Epidemiologia molecular de linhagens invasivas de Corynebacterium diphtheriae utilizando o método MLST

• Ano de defesa: 2010
• Autor(a) principal: Sarah Carolina Zanetti e Viguetti
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Genética; Genetica molecular; Biologia molecular; Endocardite bacteriana; Corynebacterium diphtheriae
• Link de acesso: http://hdl.handle.net/1843/BUOS-8W2JKK

Diphtheria is a reemerging disease worldwide. The classic form of the infection, caused by the bacterium Corynebacterium diphtheriae, primarily affects the upper respiratory tract. However, there are some strains of this bacterium that can cause invasive infections such as endocarditis. In Brazil, strains of C. diphtheriae causing this type of infection have been isolated in recent years. These strains were able to infect vaccinated and non-vaccinated individuals. The main distinguishing features of the invasive strains were mostly the ability to ferment sucrose and the non-toxigenic profile. The mechanisms leading to the invasive phenotype are poorly understood; this demonstrates the need for genetic studies of this subpopulation of C. diphtheriae. The aim of this study was to perform a molecular epidemiological analysis of the invasive C. diphtheriae strains isolated in Brazil, using the Multilocus Sequence Typing (MLST) method. A standardized MLST scheme for typing this bacterium was used, composed of seven housekeeping genes: atpA, dnaE, dnaK, fusA, leuA, odha, e rpoB. Type strains of C. diphtheriae were used as controls. The results obtained were compared with MLST profiles of strains isolated in different countries, which are accessible in the public database PubMLST. The profiles obtained for the invasive strains were divided into three clonal complexes by eBURST program. The strains were considered to be of the same clonal complex when at least six of the seven alleles studied in the MLST were shared. The Brazilian strains of biotype gravis were grouped into clonal complexes with strains from Europe, indicating a worldwide circulation of clones of this biotype and some genetic stability. Moreover, invasive strains of biotype mitis had a higher genetic diversity and an apparently associated with movement within South America. Analyzes suggest that high genetic diversity found among the invasive strains is due to a high recombinogenic potential of the isolates.