Whole Genome Sequencing Reveals Insight into Pneumococcal Disease Causes

Whole Genome Sequencing Reveals Insight into Pneumococcal Disease Causes

A new study published by a research team from the HSPH (Harvard School of Public Health), in the United States, in collaboration with WTSI (Wellcome Trust Sanger Institute), in the United Kingdom, reveals the first genome sequencing technology capable of tracking the various changes that occur in the bacterial population after a vaccine injection. The research team followed changes that occur in the pneumococcal bacteria family after the injection of a vaccine called “Prevnar”. The vaccine is currently related to a substantial reduction in pneumococcal diseases across the United States. The current study shows that this genome sequencing technology can be used to monitor the effects of various vaccines against different populations of bacteria, thus evaluating their effectiveness. The study was published yesterday, the 5th of May, in the online journal Nature Genetics.

Streptococcus Pneumoniae

“This gives an unprecedented insight into the bacteria living and transmitting among us”, noted the co-author of the study, associate professor William Hanage. He added that the technology allowed them to thoroughly investigate the bacteria populations, helping them understand the mechanisms that allow these bacteria to survive and continue to proliferate even when the compounds of a vaccine are present. The cause of pneumococcal disease is known as Streptococcus pneumoniae, a bacteria present in the superior respiratory system (throat & nose) of most people. The main pathways of transmission between infected patients include sneezing and coughing. Penumococal disease can lead to meningitis, pneumonia and several other respiratory illnesses, however, the pathogenesis of the disease isn’t yet completely understood.

The research team, led by associate professor Hanage, professor Lipsitch, from HSPH, and senior scientist Stephen Bentley, from WTSI, was aiming to understand the response of bacteria to vaccination. The technology used by researchers, called whole genome sequencing, can reveal the entire DNA coding of each bacterial strain. For the study, more than 616 samples of pneumococci were used. According to the researchers, the vaccine is responsible for the destruction of different parts of the bacteria, however, those parts are replaced by pre-existing bacteria types. This translates into a new family of bacteria, very similar to the original family, with only a few genes being affected by the vaccine.

Researchers affirm that these genetic modifications suffered by the bacterial DNA are responsible for the decreasing rates of the disease occurrence. “The widespread use of whole genome sequencing will allow better surveillance of bacterial populations and improve understanding of their evolution”, said professor Lipsitch. He also noted that during the study, the research team managed to identify the genes that are associated to the bacteria found in children at different ages. Stephen Bentley concludes that in the near future, researchers will be able to monitor the evolution of bacterial DNA in real-time.