Massive shift in the pneumococcal nasopharyngeal flora after the 7-valent conjugate vaccine: epidemiological studies and testing pathogenic potential in animal models

Dissertation presented to obtain the PhD degree in Biology/Molecular Biology by Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica

Although it exists mostly as a commensal bacterium colonizing the human nasopharynx, particularly in children, the Gram-positive bacterium Streptococcus pneumoniae, is also a major human pathogen that can cause a wide range of diseases, which include otitis media, sinusitis, pneumonia, and such life-threatening afflictions as bloodstream infection and meningitis. Created to protect children against pneumococcal disease, the 7-valent pneumococcal conjugate vaccine (PCV7) showed high efficacy in preventing disease caused by the serotypes included in the vaccine, the so-called vaccine types (VTs). Since colonization is an essential first step to develop pneumococcal disease, it is of importance to investigate the effect of this vaccine on the degree of colonization, on changes in the composition of the nasopharyngeal flora and the virulence potential of the non vaccine type (NVT) strains.(...)

Financial support from Fundação para a Ciência e a Tecnologia, Portugal through grant SFRH/BD/30103/2006 awarded to Nelson Frazão.