Streptococcal disease

Definition

Streptococcal diseases are infectious diseases caused by various types of bacteria belonging to the genus Streptococcus. All bacteria classified as streptococci are sphere-shaped Gram-positive organisms that grow in chains or pairs. The name streptococcus comes from two Greek words that mean “twisted chain” and “spherical.”

Description

Streptococci are classified according to their hemolytic properties. Hemolysis is the process in which bacteria break down red blood cells on an agar plate in the laboratory.

• Alpha-hemolytic streptococci. These bacteria cause a greenish discoloration of the agar plate when they are cultured. This group includes such bacteria as S. pneumoniae, a major cause of bacterial pneumonia in the elderly; S. mutans, which is involved in tooth decay; and S. viridans, which can cause infections of the heart tissue as well as dental abscesses.
• Beta-hemolytic streptococci. These bacteria completely destroy the blood cells in the culture medium, causing the area around them to lose color and become transparent. The four major subgroups of beta-hemolytic streptococci are described in the next paragraph.
• Nonhemolytic streptococci. Bacteria in this group do not cause any change in the appearance of the culture medium. They are rarely implicated in disease in humans.

Beta-hemolytic streptococci are further classified into four groups:

• Group A. The most important Group A beta-hemolytic streptococcus is S. pyogenes, which is also known as GAS. Infections caused by GAS include strep throat, erysipelas, scarlet fever, rheumatic fever, and necrotizing fasciitis, or flesh-eating bacteria disease.
• Group B. Group B hemolytic streptococci include S. agalactiae, sometimes known as GBS. GBS can cause meningitis, cellulitis, pneumonia, or infection of the bloodstream in seniors.
• Group C. These streptococci are unlikely to infect humans; they are primarily responsible for infections in cattle and horses.
• Group D. Group D primarily contains enterococci, which grow in the digestive tract. The most important organism in this group is S. bovis, which is responsible for many cases of bacterial endocarditis, an inflammation of the tissue that lines the valves of the heart.

Demographics

The demographics of streptococcal diseases vary widely, depending on their severity and whether there is a vaccine for the specific disease. For example, there are millions of cases of strep throat and mild GAS infections of the skin each year. By contrast, there are only about 600 cases of necrotizing fascitiis in the United States each year. About 46 out of every 1000 people over the age of 65 develop streptococcal pneumonia each year.

An example of the difference made by the introduction of a vaccine is pneumonia caused by S. pneumoniae. Before 2002, S. pneumoniae caused between 100,000 and 135,000 hospitalizations for pneumonia each year and 6 million cases of otitis media (infection of the middle ear). Since the introduction of a vaccine in 2002, the number of hospitalizations for pneumonia caused by this specific streptococcus has dropped to 13 cases per 100,000 people in the general population.

With regard to seniors, streptococci are responsible for about 70 percent of cases of endocarditis and 50 percent of all cases of pneumonia in this age group. In many cases, however, the specific organism that causes these illnesses is never identified.

Bacterial endocarditis is on the rise among the elderly population in recent years because of the increased number of seniors who have had heart valves replaced and the increased incidence of hospital-acquired infections. About of all cases of endocarditis occur in people over 60; elderly men are 8 times as

likely to develop endocarditis as elderly women. In addition to a history of heart surgery, other risk factors for endocarditis include hardening of the arteries and congenital heart malformations.

Streptococcal skin infections are particularly common in seniors; the highest incidence of erysipelas is in people between 60 and 80 years of age.

Causes and symptoms

This section will describe the diseases caused by streptococci that are most likely to affect seniors. It is important to keep in mind, however, that the same species of streptococcus can cause several different diseases, and that some of the diseases described here can be caused by organisms other than streptococci.

Strep throat

Strep throat is caused by Group A streptococci, usually S. pyogenes. It is spread by direct contact with the nasal discharges of an infected person or by respiratory droplets in the air; in a few rare cases, seniors have gotten strep throat from contaminated food. The incubation period is between two and five days.

The most noticeable symptom of strep throat is the sudden onset of severe sore throat; the patient may find it hard to talk or even swallow. A fever of 101°F or higher is typical, as are white spots or patches on the tonsils, sore or swollen lymph nodes in the neck, and the absence of a cough. Some patients also develop a headache and skin rash. The patient usually feels better within five days to a week, but may be contagious for several weeks.

Endocarditis

Endocarditis in seniors is most likely to be caused by Group B streptococci or enterococci. The disease develops when the streptococci enter the bloodstream (often through surgical incisions or open sores on the skin) and settle on the tissues lining the valves of the heart. If the surface of the valves has been changed or damaged in some way, it is easier for the streptococci to form a colony on the tissue and multiply.

