Yes, MSSA Absolutely Causes Toxic Shock Syndrome
Methicillin-susceptible Staphylococcus aureus (MSSA) is a well-established cause of toxic shock syndrome (TSS), and in fact, MSSA strains may carry the toxic shock syndrome toxin-1 (TSST-1) gene MORE frequently than MRSA strains.
Key Evidence Supporting MSSA as a TSS Pathogen
Molecular and Epidemiological Data
The most compelling evidence comes from recent molecular studies showing that MSSA isolates carry the tst-1 gene (which encodes TSST-1) at significantly higher rates than MRSA:
- In a large contemporary study, 16.7% of MSSA isolates carried the tst-1 gene compared to only 0.2% of MRSA isolates (p < .001) 1
- Another study found 18.1% of MSSA versus 11.6% of MRSA isolates were tst-positive 2
- An NICU outbreak demonstrated MSSA producing both TSST-1 and Enterotoxin A, resulting in two neonatal deaths from toxic shock syndrome 3
Clinical Case Documentation
Multiple recent case reports confirm MSSA as the causative organism in confirmed TSS cases:
- A 9-year-old with automated insulin delivery developed confirmed TSS from an infected infusion site that grew MSSA, meeting full CDC criteria for TSS 4
- A 51-year-old developed TSS from MSSA following a scuba diving knee injury 5
Clinical Implications
Recognition and Diagnosis
When evaluating a patient with suspected TSS, do not exclude the diagnosis based on methicillin susceptibility. Look for:
- Sudden onset fever, hypotension, and shock
- Diffuse erythematous "sunburn-like" rash with subsequent desquamation
- Multiorgan involvement (≥3 organ systems)
- Any potential S. aureus source (skin wounds, surgical sites, tampons, infusion sites, infected devices)
Treatment Approach
For suspected staphylococcal TSS (regardless of methicillin susceptibility):
Source control is paramount - remove tampons, drain abscesses, debride infected tissue, remove infected devices 6, 7
Empiric antibiotic coverage should include anti-toxin therapy:
Aggressive supportive care with fluid resuscitation and vasopressor support as needed
Common Pitfall to Avoid
Do not assume TSS is only caused by MRSA or only occurs in menstrual-related cases. The epidemiology has shifted - MSSA remains a significant TSS pathogen, and non-menstrual cases (surgical wounds, skin infections, device-related infections) are increasingly common 4, 3, 5. Any S. aureus infection site can potentially lead to TSS if the strain produces TSST-1 or other superantigens.
The molecular data clearly demonstrates that MSSA strains frequently carry toxin genes and cause clinical TSS, making methicillin susceptibility irrelevant to TSS risk assessment.