Streptococcal Pharyngitis

Streptococcal pharyngitis, commonly known as strep throat, is caused by the Gram-positive bacterium Streptococcus pyogenes.

The pathogen spreads through respiratory droplets. After entering the host, it attaches to epithelial cells of the throat using surface proteins such as lipoteichoic acid and M protein.

The bacteria also possess a capsule made of hyaluronic acid. This capsule mimics the host tissue and evades immune detection.

Once established, the pathogen releases several enzymes and toxins.

Streptolysins lyse host epithelial cells and infiltrating leukocytes.

Hyaluronidase degrades connective tissue, facilitating bacterial invasion. The host confines the infection by forming fibrin clots around the bacteria.

Streptokinase converts plasminogen into plasmin, which degrades fibrin clots and enables further bacterial spread.

These actions cause throat inflammation with redness, swelling, and white patches.

Symptoms typically begin two to five days after exposure and include sore throat, fever, headache, and tender neck lymph nodes.