SIDS Implications of Temperature Dependent Toxin Production by Staphylococcus aureus Strains

McConnell, T. J. and Bishop, L. and Lauder, Robert M. and Harrison, L. and Morris, J. (2012) SIDS Implications of Temperature Dependent Toxin Production by Staphylococcus aureus Strains. The Journal of Pathology, 228. S20-S20. ISSN 0022-3417

Abstract

Introduction Staphylococcus aureus toxins are implicated in sudden infant death syndrome (SIDS) as there is an inverse relationship between incidence and circulating anti-toxin levels. A recent retrospective review of autopsy reports found that S. aureus was isolated more commonly from cases of SIDS compared to an explained non-infection group. Another study detected the toxins in tissues of over 50% of cases from three different countries. However, these toxins could be due to contamination at sampling. We have hypothesised that toxins not neutralised by IgG will be eliminated to the urine and detected. Here we demonstrate a temperature dependant pattern of secretion which does not support contamination as a source of toxins. Methods TSST-1 and SEB producing strains of S. aureus were cultured for 24h at 41°C, 37°C, 30°C, 22°C or 4°C in either Brain Heart Infusion broth (BHI) or clean catch mid-stream urine. The OD600 of the suspensions were measured prior to centrifugation at 900g. Toxin levels in the resulting media supernatants were determined by ELISA, gel electrophoresis and western blotting (WB). Results Maximum bacterial growth was observed at 30°C and 37°C while it was diminished at 22°C and 41°C and undetectable at 4°C. In contrast, maximal TSST-1 release occurred at 41°C (0.10µg/ml) with less at 37°C (0.052µg/ml), while at 4°C, 22°C and 30°C TSST-1 was undetectable. Similar results were obtained for SEB. Conclusions Contamination of urine samples stored at room or refrigerated temperature does not result in the release of biologically significant levels of toxin. These results support the interpretation of our previous findings that the detection of S. aureus toxins in infant urine results from a transient bacteraemia rather than contamination. ELISA and WB for bacterial toxins in body fluids taken at autopsy can be used to distinguish between genuine infection with S. aureus and contamination.