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Lethal synergy between toxins of staphylococci and enterobacteria: implications for sudden infant death syndrome
N M Sayers1, D B Drucker, J A Morris
1School of Biological Sciences, University of Manchester.
Aim:
To test the hypothesis that lethal synergy occurs between toxin preparations of nasopharyngeal staphylococci and enterobacteria from sudden infant death syndrome (SIDS) victims and matched healthy infants.
Methods:
SIDS and matched healthy babies were studied if both staphylococcal and enterobacterial strains were isolated from the nasopharynx. The lethality of toxin preparations from each bacterial isolate (separately and combined) was assessed over a range of dilutions using the chick embryo assay system.
Results:
Staphylococci and enterobacteria were isolated together from the nasopharynx of seven SIDS babies but from only one normal healthy infant. Enterobacterial toxins were lethal at high dilutions. Staphylococcal toxins were less toxic. Simultaneous testing in the chick assay of staphylococcal and enterobacterial toxins, from each baby, at non-lethal concentrations enhanced lethality levels by 177 to 1011% compared with lethality expected by an additive effect alone.
Conclusions:
Synergy occurs between the toxins of nasopharyngeal staphylococci and enterobacteria. This combination of strains is more likely to occur in the nasopharynx of SIDS victims than that of healthy infants.
Insights
Bacterial toxins from Staphylococcus and Enterobacter species found in the nasopharynx of infants can work together, a phenomenon known as lethal synergy. This synergistic effect was more prevalent in sudden infant death syndrome (SIDS) cases.
Area of Science:
- Microbiology
- Infant Health
- Toxicology
Background:
- Nasopharyngeal colonization by Staphylococcus and Enterobacter species is common in infants.
- Sudden Infant Death Syndrome (SIDS) remains a significant concern in infant mortality.
- The potential role of microbial toxins in SIDS pathogenesis requires further investigation.
Purpose of the Study:
- To investigate the hypothesis of lethal synergy between toxins of nasopharyngeal staphylococci and enterobacteria.
- To compare the co-occurrence of these bacterial strains in SIDS victims versus healthy infants.
- To assess the combined toxic effects of these bacteria in a chick embryo model.
Main Methods:
- Bacterial strains (Staphylococcus and Enterobacter) were isolated from the nasopharynx of SIDS victims and matched healthy infants.
- Toxin preparations from individual and combined isolates were tested for lethality using a chick embryo assay.
- Lethality was assessed across a range of bacterial toxin dilutions.
Main Results:
- Co-isolation of Staphylococcus and Enterobacter occurred in 7 SIDS infants versus 1 healthy infant.
- Enterobacterial toxins demonstrated lethality at high dilutions; staphylococcal toxins were less potent.
- Combined toxins, even at non-lethal concentrations, significantly enhanced lethality by 177-1011% compared to additive effects.
Conclusions:
- Lethal synergy exists between toxins of nasopharyngeal staphylococci and enterobacteria.
- This synergistic combination of bacteria is more frequently found in the nasopharynx of SIDS victims.
- The findings suggest a potential contributing factor to SIDS pathogenesis.