Dr. Rae Osborn 26 May 2023

Group A Streptococcal infections are illnesses caused by Streptococcus bacteria. Several diseases are caused by these bacteria, some of which can be fatal. Correct diagnosis and treatment are important to avoid life-threatening complications.

What is Streptococcus?

Streptococcus is in the gram-positive group of bacteria (named for how the bacteria respond to a gram stain during microscopy). The Group A Streptococcus are also known as Streptococcus pyogenes and occur even in healthy people, where they make up roughly 1% of the microbes of the skin and mucosal membranes of the throat, mouth, and vagina.

There are various strains of Group A Streptococcus, with some being invasive and causing illness. Pathogenic strains release toxins and can even destroy blood cells.

Symptoms of Group A Streptococcal infections

The symptoms of an infection with this type of bacteria do vary depending on which part of the body is affected. Symptoms may include pain, skin rashes, and blisters.

Diagnosis of Group A Streptococcal infections

Diagnostic methods for Group A strep (Streptococcus) infections include:

  • Rapid antigen detection tests (RADT): The test is done on a throat culture and looks for antigens to the Streptococcus bacteria.
  • Skin samples: A skin biopsy and culturing of the bacteria can be done.
  • Blood tests: This includes an Anti-DNase B test, where the antigens to strep are searched for in a blood sample.

Diseases and Complications caused by Group A Streptococcus

  1. Impetigo
  2. Erysipelas
  3. Cellulitis
  4. Necrotizing fasciitis
  5. Myonecrosis
  6. Strep throat
  7. Scarlet fever
  8. Bacteremia
  9. Streptococcal toxic shock syndrome (TSS)
  10. Post-streptococcal glomerulonephritis (PSGN)
  11. Rheumatic fever
  12. Pneumonia

1. Impetigo

This is a skin problem where the bacteria cause blisters to form. It is most prevalent in young children. The symptoms are:

  • Blisters that form on the legs and face
  • Blisters that crust over and are yellow
  • Fever

2. Erysipelas

This is another type of skin infection involving Group A strep. In this condition, the outer layers of the skin are affected. The signs of erysipelas are as follows:

  • Rash on the skin
  • Blisters on the skin that are red, shiny, and raised
  • Painful skin
  • Chills and fever

3. Cellulitis

This is similar to impetigo in that it affects the skin; however, cellulitis affects the deeper layers of the skin. The symptoms of cellulitis are:

  • Swollen and red areas of skin
  • Skin that has a pitted appearance
  • Pain in the affected region of the skin

It is essential that healthcare providers carefully assess the patient to rule out necrotizing fasciitis.

4. Necrotizing fasciitis

This is a soft tissue infection that resembles cellulitis, but, in this case, the soft tissue is destroyed. The bacteria invade the deeper tissues causing necrosis. Without treatment, gangrene can occur, which can result in sepsis and death.

Some of the symptoms of necrotizing fasciitis are similar to those of cellulitis, for instance:

  • Red and swollen area of skin
  • Pain in the affected part of the skin that is worse than in the case of cellulitis

The risk of death due to necrotizing fasciitis is high, with 20% mortality.

5. Myonecrosis

This condition leads to the destruction of muscle tissue. S. pyogenes can invade skeletal muscle producing the following symptoms:

  • Fever
  • Pain in the area
  • Swelling of the area
  • Fatigue

6. Strep throat

Strep throat is also called strep pharyngitis. This is when the Streptococcus bacteria invade the mouth and throat.

Strep throat has the following symptoms:

  • Sore and red throat
  • Pus in the throat and on the tonsils
  • Fever and chills
  • Nausea
  • Muscle aches

Complications of strep throat include the following:

  • Abscesses around the tonsils or at the back of the throat
  • Mastoiditis (infection of the bony area behind the ear)

7. Scarlet fever

Scarlet fever is not as common today, but it can still be dangerous. The symptoms of scarlet fever include the following:

  • A red rash that is widespread over the body
  • The tongue turning strawberry-red in appearance
  • A high fever
  • An aching throat
  • A flushed face

8. Bacteremia

The condition occurs when bacteria enter the bloodstream. The symptoms of bacteremia may be mild at first and then worsen to include the following:

  • Shaking chills
  • Low blood pressure
  • Fever
  • Gastrointestinal upset

9. Streptococcal toxic shock syndrome (TSS)

This is an uncommon complication of group A strep infections. The condition is life-threatening and can lead to death due to organ failure. Signs of TSS include the following:

  • Fever
  • Chills
  • Sore muscles
  • Nausea and vomiting

This can worsen to sepsis with symptoms such as:

  • Fast heart rate
  • Low blood pressure
  • Rapid breathing

10. Rheumatic fever

Rheumatic fever is an inflammation of the skin, joints, heart, or nervous system. It is a complication of strep throat or scarlet fever. The symptoms of rheumatic fever are as follows:

  • Fever
  • Painful joints
  • A heart murmur
  • Chest pain
  • Exhaustion
  • Skin rash and bumps under the skin
  • Sydenham chorea: odd movements of the feet, hands, or face

11. Post-streptococcal glomerulonephritis (PSGN)

This is a condition that occurs as a complication of strep pharyngitis or strep skin infections. In post-streptococcal glomerulonephritis, the kidneys are affected.

Symptoms of PSGN include the following:

  • Presence of protein in the urine
  • Elevated blood pressure
  • Loss of appetite
  • Tiredness
  • Weakness
  • Swelling around the face and eyes (most obvious when the person awakens in the morning)

12. Pneumonia

Pneumonia can result from S. pyogenes infections. Symptoms include the following:

  • Chills and fever
  • Shaking
  • Chest pain
  • Cough
  • Shortness of breath

Treatment of Group A Streptococcal infections

Group A strep infections are treated using readily available antibiotics.

  • Usually, the antibiotics that are used to treat strep throat are penicillin or erythromycin (when the patient has a penicillin allergy). Amoxicillin is another antibiotic sometimes used to treat strep pharyngitis.
  • Cellulitis is usually treated with cephalexin.
  • Treating necrotizing fasciitis entails surgical removal of dead tissue along with using antibiotics. Antibiotics used include those in the beta-lactam group and clindamycin or vancomycin. Vancomycin is used when doctors suspect methicillin resistance of the bacteria.
  • Patients with TSS need to be in a hospital where they can be given fluids and supportive care. Antibiotics such as clindamycin are also given.
  • A combination of antibiotics and supportive therapy, including intravenous fluids and oxygen therapy, may be needed to treat severe infections caused by group A strep.


Group A Streptococcal infections can vary from mild to serious, with some even leading to death due to complications. It is important to seek treatment as soon as possible to avoid complications.

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About the Author:

Dr. Rae Osborn has a Ph.D. in Biology from the University of Texas at Arlington. She was a tenured Associate Professor of Biology at Northwestern State University where she taught many courses for Pre-nursing and Pre-medical students. She has written extensively on medical conditions and healthy lifestyle topics, including nutrition. She is from South Africa but lived and taught in the United States for 18 years.


  • Bryant, A. E., Bayer, C. R., Huntington, J. D., & Stevens, D. L. (2006). Group A streptococcal myonecrosis: increased vimentin expression after skeletal-muscle injury mediates the binding of Streptococcus pyogenes. Journal of Infectious Diseases, 193(12), 1685-1692.

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