Question

Can someone differentiate between Streptococcus pyogenes causing strep throat and Streptococcus pyogenes causing scarlet fever? Thank you

Answer 1

Streptococcus pyogenes is a Gram-positive bacterium.  It is non motile, and does not produce spores. It is comes under Group A streptococcus.  Group A streptococci typically have a capsule composed of hyaluronic acid and are beta-hemolytic. Beta-hemolytic streptococci produce a toxin that forms a clear zone of hemolysis of blood, it has the ability to destroy red blood cells.  This hemolysis is attributed to toxins formed by Group A streptococci called streptolysins.  Streptolysins can destroy not only red blood cells, but also the white blood cells responsible for fighting off bacteria and disease, as well as other body cells.

Streptococcus pyogenes is unique. It does not cause just one disease, but is capable of causing many different diseases.  These diseases range from mild, like strep throat and impetigo, to severe, like necrotizing fasciitis and streptococcal toxic shock syndrome.

Streptococcus pyogenes is the most common bacterial cause of sore throat. A painful, red throat with white patches on your tonsils is characteristic of pharyngitis. It is also known as strep throat.  It is usually accompanied by swollen lymph nodes, fever, and headache.  Occasionally it is also accompanied by nausea, vomiting, and abdominal pain.  Strep throat can be diagnosed by a doctor through a throat culture or a rapid strep test.

If left untreated strep throat can lead to further complications, including scarlet fever.  Scarlet fever is characterized by a red rash on the chest that may spread to the rest of the body.  The rash has a sandpaper-like texture and appears as tiny red pinpoints. Streptococcus pyogenes produces three types of exotoxins.  These toxins are responsible for causing fever and scarlet fever rashes; they also increase the risk of endotoxic shock and depress antibody synthesis. Scarlet fever is mainly seen in children under ten and can easily be diagnosed by a doctor by the appearance of the rash.