PhD highlight: Sónia Leitão

Title: Studies of Streptococcus pneumoniae carriage in the post-vaccination era among two risk groups: children and the elderly.

Abstract: Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. S. pneumoniae colonizes asymptomatically the human nasopharynx. Colonization not only precedes disease but is also important for transmission. Colonization studies are therefore important to monitor changes in pneumococcal epidemiology that may result from the use of antibiotics or vaccines. We have conducted four studies aimed to gain insights on the pneumococcal epidemiology of carriage among the two age groups where the incidence of pneumococcal disease is highest: young children (up to six years old), and adults older than 60 years. We have found that: (i) the recently discovered serotype 6C has been circulating in Portugal since at least 1996, it is genetically diverse, and has become multidrug resistant in recent years (Nunes et al., 2009); (ii) the patterns of pneumococcal colonization among healthy children living in two distinct urban areas – Oeiras and Coimbra – are similar (Rodrigues et al., 2009); (iii) in the era of widespread use of conjugate vaccines, antibiotic consumption remains a main cause for the maintenance of antimicrobial resistance rates among pneumococci; (iv) the rates of pneumococcal colonization in the elderly are low and the serotype and genotype diversity is high; and (v) the recently developed MLVA (multiple-locus variable tandem repeat analysis) has been validated and is a promising genotyping method for S. pneumoniae (Elberse et al., 2011).


Acknowledgments: This study was partially supported by projects PREVIS (LSHM-CT-2003-503413), and GRACE (LSHM-CT-2005-518226) from the European Commission; PTDC/BIA-BEC/098289/2008, PTDC/SAU-ESA/65048/2006, PEst-OE/EQB/LA0004/2011, and PhD grant SFRH/BD/40706/2007 from Fundação para a Ciência e Tecnologia, Portugal; and an unrestricted, investigator-initiated research grant from Laboratórios Pfizer, Portugal.


Nunes S, Valente C, Sá-Leão R, de Lencastre H. (2009), Temporal trends and molecular epidemiology of recently described serotype 6C of Streptococcus pneumoniae. J. Clin. Microbiol. 47: 472-474.

Rodrigues F, Nunes S, Sá-Leão R, Gonçalves G, Lemos L, de Lencastre H.(2009), Streptococcus pneumoniae nasopharyngeal carriage in children attending day-care centers in the central region of Portugal, in the era of 7-valent pneumococcal conjugate vaccine. Microb. Drug Resist. 15: 269-277.

Elberse KE, Nunes S, Sá-Leão R, van der Heide HG, Schouls LM. (2011),Multiple-locus variable number tandem repeat analysis for Streptococcus pneumoniae: comparison with PFGE and MLST. PLoS ONE 6:19668.

PhD Degree: Biology/Molecular Biology; Year of conlusion: 2012

Institution: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Supervision(s): Raquel Sá-Leão and Hermínia de Lencastre

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