; Gram-Negative Bacterial Infections; Hemolysin Proteins; Humans; Mice; Oncorhynchus mykiss; Pore Forming Cytotoxic Proteins; Temperature; Toxicity Tests; Vero Cells; Virulence
PubMed: 12174039
DOI: 10.1046/j.1365-2672.2002.01705.x -
The ISME Journal Mar 2008Species of the genus Aeromonas are native inhabitants of aquatic environments and have recently been considered as an emergent human pathogen. It is estimated that...
Species of the genus Aeromonas are native inhabitants of aquatic environments and have recently been considered as an emergent human pathogen. It is estimated that aeromonads cause up to 13% of reported gastroenteritis cases in the United States. Although the autochthonous existence of Aeromonas in the aquatic environment has been established, its natural reservoir is as yet unknown. Chironomids are closely related to mosquitoes except they do not bite and they are the most widely distributed insects in freshwater. They infest drinking water systems in Israel and all over the world. Vibrio cholerae inhabit chironomids and are able to degrade their egg masses. The degradation of the egg masses is followed by failure of the eggs to hatch. In the current study, egg masses from a waste stabilization pond and a river in northern Israel were collected and cultured during a five-month period. Bacterial colonies were randomly chosen and checked for their egg mass degradation abilities. In addition to V. cholerae, most of the other isolates that had the ability to degrade the egg masses were identified as Aeromonas species, thus, demonstrating that Aeromonas species are natural inhabitants of chironomid egg masses. The following virulence-associated genes were detected in Aeromonas species that were isolated from chironomid egg masses: alt (78%); ahpB (76%); act/aerA/hlyA (65%); fla (59%); pla/lipH3/apl-1/lip (43%); and ast (2%). These findings indicate that the Aeromonas species inhabiting chironomid egg masses pose a potential health risk. Understanding the natural reservoir of Aeromonas will help to develop methods to monitor and control the bacteria in fresh and drinking water reservoirs and to better understand the relationships between chironomids, V. cholerae and Aeromonas populations.
Topics: Aeromonas; Animals; Bacterial Proteins; Chironomidae; Disease Reservoirs; Ecosystem; Fresh Water; Genotype; Molecular Sequence Data; Ovum; Phylogeny; Sequence Analysis, DNA; Vibrio cholerae; Virulence Factors
PubMed: 18317460
DOI: 10.1038/ismej.2007.114