| 1. |
Iwanaga M,
Hokama A,
( 1992 ) Characterization of Aeromonas sobria TAP13 pili: a possible new colonization factor. PMID : 1357078 : DOI : 10.1099/00221287-138-9-1913 Abstract >>
Pili of Aeromonas sobria TAP13 were purified and characterized. The molecular mass of the pilin was estimated to be about 23 kDa by SDS-PAGE. The TAP13 pili were immunologically different from A. sobria Ae1 pili and A. hydrophila Ae6 W pili as previously reported, nevertheless all three had indistinguishable morphology and shared a high degree of homology in their N-terminal amino acid sequences. Strain TAP13 and its purified pili did not agglutinate human, rabbit or sheep erythrocytes. However, they adhered to rabbit intestine. Organisms pretreated with the Fab fraction of an antipilus antibody failed to adhere to rabbit intestine, and organisms did not adhere to intestine pretreated with purified pili. These results suggest that the pili are a colonization factor of A. sobria TAP13 for the rabbit intestine.
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2. |
Hokama A,
Iwanaga M,
( 1992 ) Purification and characterization of Aeromonas sobria Ae24 pili: a possible new colonization factor. PMID : 1363704 : Abstract >>
Pili of Aeromonas sobria Ae24 were purified and characterized. The molecular mass of the pilin was estimated to be about 19 kDa by SDS-PAGE. The Ae24 pili were electrophoretically distinguishable from previously reported Aeromonas hydrophila Ae6 W pili and A. sobria Ae1 pili, although all three had indistinguishable morphology and shared a high degree of homology in the N-terminal amino acid sequences. Strain Ae24 and its purified pili adhered to rabbit intestine and agglutinated human and rabbit erythrocytes. Hemagglutination was inhibited by D-galactose and D-mannose, but not by L-fucose. Organisms pretreated with Fab fraction of the antipilus antibody failed to adhere to the intestine. Organisms did not adhere to intestine pretreated with the purified pili. These findings suggest that the pili are a colonization factor of A. sobria Ae24 for the rabbit intestine, and that the receptor is galactose- and mannose-containing structure.
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3. |
Hirono I,
Aoki T,
Asao T,
Kozaki S,
( 1992 ) Nucleotide sequences and characterization of haemolysin genes from Aeromonas hydrophila and Aeromonas sobria. PMID : 1302284 : Abstract >>
Extracellular haemolysin is thought to be one of the important virulence factors in Aeromonas infection. Two extracellular haemolysin genes (AHH3 and AHH4) from Aeromonas hydrophila strain 28SA, one (AHH5) from A. hydrophila strain AH-1 and one (ASA1) from Aeromonas sobria strain 33 were cloned into cosmid and plasmid vector DNA in Escherichia coli. The nucleotide sequences of the open reading frames of AHH3 and AHH4 are both 1476 basepairs (bp), whereas AHH5 and ASA1 are 1455 and 1467 bp in length, respectively. The deduced amino acid sequences of AHH3, AHH4, AHH5 and the previously reported aerolysin from A. hydrophila showed a significant degree of sequence homology of over 90% each. The amino acid identity of the ASA1 haemolysin and those from A. hydrophila and Aeromonas trota aerolysins ranged from 58-68%. From DNA hybridization analysis using our cloned haemolysin genes as probes, we found that the AHH5 and ASA1 DNA probes hybridized with about 31 and 75% strains of motile Aeromonas species, respectively. The activity of haemolysins of cloned genes were different in medium agar containing various erythrocytes.
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4. |
Pidiyar VJ,
Jangid K,
Dayananda KM,
Kaznowski A,
Gonzalez JM,
Patole MS,
Shouche YS,
( 2003 ) Phylogenetic affiliation of Aeromonas culicicola MTCC 3249(T) based on gyrB gene sequence and PCR-amplicon sequence analysis of cytolytic enterotoxin gene. PMID : 12866846 : DOI : 10.1078/072320203322346047 Abstract >>
We determined the gyrB gene sequences of all 17 hybridizations groups of Aeromonas. Phylogenetic trees showing the evolutionary relatedness of gyrB and 16S rRNA genes in the type strains of Aeromonas were compared. Using this approach, we determined the phylogenetic position of Aeromonas culicicola MTCC 3249(T), isolated from midgut of Culex quinquefasciatus. In the gyrB based-analysis A. culicicola MTCC 3249(T) grouped with A. veronii whereas, it grouped with A. jandaei in the 16S rRNA based tree. The number of nucleotide differences in 16S rRNA sequences was less than found with the gyrB sequence data. Most of the observed nucleotide differences in the gyrB gene were synonymous. The Cophenetic Correlation Coefficient (CCC) for gyrB sequences was 0.87 indicating this gene to be a better molecular chronometer compared to 16S rRNA for delineation of Aeromonas species. This strain was found to be positive for the cytolytic enterotoxin gene. PCR-Amplicon Sequence Analysis (PCR-ASA) of this gene showed that the isolate is affiliated to type I and is potentially pathogenic. These PCR-ASA results agreed in part with the gyrB sequence results.
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5. |
Yáñez MA,
Catalán V,
Apráiz D,
Figueras MJ,
Martínez-Murcia AJ,
( 2003 ) Phylogenetic analysis of members of the genus Aeromonas based on gyrB gene sequences. PMID : 12807216 : DOI : 10.1099/ijs.0.02443-0 Abstract >>
The phylogenetic relationships of all known species of the genus Aeromonas were investigated by using the sequence of gyrB, a gene that encodes the B-subunit of DNA gyrase. Nucleotide sequences of gyrB were determined from 53 Aeromonas strains, including some new isolates, which were also characterized by analysis of the 16S rDNA variable regions. The results support the recognition of the family Aeromonadaceae, as distinct from Plesiomonas shigelloides and other enteric bacteria. This phylogenetic marker revealed strain groupings that are consistent with the taxonomic organization of all Aeromonas species described to date. In particular, gyrB results agreed with 16S rDNA analysis; moreover, the former showed a higher capacity to differentiate between species. The present analysis was useful for the elucidation of reported discrepancies between different DNA-DNA hybridization sets. Additionally, due to the sequence diversity found at the intraspecies level, gyrB is proposed as a useful target for simultaneous identification of species and strains. In conclusion, the gyrB gene has proved to be an excellent molecular chronometer for phylogenetic studies of the genus Aeromonas.
