Pneumonia mapped in largest genomic survey

Researchers have mapped the most common bacterial cause of pneumonia around the world and revealed how these bacteria evolve in response to vaccination. Scientists from the Wellcome Sanger Institute, Emory University (Atlanta, USA), and the U.S. Centers for Disease Control and Prevention carried out a global genomic survey of Streptococcus pneumoniae, discovering 621 strains across more than fifty countries.

The research reveals which strains of S. pneumoniae (also known as the pneumococcus) are circulating around the world and explains why pneumococcal pneumonia rates are still high despite the existing vaccines. Funded by a grant from the Bill & Melinda Gates Foundation, this work will help predict which strains will be important for new pneumococcal vaccines, and shows that ongoing global genomic surveillance is vital.

Pneumonia is an infection of the lungs that is responsible for the deaths of hundreds of thousands of people a year globally and is the single largest infectious cause of death of children under 5 years old worldwide. Streptococcus pneumoniae is the most common cause of bacterial pneumonia. Healthy people often carry these bacteria without becoming ill, but they can cause fatal infection, especially in young children and some adults.

Samples were collected both before and after PCV introduction, and the DNA sequences and health data were compared. This makes it possible to determine changes in the bacteria that could affect how well the vaccine protects against the pneumococcus, and whether new strains are emerging that would impact disease severity and ease of treatment.

The researchers discovered 621 genetic strains globally, each associated with one or more coat types. They also saw that the levels of non-vaccine type bacteria rose after the introduction of PCV, showing how bacteria evolve in response to the vaccine.

The pneumococcus can cause disease in other areas of the body too, for example infecting the brain or blood, causing meningitis or bloodstream infections, which can all lead to sepsis. Infant vaccination with PCV protects against these pneumococcal infections too. By reducing the transmission of S. pneumoniae between children, PCV also reduces the number of adult infections through herd immunity.

See:

Stephanie W Lo, Rebecca A Gladstone, Andries J van Tonder et al.  Pneumococcal lineages associated with serotype replacement and antibiotic resistance in childhood invasive pneumococcal disease in the post-PCV13 era: an international whole-genome sequencing study. The Lancet Infectious Diseases, 2019; DOI: 10.1016/S1473-3099(19)30297-X

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology