<prompt> Toxic Shock Syndrome is most commonly caused by: March 2005Sterptococcus pneumoniaeStaphylococcus aureusVibrio choleraeClostridium tetani  <response>: Ans. B: Staphylococcus aureus Toxic shock syndrome TSS is caused by the reaction of the human immune system to bacterial superantigens. A defect of protective immunity is postulated to be a major risk factor for recurrence of TSS. Superantigens are produced by various species of coagulase-positive staphylococci, most notably Staphylococcus aureus but also the zoonoses Streptococcus suis common in pigs, Streptococcus mitis in mice, and Streptococcus agalactiae. Group A beta-hemolytic streptococci notably Streptococcus pyogenes also produce superantigens. 