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6. |
Goñi-Urriza M,
Arpin C,
Capdepuy M,
Dubois V,
Caumette P,
Quentin C,
( 2002 ) Type II topoisomerase quinolone resistance-determining regions of Aeromonas caviae, A. hydrophila, and A. sobria complexes and mutations associated with quinolone resistance. PMID : 11796341 : DOI : 10.1128/aac.46.2.350-359.2002 PMC : PMC127024 Abstract >>
Most Aeromonas strains isolated from two European rivers were previously found to be resistant to nalidixic acid. In order to elucidate the mechanism of this resistance, 20 strains of Aeromonas caviae (n = 10), A. hydrophila (n = 5), and A. sobria (n = 5) complexes, including 3 reference strains and 17 environmental isolates, were investigated. Fragments of the gyrA, gyrB, parC, and parE genes encompassing the quinolone resistance-determining regions (QRDRs) were amplified by PCR and sequenced. Results obtained for the six sensitive strains showed that the GyrA, GyrB, ParC, and ParE QRDR fragments of Aeromonas spp. were highly conserved (> or =96.1% identity), despite some genetic polymorphism; they were most closely related to those of Vibrio spp., Pseudomonas spp., and members of the family Enterobacteriaceae (72.4 to 97.1% homology). All 14 environmental resistant strains carried a point mutation in the GyrA QRDR at codon 83, leading to the substitution Ser-83-->Ile (10 strains) or Ser-83-->Arg. In addition, seven strains harbored a mutation in the ParC QRDR either at position 80 (five strains), generating a Ser-80-->Ile (three strains) or Ser-80-->Arg change, or at position 84, yielding a Glu-84-->Lys modification. No amino acid alterations were discovered in the GyrB and ParE QRDRs. Double gyrA-parC missense mutations were associated with higher levels of quinolone resistance compared with the levels associated with single gyrA mutations. The most resistant strains probably had an additional mechanism(s) of resistance, such as decreased accumulation of the drugs. Our data suggest that, in mesophilic Aeromonas spp., as in other gram-negative bacteria, gyrase and topoisomerase IV are the primary and secondary targets for quinolones, respectively.
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7. |
Beutin L,
Strauch E,
Ehrich JH,
Filler G,
( 2000 ) Acute renal failure in an infant associated with cytotoxic Aeromonas sobria isolated from patient's stool and from aquarium water as suspected source of infection. PMID : 10681210 : PMC : PMC88758 Abstract >>
N/A
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8. |
Saavedra MJ,
Figueras MJ,
Martínez-Murcia AJ,
( 2006 ) Updated phylogeny of the genus Aeromonas. PMID : 17012583 : DOI : 10.1099/ijs.0.64351-0 Abstract >>
Recent phylogenetic studies of the genus Aeromonas based on gyrB and rpoD gene sequences have improved the phylogeny based on 16S rRNA gene sequences first published in 1992, particularly in the ability to split closely related species. These studies did not include the recently described species Aeromonas simiae and Aeromonas molluscorum and only a single strain of Aeromonas culicicola was available for analysis at that time. In the present work, these Aeromonas species and newly isolated strains of A. culicicola were examined. Sequence analysis indicates that A. simiae and A. molluscorum belong to non-described phylogenetic lines of descent within this genus, which supports the original description of both species. The most closely related species are Aeromonas schubertii and Aeromonas encheleia, respectively, which is consistent with 16S rRNA gene sequencing results. However, while the five strains of A. molluscorum showed nucleotide differences in their gyrB and rpoD gene sequences, the only two known A. simiae strains exhibited identical gene sequences, suggesting that they are isolates of the same strain. On the basis of the rpoD gene sequence phylogeny, A. culicicola strains from the original description and new isolates from drinking water and ornamental fish clustered within the species Aeromonas veronii, suggesting inconsistencies with previous results. Other strains with previously controversial taxonomy and new isolates from other studies were included in this study in order to clarify their phylogenetic affiliation at the species level.
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9. |
Sen K,
( 2005 ) Development of a rapid identification method for Aeromonas species by multiplex-PCR. PMID : 16333335 : DOI : 10.1139/w05-089 Abstract >>
Existing biochemical methods cannot distinguish among some species of Aeromonads, while genetic methods are labor intensive. In this study, primers were developed to three genes of Aeromonas: lipase, elastase, and DNA gyraseB. In addition, six previously described primer sets, five corresponding to species-specific signature regions of the 16S rRNA gene from A. veronii, A. popoffii, A. caviae, A. jandaei, and A. schubertii, respectively, and one corresponding to A. hydrophila specific lipase (hydrolipase), were chosen. The primer sets were combined in a series of multiplex-PCR (mPCR) assays against 38 previously characterized strains. Following PCR, each species was distinguished by the production of a unique combination of amplicons. When the assays were tested using 63 drinking water isolates, there was complete agreement in the species identification (ID) for 59 isolates, with ID established by biochemical assays. Sequencing the gyrB and the 16S rRNA gene from the remaining four strains established that the ID obtained by mPCR was correct for three strains. For only one strain, no consensus ID could be obtained. A rapid and reliable method for identification of different Aeromonas species is proposed that does not require restriction enzyme digestions, thus simplifying and speeding up the process.
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10. |
Takahashi A,
Tanoue N,
Nakano M,
Hamamoto A,
Okamoto K,
Fujii Y,
Harada N,
Nakaya Y,
( 2005 ) A pore-forming toxin produced by Aeromonas sobria activates Ca2+ dependent Cl- secretion. PMID : 15797812 : DOI : 10.1016/j.micpath.2005.01.003 Abstract >>
Bacteria produce many types of hemolysin that induce diarrhea by mechanisms that are not completely understood. Aeromonas sobria hemolysin (ASH) is a major virulence factor produced by A. sobria, a human pathogen that causes diarrhea. Since epithelial cells in the intestine are the primary targets of hemolysin, we investigated the effects of ASH on ion transport in human colonic epithelial (Caco-2) cells. ASH increased short-circuit currents (Isc) in a dose-dependent manner, and it also activated a 125I efflux from Caco-2 cells. ASH-induced Isc increases and 125I efflux activations were both suppressed by low Ca2+ levels in the extracellular solution or by pretreatment with the Ca2+ chlelator BAPTA-AM. Intracellular Ca2+ levels were increased by ASH in a biphasic fashion characterized by a rapid sharp increase (peak 1) followed by a sustained low plateau (peak 2). ASH-induced peak 1 was inhibited by pretreatment with pertussis toxin, indicating that Ca2+ was mobilized from intracellular stores, and peak 2 was induced by an influx of extracellular Ca2+. Peak 2 but not peak 1 was related to Cl- secretion. These results indicate that ASH activates Ca2+-dependent Cl- secretion.
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11. |
Wahli T,
Burr SE,
Pugovkin D,
Mueller O,
Frey J,
( 2005 ) Aeromonas sobria, a causative agent of disease in farmed perch, Perca fluviatilis L. PMID : 15752274 : DOI : 10.1111/j.1365-2761.2005.00608.x Abstract >>
Significant numbers of perch, Perca fluviatilis, raised on a pilot fish farm in Switzerland presented focal skin lesions on the lateral sides and fin rot. Mortality rates reached levels of up to 1% of the total fish on the farm per day. Virtually pure cultures of Aeromonas sobria were isolated from the liver, kidney, spleen and skin lesions of affected fish. Aeromonas sobria isolated from the farmed perch had a haemolytic effect on sheep and trout erythrocytes, autoaggregated, was cytotoxic for cultured fish cells and possessed genes involved in type III protein secretion. Experimental infection of naive perch with a single colony isolate of A. sobria from an affected farm fish resulted in the development of clinical signs identical to those seen on the farm. The results indicate that A. sobria can act as a primary pathogen of perch.
