Resumo

Background: Bordetella pertussis pertussis is responsible for the pertussis disease, commonly called whooping cough. Acellular vaccines are usually composed by surface proteins, such as pertussis toxin (ptx), pertactin (prn), and fimbrias (fim2 and fim3).Pertussis ressurgence and clonal expansion of strains, presenting polymorphisms in genes encoding proteins composing the vaccine, have been observed in countries with high vaccination coverage. Recently, it has been shown that strains carrying a new alelle for the pertussis toxin promoter (ptxP) not only produce more pertussis toxin, but have also an increased expression level of other virulence genes. These strains present better fitness in colonizing the respiratory tract and are able to persist in populations despite vaccination. Moreover, antibiotic resistance phenotypes are also emerging. B. pertussis strains with these profiles have been characterized in several countries and continents. In Brazil, where pertussis outbreaks have been occurring in recent years, there is a lack of information concerning the allelic profile and genetic background of B. pertussis. Objectives: Determination of allelic profile of B. pertussis circulating in Brazil considering housekeeping and protein surface genes. Methodology: B. pertussis isolated in 2008 and 2009 from outbreaks in Rio Grande do Sul and Alagoas were analyzed by MLST based on housekeeping and virulence genes in order to determine their clonal relationship and the allelic profile. We also investigated genes associated with antibiotic resistance. PCR and sequencing were performed to amplicons corresponding to: gyrA, gyrB, parC, parE, rpoB, 23S (antibiotic resitance to quinolones, rifampin and erythromycin); ptxA/S1, prn, fim3 and ptxP (virulence genes) and and adk, fumC, tyrB, icd, pepA, pgm (housekeeping genes). Results and Conclusions: Both MLST approaches, housekeeping and virulence genes, revealed the presence of a unique lineage circulating in both Brazilian regions. This lineage is characterized by the presence of ptxP3 related to high level of pertussis toxin expression, and the allelic profile prn2-ptxA1-fim3B, which is the prevalent among the recent worldwide whooping cough causing strains. No mutations related to emergent antibiotic resistance phenotype were observed in the genes (gyrA, gyrB, parC, parE, rpoB, 23S) analyzed. Current pertussis in Brazil, as well in countries with high vaccination coverage, has been driven by modern B. pertussis strains.