The symptoms of endocarditis in seniors usually appear about 2 weeks after the bacteria entered the bloodstream. Not all patients have the same symptoms, but a common pattern is fever accompanied by back pain , night sweats, loss of appetite, and mental confusion. Some elderly patients may also develop rapid-onset dementia. About 40 percent of patients will develop skin problems, ranging from small tender nodules in the fingertips to pinpoint hemorrhages in the tissues lining the mouth or on the skin above the shoulder blades. Some patients will develop the signs of a stroke if the endocarditis is not detected early; this complication develops when the bacteria growing on the heart tissue form clumps that travel through the bloodstream and block some of the blood vessels in the brain.

Pneumonia

About half of all cases of pneumonia in seniors are caused by S. pneumoniae. Pneumonia develops when the streptococci are carried into the lungs from the mouth or throat by inhaling air containing the organisms, or more commonly, by aspiration (food or oral fluid getting into the airway because of abnormal swallowing). Seniors who are hospitalized are at increased risk of aspiration pneumonia because they often have poor oral hygiene and swallowing problems . The use of sedatives and painkillers is also a risk factor because these medications often slow down the patient's breathing.

The usual signs of pneumonia are fever, cough, and sputum (matter from the throat or lungs brought up by coughing). Many elderly patients with pneumonia may have delirium or mental confusion as the most noticeable symptom, however; only about half of seniors have high fever as an early symptom of streptococcal pneumonia.

Skin and wound infections

Seniors may develop skin infections caused by streptococci belonging to either Group A or Group B. One of the more common skin infections caused by S. pyogenes is erysipelas, also known as Saint Anthony's fire. Erysipelas is an infection of the dermis, the portion of the skin lying below the epidermis. It develops when S. pyogenes gets beneath the epidermis through a crack in the skin, a surgical incision, a patch of eczema, or an ulcer. Within 48 hours, the area of infection becomes red and swollen, with a sharply raised edge. It is bright red or orange in color and is painful to touch. Erysipelas is most likely to appear on the face, arms or legs, but may affect almost any area of the body. In addition to the rash, the patient typically develops a high fever, chills, headache, nausea and vomiting, and fatigue.

Cellulitis is another infection caused by S. pyogenes that is likely to occur in the elderly and in others with weakened immune systems. Like erysipelas, cellulitis develops when streptococci get below the outer layer of skin through insect bites, recent surgical incisions, patches of eczema, or other skin rashes that have been scratched open. Cellulitis differs from erysipelas in that it is usually slower to develop and does not have a sharp border between affected and unaffected skin.

Diagnosis

Diagnosis of streptococcal infections begins with a physical examination of the affected part of the body. In the case of strep throat, the doctor will look inside the patient's throat to examine the tonsils, touch the lymph nodes in the neck, and record the patient's temperature. The next step is a rapid strep test, which involves swabbing the back of the throat to collect a sample of mucus. The test takes about 15 minutes to yield results. Because the rapid test has an error rate of about 20 percent, the doctor will usually send another sample of mucus on a swab to a laboratory for culture. The results of this test take about 2 days.

Infective endocarditis is often diagnosed when the doctor listens to the senior's heart. A heart murmur can be heard in more than 90 percent of cases. The patient's spleen is often enlarged; this can be detected when the doctor palpates (feels) the patient's abdomen. The doctor may order an echocardiogram , which is a test that uses ultrasound to detect growths of bacteria on the heart valves as well as other abnormalities. The definitive diagnosis is provided by a culture of the patient's blood.

Streptococcal pneumonia is diagnosed by taking a chest x-ray and making a culture of the patient's blood.

Erysipelas and cellulitis are usually diagnosed by the appearance of the patient's skin. Blood cultures are usually not helpful in diagnosing these conditions.

Treatment

Treatment of streptococcal infections depends on the location of the disease and the type of organism involved.

• Strep throat: Antibiotics are usually given for strep throat, most commonly a 10-day course of penicillin or erythromycin (for patients who are allergic to penicillin.) The patient may also be given ibuprofen or acetaminophen to bring down the fever. It is important for the patient to take the complete course of antibiotic even if the symptoms go away in a day or two in order to prevent possible complications. Complications of S. pyogenes throat infections include otitis media (ear infection), rheumatic fever, glomerulonephritis (inflammation of small blood vessels in the kidneys), or meningitis (inflammation of the membranes overlying the brain).
• Endocarditis: Most species of streptococci that cause endocarditis are sensitive to penicillin and ceftriaxone. The usual treatment schedule is four weeks of intravenous penicillin in doses of 12 million to 18 million units every 24 hours or 2 g of ceftriaxone (Rocephin) in a single daily dose given intravenously or intramuscularly. The penicillin can be administered continuously or in six divided doses. In some cases the patient may need surgery after the antibiotic treatment to replace damaged heart valves.
• Pneumonia: Streptococcal pneumonia is treated with a combination of antibiotics and respiratory therapy (suctioning of chest secretions or chest percussion). The antibiotics usually given for streptococcal pneumonia are penicillin, a first-generation cephalosporin, levofloxacin, or a macrolide antibiotic.
• Erysipelas and cellulitis are treated by a 10-day course of penicillin or erythromycin, given either orally or intramuscularly. Cellulitis may also be treated with ceftriaxone given intravenously. The affected limb should be elevated and treated with wet saline dressings to bring down inflammation and swelling. Some patients with cellulites may require surgery to drain the infection if treatment has been delayed. Hospitalization is not usually needed unless the senior has an immune disorder.

