A "survivor gene" has been identified that could double carriers' chances of surviving severe infections, according to a report.
The 'survivor gene' may increase infection survival chances
University of Newcastle researchers found patients with a certain variation in mitochondrial DNA - the "powerhouse" of cells - had higher survival rates.
The DNA of 150 intensive care patients was studied, the Lancet reported.
Experts said the finding could lead to screening of patients for the variation and subsequent targeted treatment.
It has long been thought that there may be a connection between the workings of the mitochondria and how the body reacts to fight infections, such as MRSA and pneumonia.
Researchers identified 10 major variants of mtDNA.
Patients from each variant group were monitored and researchers found people with a particular variant - called haplogroup H - were more than twice as likely as those from any of the other groups to survive for six months.
There was no evidence to suggest that people from haplogroup H were any less likely to contract a severe infection in the first instance.
The mtDNA is inherited from the mother and has evolved over tens of thousands of years to produce 10 main variations.
Haplogroup H is the most recent genetic variation to evolve, but is also the most common - 40% of people have it.
Lead researcher Professor Patrick Chinnery, a senior clinical fellow at the Wellcome Trust, said: "In identifying that some patients may be predisposed to survival or death on the intensive care unit is an important development and opens up new avenues to develop novel treatment.
"Those who seem to have less chance of survival may benefit from more aggressive clinical care."
Dr Giles Edwards, of Scottish MRSA Reference Laboratory, said the findings sounded "interesting", but that it had always been expected a genetic variation would play a role in surviving infection.
"To be of use for treating patients, a cheap and easy test to screen for this has to be available early on," he said.