A 24-year-old woman develops high fever, hypotension, and a diffuse erythematous rash 2 days after using a superabsorbant tampon. Blood cultures remain negative. Staphylococcus aureus is isolated from the tampon. In staphylococcal toxic shock syndrome with negative blood cultures, which feature of TSST-1 best explains the absence of bacteremia despite systemic toxicity?

• A TSST-1 directly lyses endothelial cells allowing toxin but not bacteria to enter the bloodstream
• B TSST-1 causes neutropenia so rapidly that blood cultures become falsely negative
• C The organism remains strictly confined to mucosal surfaces and never produces a bacteremic phase
• D TSST-1 is a preformed exotoxin produced locally that acts systemically without requiring bloodstream invasion by the organism ✓

Explanation

In menstrual toxic shock syndrome, S. aureus colonizes the vagina and produces TSST-1 locally. The superantigen enters the bloodstream and causes massive cytokine release without the organism itself requiring bacteremia. This explains negative blood cultures in a classic TSST-1-mediated syndrome. Option A misrepresents the mechanism. Option C is wrong because the organism can occasionally be cultured from blood. Option B is not the standard explanation.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.