Virulence of killer bacteria “like roll of a dice”

Pneumococcus plays dice

An international team of scientists has uncovered a genetic switch that turns the global killer bacteria,Streptococcus pneumoniae, from a seemingly benign form into a lethal one.

The researchers say this discovery could pave the way to improved vaccines to fight thisleading cause of serious illness and death worldwide − from diseases such as pneumonia, septicaemia and meningitis.

Published today in the prestigious journalNature Communications, the research is a collaboration of researchers from Griffith University and the University of Adelaide in Australia, and the University of Leicester (UK) and Pacific Biosciences (USA).

The team has, for the first time, shown howStreptococcus pneumoniaeuses a six-way genetic switch to randomly change between six alternative states that determine its virulence.

Professor Michael Jennings, Deputy Director of the Institute for Glycomics at Griffith University,says this study represents a significant breakthrough in the fight against these infectious diseases.

“Each time the bacteria divide it is like throwing a dice,” Professor Jennings says. “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.”

Professor James Paton, Director of the University of Adelaide’s Research Centre for Infectious Diseases and NHMRC Senior Principal Research Fellow, says the stakes are high, with each ‘roll of the dice’ having a major impact on survival of both the bacteria and the person infected.

Streptococcus pneumoniaekills somebody every ten seconds, but paradoxically can also live harmlessly in the upper respiratory tract of healthy people,” Professor Paton says.

“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.”