COMMON bugs may play an important role in some cases of unexplained cot death, according to a study.
Postmortems of hundreds of babies who had died suddenly revealed many were harbouring potentially harmful bacteria.
High levels of two microbes, Staphylococcus aureus and Escherichia coli, were obtained from infants who died for no apparent reason.
Both bugs, categorised as “group 2 pathogens”, can kill without showing any signs of damage to the body.
But scientists still do not know if the bacteria are directly responsible for the unexplained deaths.
One possibility is that the toxins they release are proving fatal. Another is that other factors linked to cot death, such as overheating or passive smoking, might be promoting bacterial growth.
No cause is found for most cases of cot death or SUDI (sudden unexpected death in infancy).
The research, published in The Lancet medical journal, includes a systematic review of infant postmortems carried out at London’s Great Ormond Street Hospital for Children between 1996 and 2005.
The scientists identified 546 infants between seven days and one year old who died suddenly and unexpectedly.
Swab and blood samples were taken from 470 of the dead babies, yielding a total of 2,871 separate bacterial cultures.
Of these deaths, 365 were unexplained, 53 were due to non-infectious causes such as heart defects, and 52 had signs of tissue damage suggesting a bacterial infection.
Surprisingly, the samples revealed about half the unexplained group carried bacteria which could trigger disease.
Almost as many babies whose death could not be explained had the bugs as infants suspected of having died from infection.
Professor Nigel Klein, one of the researchers, said: “There are two possible explanations. One is that these bacteria genuinely play some role in the process of sudden infant death. The second is that there may be a [complication] due to another risk factor. For instance, being in a smoking environment may encourage the growth of bacteria, and so might having a slightly higher temperature.
“A small proportion of these unexplained deaths may be directly caused by infection. It’s possible that in other cases the increased growth of bacteria could be due to other reasons.
“Further studies will show any role bacteria play, but we can’t draw any conclusions yet.”
In an accompanying article, two experts from the Royal Infirmary in Lancaster suggest bacteria are directly responsible for the deaths.
Dr James Morris and Dr Linda Harrison wrote: “If bacteria have a role, this points to direct action of bacterial toxins on cardio- respiratory 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.”
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