Pneumonia, meningitis evolving to evade vaccines

A recent study by French researchers has shown how the bacteria that cause childhood pneumonia and meningitis have evolved to evade vaccines by switching portions of their genes with other bacteria.

The research, published in the journal Nature Genetics, proves that these life-threatening pathogens are capable of evolving rapidly and developing genetic decoys that serve to disguise them from even the most powerful drugs, according to

Vaccines designed to protect against pneumococcal infections recognize the polysaccharides on the outer surface of a bacterium cell.

In 2000, American scientists developed a vaccine that targeted seven different kinds of the approximately 90 different polysaccharide serotypes. Initially, the vaccine worked well, but, over time, its effectiveness waned. A team led by University of Oxford researcher Rory Bowden wanted to find out how this process occurred.

Bowden found that the pathogen switched genetic material with other bacteria, but predominantly for the part of the genome responsible for making the cell coating, which is the area targeted by the vaccine.

"Imagine that each strain of the pneumoccoccus bacteria is a class of schoolchildren all wearing the school uniform," Dr. Bowden said, reports. "If a boy steals from the corner shop, a policeman - the vaccine - can easily identify which school he belongs to by his uniform. But if the boy swaps his sweater with a friend from another school, the policeman will no longer know where to look and the thief, like the bacteria, will escape."

The research team also found that the bacteria were able to switch multiple portions of their genome at the same time, meaning resistance can develop more quickly than originally thought.

"This is of particular concern, as recombination involving multiple fragments of DNA allows rapid and simultaneous exchange of key regions of the genome within the bug, potentially allowing it to quickly develop antibiotic resistance," the researchers said, reports.