January 28, 2011
With Sleight of DNA, Pneumonia Bacterium Dodges Vaccines
By SINDYA N. BHANOO

Researchers from seven countries have collaborated to analyze how a single strain of Streptococcus pneumoniae bacteria has morphed over 30 years and spread across the world, in an attempt to overcome the development of antibiotics and vaccines.

The research is the first detailed genetic picture of the evolution of a specific strain of pneumonia, resulting in a family tree of sorts. The researchers analyzed samples from North and South America, Africa and Southeast Asia.

Their findings appear in the current issue of the journal Science.

In looking at more than 240 samples, they found that since 1984, when the strain was first identified in Spain, it has turned over about three-quarters of its genome.

Over time, the bacteria mutated to better resist antibiotics and vaccines. The researchers found that it underwent both recombination, in which the DNA shuffles around, and base substitutions, in which individual nucleic acids in a DNA sequence change.

That means that certain samples they tested are not treatable with existing vaccines, which target certain gene clusters that have now changed.

In the past, genomic sequencing of bacteria was time-consuming and laborious, but new technology has sped up the process, and will perhaps help speed up the development of new vaccines, said Stephen Bentley, a geneticist at the Wellcome Trust Sanger Institute and one of the study’s authors.

“I think this going to be really important going forward,” he said. “We can start to do this kind of analysis routinely; then we will be able to have really valuable information for how to introduce antibiotics and new vaccines.”

He and his colleagues are now studying several other strains of the pneumonia bacteria.

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