Scientists link common bugs to unexplained cot deaths » Communities » 24dash.com

Common bugs may play an important role in some cases of unexplained cot death, a study suggests.

Post-mortems of hundreds of babies who had died suddenly revealed that 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 these bugs, categorised as "group 2 pathogens", can kill without showing any signs of damage to the body.

But scientists still do not know whether or not 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 death of an infant - resulting in great anguish for the parents.

The new research, published in The Lancet medical journal, suggests that bacterial infection may be linked to these unexplained cases in previously unsuspected ways.

Scientists carried out a systematic review of infant post-mortems carried out at London's Great Ormond Street Hospital for Children between 1996 and 2005.

They identified 546 infants between seven days and one year old who had 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 that around half the unexplained group carried bacteria which in life could trigger disease.

Almost as many babies whose death could not be explained had the bugs as infants suspected of having died from infection.

Many of the bacteria were obtained from the lungs and spleen.

Professor Nigel Klein, one of the researchers, said: "Our first thought was 'is this an artefact because of the time or year or age differences?' But we found that couldn't be the reason.

"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 an epiphenominal association 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.

"My guess is that 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.

"We've got an interesting observation here that needs exploring. It's the first stage of an investigation; further studies will show any role bacteria play, but we can't draw any conclusions yet. None of these findings undermine any of the excellent advice given to parents on avoiding sudden infant death."

In an accompanying article, two experts from the Royal Infirmary in Lancaster suggest that bacteria are directly responsible for the deaths.

Dr James Morris and Dr Linda Harrison wrote: "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."

Professor Alan Craft, president of the Royal College of Paediatrics and Child Health, said: "Every year around 250 infants die suddenly and unexpectedly. These are known as SUDI deaths (Sudden unexpected deaths in infancy).

"Some will have a recognised cause but most will remain unexplained. It has long been thought that infection might be a cause of some SUDI but until now it was only if there was evidence of a baby's response to the infection that this was taken to be the cause.

"If bacteria are isolated from a body after death, and there is no evidence of a tissue response, then it has usually been put down as a chance finding.

"This well conducted study provides us with new evidence suggesting that even in the absence of a tissue reaction a bacterium grown at post-mortem may be of significance.

"A possible mechanism would be that the bacterium produces a toxin which contributes to the death of the infant. The bacteria found are ones which are in all of our bodies most of the time and there is nothing that can be done to avoid them."

Professor George Haycock, scientific adviser at the Foundation for the Study of Infant Deaths (FSID), which funded the research, said: "Bacteria can cause death by more than one mechanism.

"The first and most obvious is by causing invasive infection, where the bacteria actually enter the body and cause, for example, septicaemia, meningitis or pneumonia.

"There is also evidence that they can cause death without invading the body, for example by colonising the pharynx (the upper airway) from where toxins produced by the bacteria may enter the bloodstream.

"Several studies, some of them funded by FSID, suggest that small genetic variations in the chemicals (cytokines) that control the inflammatory response to infections and to exposure to toxins may cause some infants to have an exaggerated, possibly overwhelming, inflammatory reaction whereas others might experience little or no disturbance.

"More research funded by FSID is currently being conducted along these lines."