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Raquel Sá-Leão Lab


In our group we are studying how human interventions, such as the use of vaccines and antibiotics, impact on the nasopharyngeal ecosystem, a rich niche frequently inhabited by potentially pathogenic bacteria such as Streptococcus pneumoniae.

Raquel Sá-Leão
Investigador Principal
PhD in 2002 in Biology, ITQB NOVA

Phone (+351) 214469621


Research Interests

The human microbiota consists of all the microbes that live in and on the human body. To improve our understanding of human health and disease, we need to gain a deeper knowledge on the intra- and interspecies bacterial interactions, and host-bacteria interactions that occur in the human body influencing which species and strains persist in it.

In our group we are focusing on the nasopharyngeal ecosystem, a rich niche frequently inhabited by potentially pathogenic bacteria such as Streptococcus pneumoniae (or pneumococcus), Haemophilus influenzae, and Moraxella catarrhalis. Colonization by these bacteria, which is typically asymptomatic, is particularly frequent among young children. Although disease per se is incidental in the lifestyle of these bacteria, the burden of disease caused by them is substantial worldwide.

In recent years, multivalent pneumococcal conjugate vaccines, targeting a limited subset of the circulating pneumococcal capsular types have been introduced in several countries. We are studying how these vaccines, together with antibiotic use, impact on the pneumococcal population and on the nasopharyngeal ecosystem as a whole. Depending on local vaccine coverage, antibiotic use, circulating strains and relationship between competitors, different outcomes in colonization and disease overall may be observed. Our studies are contributing to estimate the medium and long-term public health impact of the use of vaccines and antibiotics.


Group Members

  •  Alexandra Simões, PhD, Project Manager

  •  Ana Cristina Paulo, Post Doc

  •  Carina Valente, Post Doc

  •  Sónia Almeida, Post Doc

  •  Bárbara Ferreira, PhD student

  •  Catarina Candeias, PhD student

  •  João Borralho, PhD student

  •  João Lança, PhD student

  • Sara Handem, PhD student

  • Konil Solanki, Master student


Selected Publications

  1. Paulo AC and R. Sá-Leão. 2022. Evidence for the intermediate disturbance hypothesis and exponential decay in replacement in Streptococcus pneumoniae following use of conjugate vaccines. Sci Rep. Accepted

  2. Valente C, AR Cruz, AO Henriques AO, R. Sá-Leão. 2022 Intra-Species interactions in Streptococcus pneumoniae biofilms. Front. Cell. Infect. Microbiol. 11:803286. doi: 10.3389/fcimb.2021.803286

  3. Simões AS, T Touret, NA Faria, SP Ladeiro, J Costa, S Bispo, M Serrano, C Palos, M Miragaia, RB Leite, R Sá-Leão. 2022. Using whole genome sequencing to investigate a mock-outbreak of carbapenem-resistant Klebsiella pneumoniae in real-time. Acta Med Port. 35(1):36-41. doi 10.20344/amp.15174

  4. Félix S, S Handem, S Nunes, AC Paulo, C Candeias, C Valente, AS Simões, ST Almeida, DA Tavares, A Brito-Avô, H de Lencastre, R. Sá-Leão. 2021. Impact of private use of the 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal carriage among Portuguese children living in urban and rural regions. Vaccine. 39(32):4524-4533. doi: 10.1016/j.vaccine.2021.06.035

  5. Almeida ST, AC Paulo, F Froes, H de Lencastre, R Sá-Leão. 2021. Dynamics of pneumococcal carriage in adults: a new look at an old paradigm. J Infect Dis.  223(9):1590-1600. doi: 10.1093/infdis/jiaa558


Laboratory's Webpage

For further information visit the laboratory's website (soon available)


Microbiologia Molecular de Patogéneos Humanos (PT)

A microbiota humana é constituída por todos os microorganismos que vivem no corpo humano. Estes microorganismos interagem entre si e com o hospedeiro contribuindo para o estado de saúde do indivíduo.
O objectivo principal do nosso grupo é o estudo da microbiologia da nasofaringe, um nicho ecológico que é frequentemente colonizado por bactérias potencialmente patogénicas entre as quais se encontram os pneumococos. Em particular, estamos interessados em compreender de que forma intervenções como o uso de vacinas e antibióticos afetam este ecossistema, a saúde do indivíduo e, em última análise, a saúde pública.


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