Is a single nucleotide mutation is related to the increased ability of Bordetella pertussis clinical isolates to produce biofilms?

ARNAL, L; GRUNERT, T; CATTELAN, N; SERRA, DO; YANTORNO, OM; EHLING-SCHULZ, M

París

Conferencia; Biofilms 5; 2012

Institut National de la Recherche Agronomique

After more than 50 years of vaccine introduction, Bordetella pertussis, the etiological agent of whooping cough, remains a serious public health problem worldwide. Interestingly whooping cough re-emerged in countries with high vaccination rates in the decade of 1990, registering a significant increase of cases in adolescents and adults, with more attenuated symptoms of the disease. Very little is known about colonization and persistence of B. pertussis in humans. However, knowledge of the survival mechanisms of the bacteria in the host is of utmost importance to reduce the risk of transmission and for the development of improved vaccines. Analysis of clinical isolates from infected children in Argentina showed that they produced significantly more biofilm compared to the laboratory strain used for vaccine production. A combinatorial approach, including proteomic as well as metabolic studies and real-time PCR assays, was therefore used to gain the first insights into the mechanisms explaining the different apacities for biofilm production of clinical isolates and the vaccine strain Tohama I. Firsts results showed that for the clinical islotale Bp2723 many known virulence factors regulated by the principal two-component system BvgAS were upregulated in both biofilm and planktonic cultures, these results correlated well with gene expression measurements including all the virulence factors regulated positively by the system. NeverthelessAnyway, the expression level of the proteins BvgA and BvgS did not show significant differences with Tohama I. The Sequence of the BvgS gene was obtained in order to detect any mutation that could be related to the observed phenomena. We found that for Bp2327, a single nucleotide mutation is present in the position 2113 (A→G) generating a K→E mutation in the 705 position in the linker region of the BvgS protein. This aminoacid exchange was also observed for other 6 strains that showed to produce more robust biofilms than the reference strain. In our knowledge this is the first time that a mutation in the BvgS protein is reported to enhance the ability of clinical isolates of Bordetella pertussis to produce biofilms and reinforces the hypothesis that biofilm lifestyle should be considered as a mechanism of persistence in Bordetella pertussis infections.