Nutrition/Dietetic concerns

Seniors with strep throat should be careful to drink plenty of fluids even if their throat hurts because fever causes the body to lose fluids more rapidly. They should avoid coffee or other beverages containing caffeine and drink soup broth or soft drinks containing sugar instead.

Therapy

Therapy for streptococcal infections is intended to kill the organisms causing the infection as well as relieve the patient's symptoms. In most cases the senior will be given antibiotics either by mouth or intravenously. Treatment of pneumonia may require suctioning or other forms of treatment to remove secretions from the lungs and airway

QUESTIONS TO ASK YOUR DOCTOR

• What can I do to protect myself against streptococcal infections?
• If I am allergic to penicillin, what medications can I take for streptococcal infections?
• When should I receive a dose of pneumonia vaccine?.

Prognosis

The prognosis of streptococcal infections varies considerably:

• Strep throat: Most seniors will recover completely in a week to 10 days.
• Endocarditis: The prognosis depends on the speed of diagnosis and treatment. The mortality rate for streptococcal endocarditis is about 25 percent.
• Pneumonia: The prognosis depends on the senior's basic health and the presence of other diseases or disorders. Elderly patients who are basically healthy can recover in four to six weeks with appropriate treatment. Those with cancer, heart failure, diabetes, Alzheimer's disease, and chronic obstructive pulmonary disease, however, are likely to have severe complications from pneumonia and may be given end-of-life palliative care. The mortality rate in seniors with bacterial pneumonia runs as high as 47 percent in those with cancer or other systemic diseases.
• Skin infections: The prognosis is usually good, especially if the infection is treated early. The mortality rate for cellulitis in seniors with weakened immune systems is reported to be about 5 percent.

Prevention

Streptococcal infections of the upper respiratory tract can be prevented by avoiding contact with infected persons and by washing one's hands frequently. The risk of endocarditis can be reduced by giving the senior an antibiotic (usually amoxicillin, ampicillin, or clindamycin) an hour before dental work or a procedure involving the mouth, throat, or esophagus. This prophylaxis minimizes the possibility of streptococci getting into the senior's bloodstream through small breaks in the tissues of the mouth or throat.

KEY TERMS

Agar —A gel-like substance derived from red seaweed that is used to make a culture medium for growing bacteria on laboratory plates.

Aspiration —The passage of food from the throat into the airway during swallowing rather than further down the esophagus.

Cellulitis —An infection of the deeper layers of the skin caused by streptococci or other bacteria entering through a break in the skin.

Endocarditis —An inflammation of the tissues lining the inside of the heart and its valves.

Enterococci —Streptococci that live in the digestive tract. Most of these organisms are Group D beta-hemolytic streptococci.

Erysipelas —An acute bacterial infection of the lower layer of the skin, most often caused by S. pyogenes. Its name comes from a Greek word meaning “red skin.” It is sometimes known as Saint Anthony's fire.

Gram-positive —A term that refers to the amount of a crystal violet dye picked up by a bacterium during the Gram stain process. A Gram-positive organism looks blue or violet under a microscope whereas Gram-negative bacteria look red or pink. Streptococci are Gram-positive bacteria.

Hemolysis —The destruction of red blood cells, whether by bacteria or some other agent.

Necrotizing fasciitis —An infection of the deeper layers of skin and connective tissue caused by bacteria, most commonly S. pyogenes. Necrotizing fasciitis is sometimes called flesh-eating bacteria disease.

Prophylaxis —A measure intended to preserve health or prevent the spread of disease. Taking an antibiotic before oral surgery to prevent bacteria from entering the bloodstream is an example of prophylaxis.

Sputum —Matter from the lungs or throat that is brought up by coughing.

Quitting smoking lowers a senior's risk of pneumonia, as does immunization with a vaccine against S. pneumoniae that was developed in the early 2000s. The pneumonia vaccine is recommended for all persons over the age of 65. Healthy seniors need only one immunization; those with diabetes, cancer , kidney failure, chronic obstructive pulmonary disease , or kidney disease should be reimmunized every 6 to 10 years.

