S. aureus is a common bacteria found on the skin and in the nose and throats of healthy human beings including infants.
It has been reported by Blackwell et al. (2002) that toxins released from Staphylococcus aureus were identified in tissues of 53% of SIDS infants in five different countries.
Although toxins were isolated in these infants it is not known whether they contributed to their deaths.
A study by Molony et al. (1999) found that laying infants on their tummy raises the airway temperature to a level required for S. aureus to produce harmful toxins and postulated that this could explain one reason why infants are more at risk of SIDS in the tummy position.
A recent article by Jenkins and Sherburn (2005) reports that cot mattresses made from polyurethane foam and PVC covers can act as a reservoir for S. aureus even whilst the mattress is in storage.
In a separate study these same researchers found that simulated infant movement can influence the release of bacteria from cot mattress materials.
As it is normal for the airways of infants to contain S. aureus, it is not known how relevant this is.
An earlier study by Sherburn and Jenkins (2004) found that the frequency of isolation of S. aureus from cot mattress (exposed polyurethane foam) was significantly higher than from foams from the integral type i.e. completely covered by polyvinyl chloride, particularly if another child had previously used the mattress. This study also found that the prone sleeping position significantly increased bacterial population of S. aureus.
In 2002, a study by Tappin et al. found an association between use of a used infant mattress and increased risk of SIDS, particularly if the mattress was from another home. Unfortunately this paper did not provide details of the condition of the mattresses used in the study (i.e. if the surface was torn, dirty, no longer firm etc).
Conclusion
S. aureus is a common organism that normally lives on the skin and in the nose and throats of healthy infants. It is therefore not surprising that S. aureus has been found in the foam of cot mattresses particularly if the foam is exposed and previously used by other infants.
Although there is some evidence to show that there is a higher incidence of SIDS on some second hand mattresses, it is not known what condition these mattresses were in or what position these babies slept in. There is no evidence to show that the risk of SIDS increases for babies who sleep on their back and on a firm, clean, well fitting mattress that is in good condition.
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