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Lethal Bacteria’s Virulence a “Roll of the Dice”

An international team of scientists has uncovered a genetic switch that transforms Streptococcus pneumoniae bacteria from a seemingly benign form to a global killer. The discovery, published in Nature Communications, could lead to improved vaccines to fight the microbe, which causes serious illness and death worldwide from diseases such as pneumonia, septicaemia and meningitis.

Researchers from Griffith University, The University of Adelaide and international colleagues found that Streptococcus pneumoniae uses a six-way genetic switch to randomly change between six alternative states that determine its virulence.

“Each time the bacteria divide it is like throwing a dice,” said Prof Michael Jennings of Griffith University. “Any one of six different cell types can appear. Understanding the role this six-way switch plays in pneumococcal infections is key to how we respond to the disease, and is crucial in the development of new and improved vaccines.”

Prof James Paton of Adelaide University said that each “roll of the dice” has a major impact on the survival of both the bacteria and the person infected. “Streptococcus pneumoniae kills somebody every 10 seconds, but paradoxically can also live harmlessly in the upper respiratory tract of healthy people,” he said.

“Some of these six alternative states of the bacteria favour harmless colonisation or spread from person to person, while others promote invasive, life-threatening disease.”