Genotipos de aislados de campo de Brucella abortus de distintas regiones geográficas de Chile

Mancilla, Marcos; Villarroel, M.; Saldías, ME; Soto, Juan I.; Zárraga, AM

doi:10.4067/s0301-732x2008000200011

Cited by 5 publications

(7 citation statements)

References 20 publications

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“…Restriction analysis with XbaI showed a low variability among strains. These results are consistent with previous findings of other authors (13,22), However, the genetic homogeneity observed in most B. abortus isolates showed the need to complement this study with a methodology able to provide a higher resolution power, incorporating MLVA analysis and specifically MLVA-16 (comprising 16 loci). MLVA-16 has been shown to have good discriminatory power to determine genetic relationships among strains of the same species of Brucella (19).…”

Section: Resultssupporting

confidence: 82%

“…This finding is not surprising, since in Chile and in countries such as the United States (2), Argentina (33), and countries in Central America (23), B. abortus biovar 1 was responsible for the greatest percentages of cases of bovine brucellosis. Our results also confirmed the report of Mancilla et al on a previous study with Chilean isolates (22). Pattern A1 showed no appreciable banding differences among the 67 isolates, indicating, according to the interpretive criteria of PFGE patterns published by Tenover et al (35), that these 67 isolates were genetically indistinguishable and therefore were clonally related.…”

Section: Discussionsupporting

confidence: 82%

“…Although most genomes of the Brucella strains we studied were identified as members of the same clone and are identical or nearly so, several of them might have, based on the proposition by Jensen et al (16), different ancestries and be derived by horizontal (transmissible) transfer from other clones of the same or different species. This finding for Chilean (22). Besides this, our goal of incorporating greater variability and discriminatory power was met by introducing MLVA-16 analysis (20) into the study.…”

Section: Discussionmentioning

confidence: 99%

“…Distinct is cluster III, in which all strains have their origin in the south of Chile and are less related to the reference strains 544 and S19 (cluster I) and 2308 and RB51 (cluster II). This very close genetic association between the reference strains used in this study was described by Mancilla et al (22) using IS711-RFLP. In summary, our results on the diversity (HGDI) for each of those loci studied by MLVA-16 (panel 1, panel 2, and panel 2B) (Table 3) were similar to those previously described by other authors (10,19).…”

Section: Discussionmentioning

confidence: 99%

“…Mancilla et al (22), in a previous study in Chile, compared the genotypes of B. abortus by IS711 restriction fragment length polymorphism analysis (RFLP). Apart from their work, there is little information about the genetic characteristics of the B. abortus strains infecting fields in Chile.…”

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confidence: 99%

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Characterization of Genomic Island 3 and Genetic Variability of Chilean Field Strains of Brucella abortus

et al. 2011

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One of the capabilities developed by bacteria is the ability to gain large fragments of DNA from other bacteria or to lose portions of their own genomes. Among these exchangeable fragments are the genomic islands (GIs). Nine GIs have been identified in Brucella, and genomic island 3 (GI-3) is shared by two pathogenic species, B. melitensis and B. abortus. GI-3 encodes mostly unknown proteins. One of the aims of this study was to perform pulsed-field gel electrophoresis (PFGE) on field isolates of B. abortus from Chile to determine whether these isolates are clonally related. Furthermore, we focused on the characterization of GI-3, studying its organization and the genetic conservation of the GI-3 sequence using techniques such as tilingpath PCR (TP-PCR) and restriction fragment length polymorphism-PCR (RFLP-PCR). Our results, after PFGE was performed on 69 field isolates of B. abortus from Chile, showed that the strains were genetically homogeneous. To increase the power of genetic discrimination among these strains, we used multiple locus variable-number tandem-repeat (VNTR) analysis with 16 loci (MLVA-16). The results obtained by MLVA-16 showed that the strains of B. abortus were genetically heterogeneous and that most of them clustered according to their geographic origin. Of the genetic loci studied, panel 2B was the one describing the highest diversity in the analysis, as well as locus Bruce19 in panel 2A. In relation to the study of GI-3, our experimental analysis by TP-PCR identified and confirmed that GI-3 is present in all wild strains of B. abortus, demonstrating the high stability of gene cluster GI-3 in Chilean field strains.Brucellosis is a zoonotic and endemic disease in many areas of the world (8). Similarly to other facultative intracellular parasites, Brucella strains survive outside cells, but they must infect and replicate intracellularly in animals to perpetuate themselves (11). Brucella strains are extremely well adapted to the intracellular niche, and therefore they should be described as facultative extracellular intracellular parasites (24). Brucella causes abortion in cattle, goats, and sheep and a febrile illness (undulant fever) in humans (28). The genus Brucella has six recognized species, all of which exhibit distinct host preferences. Common host-pathogen associations among the classical Brucella species are as follows: B.

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Section: Resultssupporting

confidence: 82%

Section: Discussionsupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Characterization of Genomic Island 3 and Genetic Variability of Chilean Field Strains of Brucella abortus

et al. 2011

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Genomic Island 2 Is an Unstable Genetic Element Contributing toBrucellaLipopolysaccharide Spontaneous Smooth-to-Rough Dissociation

