Bacterial throat infection (pharyngitis)

Bacterial throat infections are most commonly caused by Streptococcus bacteria. It is often difficult to tell the difference between strep throat and a viral infection. However, a throat swab can ensure a reliable diagnosis so that the bacteria causing the infection can be treated effectively with an antibiotic.

At a glance

  • If a throat infection is caused by bacteria from the Streptococcus group, this is known as streptococcal pharyngitis (strep throat).
  • It occurs most commonly between the ages of 5 and 15. It is rarer in adults.
  • A sore throat, difficulty swallowing and a high temperature are typical symptoms.
  • Doctors normally use a throat swab to make an accurate diagnosis of strep throat.
  • Once an infection is confirmed, it can be treated effectively with an antibiotic.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Treatment room – a doctor looking into a girl’s mouth

What is streptococcal pharyngitis (strep throat)?

Streptococcal pharyngitis (strep throat) is a bacterial throat infection, which normally causes sore throat, difficulty swallowing and a high temperature. It is caused by bacteria from the Streptococcus group – in most cases Streptococcus pyogenes.

This type of bacterial throat infection is much less common among adults than among children and adolescents. It tends to occur most frequently in winter and spring.

Throat infections are contagious. Those infected should avoid close contact with others to avoid spreading the illness.

What are the signs of strep throat?

Common symptoms of a bacterial throat infection caused by streptococcal bacteria are:

  • sore throat
  • difficulty swallowing
  • high temperature, fever
  • swollen lymph nodes
The most common symptoms of strep throat include: sore throat, difficulty swallowing, high temperature and swollen lymph nodes

Among children in particular, other symptoms may include headache, stomach ache, nausea and vomiting.

Symptoms typically develop very quickly. Each of these symptoms can vary widely and can occur on their own.

Important: Viral throat infections cause similar symptoms. A viral infection also causes symptoms such as rhinitis (sneezing, itchiness and a blocked or runny nose), cough, diarrhea and conjunctivitis.

What causes strep throat?

A streptococcal throat infection is caused by the Streptococcus pyogenes pathogen – a member of the group A Streptococcus genus of bacteria. These bacteria are transmitted from person to person.

Infection often occurs as a result of direct close contact with a sick or contagious person. The bacteria can spread in droplets when a person sneezes or coughs (droplet infection) or through touching of contaminated surfaces (smear infection), e.g. when shaking hands.

Many people are also infected through indirect contact when touching contaminated door handles or toys, for example. This is another type of smear infection.

In rare cases, group A Streptococcus bacteria are spread by means of food or water.

Interesting fact: Streptococcus pyogenes bacteria can also cause other illnesses, such as tonsillitis, scarlet fever or impetigo.

How common is strep throat?

In general, more people contract strep throat during the months of winter and spring.

This type of infection occurs most commonly between the ages of 5 and 15. Strep throat causes up to 30 percent of all cases of sore throat in this age group. In adults, this figure is only about 10 percent.

Strep throat occurs most commonly in children and adolescents between the ages of 5 and 15.

A bacteria throat infection is very rare in children younger than 3.

How does strep throat progress?

In general, an acute bacterial throat infection with streptococcal bacteria heals on its own and most symptoms disappear after one week.

However, secondary conditions or complications may occur in rare cases. These include:

Treatment with antibacterial antibiotics can slightly shorten the course of the infection and reduce the risk of complications. People treated with antibiotics are no longer contagious once they have been symptom-free for at least 24 hours.

How can strep throat be prevented?

There is no vaccine against streptococcal throat infections. It is not normally advisable to take antibiotics on a precautionary basis.

However, if someone has already had a secondary streptococcal infection (such as rheumatic fever) in the past, they may be advised by their doctor to take preventive antibiotics to avoid another infection.

There are a number of simple steps that people can take to avoid infection, for example:

  • avoid contact with people who have an acute infection
  • wash hands thoroughly and often with soap and warm water
  • frequently disinfect items like toys and door handles

How is strep throat diagnosed?

Doctors cannot normally diagnose a streptococcal throat infection based on symptoms alone.

This is why they also use a throat swab. The sample taken can be analyzed on-site at the doctor’s practice using a rapid screening test or sent for testing in a lab. If the result of the rapid strep screen is negative, it may be useful to have another throat swab analyzed in the lab. If the rapid strep screen is positive, this is sufficient to verify a streptococcal infection requiring a prescription for antibiotics.

Important: It is important to verify that the infection is bacterial so that the streptococcal pharyngitis can be treated properly. Antibiotics are ineffective against viral throat infections.

How is strep throat treated?

A sore throat, even if caused by a bacterial infection, is not automatically a reason to take an antibiotic.

If it is clear that an acute inflammation of the throat has been caused by streptococcal bacteria, the doctor can prescribe a suitable antibiotic.

Penicillin or amoxicillin in tablet form are most commonly used to treat strep throat. The tablets are taken two to three times a day for a period of 10 days. Other antibiotics can be used for anyone who is allergic to penicillins.

In most cases, the symptoms disappear at the latest on the third day of treatment with antibiotics. Despite this, it’s important to continue taking the tablets for the full period prescribed by the doctor. Otherwise, the infection may not clear up completely and may flare up again.

Important: Some bacteria can gradually become insensitive (resistant) over time to antibiotics that were previously highly effective. A carefully considered, responsible use of antibiotics ensures that they remain effective for as long as possible.

In the case of severe pain or fever, medication to relieve pain and reduce temperature can also be taken (e.g paracetamol or ibuprofen).

Some people suffer acute strep throat on a recurring basis. The tonsils may also become inflamed (tonsillitis). If this happens frequently or if the symptoms are severe, surgical removal of the tonsils may be considered.

Other important measures

If someone has a streptococcal infection, it’s important that they don’t attend any community facilities (including school) until they have begun antibiotic treatment and until they have been symptom-free for at least 24 hours. At that stage, people with a streptococcal infection are no longer contagious.

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen – IQWiG). As at:

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