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12. |
Soler L,
Yáñez MA,
Chacon MR,
Aguilera-Arreola MG,
Catalán V,
Figueras MJ,
Martínez-Murcia AJ,
( 2004 ) Phylogenetic analysis of the genus Aeromonas based on two housekeeping genes. PMID : 15388703 : DOI : 10.1099/ijs.0.03048-0 Abstract >>
The phylogenetic relationships of all known species of the genus Aeromonas, and especially Aeromonas bestiarum and Aeromonas salmonicida, were investigated on 70 strains using the rpoD sequence, which encodes the sigma70 factor. This analysis was complemented with the sequence of gyrB, which has already proven useful for determining the phylogenetic relationships in the genus. Nucleotide sequences of rpoD and gyrB showed that both genes had similar substitution rates (< 2 %) and a similar number of variable positions (34 % for rpoD versus 32 % for gyrB). Strain groupings by analysis of rpoD, gyrB and a combination of both genes were consistent with the taxonomic organization of all Aeromonas species described to date. However, the simultaneous analysis of both clocks improved the reliability and the power to differentiate, in particular, closely related taxa. At the inter-species level, gyrB showed a better resolution for differentiating Aeromonas sp. HG11/Aeromonas encheleia and Aeromonas veronii/Aeromonas culicicola/Aeromonas allosaccharophila, while rpoD more clearly differentiated A. salmonicida from A. bestiarum. The analysis of rpoD provided initial evidence for clear phylogenetic divergence between the latter two species.
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13. |
Martinez-Murcia AJ,
Monera A,
Saavedra MJ,
Oncina R,
Lopez-Alvarez M,
Lara E,
Figueras MJ,
( 2011 ) Multilocus phylogenetic analysis of the genus Aeromonas. PMID : 21353754 : DOI : 10.1016/j.syapm.2010.11.014 Abstract >>
A broad multilocus phylogenetic analysis (MLPA) of the representative diversity of a genus offers the opportunity to incorporate concatenated inter-species phylogenies into bacterial systematics. Recent analyses based on single housekeeping genes have provided coherent phylogenies of Aeromonas. However, to date, a multi-gene phylogenetic analysis has never been tackled. In the present study, the intra- and inter-species phylogenetic relationships of 115 strains representing all Aeromonas species described to date were investigated by MLPA. The study included the independent analysis of seven single gene fragments (gyrB, rpoD, recA, dnaJ, gyrA, dnaX, and atpD), and the tree resulting from the concatenated 4705 bp sequence. The phylogenies obtained were consistent with each other, and clustering agreed with the Aeromonas taxonomy recognized to date. The highest clustering robustness was found for the concatenated tree (i.e. all Aeromonas species split into 100% bootstrap clusters). Both possible chronometric distortions and poor resolution encountered when using single-gene analysis were buffered in the concatenated MLPA tree. However, reliable phylogenetic species delineation required an MLPA including several "bona fide" strains representing all described species.
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14. |
Farfán M,
Miñana-Galbis D,
Garreta A,
Lorén JG,
Fusté MC,
( 2010 ) Malate dehydrogenase: a useful phylogenetic marker for the genus Aeromonas. PMID : 21095084 : DOI : 10.1016/j.syapm.2010.09.005 Abstract >>
The reconstruction of correct genealogies among biological entities, the estimation of the divergence time between organisms or the study of the different events that occur along evolutionary lineages are not always based on suitable genes. For reliable results, it is necessary to look at full-length sequences of genes under stabilizing selection (neutral or purifying) and behaving as good molecular clocks. In bacteria it has been proved that the malate dehydrogenase gene (mdh) can be used to determine the inter- and intraspecies divergence, and hence this gene constitutes a potential marker for phylogeny and bacterial population genetics. We have sequenced the full-length mdh gene in 36 type and reference strains of Aeromonas. The species grouping obtained in the phylogenetic tree derived from mdh sequences was in agreement with that currently accepted for the genus Aeromonas. The maximum likelihood models applied to our sequences indicated that the mdh gene is highly conserved among the Aeromonas species and the main evolutionary force acting on it is purifying selection. Only two sites under potential diversifying selection were identified (T 108 and S 193). In order to determine if these two residues could have an influence on the MDH structure, we mapped them in a three-dimensional model constructed from the sequence of A. hydrophila using the human mitochondrial MDH as a template. The presence of purifying selection together with the linear relationship between substitutions and gene divergence makes the mdh an excellent candidate gene for a phylogeny of Aeromonas and probably for other bacterial groups.
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15. |
Chan KG,
Puthucheary SD,
Chan XY,
Yin WF,
Wong CS,
Too WS,
Chua KH,
( 2011 ) Quorum sensing in Aeromonas species isolated from patients in Malaysia. PMID : 20544198 : DOI : 10.1007/s00284-010-9689-z Abstract >>
Bacterial quorum sensing signal molecules called N-acylhomoserine lactone (AHL) controls the expression of virulence determinants in many Gram-negative bacteria. We determined AHL production in 22 Aeromonas strains isolated from various infected sites from patients (bile, blood, peritoneal fluid, pus, stool and urine). All isolates produced the two principal AHLs, N-butanoylhomoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL). Ten isolates also produced additional AHLs. This report is the first documentation of Aeromonas sobria producing C6-HSL and two additional AHLs with N-acyl side chain longer than C(6). Our data provides a better understanding of the mechanism(s) of this environmental bacterium emerging as a human pathogen.
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16. |
Lorén JG,
Farfán M,
Miñana-Galbis D,
Fusté MC,
( 2010 ) Prediction of whole-genome DNA G+C content within the genus Aeromonas based on housekeeping gene sequences. PMID : 20466501 : DOI : 10.1016/j.syapm.2010.03.007 Abstract >>
Different methods are available to determine the G+C content (e.g. thermal denaturation temperature or high performance liquid chromatography, HPLC), but obtained values may differ significantly between strains, as well as between laboratories. Recently, several authors have demonstrated that the genomic DNA G+C content of prokaryotes can be reliably estimated from one or several protein coding gene nucleotide sequences. Few G+C content values have been published for the Aeromonas species described and the data, when available, are often incomplete or provide only a range of values. Our aim in this current work was twofold. First, the genomic G+C content of the type or reference strains of all species and subspecies of the genus Aeromonas was determined with a traditional experimental method in the same laboratory. Second, we wanted to see if the sequence-based method to estimate the G+C content described by Fournier et al. [7] could be applied to determine the G+C content of the different species of Aeromonas from the sequences of the genes used in taxonomy or phylogeny for this genus.
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17. |
Li Y,
Cai SH,
( 2011 ) Identification and pathogenicity of Aeromonas sobria on tail-rot disease in juvenile tilapia Oreochromis niloticus. PMID : 20853167 : DOI : 10.1007/s00284-010-9753-8 Abstract >>
Thirty-six strains, numbered from PY01 to PY36, were isolated from six moribund Oreochromis niloticus. The biochemical characteristics of all strains conformed to the species description of Aeromonas sobria on the basis of API 20E and Biolog GN system. Furthermore, gyrB sequence of strain PY36 was sequenced and showed high similarity (99.8%) with A. sobria in Genbank. Antibiotic-resistance of strain PY36 was assessed by the Kirby-Bauer disk diffusion method, and the results showed it was susceptible and moderately susceptible to 12 and 3 of the 19 antimicrobials tested. Virulence of strain PY36 to juvenile tilapia was also tested, and we found that LD?? was about 4.17 �� 10? CFU per fish in intraperitoneal injection. This is the first article to report that A. sobria was the pathogenic agent of tail-rot disease in juvenile tilapia. A. sobria was multi-resistant to the most frequently used antimicrobial drugs in China, so the antimicrobial resistance test should be carried out when these bacteria are isolated from biological samples in order to avoid therapeutic failures and spread of the pathogenic organisms in the environment.
