Strep Throat

Strep throat, or streptococcal pharyngitis, is the most common throat infection caused by a bacteria. It is found most often in children between the ages of 4 and 15, although it also occurs in adults. Children younger than 3 years old rarely get throat infections, although they can get strep infections of other places.

Strep throat infections usually occur in the late fall, winter, and early spring.

Strep throat in a child, Source:CDC

Other Names

Streptococcal pharyngitis

Cause

Strep throat (also known as acute streptococcal pharyngitis) is usually caused by Group A Streptococcus bacteria.

Group A S. pyogenes colonies showing beta-hemolysis. Source: CDC

The most commonly encountered Group A Streptococcus is Streptococcus pyogenes. Often S. pyogenes and related bacteria are classified as Group A beta-hemolytic streptococcus or GABHS.

People may carry Group A streptococci in the throat or on the skin and have no symptoms of illness. Group A streptococci, in addition to strep throat, can cause skin infections (impetigo, cellulitis, and erysipelas). Group A streptococci also are one cause of a serious invasive infection called necrotizing fasciitis.

Symptoms

The most common sign/symptom of a strep throat infection is a red, painful sore throat. White patches of pus (exudates) on the tonsils are also common findings. Other symptoms can include swollen lymph nodes in the neck, fever, and headache. Nausea, vomiting, and abdominal pain can occur but are more common in children than adults.

The symptoms of strep throat can vary quite a bit depending on the age of the infected person.

In toddlers and younger chilren:

• sore throat
• trouble swallowing
• moderate fever
• poor appetite
• fussiness/crankiness
• swollen lymph nodes beneath the jaw

In older children and adults:

• high fevers
• very painful throat
• difficulty swallowing
• pus on the tonsils

Symptoms appear within 3 days after being exposed to the bacteria. Once infected, people are contagious (able to pass the infection to others) for up to 2 to 3 weeks, even in the absence of symptoms. After 24 hours of taking antibiotics, patients are no longer contagious, although the entire course of antibiotics should always be completed.

How Strep Throat is Spread

Group A streptococci 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. Acutely ill persons such as those who actively have strep throat or skin infections, are most likely to spread the infection. Those 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.

Most people do not get Group A strep infections from casual contact with others. A crowded environment like a dormitory, school, or nursing home, however, can make it easier for the bacteria to spread. There have also been reports of contaminated food, especially milk and milk products, causing infection.

Epidemiology

On average, children experience 5 or more upper respiratory infections per year. Most of these infections are not caused by Streptococcus, but rather many different types of viruses. It is estimated that, on average, one streptococcal infection occurs every 4 years in children. The incidence in adults is about one infection every eight years. ^[1]

Diagnosis

Because strep throat can look like many other diseases but can have severe consequences if not treated, an accurate diagnosis is essential. While a physical examination by a physician may led to suspicion of strep throat, tests are required to confirm the diagnosis.

Two tests are usually performed: a rapid test and a culture:

• Rapid antigen test: A rapid strep test can be done in the doctor's office. A swab is used to take a sample of the fluids from the back of the throat. The test only takes about 5 minutes. If the result is positive for streptococcal bacteria, the diagnosis is confirmed, but a negative test result does not rule out strep throat. Rapid tests have an error rate of about 20%.

• Throat swab culture: A throat swab for culture of the bacteria is often also sent to the lab for further testing, especially is the rapid test is negative and a high index of clinical suspicion exists. This takes 24-48 hours for a result. If streptococcal bacteria grow during this time, the test result is positive, and the diagnosis of strep throat is confirmed.

The use of an algorithm such as Centor or McIsaac will help you decide the post-test probability.

CENTOR - gives one point for each:

• History of fever
• Anterior cervical lymphadenopathy
• Tonsilar exudate
• Absence of cough

The likelihood ratio of a positive result for 2 points is 0.75, for 3 points 2.1, and for 4 points 6.3. The post-test probability of this score will depend on your pretest probability (the prevalence of strep in your community). There is wide variation between 4% and 25% in adults with sore throat. Even with 3 points and a pretest probability of 15% the prevalence of strep would be 27%. What is less certain is the threshold at which we should treat possible strep throat. ^[2]

It is important to confirm a strep throat diagnosis before treatment since most sore throats are caused by viruses, and antibiotics are useless against viruses and may promote resistance of bacteria in future strains. However, if a high index of clinical suspicion exists and regardless of results of the rapid antigen test (or absence of testing), antibiotic therapy may be started immediately to prevent the complications of strep throat.

