Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.
A common bacterium, group A Streptococcus , mysteriously causes a range of diseases from benign strep throat to 'flesh-eating' wounds. The difference between pharyngeal and invasive disease is now traced to mutations in two regulatory genes.
The wide spectrum of group A streptococcal GAS disease spans uncomplicated strep throat to 'flesh-eating' wound infections. A genome-wide analysis of streptococcal gene expression by Sumby et al. Katie Ris. Sumby, P. Article Google Scholar. Shulman, S. Carapetis, J. Lancet , — Cleary, P. Stevens, D. If untreated, streptococcal infections can lead to complications. Some complications result from spread of the infection to nearby tissue.
For example, an ear infection may spread to the sinuses, causing sinusitis Sinusitis Sinusitis is inflammation of the sinuses, most commonly caused by a viral or bacterial infection or by an allergy. Some of the most common symptoms of sinusitis are pain, tenderness, nasal congestion Mastoiditis usually occurs when untreated or inadequately treated acute otitis media Other complications involve distant organs. For example, some people develop kidney inflammation glomerulonephritis Glomerulonephritis Glomerulonephritis is a disorder of glomeruli clusters of microscopic blood vessels in the kidneys with small pores through which blood is filtered.
It is characterized by body tissue swelling This condition is a reaction Toxic shock syndrome Toxic Shock Syndrome Toxic shock syndrome is a group of rapidly progressive and severe symptoms that include fever, rash, dangerously low blood pressure, and failure of several organs.
It is caused by toxins produced It is caused by toxins produced by group A streptococci or Staphylococcus aureus. The main reason for diagnosing strep throat is to reduce the chance of developing complications such as rheumatic fever Rheumatic Fever Rheumatic fever is inflammation of the joints, heart, skin, and nervous system, resulting from a complication of untreated streptococcal infection of the throat.
Because symptoms of group A strep throat are often similar to those of throat infection due to a virus and viral infections should not be treated with antibiotics , testing with a throat culture or another test is necessary to confirm the diagnosis and to determine how to treat the infection.
Several diagnostic tests called rapid tests can be completed in minutes. For these tests, a swab is used to take a sample from the throat. If these results indicate infection positive results , the diagnosis of strep throat is confirmed, and a throat culture, which takes longer to process, is not needed.
However, results of rapid tests sometimes indicate no infection when infection is present called false-negative results. If results are negative in children and adolescents, culture is needed.
A sample taken from the throat with a swab is sent to a laboratory so that group A streptococci, if present, can be grown cultured overnight. In adults, negative results do not require confirmation by culture because the incidence of streptococcal infection and risk of rheumatic fever in adults is so low. If group A streptococci are identified, they may be tested to see which antibiotics are effective a process called susceptibility testing Testing of a Microorganism's Susceptibility and Sensitivity to Antimicrobial Drugs Infectious diseases are caused by microorganisms, such as bacteria, viruses, fungi, and parasites.
Doctors suspect an infection based on the person's symptoms, physical examination results, Close contacts of a person with a streptococcal infection should be checked for the bacteria if they have symptoms or have ever had complications due to streptococcal infection. Doctors cannot tell just by looking whether a sore throat is caused by a streptococcal infection or a virus. Cellulitis and impetigo can often be diagnosed based on symptoms, although culture of a sample taken from impetigo sores can often help doctors identify other microorganisms that may be the cause, such as Staphylococcus aureus.
To diagnose necrotizing fasciitis, doctors frequently use x-rays, computed tomography CT , or magnetic resonance imaging MRI and culture. Exploratory surgery is often required to confirm the diagnosis. Antibiotics shorten the duration of symptoms in young children but have only a modest effect on symptoms in adolescents and adults.
Nevertheless, antibiotics are given to help prevent the spread of the infection to the middle ear, sinuses, and mastoid bone, as well as to prevent spread to other people.
Antibiotic therapy also helps prevent rheumatic fever, although it may not prevent kidney inflammation glomerulonephritis. Usually, antibiotics do not need to be started immediately. Waiting 1 to 2 days for culture results before starting antibiotics does not increase the risk of rheumatic fever. An exception is when a family member has or has had rheumatic fever. Then, every streptococcal infection in any family member should be treated as soon as possible. Usually, penicillin or amoxicillin is given by mouth for 10 days.
One injection of a long-lasting penicillin benzathine can be given instead. People who cannot take penicillin can be given erythromycin , clarithromycin , or clindamycin by mouth for 10 days or azithromycin for 5 days. The bacteria that cause strep throat have never been resistant to penicillin. Fever, headache, and sore throat can be treated with acetaminophen or nonsteroidal anti-inflammatory drugs NSAIDs , which reduce pain and fever.
However, children should not be given aspirin because it increases the risk of Reye syndrome Reye Syndrome Reye syndrome is a very rare but life-threatening disorder that causes inflammation and swelling of the brain and impairment and loss of function of the liver.
The cause of Reye syndrome is Prompt treatment with antibiotics can prevent streptococcal infection from spreading rapidly and reaching the blood and internal organs. Consequently, cellulitis is often treated without doing a culture to identify the bacteria that are causing it. In such cases, doctors use antibiotics that are effective against both streptococci and staphylococci such as dicloxacillin or cephalexin. The vast majority of GAS infections are relatively mild illnesses, such as strep throat and impetigo.
Occasionally, however, these bacteria can cause much more severe and even life threatening diseases such as necrotizing fasciitis occasionally described as "the flesh-eating bacteria" and streptococcal toxic shock syndrome STSS.
In addition, people may carry group A streptococci in the throat or on the skin and have no symptoms of disease. These bacteria are spread by direct contact with nose and throat discharges of an infected individual or with infected skin lesions. The risk of spread is greatest when an individual is ill, such as when people have strep throat or an infected wound. Individuals who carry the bacteria but have no symptoms are much less contagious. Treatment of an infected person with an appropriate antibiotic for 24 hours or longer eliminates contagiousness.
However, it is important to complete the entire course of antibiotics as prescribed. Household items like plates, cups and toys do not play a major role in disease transmission. Invasive GAS disease is a severe and sometimes life-threatening infection in which the bacteria have invaded parts of the body, such as the blood, deep muscle and fat tissue or the lungs.
Approximately 20 percent of patients with necrotizing fasciitis and 60 percent with STSS die. About percent of patients with other forms of invasive group A streptococcal disease die. Early signs and symptoms of necrotizing fasciitis include fever, severe pain and swelling, and redness at the wound site. Early signs and symptoms of STSS may include fever, dizziness, confusion, low blood pressure, rash and abdominal pain.
Approximately 9,, cases of invasive GAS disease occur in the United States each year resulting in 1,, deaths. In contrast, there are several million cases of strep throat and impetigo annually. Clusters of cases or outbreaks of invasive GAS have not been reported in any schools or communities in New York State.
Invasive group A streptococcal infections occur when the bacteria gets past the defenses of the person who is infected.
0コメント