A new study published in the Archives of Disease in Childhood suggests that Staphylococcus aureus and other bacterial infections may have been overlooked as possible causes of sudden infant death syndrome (SIDS).

In 2006, a paper written by Morris et al. found that a pure growth of a pathogen in blood or CSF was a potential contributing factor to death for people at all ages. Subsequently, researchers published a retrospective study that provided causal evidence for the role of Staphylococcus aureus and Escherichia coli in sudden unexpected death in infancy (SUDI).

Paul Goldwater (The Women’s and Children’s Hospital and The University of Adelaide, Australia) continued studying the relationship by analyzing post mortem reports three groups of babies:

  • 130 babies who had died of sudden infant death syndrome (SIDS)
  • 32 who had died suddenly as a result of infection (SUDI)
  • 33 who had died of non-infectious cause, such as a car accident

The researcher looked at bacterial isolates from the typically-sterile heart blood, spleen, or cerebrospinal fluid in the SIDS babies and compared observations with samples from the other 65 babies. Goldwater noted that it was rare to find infection at a sterile site in babies who had died of non-infectious causes, and it was common to find infection in the SUDI and SIDS babies. About 20% of SUDI and 10% of SIDS babies at infections at sterile sites.

Studies of the infections revealed that they were caused by the particularly virulent bacteria Staphylococcus aureus – one that is known to produce potentially lethal toxins. Though confirmation of infection at a sterile site in a living person indicates systemic infection, the author maintains that findings in SIDS babies have been considered some form of contamination and usually are dismissed as a cause of death. The relatively high proportion of infants that present S aureus in sterile sites, however, suggests that several of the babies would have perished due to their staphylococcal bacterial infection.

It is highly probably, according to other researchers, that immune responses to bacterial infection and/or toxins create a “chemical storm”, which can overwhelm a baby and lead to sudden death. The author suggests that cases of SIDS where autopsy reports have found S aureus in sterile sites should perhaps be reconsidered for reclassification.

Sterile site infection at autopsy in sudden unexpected deaths in infancy
P N Goldwater
Archives of Disease in Childhood (2008).
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Written by: Peter M Crosta