Treatment

Treatment for strep throat is usually antibiotics and perhaps analgesics to alleviate the symptoms. After 24 hours of taking the antibiotics, patients are no longer contagious. Treatment will also reduce the chance of complications.

Current guidelines by expert groups recommend penicillin as the medicine of choice for treating strep throat because penicillin has been proven to be effective, safe, and inexpensive.^[3] In chilren, amoxicillin is the most commonly used antibiotic as it is available in liquid form and tastes better than other antibiotics (resulting in better patient tolerance and compliance).

Recurrent Infections and Tonsillectomy

Recurrent strep throat infections are often treated with surgical removal of the tonsils. While tonsillectomies are performed less frequently now than in the 1970s, they are still the most common surgical procedure in children.

There is some debate on the efficacy of tonsillectomy, especially in adults.^[4]

Holistic and Alternative Treatments

A number of natural remedies for sore throats have been proposed but most have not been verified as being effective in scientific studies. Some of the most popular are:

• Zinc lozenges. Each lozenge contains about 23 mg of zinc and can be taken every four hours. Do not use these lozenges for more than a week.
• Gargling with a mixture of water and table salt. The more salt one can tolerate, the better the efficacy in symptom relief. Do not swallow this mixture.
• Gargle with crushed aspirin mixed with water to relieve pain.
• Warm tea with honey.
• Humidification of ambient air

Please consult your medical doctor before initiating treatment with these alternatives, as strep throat needs rapid antibiotic therapy to avoid complications.

Complications

Strep throat can lead to serious complications if left untreated. These complications include:

• Tonsillitis or peri-tonsillar abscess
• Sinus infection (sinusitis)
• Ear infection
• Scarlet fever
• Streptococcal Toxic Shock Syndrome
• Rheumatic Fever

Severe Streptococcus infections can lead to inflammatory diseases in the joints, kidneys, and other tissues. In Rheumatic Fever, the host immune system, activated by Group A Streptococcus infection, forms immune complexes, or inflammatory deposits. Affected tissues include the joints, skin, and muscle (including the heart). These deposits, when formed on the heart and especially the heart valves, can cause scarring. This scarring can interfere with the flow of blood inside the heart leading, in some cases, to heart failure. ^[5]

Until the advent of antibiotic therapy for strep throat, Rheumatic Fever was a leading cause of death among children in the US. However, today the risk of developing severe complications from strep throat is low in the United States.^[6] Another very dangerous complication of Group A strep infection is Post-Streptococcal Glomerulonephritis, which is an acute inflammation of the kidneys that can cause life-threatening kidney failure.

References

1. ↑ Martin JM, Green M, Barbadora KA, Wald ER . "Group A streptococci among school-aged children: clinical characteristics and the carrier state". Pediatrics 114 (5): 1212-9 (2004). Abstract | Full Text
2. ↑ Does This Patient Have Strep Throat? Mark H. Ebell, MD; Mindy A. Smith, MD; Henry C. Barry, MD; Kathy Ives, BS; Mark Carey, BS JAMA. 2000;284:2912-2918
3. ↑ Richelle J. Cooper, Jerome R. Hoffman, John G. Bartlett, Richard E. Besser, Ralph Gonzales, John M. Hickner, and Merle A. Sande. Principles of Appropriate Antibiotic Use for Acute Pharyngitis in Adults: Background. Ann Intern Med, Mar 2001; 134: 509 - 517.Abstract
4. ↑ Olli-Pekka Alho, Petri Koivunen, Tomi Penna, Heikki Teppo, Markku Koskela, and Jukka Luotonen. Tonsillectomy versus watchful waiting in recurrent streptococcal pharyngitis in adults: randomised controlled trial. BMJ, May 2007; 334: 939.Abstract | Full Text
5. ↑ García-Suárez Mdel M, Vázquez F, Méndez FJ. Streptococcus pneumoniae virulence factors and their clinical impact: An update. Enferm Infecc Microbiol Clin. 2006 Oct;24(8):512-7. Abstract | Full Text
6. ↑ Pace B. JAMA patient page. Strep throat. JAMA. 2000 Dec 13;284(22):2964. Abstract | Full Text

External Links

Group A Streptococcal Infections - National Institute of Allergy and Infectious Diseases

Medical college of Wisconsin: Strep Throat