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18. |
Farfán M,
Miñana-Galbis D,
Fusté MC,
Lorén JG,
( 2009 ) Divergent evolution and purifying selection of the flaA gene sequences in Aeromonas. PMID : 19622168 : DOI : 10.1186/1745-6150-4-23 PMC : PMC2724415 Abstract >>
The bacterial flagellum is the most important organelle of motility in bacteria and plays a key role in many bacterial lifestyles, including virulence. The flagellum also provides a paradigm of how hierarchical gene regulation, intricate protein-protein interactions and controlled protein secretion can result in the assembly of a complex multi-protein structure tightly orchestrated in time and space. As if to stress its importance, plants and animals produce receptors specifically dedicated to the recognition of flagella. Aside from motility, the flagellum also moonlights as an adhesion and has been adapted by humans as a tool for peptide display. Flagellar sequence variation constitutes a marker with widespread potential uses for studies of population genetics and phylogeny of bacterial species. We sequenced the complete flagellin gene (flaA) in 18 different species and subspecies of Aeromonas. Sequences ranged in size from 870 (A. allosaccharophila) to 921 nucleotides (A. popoffii). The multiple alignment displayed 924 sites, 66 of which presented alignment gaps. The phylogenetic tree revealed the existence of two groups of species exhibiting different FlaA flagellins (FlaA1 and FlaA2). Maximum likelihood models of codon substitution were used to analyze flaA sequences. Likelihood ratio tests suggested a low variation in selective pressure among lineages, with an omega ratio of less than 1 indicating the presence of purifying selection in almost all cases. Only one site under potential diversifying selection was identified (isoleucine in position 179). However, 17 amino acid positions were inferred as sites that are likely to be under positive selection using the branch-site model. Ancestral reconstruction revealed that these 17 amino acids were among the amino acid changes detected in the ancestral sequence. The models applied to our set of sequences allowed us to determine the possible evolutionary pathway followed by the flaA gene in Aeromonas, suggesting that this gene have probably been evolving independently in the two groups of Aeromonas species since the divergence of a distant common ancestor after one or several episodes of positive selection. This article was reviewed by Alexey Kondrashov, John Logsdon and Olivier Tenaillon (nominated by Laurence D Hurst).
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19. |
Miñana-Galbis D,
Urbizu-Serrano A,
Farfán M,
Fusté MC,
Lorén JG,
( 2009 ) Phylogenetic analysis and identification of Aeromonas species based on sequencing of the cpn60 universal target. PMID : 19567585 : DOI : 10.1099/ijs.0.005413-0 Abstract >>
An analysis of the universal target (UT) sequence from the cpn60 gene was performed in order to evaluate its usefulness in phylogenetic and taxonomic studies and as an identification marker for the genus Aeromonas. Sequences of 555 bp, corresponding to the UT region, were obtained from a collection of 35 strains representing all of the species and subspecies of Aeromonas. From the analysis of these sequences, a range of divergence of 0-23.3% was obtained, with a mean of 11.2+/-0.9%. Comparative analyses between cpn60 and gyrB, rpoD and 16S rRNA gene sequences were carried out from the same Aeromonas strain collection. Sequences of the cpn60 UT region showed similar discriminatory power to gyrB and rpoD sequences. The phylogenetic relationships inferred from cpn60 sequence distances indicated an excellent correlation with the present affiliation of Aeromonas species with the exception of Aeromonas hydrophila subsp. dhakensis, which appeared in a separate phylogenetic line, and Aeromonas sharmana, which exhibited a very loose phylogenetic relationship to the genus Aeromonas. Sequencing of cpn60 from 33 additional Aeromonas strains also allowed us to establish intra- and interspecific threshold values. Intraspecific divergence rates were
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20. |
Kobayashi H,
Utsunomiya H,
Yamanaka H,
Sei Y,
Katunuma N,
Okamoto K,
Tsuge H,
( 2009 ) Structural basis for the kexin-like serine protease from Aeromonas sobria as sepsis-causing factor. PMID : 19654332 : DOI : 10.1074/jbc.M109.006114 PMC : PMC2785694 Abstract >>
The anaerobic bacterium Aeromonas sobria is known to cause potentially lethal septic shock. We recently proposed that A. sobria serine protease (ASP) is a sepsis-related factor that induces vascular leakage, reductions in blood pressure via kinin release, and clotting via activation of prothrombin. ASP preferentially cleaves peptide bonds that follow dibasic amino acid residues, as do Kex2 (Saccharomyces cerevisiae serine protease) and furin, which are representative kexin family proteases. Here, we revealed the crystal structure of ASP at 1.65 A resolution using the multiple isomorphous replacement method with anomalous scattering. Although the overall structure of ASP resembles that of Kex2, it has a unique extra occluding region close to its active site. Moreover, we found that a nicked ASP variant is cleaved within the occluding region. Nicked ASP shows a greater ability to cleave small peptide substrates than the native enzyme. On the other hand, the cleavage pattern for prekallikrein differs from that of ASP, suggesting the occluding region is important for substrate recognition. The extra occluding region of ASP is unique and could serve as a useful target to facilitate development of novel antisepsis drugs.
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21. |
Reith ME,
Singh RK,
Curtis B,
Boyd JM,
Bouevitch A,
Kimball J,
Munholland J,
Murphy C,
Sarty D,
Williams J,
Nash JH,
Johnson SC,
Brown LL,
( 2008 ) The genome of Aeromonas salmonicida subsp. salmonicida A449: insights into the evolution of a fish pathogen. PMID : 18801193 : DOI : 10.1186/1471-2164-9-427 PMC : PMC2556355 Abstract >>
Aeromonas salmonicida subsp. salmonicida is a Gram-negative bacterium that is the causative agent of furunculosis, a bacterial septicaemia of salmonid fish. While other species of Aeromonas are opportunistic pathogens or are found in commensal or symbiotic relationships with animal hosts, A. salmonicida subsp. salmonicida causes disease in healthy fish. The genome sequence of A. salmonicida was determined to provide a better understanding of the virulence factors used by this pathogen to infect fish. The nucleotide sequences of the A. salmonicida subsp. salmonicida A449 chromosome and two large plasmids are characterized. The chromosome is 4,702,402 bp and encodes 4388 genes, while the two large plasmids are 166,749 and 155,098 bp with 178 and 164 genes, respectively. Notable features are a large inversion in the chromosome and, in one of the large plasmids, the presence of a Tn21 composite transposon containing mercury resistance genes and an In2 integron encoding genes for resistance to streptomycin/spectinomycin, quaternary ammonia compounds, sulphonamides and chloramphenicol. A large number of genes encoding potential virulence factors were identified; however, many appear to be pseudogenes since they contain insertion sequences, frameshifts or in-frame stop codons. A total of 170 pseudogenes and 88 insertion sequences (of ten different types) are found in the A. salmonicida genome. Comparison with the A. hydrophila ATCC 7966T genome reveals multiple large inversions in the chromosome as well as an approximately 9% difference in gene content indicating instances of single gene or operon loss or gain.A limited number of the pseudogenes found in A. salmonicida A449 were investigated in other Aeromonas strains and species. While nearly all the pseudogenes tested are present in A. salmonicida subsp. salmonicida strains, only about 25% were found in other A. salmonicida subspecies and none were detected in other Aeromonas species. Relative to the A. hydrophila ATCC 7966T genome, the A. salmonicida subsp. salmonicida genome has acquired multiple mobile genetic elements, undergone substantial rearrangement and developed a significant number of pseudogenes. These changes appear to be a consequence of adaptation to a specific host, salmonid fish, and provide insights into the mechanisms used by the bacterium for infection and avoidance of host defence systems.
