Streptococcus pyogenes (group A β-hemolytic Streptococcus) is a bacteria that is the most common bacterial cause of a sore throat (pharyngitis). Streptococcus pyogenes infection can lead to scarlet fever or, if not treated, rheumatic fever. Strep pharyngitis is uncommon in children under 2 years old. Pharyngitis is spread from person-to-person and is most common in the Winter and Spring when children spend more time indoors with other potentialy-infected children.
- Strep throat (pharyngitis)
- Otitis media
- Bacterial skin infections
- Scarlet fever (caused by a toxin produced by Streptococcus pyogenes)
- Rheumatic fever (caused by a late immune response to Streptococcus pyogenes)
- Acute glomerulonephritis - kidney inflammation (caused by a late immune response to Streptococcus pyogenes)
Habitat and Transmission
- Found on the skin and inside the nose, mouth and throat in small numbers
- Produces disease when it gains access to the blood and tissues
- Spread from person to person in respiratory secretions
Weapons and Defenses
- M protein - a protein on the outside of the bacteria that interferes with phagocytosis (destruction by white blood cells). There are around 80 known strains of Streptococcus pyogenes, each with it's own M protein and serotype.
- Pili - allow attachment of the bacteria to human mucous membranes (such as the inside of the throat).
- Streptokinase - an enzyme that dissolves blood clots
- DNase - breaks down human DNA. Antibody to this component can be used for diagnosis of infection (nti-DNase B titer).
- Hyaluronidase - breaks down connective tissue, allowing spread of the bacteria in skin infections
- Erythrogenic toxin - causes the rash of scarlet fever
- Streptolysin O - breaks down red blood cells. Antibody to this component can be used for diagnosis of infection (ASO titer).
- Streptolysin S - breaks down red blood cells
- Pyrogenic endotoxin A - causes inflammation
- Exotoxin B - causes tissue destruction. Found in strains that cause necrotizing fascititis.
- Infection with Streptococcus pyogenes leads to the production of antibodies against the specific serotype (based in part on the M protein). This leads to immunity and protection against re-infection with that serotype. Unfortunately, there are approximately 80 known serotypes, so re-infection is possible with a different strain.
- Streptococcus pyogenes is sensitive to antibiotics such as penicillin, amoxicillin, erythromycin or azithromycin.
Photo - Note the inflammation of the oropharynx and petechiae, or small red spots on the soft palate caused by Strep Throat.CDC/Dr. Heinz F. Eichenwald. 1958. Used with permission.
Photo 2 - A photomicrograph of Streptococcus spp. bacteria using Gram stain technique. CDC. 1970. Used with permission.
Last Updated (Thursday, 06 October 2011 11:50)