Toxigenic bacteria and sudden infant death syndrome (SIDS): nasopharyngealflora during the first year of life

Many developmental and environmental risk factors for sudden infant death s yndrome (SIDS) are similar to those for susceptibility to respiratory tract infection, and toxigenic bacteria have been implicated in some SIDS cases. We assessed nasopharyngeal flora of healthy infants in relation to risk fa ctors to determine which species best fit the mathematical model proposed f or the common bacterial toxin hypothesis and if these findings complemented results obtained from SIDS cases which occurred during the period of the s urvey. Longitudinal studies were carried out between April 1993 and March 1 996 on 253 healthy infants and their mothers, 150 from a multiply deprived area, 103 from an affluent area. Concurrent SIDS infants (37) were screened for nasopharyngeal nora. Among healthy infants less than or equal to 3 mon ths of age, the predominant isolate was Staphylococcus aureus, 57% compared with 86% for SIDS infants in that age range (P<0.02). Then were significan t associations between isolation of different species from both mother and baby but no association between isolation of any species with: area of resi dence; parental smoking habits; breast or bottle feeding; symptoms of viral infection; seasonality. We conclude that S. aureus fits the mathematical m odel for SIDS. Both staphylococci and/or their toxins were identified in a significant proportion of SIDS cases. Isolation of staphylococci from healt hy infants was associated with the 2-4-month age range, a risk factor consi stently found in all epidemiological studies of SIDS. This might reflect th e developmental stage in which 80-90% of infants express the Lewis(a) antig en which we have shown to be one of the receptors for S. aureus. (C) 1999 F ederation of European Microbiological Societies. Published by Elsevier Scie nce B.V. All rights reserved.