Group A streptococcal infection

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The group A streptococcus bacterium (Streptococcus pyogenes, or GAS) is a form of Streptococcus bacteria responsible for most cases of streptococcal illness. Other types (B, C, D, and G) may also cause infection. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes. For further explanation of these virulence factors, see the main article on Streptococcus pyogenes.

Also known as: Strep. throat, necrotizing fasciitis, impetigo.

Epidemiology and Demographics

Approximately 9,000 cases of invasive disease (3.2/100,000 population) occurred in 2002; STSS and NF each accounted for approximately 6% of cases. Over 10 million noninvasive GAS infections (primarily throat and skin infections) occur annually.

National passive surveillance for invasive infection and STSS since 1995. Active, population-based surveillance is conducted in 10 states in the Emerging Infection Program (total population: 31.5 million).

Worldwide, rates of invasive disease, STSS and NF increased from the mid-1980s to early 1990s. Rates of invasive disease have been stable over the last 5 years in the United States. Increases in the rate and severity of disease associated with increases in prevalence of M-1 and M-3 serotypes (emm types 1 and 3). Resistance to erythromycin has increased worldwide.

Transmission

Person to person by contact with infectious secretions. Asymptomatic pharyngeal carriage occurs among all age groups but is most common among children.

Risk Factors

Invasive disease: elderly, immunosuppressed, persons with chronic cardiac or respiratory disease, diabetes, skin lesions (i.e. children with varicella chicken pox, intravenous drug users) African-Americans, American Indians.

Noninvasive disease: children (especially elementary school age) at highest risk.

Types of infection

Infections are largely categorized by the location of infection:

• bacteremia -- bloodstream
• impetigo, cellulitis, and erysipelas -- skin and underlying tissues
• focal infections -- limited to a particular site. Bacteremia can be associated with these infections, but it is not always present. Treatment depends on the specific clinical findings. Types include:
  • pneumonia -- pulmonary alveolus
  • tonsillitis -- tonsils
  • septic arthritis -- joints
  • osteomyelitis -- bones
  • peritonitis -- peritoneum
  • meningitis -- meninges
• necrotizing fasciitis -- skin, fascia and muscle
• scarlet fever -- upper body
• sinusitis - nose.
• strep throat -- pharynx
• toxic shock syndrome -- multiple systems

(Note that some of these diseases can be caused by other infectious agents as well.)

Severe streptococcal infections

Some strains of group A streptococci (GAS) cause severe infection. Those at greatest risk include children with chickenpox; persons with suppressed immune systems; burn victims; elderly persons with cellulitis, diabetes, blood vessel disease, or cancer; and persons taking steroid treatments or chemotherapy. Intravenous drug users also are at high risk. GAS is an important cause of puerperal fever world-wide, causing serious infection and, if not promptly diagnosed and treated, death in newly delivered mothers. Severe GAS disease may also occur in healthy persons with no known risk factors.

All severe GAS infections may lead to shock, multisystem organ failure, and death. Early recognition and treatment are critical. Diagnostic tests include blood counts and urinalysis as well as cultures of blood or fluid from a wound site. The antibiotic of choice is penicillin, to which GAS is particularly susceptible and has never been found to be resistant. Erythromycin and clindamycin are other treatment options, though resistance to these antibiotics exists.

Pathophysiology & Etiology

Streptococcus pyogenes or group A streptococcus.

These bacteria are spread through direct contact with mucus from the nose or throat of persons who are infected or through contact with infected wounds or sores on the skin. Ill persons, such as those who have strep throat or skin infections, are most likely to spread the infection. Persons who carry the bacteria but have no symptoms are much less contagious. Treating an infected person with an antibiotic for 24 hours or longer generally eliminates their ability to spread the bacteria. However, it is important to complete the entire course of antibiotics as prescribed. It is not likely that household items like plates, cups, or toys spread these bacteria.

Why does invasive group A streptococcal disease occur?

Invasive GAS infections occur when the bacteria get past the defenses of the person who is infected. This may occur when a person has sores or other breaks in the skin that allow the bacteria to get into the tissue, or when the person’s ability to fight off the infection is decreased because of chronic illness or an illness that affects the immune system. Also, some virulent strains of GAS are more likely to cause severe disease than others.

