Streptococcus

The genus Streptococcus is comprised of Gram-positive, microaerophilic cocci (round), which are not motile and occur in chains or pairs. The genus is defined by a combination of antigenic, hemolytic, and physiological characteristics into Groups A, B, C, D, F, and G. Groups A and D can be transmitted to humans via food.

Group A Streptococcal Disease (GAS)

What is group A streptococcus (GAS)?

Group A streptococcus is a bacterium often found in the throat and on the skin. People may carry group A streptococci in the throat or on the skin and have no symptoms of illness. Most GAS infections are relatively mild illnesses such as “strep throat,” or impetigo. On rare occasions, these bacteria can cause other severe and even life-threatening diseases

How are group A streptococci spread?

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.

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.

How common is invasive group A streptococcal disease?

About 9,400 cases of invasive GAS disease occurred in the United States in 1999. Of these, about 300 were STSS and 600 were necrotizing fasciitis. In contrast, there are several million cases of strep throat and impetigo each year.

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.

Who is most at risk of getting invasive group A streptococcal disease?

Few people who come in contact with GAS will develop invasive GAS disease. Most people will have a throat or skin infection, and some may have no symptoms at all. Although healthy people can get invasive GAS disease, people with chronic illnesses like cancer, diabetes, and kidney dialysis, and those who use medications such as steroids have a higher risk.

What are the early signs and symptoms of necrotizing fasciitis and streptococcal toxic shock syndrome?

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

How is invasive group A streptococcal disease treated?

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

What can be done to help prevent group A streptococcal infections?

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 your doctor.

Group B Streptococcal Disease (GBS)

Group B streptococcus (GBS) is a type of bacterium that causes illness in newborn babies, pregnant women, the elderly, and adults with other illnesses, such as diabetes or liver disease. GBS is the most common cause of life-threatening infections in newborns.

How common is GBS disease?

GBS is the most common cause of sepsis (blood infection) and meningitis (infection of the fluid and lining surrounding the brain) in newborns. GBS is a frequent cause of newborn pneumonia and is more common than other, better known, newborn problems such as rubella, congenital syphilis, and spina bifida.

Before prevention methods were widely used, approximately 8,000 babies in the United States would get GBS disease each year. One of every 20 babies with GBS disease dies from infection. Babies that survive, particularly those who have meningitis, may have long-term problems, such as hearing or vision loss or learning disabilities.

In pregnant women, GBS can cause bladder infections, womb infections (amnionitis, endometritis), and stillbirth. Among men and among women who are not pregnant, the most common diseases caused by GBS are blood infections, skin or soft tissue infections, and pneumonia. Approximately 20% of men and nonpregnant women with GBS disease die of the disease.

Does everyone who has GBS get sick?

Many people carry GBS in their bodies but do not become ill. These people are considered to be “carriers.” Adults can carry GBS in the bowel, vagina, bladder, or throat. One of every four or five pregnant women carries GBS in the rectum or vagina. A fetus may come in contact with GBS before or during birth if the mother carries GBS in the rectum or vagina. People who carry GBS typically do so temporarily — that is, they do not become lifelong carriers of the bacteria.

How does GBS disease affect newborns?

Approximately one of every 100 to 200 babies whose mothers carry GBS develop signs and symptoms of GBS disease. Three-fourths of the cases of GBS disease among newborns occur in the first week of life (“early-onset disease”), and most of these cases are apparent a few hours after birth. Sepsis, pneumonia, and meningitis are the most common problems. Premature babies are more susceptible to GBS infection than full-term babies, but most (75%) babies who get GBS disease are full term.

GBS disease may also develop in infants 1 week to several months after birth (“late-onset disease”). Meningitis is more common with late-onset GBS disease. Only about half of late-onset GBS disease among newborns comes from a mother who is a GBS carrier; the source of infection for others with late-onset GBS disease is unknown. Late-onset disease is very rare.

How is GBS disease diagnosed and treated?

GBS disease is diagnosed when the bacterium is grown from cultures of sterile body fluids, such as blood or spinal fluid. Cultures take a few days to complete. GBS infections in both newborns and adults are usually treated with antibiotics (e.g., penicillin or ampicillin) given through a vein.

Can pregnant women be checked for GBS?

GBS carriage can be detected during pregnancy by taking a swab of both the vagina and rectum for special culture. Physicians who culture for GBS carriage during prenatal visits should do so late in pregnancy (35-37 weeks’ gestation); cultures collected earlier do not accurately predict whether a mother will have GBS at delivery.

A positive culture result means that the mother carries GBS — not that she or her baby will definitely become ill. Women who carry GBS should not be given oral antibiotics before labor because antibiotic treatment at this time does not prevent GBS disease in newborns. An exception to this is when GBS is identified in urine during pregnancy. GBS in the urine should be treated at the time it is diagnosed. Carriage of GBS, in either the vagina or rectum, becomes important at the time of labor and delivery — when antibiotics are effective in preventing the spread of GBS from mother to baby.

Can GBS disease among newborns be prevented?

Most GBS disease in newborns can be prevented by giving certain pregnant women antibiotics through the vein during labor. Any pregnant woman who previously had a baby with GBS disease or who has a urinary tract infection caused by GBS should receive antibiotics during labor. Pregnant women who carry GBS should be offered antibiotics at the time of labor or membrane rupture. GBS carriers at highest risk are those with any of the following conditions:

  • fever during labor
  • rupture of membranes (water breaking) 18 hours or more before delivery
  • labor or rupture of membranes before 37 weeks

Because women who carry GBS but do not develop any of these three complications have a relatively low risk of delivering an infant with GBS disease, the decision to take antibiotics during labor should balance risks and benefits. Penicillin is very effective at preventing GBS disease in the newborn and is generally safe. A GBS carrier with none of the conditions above has the following risks:

  • 1 in 200 chance of delivering a baby with GBS disease if antibiotics are not given
  • 1 in 4000 chance of delivering a baby with GBS disease if antibiotics are given
  • 1 in 10 chance, or lower, of experiencing a mild allergic reaction to penicillin (such as rash)
  • 1 in 10, 000 chance of developing a severe allergic reaction–anaphylaxis–to penicillin. Anaphylaxis requires emergency treatment and can be life-threatening.

If a prenatal culture for GBS was not done or the results are not available, physicians may give antibiotics to women with one or more of the risk conditions listed above.

What research is being done on prevention of GBS disease?

In spite of testing and antibiotic treatment, some babies still get GBS disease. Vaccines to prevent GBS disease are being developed. In the future, women who are vaccinated may make antibodies that cross the placenta and protect the baby during birth and early infancy.

Who is at higher risk for GBS disease?

Pregnant women with the following conditions are at higher risk of having a baby with GBS disease:

  • previous baby with GBS disease
  • urinary tract infection due to GBS
  • GBS carriage late in pregnancy
  • fever during labor
  • rupture of membranes 18 hours or more before delivery
  • labor or rupture of membranes before 37 weeks