et al. 2010

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Brucella is a Gram-negative bacterium that causes a worldwide-distributed zoonosis. The genus includes smooth (S) and rough (R) species that differ in the presence or absence, respectively, of the O-polysaccharide of lipopolysaccharide. In S brucellae, the O-polysaccharide is a critical diagnostic antigen and a virulence determinant. However, S brucellae spontaneously dissociate into R forms, a problem in antigen and S vaccine production. Spontaneous R mutants of Brucella abortus, Brucella melitensis, and Brucella suis carried the chromosomal scar corresponding to genomic island 2 (GI-2) excision, an event causing the loss of the wboA and wboB O-polysaccharide genes, and the predicted excised circular intermediate was identified in B. abortus, B. melitensis, and B. suis cultures. Moreover, disruption of a putative phage integrase gene in B. abortus GI-2 caused a reduction in O-polysaccharide loss rates under conditions promoting S-R dissociation. However, spontaneous R mutants not carrying the GI-2 scar were also detected. These results demonstrate that the phage integrase-related GI-2 excision is a cause of S-R brucella dissociation and that other undescribed mechanisms must also be involved. In the R Brucella species, previous works have shown that Brucella ovis but not Brucella canis lacks GI-2, and a chromosomal scar identical to those in R mutants was observed. These results suggest that the phage integrase-promoted GI-2 excision played a role in B. ovis speciation and are consistent with other evidence, suggesting that this species and B. canis have emerged as two independent lineages.Brucellosis is one of the most important bacterial zoonotic diseases. This infection is caused by the members of the genus Brucella, a group of Gram-negative, intracellular facultative microorganisms (13). Brucella abortus, Brucella melitensis, Brucella suis, Brucella neotomae, Brucella ceti, and Brucella pinnipedialis are denominated smooth (S) brucellae because their colonies have glossy, bluish surfaces that contrast with the rough (R), granular aspect of the Brucella canis and Brucella ovis colonies. Moreover, S brucellae had a marked tendency to yield mixtures of S and R colonies, a phenomenon known as Brucella S-R dissociation (4). These colony phenotypes respectively relate to the presence or absence of the O-polysaccharide of lipopolysaccharide (LPS) (1, 14), and since this structure is a major diagnostic antigen and virulence factor, S-R dissociation has drawn considerable attention (1, 4, 14, 21). Indeed, S-R dissociation is a problem in the production of diagnostic antigens and vaccines (3). Although first observed over 70 years ago, the genetic bases of Brucella S-R dissociation have not been elucidated as of yet.Up to now, 10 Brucella O-polysaccharide genes (putatively coding for enzymes furnishing sugar precursors, glycosyltransferases, and the O-chain transport system) have been identified, and the corresponding mutants show the R phenotype (1, 9). These genes are located in two major genetic regions, wbo and w...

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Spontaneous Excision of the O-Polysaccharide wbkA Glycosyltranferase Gene Is a Cause of Dissociation of Smooth to Rough Brucella Colonies

et al. 2012

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The brucellae are Gram-negative pathogens that cause brucellosis, a zoonosis of worldwide importance. The genus Brucella includes smooth and rough species that differ in that they carry smooth and rough lipopolysaccharides, respectively. Brucella abortus, B. melitensis, and B. suis are typical smooth species. However, these smooth brucellae dissociate into rough mutants devoid of the lipopolysaccharide O-polysaccharide, a major antigen and a virulence determinant encoded in regions wbo (included in genomic island-2) and wbk. We demonstrate here the occurrence of spontaneous recombination events in those three Brucella species leading to the deletion of a 5.5-kb fragment carrying the wbkA glycosyltranferase gene and to the appearance of rough mutants. Analysis of the recombination intermediates suggested homologous recombination between the ISBm1 insertion sequences flanking wbkA as the mechanism generating the deletion. Excision of wbkA was reduced but not abrogated in a recA-deficient mutant, showing the existence of both RecA-dependent and -independent processes. Although the involvement of the ISBm1 copies flanking wbkA suggested a transpositional event, the predicted transpositional joint could not be detected. This absence of detectable transposition was consistent with the presence of polymorphism in the inverted repeats of one of the ISBm1 copies. The spontaneous excision of wbkA represents a novel dissociation mechanism of smooth brucellae that adds to the previously described excision of genomic island-2. This ISBm1-mediated wbkA excision and the different %GC levels of the excised fragment and of other wbk genes suggest that the Brucella wbk locus is the result of at least two horizontal acquisition events.T he brucellae are a group of Gram-negative pathogens that cause brucellosis, one of the most important bacterial zoonosis worldwide. Based on the appearance of the colony surface and the structure of the lipopolysaccharide (LPS), these bacteria are divided into rough (R) and smooth (S) species. The R species are represented by Brucella ovis and B. canis, produce matte, granular colonies, and carry an R-type LPS lacking the O-polysaccharide (O-PS). The S species, which are zoonotically more important, include B. melitensis, B. abortus, and B. suis, have an LPS with an N-formyl-perosamine O-PS, and produce glossy colonies. The S phenotype, however, is not stable, and S brucellae dissociate to generate R mutants closely similar to the R species in colony morphology and LPS structure. Under unfavorable growth conditions or after prolonged incubation, this dissociation is very noticeable. Thus, it soon caught the attention of brucellosis researchers, who described the colonial dissociation in great detail in the first half of the past century. This early work also established that R mutants are attenuated and not useful for serological diagnostic purposes (for a review of the early literature, see reference 37), two observations accounted for by the role of the O-PS as both a key virulence factor and a m...

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Genotipos de aislados de campo de Brucella abortus de distintas regiones geográficas de Chile

Cited by 5 publications

References 20 publications

Characterization of Genomic Island 3 and Genetic Variability of Chilean Field Strains of Brucella abortus

Characterization of Genomic Island 3 and Genetic Variability of Chilean Field Strains of Brucella abortus

Genomic Island 2 Is an Unstable Genetic Element Contributing toBrucellaLipopolysaccharide Spontaneous Smooth-to-Rough Dissociation

Spontaneous Excision of the O-Polysaccharide wbkA Glycosyltranferase Gene Is a Cause of Dissociation of Smooth to Rough Brucella Colonies

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