Signs and Symptoms

Early signs and symptoms of necrotizing fasciitis

• Fever
• Severe pain and swelling
• Redness at the wound site

Early signs and symptoms of STSS

• Fever
• Dizziness
• Confusion
• A flat red rash over large areas of the body

Noninvasive disease (strep throat, cellulitis, impetigo); invasive disease (necrotizing fasciitis [NF], streptococcal toxic shock syndrome [STSS], bacteremia, pneumonia); nonsuppurative sequelae (rheumatic fever, post-streptococcal glomerulonephritis). STSS is a severe illness characterized by shock, multiorgan failure. NF presents with severe local pain, destruction of tissue. Rheumatic fever is a leading cause of acquired heart disease in young people worldwide.

Risk Stratification and Prognosis

What kind of illnesses are caused by group A streptococcal infection?

Infection with GAS can result in a range of symptoms:

• No illness
• Mild illness (strep throat or a skin infection such as impetigo)
• Severe illness (necrotizing faciitis, streptococcal toxic shock syndrome)

Severe, sometimes life-threatening, GAS disease may occur when bacteria get into parts of the body where bacteria usually are not found, such as the blood, muscle, or the lungs. These infections are termed "invasive GAS disease." Two of the most severe, but least common, forms of invasive GAS disease are necrotizing fasciitis and Streptococcal Toxic Shock Syndrome. Necrotizing fasciitis (occasionally described by the media as "the flesh-eating bacteria") destroys muscles, fat, and skin tissue. Streptococcal toxic shock syndrome (STSS), causes blood pressure to drop rapidly and organs (e.g., kidney, liver, lungs) to fail. STSS is not the same as the "toxic shock syndrome" frequently associated with tampon usage. About 20% of patients with necrotizing fasciitis and more than half with STSS die. About 10%-15% of patients with other forms of invasive group A streptococcal disease die.

Treatment

GAS infections can be treated with many different antibiotics. Early treatment may reduce the risk of death from invasive group A streptococcal disease. However, even the best medical care does not prevent death in every case. For those with very severe illness, supportive care in an intensive care unit may be needed.

Surgery and Device Based Therapy

For persons with necrotizing fasciitis, surgery often is needed to remove damaged tissue.

Complications

Acute rheumatic fever

Acute rheumatic fever (ARF) is a complication of a strep throat caused by particular strains of GAS. Although common in developing countries, ARF is rare in the United States, with small isolated outbreaks reported only occasionally. It is most common among children between 5-15 years of age. A family history of ARF may predispose an individual to the disease. Symptoms typically occur 18 days after an untreated strep throat. An acute attack lasts approximately 3 months. The most common clinical finding is a migratory arthritis involving multiple joints. The most serious complication is carditis, or heart inflammation (rheumatic heart disease), as this may lead to chronic heart disease and disability or death years after an attack. Less common findings include bumps or nodules under the skin (usually over the spine or other bony areas) and a red expanding rash on the trunk and extremities that recurs over weeks to months. Because of the different ways ARF presents itself, the disease may be difficult to diagnose. A neurological disorder, chorea, can occur months after an initial attack, causing jerky involuntary movements, muscle weakness, slurred speech, and personality changes. Initial episodes of ARF as well as recurrences can be prevented by treatment with appropriate antibiotics.

Post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis (PSGN) is an uncommon complication of either a strep throat or a streptococcal skin infection. Symptoms of PSGN develop within 10 days following a strep throat or 3 weeks following a GAS skin infection. PSGN involves inflammation of the kidney. Symptoms include pale skin, lethargy, loss of appetite, headache and dull back pain. Clinical findings may include dark-colored urine, swelling of different parts of the body (edema), and high blood pressure. Treatment of PSGN consists of supportive care.

Primary Prevention

The spread of all types of GAS infection can be reduced by good hand washing, especially after coughing and sneezing and before preparing foods or eating. Persons with sore throats should be seen by a doctor who can perform tests to find out whether the illness is strep throat. If the test result shows strep throat, the person should stay home from work, school, or day care until 24 hours after taking an antibiotic. All wounds should be kept clean and watched for possible signs of infection such as redness, swelling, drainage, and pain at the wound site. A person with signs of an infected wound, especially if fever occurs, should seek medical care. It is not necessary for all persons exposed to someone with an invasive group A strep infection (i.e. necrotizing fasciitis or strep toxic shock syndrome) to receive antibiotic therapy to prevent infection. However, in certain circumstances, antibiotic therapy may be appropriate. That decision should be made after consulting with a physician.

Source

• The original text of this article is taken from the NIH Fact Sheet "Group A Streptococcal Infections", dated March 1999. As a work of the U.S. Federal Government without any other copyright notice, this is assumed to be a public domain resource.

Acknowledgements

The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.

List of contributors:

Pilar Almonacid

External links

• Group A streptococcal infection at National Institutes of Health

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