Streptococcal (strep) infections are communicable diseases that develop when bacteria normally found on the skin or in the intestines, mouth, nose, reproductive tract, or urinary tract invade other parts of the body and contaminate blood or tissue.
Some strep infections don't produce symptoms. Some are fatal.
Most people have some form of strep bacteria in their body at some time. A person who hosts bacteria without showing signs of infection is considered a carrier.
Types of infection
Primary strep infections invade healthy tissue, and most often affect the throat. Secondary strep infections invade tissue already weakened by injury or illness. They frequently affect the bones, ears, eyes, joints, or intestines.
Both primary and secondary strep infections can travel from affected tissues to lymph glands, enter the bloodstream, and spread throughout the body.
Numerous strains of strep bacteria have been identified. Types A, B, C, D, and G are most likely to make people sick.
Group A strep (GAS) is the form of strep bacteria most apt to be associated with serious illness.
Between 10, 000 and 15, 000 GAS infections occur in the United States every year. Most are mild inflammations of the throat or skin, where the bacteria are normally found; however, GAS infections can be deadly.
Two of the most severe invasive GAS infections are necrotizing fasciitis or flesh-eating bacteria (destruction of muscle tissue and fat) and toxic shock syndrome (a rapidly progressive disorder that causes shock and damages internal organs).
GROUP B. Group B strep (GBS) most often affects pregnant women, infants, the elderly, and chronically ill adults.
Since first emerging in the 1970s, GBS has been the primary cause of life-threatening illness and death in newborns. GBS exists in the reproductive tract of 20-25% of all pregnant women. Although no more than 2% of these women develop invasive infection, 40-73% transmit bacteria to their babies during delivery.
About 12, 000 of the 3.5 million babies born in the United States each year develop GBS disease in infancy. About 75% of them develop early-onset infection. Sometimes evident within a few hours of birth and always apparent within the first week of life, this condition causes inflammation of the membranes covering the brain and spinal cord (meningitis), pneumonia, blood infection (sepsis), and other problems.
Late-onset GBS develops between the ages of seven days and three months. It often causes meningitis. About half of all cases of this rare condition can be traced to mothers who are GBS carriers. The cause of the others is unknown.
GBS has also been linked to a history of breast cancer.
GROUP C. Group C strep (GCS) is a common source of infection in animals. It rarely causes human illness.
GROUP D. Group D strep (GDS) is a common cause of wound infections in hospital patients. GDS is also associated with:
- abnormal growth of tissue in the gastrointestinal tract
- urinary tract infection (UTI)
- womb infections in women who have just given birth
GROUP G. Normally present on the skin, in the mouth and throat, and in the intestines and genital tract, Group G strep (GGS) is most likely to lead to infection in alcoholics and in people who have cancer, diabetes mellitus, rheumatoid arthritis, and other conditions that suppress immune-system activity.
GGS can cause a variety of infections, including:
- bacteria in the bloodstream (bacteremia)
- inflammation of the connective tissue structure surrounding a joint (bursitis)
- endocarditis (a condition that affects the lining of the heart chambers and the heart valves)
- inflammation of bone and bone marrow (osteomyelitis)
- inflammation of the lining of the abdomen (peritonitis)
Causes and symptoms
Streptococcal infection occurs when bacteria contaminate cuts or open sores or otherwise penetrate the body's natural defenses.
GAS is transmitted by direct contact with saliva, nasal discharge, or open wounds of someone who has the infection. Chronic illness, kidney disease treated by dialysis, and steroid use increase vulnerability to infection.
About one of five people with GAS infection develops a sore, inflamed throat, and pus on the tonsils. The majority of those infected by GAS either have no symptoms or develop enlarged lymph nodes, fever, headache, nausea, vomiting, weakness, and a rapid heartbeat.
Flesh-eating bacteria is characterized by fever, extreme pain, and swelling and redness at a site where skin is broken.
A pregnant woman who has GBS infection can develop infections of the bladder, blood, and urinary tract, and deliver a baby who is infected or stillborn. The risk of transmitting GBS infection during birth is highest in a woman whose labor begins before the 37th week of pregnancy or lasts more than 18 hours or who:
- becomes a GBS carrier during the final stages of pregnancy
- has a GBS urinary-tract infection
- has already given birth to a baby infected with GBS
- develops a fever during labor
More than 13% of babies who develop GBS infection during birth or within the first few months of life develop neurologic disorders. An equal number of them die.
Among men, and in women who are not pregnant, the most common consequences of GBS infection are pneumonia and infections of blood, skin, and soft tissue.
Other symptoms associated with strep infection include:
- elevated white blood cell counts
- inflammation of the epiglottis (epiglottitis)
- heart murmur
- high blood pressure
- infection of the heart muscle
- kidney inflammation (nephritis)
- swelling of the face and ankles
Strep bacteria can be obtained by swabbing the back of the throat or the rectum with a piece of sterile cotton. Microscopic examination of the smear can identify which type of bacteria has been collected.
It takes less than 24 hours for antibiotics to eliminate an infected person's ability to transmit GAS.
Guidelines developed by the American Academy of Obstetrics and Gynecology (AAOG), the American Academy of Pediatrics (AAP), and the Centers for Disease Control and Prevention (CDC) recommend administering intravenous antibiotics to a woman at high risk of passing GBS infection on to her child, and offering the medication to any pregnant woman who wants it.
Babies infected with GBS during or shortly after birth may die. Those who survive often require lengthy hospital stays and develop vision or hearing loss and other permanent disabilities.
Conventional medicine is very successful in treating strep infections. However, several alternative therapies, including homeopathy and botanical medicine, may help relieve symptoms or support the person with a strep infection. For example, several herbs, including garlic (Allium sativum), echinacea (Echinacea spp.), and goldenseal (Hydrastis canadensis), are believed to strengthen the immune system, thus helping the body fight a current infection, as well as helping prevent future infections.
Early-onset GBS kills 15% of the infants it affects. Late-onset disease claims the lives of 10% of babies who develop it.
GBS infections are fatal in about 20% of the men and non-pregnant women who develop them.
About 10–15% of non-GAS strep infections are fatal. Antibiotic therapy, begun when symptoms first appear, may increase a patient's chance of survival.
Washing the hands frequently, especially before eating and after using the bathroom, and keeping wounds clean can help prevent strep infection. Exposure to infected people should be avoided, and a family physician should be notified by anyone who develops an extremely sore throat or pain, redness, swelling, or drainage at the site of a wound or break in the skin.
Until vaccines to prevent strep infection become available, 12 monthly doses of oral or injected antibiotics may prevent some types of recurrent infection.
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Harrison's Principles of Internal Medicine. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.
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"Infectious Diseases." The Merck Page. 17 June 1998 <http://www.merck.com>.