Issue 10 - 7 November 2011 enews home

PhD research turns up heat on complex killer

By Leanne Coleman

Dr Christabelle Darcy

CDU PhD graduand Christabelle Darcy hopes to find more treatments to help in the fight against the infection
Research by Charles Darwin University PhD graduate Christabelle Darcy could help to improve treatment of the leading cause of death in intensive care units.

Dr Darcy, who undertook her PhD through the Menzies School of Health Research, said that in Australia severe sepsis has a mortality rate of between 20 and 30 per cent, with the Northern Territory recording the highest incidence of the infection in Australia. The Indigenous population was at greatest risk.

She said that although treatments were already available for sepsis, the high mortality rates implored researchers to find more treatments to help in the fight against the infection.

"Sepsis develops when the body is unable to fight an infection effectively and can be caused by a range of organisms," Dr Darcy said. "What makes research into sepsis so complex is that there are many types of bacteria, fungi or viruses that cause it."

To help find new treatments she needed to understand how sepsis affected the body and why people died of it. It was two amino acids called arginine and tryptophan that held a vital clue and the key to unlocking a possible new treatment.

"We knew that sepsis affected the immune system and blood vessels in the body, but we weren't sure how. Arginine and tryptophan help to regulate the body's immune response and blood circulation. If these amino acids helped to regulate the body's immune response they may help lead us to a new treatment."

As part of a collaboration between the Menzies' Global Health team and the Royal Darwin Hospital Intensive Care Unit, Dr Darcy measured amino acid concentrations and tested immune cell function in blood cells, discovering that these amino acids could also be broken down into harmful toxic products.

"We found that a higher rate of breakdown of these amino acids into toxic products led to the dysfunctional immune response and impaired blood circulation found in sepsis," she said. "Patients with severe sepsis had the lowest concentrations of important amino acids and the highest concentrations of toxic breakdown products."

Her supervisor at Menzies, immunologist Dr Tonia Woodberry, agreed that Dr Darcy's work may have important implications in the fight against sepsis. "The next step in this research is to find a way to slow the breakdown of these important amino acids and to restore immune cell function to improve the treatment of sepsis in the future to help save lives," Dr Woodberry said.

Dr Darcy received her PhD at CDU's October graduation ceremony at the Darwin Convention Centre.