S. pneumoniae usually lives harmlessly in the air passages and in the first year of life most people are likely to have 'carried' at least one strain. It is passed from person to person by sneezing and other aerosols. However, it occasionally passes from the airways to invade other tissues. This can lead to any one of a range of diseases including meningitis and infections of the sinuses, ear, lungs and blood. Why it switches to become invasive is not known.
The team sequenced all genes required to make all 90 forms of the capsule (more than 1,800,000 letters of genetic code), determined their function and studied their evolution. The work gives the most complete understanding of capsule production in any bacterial species.
The new vaccine will protect children from many of the most common serotypes but monitoring is needed to check whether other serotypes start to cause some disease. It is known that pneumococci can switch their capsular polysaccharide and so, if an invasive strain changes its coat to a form not recognised by the vaccine, it might start to become more prevalent and cause disease.
The catalogue of capsules from all known strains will help in the development of new techniques for monitoring changes in capsule type so researchers can look out for such capsule switching.
"The new vaccine that will be given to UK children is very effective at protecting against serious pneumococcal disease, but it does not protect against disease caused by the rarer serotypes," said Brian Spratt, Professor of Microbiology at Imperial College and a co-author of the study. "The catalogue of capsular genes will help us develop better met
Source:Public Library of Science