Streptococcus pneumoniae is an opportunistic bacteria that is part of the natural bacterial flora of the respiratory tract. Even so, it is also responsible for a wide variety of clinical conditions and infections, which when severe fall under the umbrella of invasive pneumococcal diseases (IPD). Pneumonia and meningitis are some of the most severe manifestations of IPD, and can be fatal. Therefore, it is no coincidence that S. pneumoniae continues to be the leading cause of mortality in respiratory diseases worldwide, which makes it a major public health problem.

That is why biomedical research in this field is essential. A recent study led by researchers from the Bellvitge University Hospital (HUB), the Bellvitge Biomedical Research Institute (IDIBELL) and the respiratory diseases area of the CIBER (CIBERes) and published in the Journal of Infection and Public Health has shed light on the genetic evolution of pneumococcus and its impact on invasive pneumococcal disease in adults. This work highlights the resilience of some genetic variants included in the PCV13 vaccine, which has been used in the prevention of IPD in children. The results obtained emphasizes the need for vaccination of the adult population to prevent IPD in these age groups, especially in those over 65 years of age, as well as the surveillance of emerging serotypes of Streptococcus pneumoniae not included in current vaccines.

The study, carried out between 2019 and 2021, is part of a collaborative research that is part of the CIBERes Pneumonia Line and has been funded by the Carlos III Health Institute (ISCIII). For more than 12 years, hospitals from different regions of Spain (Hospital General Universitario Gregorio Marañón [Madrid]; University Hospital of Donostia [Basque Country]; the Vall d’Hebron Hospital, Consorci Corporació Sanitària Parc Taulí, Germans Trias i Pujol University Hospital and Bellvitge University Hospital [Catalonia]) and the Pneumococcal Reference Laboratory of the ISCIII. This study has collected more than 650 cases of IPD, with pneumonia being the focus of pneumococcal infection. In addition, the antibiotic resistance and genetic characterization of the strains responsible for the disease have been studied by whole genome sequencing. The results obtained underline the ability of pneumococcus to evolve and adapt, which highlights the need to maintain constant vigilance and update of vaccination strategies.

Genetic characterization and emergence of new serotypes

Currently, more than 100 genetic variants of S. pneumoniae, known as serotypes, have been described, which present differences in terms of invasion capacity and associated mortality. Over the years, it has been seen how vaccination has caused changes in the epidemiology of pneumococcus and its serotypes, varying the presence of these.

Now, this study has identified new changes, pointing out the persistence of some serotypes included in the PCV13 vaccine, such as serotype 3, and the emergence of new lineages, as in the case of serotype 4. In addition, it underlines the increase in serotypes not included in the PCV13 vaccine, such as serotype 8. These new emerging lineages are contributing to the increase in IPD, reaching levels that are close to those of the pre-pandemic era, and thus highlighting the importance of carrying out a genetic characterization to know the characteristics of the lineages with the greatest capacity for dissemination.

The Impact of Childhood Vaccination on Adult IPD

Despite advances in childhood vaccination and the beneficial impact it has had on protection in adults, the burden of IPD in adults remains significant. In particular, serotype 3 remains one of the main causes of severe disease in adults. For this reason, it would be necessary to increase vaccination rates in adults, especially after the introduction of the new vaccines with greater coverage, primarily in people over 65 years of age, immunocompromised and those with comorbidities, to directly protect the most vulnerable population groups.

In this way, the study reaffirms the importance of constant surveillance and updating of pneumococcal vaccines, especially for the adult population. The genetic characterization of serotypes and the monitoring of antibiotic resistance are essential to be alert to the adaptive evolution of this important pathogen.

The Bellvitge Biomedical Research Institute (IDIBELL) is a biomedical research centre created in 2004. It is participated by the Bellvitge University Hospital and the Viladecans Hospital of the Catalan Institute of Health, the Catalan Institute of Oncology, the University of Barcelona and the City Council of L’Hospitalet de Llobregat.

IDIBELL is a member of the Campus of International Excellence of the University of Barcelona HUBc and is part of the CERCA institution of the Generalitat de Catalunya. In 2009 it became one of the first five Spanish research centres accredited as a health research institute by the Carlos III Health Institute. In addition, it is part of the “HR Excellence in Research” program of the European Union and is a member of EATRIS and REGIC. Since 2018, IDIBELL has been an Accredited Centre of the AECC Scientific Foundation (FCAECC).