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22. |
Sepe A,
Barbieri P,
Peduzzi R,
Demarta A,
( 2008 ) Evaluation of recA sequencing for the classification of Aeromonas strains at the genotype level. PMID : 18346137 : DOI : 10.1111/j.1472-765X.2008.02339.x Abstract >>
To evaluate the usefulness of partial recA sequences for the identification of Aeromonas strains at the genotype level. A partial recA sequence was obtained from 21 type or reference strains and 33 Aeromonas isolates, collected in the South of Switzerland from human, animal and aquatic environments. The 272 bp long recA fragments showed a mean interspecies divergence of 7.8% and allowed the classification of strains at genotype level. However, some discrepancies could be observed with other gene sequence based analyses in the classification of some strains. The 272 bp long recA fragment is a good molecular marker to infer taxonomy of members of the genus Aeromonas, even if the primers we chose for the amplification did not allow its direct sequencing. In the genus Aeromonas, nucleotide sequences of some protein-encoding genes have already been evaluated as molecular markers to be used in taxonomical and epidemiological researches. This study suggests the usefulness of a recA fragment as a further sequence to investigate for these purposes.
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23. |
Khan R,
Takahashi E,
Ramamurthy T,
Takeda Y,
Okamoto K,
( 2007 ) Salt in surroundings influences the production of serine protease into milieu by Aeromonas sobria. PMID : 17951986 : DOI : 10.1111/j.1348-0421.2007.tb03993.x Abstract >>
Previously we have shown that the open reading frame 2 protein (ORF2 protein), which is encoded at the 3 ' end of serine protease of Aeromonas sobria (ASP), functions as a chaperone protein in periplasm in the production of ASP. Both proteins, ASP and ORF2 protein, associate in periplasm and ORF2 protein helps ASP to take an active form. ASP which is dissociated from ORF2 protein emerges in milieu . In this study, we examined the effect of sodium chloride (NaCl) in medium on ASP production by A. sobria. The ASP activity of culture supernatant was extremely decreased when A. sobria was cultured in medium containing 3.0% NaCl (concentration almost equivalent to sea water salinity). Our analysis showed that the transcription of asp by A. sobria is not inhibited by NaCl in medium and that A. sobria synthesizes and releases ASP in milieu even under the condition of 3.0% NaCl. However, these ASPs in milieu formed complex as with ORF2 proteins. This indicates that the maturation pathway of ASP is disturbed in A. sobria cultured in medium containing 3.0% NaCl. It is likely that ASP does not associate with ORF2 protein in the correct form in periplasam when A. sobria is cultured in medium containing 3.0% NaCl, though both proteins, ASP and ORF2 protein, make complexes and emerge outside of the cell. This idea suggests that the chaperone system of ASP possesses the ability to sense NaCl in surroundings and regulates the production of active ASP.
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24. |
Husslein V,
Huhle B,
Jarchau T,
Lurz R,
Goebel W,
Chakraborty T,
( 1988 ) Nucleotide sequence and transcriptional analysis of the aerCaerA region of Aeromonas sobria encoding aerolysin and its regulatory region. PMID : 2459581 : DOI : 10.1111/j.1365-2958.1988.tb00057.x Abstract >>
The nucleotide sequence of a 2510 base pair chromosomal fragment containing the aerolysin gene aerA, and its regulatory region aerC, from a clinical isolate of Aeromonas sobria was determined. The aerolysin gene coded for a 54.5 kD polypeptide and had a G + C content of 59%, indicating that it is endogenous to the genus Aeromonas. In contrast, the aerC region was characterized by its high A + T content (61%) and the presence of a core motif, aATAAAa, repeated eight times within 300 base pairs. A 12 base pair repeat, 5'AATAAAACCGGG3', present within this region occurred as a direct repeat 544 base pairs away, within the coding region of aerolysin. RNA polymerase binding studies and S1 mapping allowed the detection of two divergent non-overlapping promoters within aerC. Despite having identical transcriptional start sites in both A. sobria and Escherchia coli, the amount of aerolysin transcript produced in E. coli is 30-40 times less than that found in A. sobria. The signal peptide of preproaerolysin was shown by deletion to be essential for export of the toxin to the external medium. The mature toxin is a hydrophilic protein with no hydrophobic stretches long enough to cross a membrane. A search for similarities to the primary sequence of aerolysin revealed that the toxin may share a functional similarity to haemolysin (hlyA) of E. coli.
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25. |
Vega-Sánchez V,
Latif-Eugenín F,
Soriano-Vargas E,
Beaz-Hidalgo R,
Figueras MJ,
Aguilera-Arreola MG,
Castro-Escarpulli G,
( 2014 ) Re-identification of Aeromonas isolates from rainbow trout and incidence of class 1 integron and �]-lactamase genes. PMID : 25008317 : DOI : 10.1016/j.vetmic.2014.06.012 Abstract >>
Forty-eight Aeromonas isolates from rainbow trout previously identified by the 16S rDNA-RFLP technique were re-identified using 2 housekeeping genes (gyrB and rpoD). After sequencing the prevalences of the species were A. veronii (29.2%), A. bestiarum (20.8%), A. hydrophila (16.7%), A. sobria (10.4%), A. media (8.3%), A. popoffii (6.2%), A. allosaccharophila (2.1%), A. caviae (2.1%), A. salmonicida (2.1%) and one isolate (2.1%) belongs to a candidate new species "Aeromonas lusitana". Coincident identification results to the 16S rDNA-RFLP technique were only obtained for 68.8% of the isolates. PCR amplification of the enterobacterial repetitive intergenic consensus (ERIC-PCR) indicated that the 48 isolates belonged to 33 different ERIC genotypes. Several genotypes were isolated from different farms and organs in the same fish, indicating a systemic dissemination of the bacteria. The presence of genes (blaIMP, blaCphA/IMIS, blaTEM, blaSHV and intI1) that encode extended-spectrum beta-lactamases (ESBLs), metallo-beta-lactamases (MBLs) and class 1 integrons were studied by PCR. Only 39.6% (19/48) of the strains showed the presence of one or more resistance genes. The gene blaCphA/IMIS was detected in 29.2% of the isolates, followed by the intI1 (6.2%) and blaSHV (4.2%) genes. The variable region of class 1 integrons of the 3 positive isolates was sequenced revealing the presence of the gene cassette aadA1 (aminoglycoside transferase) that plays a role in streptomycin/spectinomycin resistance.
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26. |
Park SC,
Chai JY,
Shin SP,
Jun JW,
( 2012 ) First description of ColE-type plasmid in Aeromonas spp. carrying quinolone resistance (qnrS2) gene. PMID : 22862417 : DOI : 10.1111/j.1472-765X.2012.03293.x Abstract >>
Isolation and full sequence analysis of ColE-type plasmid, which carries the qnrS2 gene. Quinolone resistance (qnrS2) gene-carrying plasmids were isolated from Aeromonas sobria and Aeromonas hydrophila strains, and plasmid sequencing was achieved by a primer-walking approach. The total sizes of these plasmids (pAQ2-1 and pAQ2-2) were 6900 bp and 6903 bp, respectively, and they were 99�P1% identical to each other. The genes (oriV and repA) for plasmid replication were organized similar to the corresponding genes in the ColE2-type plasmids, pAsa3 and pAsa1, isolated from Aeromonas salmonicida subsp. salmonicida, but the gene (mobA) for mobilization was homologue to ColE1-type plasmid (pAsa2) from Aer. salmonicida subsp. salmonicida. Additionally, the qnrS2 gene was part of a mobile insertion cassette element in the plasmid. Two plasmids were assumed to be the same plasmid, and this identification of a plasmid-mediated qnrS2 gene from the two different strains underlines a possible diffusion of these resistance determinants in an aquaculture system. This is the first finding of the ColE-type plasmid carrying the qnrS2 gene.
