AUSTRALIAN researchers have discovered the presence of a bacterial protein in nearly 70 cases of Sudden Infant Death Syndrome (SIDS).

In what is described as the most significant discovery yet into the syndrome, doctors at the Adelaide Women's and Children's Hospital have found curlin proteins in all 68 infants involved in their research, who have died of SIDS.

In healthy bodies, no curlin protein existed.

Separate research had shown that curlin proteins could cause inflammation, low blood pressure and shock, said Dr Paul Goldwater, the hospital's acting microbiology and infectious diseases director.

Thus, he said, the proteins could have caused the babies to die of septic shock - a finding that was at odds with the common but fallacious idea that SIDS babies died of asphyxiation.

"This is the most significant thing we've found," Dr Goldwater told AAP.

"None of the previously known toxins have been associated with SIDS.

"But curlin is a relatively recently discovered bacterial protein and it seems to fit the bill (for causing SIDS)."

Dr Goldwater said post mortems of babies showed their lungs had become heavy and wet and their blood failed to clot - common reactions to curlin proteins.

He said the proteins were derived from e.coli bacteria, which could have been picked up from food or contact with unhygienic surfaces.

The bacteria could also be ingested from mattresses and sheets, Dr Goldwater said, which may explain why babies put to sleep on their backs were not as susceptible to SIDS.

The bacteria could also be transferred by parents sleeping with their infants, he said.

Dr Goldwater said he would conduct further research in an attempt to prove his preliminary findings.

He said he hoped a vaccine against curlin proteins would be available within 10 years.

In the meantime, however, Dr Goldwater said his findings could provide a important explanation for parents who had lost children to SIDS.

"There's hardly a SIDS marriage that survives. There's an enormous amount of guilt that's involved in the emotional response to your own baby's death and as a consequence most SIDS parents break up," he said.

"That doesn't occur if we can tell a (parent their) child has died of meningitis or some other known cause - parents will accept that.

"But to die of a disease that's a total enigma and no-one has excluded parents as part of the chain of blame, then parents are going to feel guilty."

AAP