The high levels of Staphylococcus aureus and Escherichia coli bacteria found during post-mortems in otherwise unexplained cases of sudden unexpected death in infancy (SUDI) suggest these bacteria could be associated with this condition. These are the conclusions of authors of an Article published in this week’s edition of The Lancet.
Sudden infant death (also known as cot death) remains one of the most common presentations of post-neonatal infant death in the UK, with many theories about its cause. SUDI is defined as the sudden and unexpected death of an infant aged less than one year. There are various cases than can be classed as SUDI, including those in which a careful review of the death scene and a meticulous post-mortem examination will disclose a cause of death, and those that remain unexplained even after such examination.
For many decades, underlying infection has been suggested to be a possible important mechanism in SUDI. Furthermore, the appropriate interpretation of microbiological findings has major medicolegal importance, as evidenced by recent UK high court reviews of child death investigations. Neil Sebire, Nigel Klein and Marian Malone, Great Ormond Street Hospital for Children, London, UK and colleagues reviewed autopsy results to determine whether infection was a cause of SUDI.
The researchers did a systematic retrospective case review of autopsies done at Great Ormond Street Hospital between 1996 and 2005, of 546 infants (aged 7-365 days) who died suddenly and unexpectedly. Cases of SUDI were categorised as unexplained, explained with evidence of bacterial infection, or explained by non-infective causes. The bacterial samples gathered at autopsy were classified as non-pathogens, group 1 pathogens (organisms usually associated with an identifiable focus of infection), or group 2 pathogens (organisms known to cause septicaemia without an obvious focus of infection, eg, S aureus, E coli).
Of the 546 SUDI cases, 39 autopsies were excluded due to viral or bacterial infection contracted during the resuscitation process. Bacterial samples were taken in 470 of the remaining 507 cases, yielding a total of 2871 separate isolates from positive cultures. In the deaths explained by bacterial infection group, 78 of 232 isolates obtained (24%) were group 2 pathogens. In the unexplained death group, 440 of 2306 (19%) isolates were group 2 pathogens, while in the deaths from non-infective causes group, the proportion of group 2 pathogens was 11% (27 out of 243). Furthermore, significantly more cultures from infants whose deaths were unexplained contained S aureus (262/1628, 16%) or E coli (93/1628, 6%), than did those from infants whose deaths were of non-infective cause (S aureus 19/211, 9%; E coli 3/211, 1%). These differences suggest that infection with these bacteria could be associated with unexplained cases of SUDI.
Significantly, 11% of isolates from the non-infective group were group 2 pathogens. Therefore positive cultures alone may be insufficient to implicate infection as the cause of death in any individual case.
The authors conclude: “We found that significantly more organisms that were potentially pathogenic were isolated from infants whose sudden, unexpected death could not be explained than from infants whose death was of non-infective cause. Although the reasons for this are unclear, our findings suggest that microbes or microbial products could be related to the pathogenesis of a proportion of unexplained SUDI. We must now investigate the pathophysiological mechanism involved in these cases.”
In an accompanying Comment, Dr James Morris and Dr Linda Harrison, Royal Infirmary, Lancaster, UK, say: “Recent evidence indicates that death in explained SUDI is often rapid, with transition from being well to death in less than one hour in many cases. If bacteria have a role, this points to direct action of bacterial toxins on cardiorespiratory or neural control. The new science of proteomics offers techniques to recognise bacterial protein products in human body fluids, and this is the obvious next step in investigating sudden infant death.”
For Neil Sebire, Nigel Klein and Marian Malone, Great Ormond Street Hospital for Children, London, UK, please contact Communications, Great Ormond Street Hospital T) +44 (0) 20 7239 3119 E) coxs@gosh.nhs.uk / BarbeJ@gosh.nhs.uk
Dr James Morris, Royal Infirmary, Lancaster, UK T) +44 (0) 1524 516013 E) Jim.A.Morris@rli.mbht.nhs.uk
http://multimedia.thelancet.com/pdf/press/suddeninfantdeath.pdf
Journal
The Lancet