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27. |
Roger F,
Marchandin H,
Jumas-Bilak E,
Kodjo A,
N/A N/A,
Lamy B,
( 2012 ) Multilocus genetics to reconstruct aeromonad evolution. PMID : 22545815 : DOI : 10.1186/1471-2180-12-62 PMC : PMC3487998 Abstract >>
Aeromonas spp. are versatile bacteria that exhibit a wide variety of lifestyles. In an attempt to improve the understanding of human aeromonosis, we investigated whether clinical isolates displayed specific characteristics in terms of genetic diversity, population structure and mode of evolution among Aeromonas spp. A collection of 195 Aeromonas isolates from human, animal and environmental sources was therefore genotyped using multilocus sequence analysis (MLSA) based on the dnaK, gltA, gyrB, radA, rpoB, tsf and zipA genes. The MLSA showed a high level of genetic diversity among the population, and multilocus-based phylogenetic analysis (MLPA) revealed 3 major clades: the A. veronii, A. hydrophila and A. caviae clades, among the eleven clades detected. Lower genetic diversity was observed within the A. caviae clade as well as among clinical isolates compared to environmental isolates. Clonal complexes, each of which included a limited number of strains, mainly corresponded to host-associated subsclusters of strains, i.e., a fish-associated subset within A. salmonicida and 11 human-associated subsets, 9 of which included only disease-associated strains. The population structure was shown to be clonal, with modes of evolution that involved mutations in general and recombination events locally. Recombination was detected in 5 genes in the MLSA scheme and concerned approximately 50% of the STs. Therefore, these recombination events could explain the observed phylogenetic incongruities and low robustness. However, the MLPA globally confirmed the current systematics of the genus Aeromonas. Evolution in the genus Aeromonas has resulted in exceptionally high genetic diversity. Emerging from this diversity, subsets of strains appeared to be host adapted and/or disease specialized" while the A. caviae clade displayed an atypical tempo of evolution among aeromonads. Considering that A. salmonicida has been described as a genetically uniform pathogen that has adapted to fish through evolution from a variable ancestral population, we hypothesize that the population structure of aeromonads described herein suggested an ongoing process of adaptation to specialized niches associated with different degrees of advancement according to clades and clusters."
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28. |
Pan ZH,
Lu CP,
( 2012 ) Identity and virulence properties of Aeromonas isolates from diseased fish, healthy controls and water environment in China. PMID : 22725694 : DOI : 10.1111/j.1472-765X.2012.03281.x Abstract >>
To investigate the species distribution in Aeromonas isolates from diseased fish, healthy controls and water environment in China; to evaluate the frequency of the aerolysin (aer), cytotonic enterotoxin (alt), cytotoxic enterotoxin (act), temperature-sensitive protease (eprCAI) and serine protease (ahp) genes in Aeromonas isolates; and to determine the potential pathogenicity of these isolates. Two hundred and two Aeromonas isolates from diseased fish (n = 42), healthy fish (n = 120) and water environment (n = 40) in China were identified to species levels based on sequencing of the housekeeping gene gyrB, while the distribution of five virulence factors, including aer, alt, act, eprCAI and ahp, was investigated by PCR. Aeromonas veronii (25/42; 60%) and Aeromonas hydrophila (14/42; 33%) were the species most commonly isolated from diseased fish, while Aer. veronii was the most common species in healthy fish (90/120; 75%) and water samples (25/40; 62�P5%). All the five virulence genes were present in 9% (19/202), among which 10 strains were from diseased fish and nine were identified as Aer. hydrophila. For the strains carrying five virulence genes, the average 50% lethal doses (LD(50s)) of strains from diseased fish were lower when compared with the strains from healthy fish and water environment. Aeromonas veronii is the most common species, but no significant difference exists in the isolates obtained from diseased fish and from healthy fish. However, Aer. hydrophila isolates were significantly more frequent from diseased fish than from healthy fish. aer+alt+act+eprCAI+ ahp+ was more frequent virulence genotype in Aeromonas isolates from diseased fish than from healthy fish and water environment, and the aer+alt+act+eprCAI+ahp+ isolates were more virulent to zebrafish comparing to the other genetic profiles. Aeromonas species in aquatic environments are various and have considerable virulence potential, and therefore, there is a need for more careful and intensive epidemiology studies.
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29. |
Han JE,
Kim JH,
Cheresca CH,
Shin SP,
Jun JW,
Chai JY,
Han SY,
Park SC,
( 2012 ) First description of the qnrS-like (qnrS5) gene and analysis of quinolone resistance-determining regions in motile Aeromonas spp. from diseased fish and water. PMID : 22024339 : DOI : 10.1016/j.resmic.2011.09.001 Abstract >>
Antimicrobial resistance patterns in a collection of 33 motile Aeromonas species were described in this study. Quinolone has been frequently employed for treatment of Aeromonas-related diseases, and prolonged use of antimicrobial compounds has led to development of resistant strains. In a sample of diseased fish and environmental water, we evaluated nalidixic acid (n = 19) and ciprofloxacin (n = 4) resistance via minimum inhibitory concentration (MIC) assays and the genetic basis was also investigated. Among the isolated Aeromonas spp., 17 strains encoded for chromosomal mutations of quinolone resistance-determining regions (QRDRs) in gyrA, 11 strains encoded for mutations of QRDRs in parC, 1 strain harbored plasmid-mediated quinolone resistance (PMQR) qnrS1-like gene and 4 strains harbored the PMQR qnrS2 gene. In particular, the new variant (qnrS1-like) differed from qnrS1 by 6 amino acid substitutions at positions 5 (Asn(5)��Arg(5)), 120 (Ser(120)��Thr(120)), 148 (Asn(148)��His(148)), 206 (Leu(206)��Glu(206)), 207 (Ile(207)�� Leu(207)), and 216 (Tyr(216)��Phe(216)), and the gene was designated qnrS5. These resistant strains may function as reservoirs of quinolone resistance.
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30. |
( 1996 ) Study of the intergenic exeF-exeG region and its application as a simple preliminary test for Aeromonas spp. PMID : 8935655 : DOI : 10.1111/j.1574-6968.1996.tb08079.x Abstract >>
The exeF-exeG intergenic regions from different hybridization groups (HG) of Aeromonas were studied by PCR amplification using a single pair of primers. Six main classes of PCR products were identified according to size: 360 bp, 320 bp, 280 bp, 230-240 bp, 220 bp and 160 bp. Direct sequencing of the PCR products indicated that the shorter intergenic regions had probably originated from deletion of DNA segments between direct repeats. Correlation of certain PCR products with Aeromonas caviae (HG4), A. caviae (HG5), A. veronii (HG8) and A. salmonicida (HG3) was revealed. The PCR reaction was also shown to be generally specific for Aeromonas spp. Thus, the usefulness of this rapid, single colony-based PCR test for both identification and preliminary differentiation of Aeromonas spp. is demonstrated.
