Descripción Isla Genomica 3

Characterization of Genomic Island 3 and Genetic Variability of Chilean Field Strains of Brucella abortus
Sandra Céspedes, Paulina Salgado, Patricio Valenzuela, Roberto Vidal and Angel A. Oñate J. Clin. Microbiol. 2011, 49(7):2461. DOI: 10.1128/JCM.01176-10. Published Ahead of Print 4 May 2011.

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JOURNAL OF CLINICAL MICROBIOLOGY, July 2011, p. 2461–2469 0095-1137/11/$12.00 doi:10.1128/JCM.01176-10 Copyright © 2011, American Society for Microbiology. All Rights Reserved.

Vol. 49, No. 7

Characterization of Genomic Island 3 and Genetic Variability of Chilean FieldStrains of Brucella abortus
Sandra Cespedes,1 Paulina Salgado,1 Patricio Valenzuela,2 Roberto Vidal,2* ´ and Angel A. Onate1* ˜
Molecular Immunology Laboratory, Department of Microbiology, Faculty of Biological Sciences, Universidad de Concepcion, ´ Concepcion,1 and Faculty of Medicine, Universidad de Chile, Santiago,2 Chile ´
Received 10 June 2010/Returned for modification 29 September2010/Accepted 18 April 2011

Downloaded from http://jcm.asm.org/ on July 5, 2012 by UNIVERSIDAD DE CONCEPCION

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) isshared 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 ofthe 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 analysisby 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 inanimals 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...