Common bugs linked to cot deaths, say scientists

Scientists have discovered that common bugs could play an important role in some cases of unexplained cot death.

Post-mortem examinations carried out on hundreds of babies who had died suddenly revealed many were harbouring potentially harmful bacteria.

It is thought toxins from the bacteria may affect nerve signals or breathing.

But the research team from Great Ormond Street hospital said parents should still follow safety guidelines such as putting babies to sleep on their backs and not smoking around them.

There are about 250 cases of sudden infant death in the UK each year, many of which are never fully explained. High-profile cases include TV presenter Anne Diamond whose baby son Sebastian died suddenly in 1991.

While the research, published in The Lancet medical journal, suggests bacterial infection may be a link, scientists say they do not know if it is directly responsible. 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 promote bacterial growth.

Researchers carried out a review of infant post-mortem examinations performed at Great Ormond Street between 1996 and 2005. They identified 546 infants aged between seven days and one year 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.

The samples also revealed about half the unexplained group carried bacteria which in life could trigger disease.

High levels of two microbes, Staphylococcus aureus and Escherichia Coli, were obtained. Both these bugs, categorised as "group 2 pathogens", can kill without showing any signs of damage to the body. Many of the bacteria were taken from the lungs and spleen.

Professor Nigel Klein, one of the researchers, said: "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." 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: "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."