Once in the throat, the bacteria colonise the respiratory tract where
they warm up and produce "supertoxins" that trigger the immune system into
abnormally severe assaults.
When a baby's developing immune system overreacts, the infant can die
of anaphylactic shock, according to an article in New Scientist.
Dr Richard Sherburn, who carried out the study, found the problem
occurred in mattresses which were two-thirds covered by PVC, but the top
section, supporting the baby's head, was covered by a plastic mesh, making
it porous.
After use, these mattresses can be heavily contaminated with bugs, the
dominant species of which is Staphylococcus aureus, a bug often found in
the throats of SIDS babies.
The bacterial levels were 100-fold higher if the baby had vomited
formula, rather than breast milk.
The abundance of S. aureus rose with the number of babies that had used
the mattress.
He said: "My gut instinct is that these bacteria last longer than other
bacteria and have a head start when a second child comes along and uses
the mattress.
"I would say it's safer to get a new mattress for each child, but if
you had one that's completely covered with PVC and it can be cleaned, I
would assume it could be used again."
PVC protection
Mimicking a baby's movement also created clouds of bugs in the air
above a mattress.
Dr Sherburn said: "Four hours after throwing up, there could be 10,000
bacteria in the air, enough to cause infection."
Ironically, the "breathable" part-PVC covered mattresses were
introduced in the 1990s to overcome perceived dangers of mattresses fully
covered with PVC.
The theory, now largely rejected, was that fungi inside the PVC
covering broke down flame retardant chemicals in the plastic and released
toxic vapours that poisoned babies.
However, Dr Sherburn's work is adding weight to other studies
suggesting breathable mattresses actually pose the highest risks.
