Which bacterium causes scarlet fever, the rash-producing illness often associated with strep throat?

Streptococcus pyogenes is the bacterium that causes scarlet fever, the rash-producing illness often associated with strep throat.

Streptococcus pyogenes is a group A streptococcus commonly called group A strep. It can infect the throat and cause streptococcal pharyngitis, or “strep throat.” In some infections, toxins produced by the bacterium lead to the widespread, finely textured rash characteristic of scarlet fever.

Scarlet fever most often affects children, although people of any age can develop it. The illness may include fever, sore throat, swollen neck glands, a red tongue, and a rash that can feel rough, like sandpaper. The rash reflects toxin activity rather than a separate microorganism.

Streptococcus pyogenes also causes skin infections such as impetigo and erysipelas, and in rare cases can produce severe invasive diseases. It is different from Streptococcus pneumoniae, a major cause of pneumococcal pneumonia and meningitis. Antibiotic treatment for confirmed group A strep infections reduces complications and transmission.