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:
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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