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31. |
( 1995 ) Sequence analysis of two chromosomally mediated inducible beta-lactamases from Aeromonas sobria, strain 163a, one a class D penicillinase, the other an AmpC cephalosporinase. PMID : 8537283 : DOI : 10.1093/jac/36.1.41 Abstract >>
Two beta-lactamase genes from Aeromonas sobria, strain 163a, have been cloned and sequenced, one encoding a typical class C cephalosporinase, designated CepS, the other a class D penicillinase, designated AmpS. CepS is predicted to be a mature protein of 38 kDa with a pI value of 7.0. The amino acid sequence of CepS is most similar to that of AmpC from Pseudomonas aeruginosa (54.7%). AmpS is predicted to be a mature protein of 27 kDa with a pI value of 7.9 that mostly closely resembles BLAD from Klebsiella pneumoniae (42.2%), and OXA-1 from Escherichia coli (36.6%), beta-lactamases that are encoded by genes carried on multiresistant transposons. AmpS differs significantly from the other class D beta-lactamases in that it hydrolyses cloxacillin poorly and is inducible. Both genes exhibit a high overall GC content and possess a high NNC and NNG codon preference, similar to that of genes from Pseudomonas spp.
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32. |
Nemec A,
Haywood-Farmer A,
Mackie GA,
( 1995 ) Conserved amino acid residues in the primary structure of ribosomal protein S20 from selected gram-negative bacteria. PMID : 7640306 : DOI : 10.1016/0167-4781(95)00100-u Abstract >>
Partial DNA sequences encoding ribosomal protein S20 have been determined for a number of Gram-negative bacteria including three species of Aeromonas, Klebsiella pneumoniae, Proteus mirabilis, and Salmonella typhimurium and compared to the known sequence from Escherichia coli. The derived amino acid sequence is well conserved, particularly in the C-terminal one-third of S20. In contrast, there is much less conservation of the nucleotide sequence or potential secondary structure in the corresponding mRNA.
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33. |
Kitazono A,
Kitano A,
Tsuru D,
Yoshimoto T,
( 1994 ) Isolation and characterization of the prolyl aminopeptidase gene (pap) from Aeromonas sobria: comparison with the Bacillus coagulans enzyme. PMID : 7883756 : DOI : 10.1093/oxfordjournals.jbchem.a124601 Abstract >>
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.
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34. |
Rasmussen BA,
Keeney D,
Yang Y,
Bush K,
( 1994 ) Cloning and expression of a cloxacillin-hydrolyzing enzyme and a cephalosporinase from Aeromonas sobria AER 14M in Escherichia coli: requirement for an E. coli chromosomal mutation for efficient expression of the class D enzyme. PMID : 7811022 : DOI : 10.1128/aac.38.9.2078 PMC : PMC284687 Abstract >>
Two beta-lactamase genes, asbA1 and asbB1, encoding AsbA1 and AsbB1, respectively, have been cloned from Aeromonas sobria AER 14M into Escherichia coli. AsbA1 was expressed at low but detectable levels in all E. coli laboratory cloning strains tested. AsbB1 was expressed well in the E. coli cloning strain DH5 alpha. However, no enzyme activity could be detected from the same clone when placed in E. coli MC1061. Ampicillin-resistant mutants of E. coli MC1061 were obtained that expressed high levels of enzymatically active AsbB1. Four independent mutants were examined. All four mutations mapped to one locus, designated blpA (beta-lactamase permissive). The blpA locus was distinct from other known loci that play a role in beta-lactamase expression, i.e., the two loci that affect expression of the Bacteroides fragilis metallo-beta-lactamase and the ampC regulatory genes, ampD, ampE, and ampG. Sequence analysis of asbA1 and asbB1 revealed that AsbA1 was a class C beta-lactamase most closely related to the Pseudomonas aeruginosa chromosomal cephalosporinase and probably represents the common A. sobria cephalosporinase. AsbB1 was a class D enzyme most closely related to the oxacillin-hydrolyzing enzyme OXA-1, with 34% amino acid sequence identity. Purified AsbA1 was a typical cephalosporinase with a substrate profile that reflected high rates of hydrolysis of cephaloridine compared with benzylpenicillin. Purified AsbB1 showed strong penicillinase activity, with hydrolysis rates for carbenicillin and cloxacillin 2 to 2.5 times that for benzylpenicillin. Hydrolysis of imipenem was < or = 1% of that for benzylpenicillin. Both clavulanic acid and tazobactam strongly inhibited AsbB1, while sulbactam inhibited the AsbB1 enzyme less effectively. None of the inhibitors worked well against the AsbA1 enzyme. The chelators EDTA and 1,10-o-phenanthroline did not affect the activity of either enzyme. A. sobria AER 14M was found to produce both a group 1 cephalosporinase and a novel group 2d cloxacillin-hydrolyzing beta-lactamase that has been designated here OXA-12.
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35. |
Hossain S,
Dahanayake PS,
De Silva BCJ,
Wickramanayake MVKS,
Wimalasena SHMP,
Heo GJ,
( 2019 ) Multidrug resistant Aeromonas spp. isolated from zebrafish (Danio rerio): antibiogram, antimicrobial resistance genes and class 1 integron gene cassettes. PMID : 30790321 : DOI : 10.1111/lam.13138 Abstract >>
Aeromonas spp. are Gram-negative opportunistic bacteria which have been commonly associated with fish diseases. In this study, antibiogram, antimicrobial resistance genes and integrons of 43 zebrafish-borne Aeromonas spp. were studied. The isolates were identified as six Aeromonas species (A. veronii biovar veronii (n = 26), A. veronii biovar sobria (n = 3), A. hydrophila (n = 8), A. caviae (n = 3), A. enteropelogenes (n = 2) and A. dhakensis (n = 1)). Antibiogram of the isolates indicated that most of them were resistant to amoxicillin (100�P00%), nalidixic acid (100�P00%), oxytetracycline (100�P00%), ampicillin (93�P02%), tetracycline (74�P42%), rifampicin (67�P44%) and imipenem (65�P15%). Multiple antimicrobial resistance (MAR) index values ranged from 0�P19-0�P44 to 90�P70% isolates showed multidrug resistance. PCR of antimicrobial resistance genes revealed that the tetracycline resistance gene (tetA) was the most predominant (67�P44%) among the isolates. The qnrS (53�P49%), tetB (30�P23%), tetE (30�P23%), qnrB (23�P26%) and aac(6')-Ib-cr (4�P65%) genes were also detected. Class 1 integrase (IntI1) gene was found in 46�P51% of the isolates. Two types of class 1 integron gene cassette profiles (qacG-aadA6-qacG and drfA1) were identified. The results showed that zebrafish-borne aeromonads can harbour different types of antimicrobial resistance genes and class 1 integrons. SIGNIFICANCE AND IMPACT OF THE STUDY: Aeromonas spp. are important pathogens found in diverse environments. Antimicrobial resistance genes and integrons of ornamental fish-borne Aeromonas spp. are not well studied. The antibiogram, antimicrobial resistance genes and class 1 integrons of Aeromonas spp. isolated from zebrafish were characterized for the first time in Korea. The prevalence of tetracycline resistance genes, plasmid-mediated quinolone resistance genes and class 1 integron gene cassettes were observed among the isolates. The qacG-aadA6-qacG gene cassette was identified for the first time in Aeromonas spp. The results suggest that the wise use of antimicrobials is necessary for the better management of the ornamental fish.
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36. |
Gauthier J,
Vincent AT,
Charette SJ,
Derome N,
( 2017 ) Strong Genomic and Phenotypic Heterogeneity in the Aeromonas sobria Species Complex. PMID : 29276504 : DOI : 10.3389/fmicb.2017.02434 PMC : PMC5727048 Abstract >>
Aeromonas sobria is a mesophilic motile aeromonad currently depicted as an opportunistic pathogen, despite increasing evidence of mutualistic interactions in salmonid fish. However, the determinants of its host-microbe associations, either mutualistic or pathogenic, remain less understood than for other aeromonad species. On one side, there is an over-representation of pathogenic interactions in the A. sobria literature, of which only three articles to date report mutualistic interactions; on the other side, genomic characterization of this species is still fairly incomplete as only two draft genomes were published prior to the present work. Consequently, no study specifically investigated the biodiversity of A. sobria. In fact, the investigation of A. sobria as a species complex may have been clouded by: (i) confusion with A. veronii biovar sobria because of their similar biochemical profiles, and (ii) the intrinsic low resolution of previous studies based on 16S rRNA gene sequences and multilocus sequence typing. So far, the only high-resolution, phylogenomic studies of the genus Aeromonas included one A. sobria strain (CECT 4245 / Popoff 208), making it impossible to robustly conclude on the phylogenetic intra-species diversity and the positioning among other Aeromonas species. To further understand the biodiversity and the spectrum of host-microbe interactions in A. sobria as well as its potential genomic diversity, we assessed the genomic and phenotypic heterogeneity among five A. sobria strains: two clinical isolates recovered from infected fish (JF2635 and CECT 4245), one from an infected amphibian (08005) and two recently isolated brook charr probionts (TM12 and TM18) which inhibit in vitro growth of A. salmonicida subsp. salmonicida (a salmonid fish pathogen). A phylogenomic assessment including 2,154 softcore genes corresponding to 946,687 variable sites from 33 Aeromonas genomes confirms the status of A. sobria as a distinct species divided in two subclades, with 100% bootstrap support. The phylogenomic split of A. sobria in two subclades is corroborated by a deep dichotomy between all five A. sobria strains in terms of inhibitory effect against A. salmonicida subsp. salmonicida, gene contents and codon usage. Finally, the antagonistic effect of A. sobria strains TM12 and TM18 suggests novel control methods against A. salmonicida subsp. salmonicida.
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37. |
( 2013 ) Characterization of Aeromonas strains isolated from Indian foods using rpoD gene sequencing and whole cell protein analysis. PMID : 23255059 : DOI : 10.1007/s11274-012-1212-1 Abstract >>
Aeromonas are responsible for causing gastroenteritis and extra-intestinal infections in humans. Twenty-two Aeromonas strains isolated from different food sources were re-identified up to species level using rpoD gene sequence analysis. Biochemical tests and 16S rRNA gene sequencing were insufficient to identify Aeromonas till species level. However, incorporation of additional biochemical tests lead to correct identification of 95.5 % strains up to species level. The 16S rRNA gene sequencing was useful to identify Aeromonas isolates at the genus level only. Sequences of the rpoD gene showed greater discriminatory power than 16S rRNA gene and provided conclusive discrimination of the strains for which the phenotypic species identification was uncertain. All these 22 strains were accurately identified up to species level by rpoD gene as A. salmonicida (6), A. veronii bv. veronii (4), A. caviae (3), A. hydrophila (2), A. veronii bv. sobria (2), A. jandaei (1), A. trota (1), A. sobria (1), A. allosaccharophila (1) and A. bivalvium (1). All these strains were also characterized using whole cell protein (WCP) analysis by gradient SDS-PAGE and showed different whole cell protein (WCP) profile [22-28 polypeptide bands (~10 to >97 kDa)], indicating high genetic diversity. The present work emphasizes the use of molecular methods such as rpoD gene sequencing along with comprehensive biochemical tests for the rapid and accurate identification of Aeromonas isolates till species level. The WCP profile can be subsequently used to characterize Aeromonas isolates below species level.
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38. |
( 2012 ) Changes in the gut microbiome of the sea lamprey during metamorphosis. PMID : 22923392 : DOI : 10.1128/AEM.01640-12 PMC : PMC3485723 Abstract >>
Vertebrate metamorphosis is often marked by dramatic morphological and physiological changes of the alimentary tract, along with major shifts in diet following development from larva to adult. Little is known about how these developmental changes impact the gut microbiome of the host organism. The metamorphosis of the sea lamprey (Petromyzon marinus) from a sedentary filter-feeding larva to a free-swimming sanguivorous parasite is characterized by major physiological and morphological changes to all organ systems. The transformation of the alimentary canal includes closure of the larval esophagus and the physical isolation of the pharynx from the remainder of the gut, which results in a nonfeeding period that can last up to 8 months. To determine how the gut microbiome is affected by metamorphosis, the microbial communities of feeding and nonfeeding larval and parasitic sea lamprey were surveyed using both culture-dependent and -independent methods. Our results show that the gut of the filter-feeding larva contains a greater diversity of bacteria than that of the blood-feeding parasite, with the parasite gut being dominated by Aeromonas and, to a lesser extent, Citrobacter and Shewanella. Phylogenetic analysis of the culturable Aeromonas from both the larval and parasitic gut revealed that at least five distinct species were represented. Phenotypic characterization of these isolates revealed that over half were capable of sheep red blood cell hemolysis, but all were capable of trout red blood cell hemolysis. This suggests that the enrichment of Aeromonas that accompanies metamorphosis is likely related to the sanguivorous lifestyle of the parasitic sea lamprey.
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39. |
( 1998 ) Purification and characterization of enterotoxin produced by Aeromonas sobria. PMID : 9858466 : DOI : 10.1111/j.1348-0421.1998.tb02343.x Abstract >>
We purified the toxin of Aeromonas sobria capable of inducing a positive response in the mouse intestinal loop assay. The purified toxin showed a positive response not only in the loop assay but also in a hemolytic assay. Subsequently, we cloned the toxin gene and demonstrated that the product of this gene possessed both hemolytic and enterotoxic activities. These results showed that the enterotoxin of A. sobria possesses hemolytic activity. Nucleotide sequence determination of the toxin gene and amino acid sequence analysis of the purified toxin revealed that it is synthesized as a precursor composed of 488 amino acid residues, and that the 24 amino-terminal amino acid residues of the precursor is removed in the mature toxin. As antiserum against the purified toxin neutralized the fluid accumulation induced by living cells not only of A. sobria but also of A. hydrophila, this and antigenically related toxin(s) are thought to play an essential role in the induction of diarrhea by these organisms. The toxin-injured Chinese hamster ovary (CHO) cells induced the release of intracellular lactose dehydrogenase (LDH). The release of LDH from CHO cells and the lysis of erythrocytes by the toxin were repressed by the addition of dextran to the reaction solution, indicating that the toxin forms pores in the membranes and that the cells were injured by the osmotic gradient developed due to pore formation. However, the histopathological examination of intestinal cells exposed to the toxin showed that it caused fluid accumulation in the mouse intestinal loop without causing cellular damage.
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