Sudden infant death syndrome (SIDS) and the toxic gas hypothesis: microbiological studies of cot mattresses.

1. Fifty infants' mattresses were studied to investigate the occurrence of viable fungal and bacterial propagules, with particular reference to Scopulariopsis brevicaulis which had been suggested to be implicated in SIDS cases. A total of 19 SIDS cases mattresses, 1 non-SIDS death, 20 used controls, and 10 new unused controls were examined. 2. Differences were found between SIDS and used controls in the variety of fungal species isolated and the numbers isolated from fillings; bacterial numbers were similar. 3. S. brevicaulis was isolated from only four mattresses, three of which were SIDS cases. It was not found in most of those on which death had occurred. 4. A number of potentially pathogenic or allergenic fungi, including Aspergillus fumigatus, were isolated more frequently from SIDS cases mattresses than new or used controls. 5. Scanning electron microscopy of mattress covers and fillings showed microbial 'biofilms' in the head areas of all SIDS cases examined. This was not seen on other samples. 6. The limited number of mattresses studied and the use of unmatched controls precludes the drawing of any general conclusions as to the significance of the biofilms or other fungi isolated. 7. Reports of the existence of a dimorphism in general growth forms of S. brevicaulis were investigated by growing and transferring authentic strains between a variety of growth media. 8. No 'slimy' state of this fungus was observed and dimorphism was not confirmed.