There is more reason than ever to believe that two common bacteria are part of the cause of sudden infant death syndrome (SIDS), commonly called cot death.
While many factors contributing to the risk for SIDS have been identified, the mechanism of its cause has remained a mystery. A link to bacterial infections was proposed decades ago, but evidence of the bacteria in SIDS victims has remained scarce.
Now, a team of researchers from the has shown that specific bacteria are more prevalent in SIDS babies.
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The team went over the results of autopsies of more than 500 infants who died aged between one week and one year. They then compared the rate of infection by the bacteria Staphylococcus aureus and Escherichia coli in infants whose cause of death was known, and those in SIDS babies.
What they found was that 26% of the autopsies in the explained cases showed infection by the bacteria, whereas in the SIDS cases, the rate of infection was nearly twice that.
Not a diagnostic
鈥淲hat鈥檚 good about this is it鈥檚 a large study at one institution where all the cases were investigated in the same way, so it鈥檚 enabled us to really provide harder evidence,鈥� says Marian Malone, one of the study鈥檚 co-authors.
The prevalence of the bacteria is certainly indicative of a connection with cause of death, but their presence even in explained deaths means that a test for them cannot be used as a diagnostic 鈥� or as evidence for or against other explanations for deaths.
George Haycock, scientific adviser to the UK鈥檚 , warns that there isn鈥檛 just one answer to the SIDS mystery.
鈥淭his is certainly not the cause of SIDS, which is almost certainly multifactorial,鈥� he says. 鈥淓ven in the cases where no cause can be identified, there may be multiple factors operating.鈥�
Toxin theory
The role of the bacteria in the so-called bacterial toxin theory could tie some of those multiple factors together. The idea is that the bacteria grow in the upper respiratory tract of babies, releasing toxins that are the ultimate cause of death.
鈥淚t鈥檚 a theory that would fit the facts,鈥� Malone says. 鈥淲e know that prone sleeping 鈥� sleeping on the front 鈥� can increase the number of pathogenic organisms in the upper airway. We know that if the mother has been smoking during pregnancy, it can alter the immune response [to toxins].鈥�
Even the genetic differences among SIDS babies are related to immune response. The theory, Malone says, could tie a lot of things together.
鈥淚t鈥檚 another piece of evidence fitting in with lots of other evidence that has been gathering, pointing to these bacteria,鈥� says , a pathologist at the Royal Infirmary, Lancaster, UK. 鈥淣one of this is proof positive, but it鈥檚 another important step to understanding what鈥檚 going on.鈥�
Journal reference: , vol 371, p 1848
