Horizontal transfer of pathogenicity islands of a virulence plasmid in Rhododoccus equi-Origin of the virulence-associated gene family-

点击翻译按钮获取中文摘要

Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus that causes suppurative pneumonia and ulcerative enteritis in foals aged 1-3 months. This organism is present in soil and sporadically causes pulmonary abscesses and lymphadenitis in other domestic animals. The discovery of virulence-associated antigens and virulence plasmids has allowed the classification of R. equi. strains and molecular epidemiological studies of virulent R. equi. By the basis of restriction fragment patterns of representative strains of VapA-and VapB-positive R. equi digested by restriction enzymes, we found at least 15 distinct plasmid types in VapA-positive, and 33 types in VapB-positive R. equi. Nucleotide sequencing of the virulence plasmids of ATCC33701(the representative of VapA-positive) and A3(the representative of VapB-positive) revealed the presence of a pathogenicity island : it is characterised by a significantly lower G+C content than the rest of the plasmid, and is flankedby genes similar to transposon resolvases. The present study demonstraed that the determination and analysis of the nucleotide sequences of virulence plasmids provid the information on the diversity of virulence plasmids of R. equi.