The risk of streptococcal skin infections can be lowered by proper care of the skin, proper care of surgical incisions, and prompt treatment of any open sores, insect bites, and other skin lesions . In addition, seniors should avoid scratching patches of eczema or other skin rashes.

Caregiver concerns

Care givers for seniors with streptococcal infections should be careful to:

• Make sure that the senior takes any antibiotic that is prescribed according to the doctor's directions and completes the full course of the medication.
• Keep a senior with a streptococcal infection away from other people until he or she is no longer infectious. The senior's clothing, bedding, towels, and food utensils should be washed separately from the rest of the family's laundry or dishes.
• Ask the senior's doctor about antibiotic prophylaxis prior to dental work or other minor surgical procedures.
• Request home health care if necessary for a senior recovering from pneumonia, and keep in close contact with the doctor, particularly if the senior develops delirium.
• Check the senior's skin for any signs of open sores, ulcers, cuts, or other breaks in the skin, and make sure that the skin is kept clean and dry.
• Follow the doctor's instructions for care of surgical incisions and notify the doctor at once if there are signs of infection (warmth, redness, swelling, or pain).

Resources

books

Beers, Mark H., M. D., and Thomas V. Jones, MD. Merck Manual of Geriatrics, 3rd ed., Chapter 76, “Pulmonary Infections”; and Chapter 90, “Infective Endocarditis.” Whitehouse Station, NJ: Merck, 2005.

Jevitz, Maria. “Streptococcus.” Chapter 13 in Samuel Baron, ed., Medical Microbiology, 4th ed. New York: Churchill Livingstone, 1991.

periodicals

Celestin, R., et al. “Erysipelas—A Common Potentially Dangerous Infection.” Acta Dermatolovenerologica Alpina 16 (September 2007): 123–127.

Giessel, Barton E., Clint J. Koenig, and Robert L. Blake, Jr. “Management of Bacterial Endocarditis.” American Family Physician 61 (March 15, 2000): 1725–1739.

Knoll, B., I. M. Tleyjeh, J. M. Steckelberg, et al. “Infective Endocarditis Due to Penicillin-Resistant Viridans Group Streptococci.” Clinical Infectious Diseases 44 (June 15, 2007): 1585–1592.

Maestro, B., and J. M. Sanz. “Novel Approaches to Fight Streptococcus pneumoniae. Recent Patents on Anti Infective Drug Discovery 2 (November 2007):188–196.

O'Laughlin, R. E., A. Robertson, P. R. Cieslak, et al. “The Epidemiology of Invasive Group A Streptococcal Infection and Potential Vaccine Implications: United States, 2000-2004.” Clinical Infectious Diseases 45 (October 1, 2007): 853–862.

Stulberg, Daniel L., Marc A. Penrod, and Richard A. Blatny. “Common Bacterial Skin Infections.” American Family Physician 66 (July 1, 2002): 119–124.

other

Centers for Disease Control and Prevention (CDC). Group A Streptococcal (GAS) Disease. Available online at http://www.cdc.gov/ncidod/dbmd/diseaseinfo/group-astreptococcal_g.htm [cited March 2, 2008].

Davis, Loretta. “Erysipelas.” eMedicine, February 11, 2008. http://www.emedicine.com/derm/topic129.htm [cited March 2, 2008].

Micali, Giuseppe. “Cellulitis.” eMedicine, October 19, 2006. http://www.emedicine.com/derm/topic464.htm [cited March 2, 2008].

Narayanan, Sharat K., and Charles S. Levy. “Streptococcus Group B Infections.” eMedicine, March 24, 2006. http://www.emedicine.com/med/topic2185.htm [cited March 1, 2008].

Sharma, Sat, and Godfrey Harding. “Streptococcus Group A Infections.” eMedicine, May 5, 2006. http://www.emedicine.com/med/topic2184.htm [cited March 1, 2008].

Sinave, Christian P. “Streptococcus Group D Infections.” eMedicine, May 8, 2007. http://www.emedicine.com/med/topic2186.htm [cited March 1, 2008].

organizations

Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA, 30333, (404) 498-1515, (800) 311-3435, http://www.cdc.gov/.

Food and Drug Administration (FDA), 5600 Fishers Lane, Rockville, MD, 20857, (888) 463-6332, http://www.fda.gov/default.htm.

National Institute of Allergy and Infectious Diseases (NIAID), 6610 Rockledge Drive, MSC 6612, Bethesda, MD, 20892, (301) 496-5717, (866) 284-4107, (301) 402-3573, http://www3.niaid.nih.gov/.

Rebecca J. Frey Ph.D.