Streptococcus pyogenes: from prevention to treatment

Streptococcus pyogenes: from prevention to treatment

Better known as Streptococcus A, Streptococcus pyogenes mainly affects children. How does the transmission take place? Is this a serious infection? Who are the people at risk? How to treat? An overview of the question with Doctor Asmaa Tazi, bacteriologist at Cochin hospital in Paris.

Streptococcus pyogenes, definition

Streptococcus pyogenes, also called group A streptococcus, is a bacteria strictly affecting the human immune system.

“However, not all of us carry this bacteria,” explains Doctor Asmaa Tazi, bacteriologist at Cochin hospital in Paris. “It is estimated that 10% of children can be carriers, mainly in the ENT area (throat) between the ages of 2 and 7 (we are talking about commensal bacteria). In adults the bacteria is rarer since it does not affect more than 5% of them.. At this latent stage, the bacteria remains silent without clinical signs or symptoms.

As the Pasteur Institute indicates in its clinical presentation of the bacteria: “Group A Streptococcus (SGA), Streptococcus pyogenes, is transmitted exclusively from man to man. It is responsible for frequent benign and non-invasive infections, such as angina and impetigo, and also for serious invasive infections: bacteremia, necrotizing skin infections, puerperal infections, pleuropneumopathies, meningitis, which can be associated with a syndrome streptococcal toxic shock.

What are the risks of infections? How do you get streptococcus pyogenes?

The causes of infection and their manifestations can be diverse.

Angine streptococcique

Sometimes the bacteria becomes pathogenic, meaning it will cause infections. The most common but mild infection in children is angina white. We do not know the causes of the infection. We do not know why some children will be carriers without clinical signs and why others will become infected. “In serious infections, the bacteria has multiplied but we do not know why. Perhaps a question of local immunity”supposes the specialist.

Scarlet fever

The scarlet fever is also a non-severe manifestation of the bacteria. Scarlet fever does not require hospitalization but exclusion from school until children take antibiotics.

Is streptococcus dangerous?

In adults, we know that streptococcal A infections are less common but more severe. Cases of invasive infection are possible. “When infections are severe and invasive in both children and adults, it is because they are infections affecting sites that are normally sterile,” specifies the biologist. “It may be a deep skin infection (the fasciitis necrotizing which affects the subcutaneous tissues up to the muscles which gave its nickname of flesh-eating bacteria), a blood infection (bacteremia), a pulmonary infection (pneumopathy or pleurisy), an infection in women after childbirth (postpartum endometritis).

We know that there are situations that are at greater risk of serious infections such as viral infections. There varicella for example leads to an increased risk of streptococcal A infection, as do respiratory infections (flu, RSV).

Toxic shock syndrome may be associated with these infections. It is due to the production of toxin by this bacteria. “And here again we don't really know why in some people there will be toxic shock syndrome and not in others. underlines the expert. “It occurs in 10% of serious infections.”

How is the diagnosis made? What are the symptoms of strep?

To make the diagnosis of angina, the doctor will identify the clinical signs of angina and perform a TROD (rapid diagnostic orientation test) to determine if it is group A strep throat. The test is very easy to do and the results are available in less than 5 minutes. It allows for virtually instant diagnosis in the doctor's office. This is a swab used to take the back of the throat at the level of the tonsils and test for the presence or absence of streptococci A. The throat swab test can be done at the general practitioner, the pediatrician, or in a pharmacy. “The swab is dipped in the liquid reagent for the reaction, explains the specialist. Once the swab is discharged into the reaction mixture, a strip is dipped, the liquid rises by capillary action and if there is Streptococcus A, a band appears on the strip (a bit like a pregnancy test).

If the presence of group A streptococcus is confirmed, treatment with antibiotics will be administered.

“Regarding angina, we must keep in mind that in 90% of cases are viral and in 10% of bacterial cases and in the latter case, it is most often streptococcus A which is the cause,” would like to clarify Doctor Asmaa Tazi.

For cases of serious infections, the doctor, during the diagnosis, will observe marked signs such as high fever. Other symptoms depend on the infected sites. If the infection streptococcus pyogenes is of pulmonary origin there will be pulmonary signs (cough, breathing difficulties), if it is cutaneous, there will be clear cutaneous signs (redness, heat, pain, impetigo). In women who have just given birth, the signs of infection will result in pelvic pain.

A local sample (sampling from the skin or vaginal with a swab or surgical sample, i.e. the patient is operated on and part of the subcutaneous tissue sent to the laboratory) and blood (for blood culture) will allow identification. the bacteria in 24 hours.

What sensitivity to antibiotics and antibiogram?

If the patient presents serious signs and complications from the start, he will be placed on probabilistic processing i.e. treatment with broad-spectrum antibiotics (for all pathologies) depending on the type of infection (3rd generation cephalosporin or amoxicillin-clavulanic acid, for example) before the bacteria is detected. “Probabilistic treatment works very well because Streptococcus A is a bacteria that remains very sensitive to antibiotics”, indicates Doctor Asmaa Tazi. Once the bacteria has been identified, the treatment can be adjusted.

What treatment?

Treatments are mainly based on taking antibiotics.

Amoxicillin, the standard treatment

“Generally the standard treatment is amoxicillin for 7 to 14 days depending on the infection, complications and severity of the patient,” indicates the biologist. Evolution is rapid. “It may take longer if they are more severe and deeper infections,” says the doctor. The treatment will be the same, i.e. amoxicillin in children in cases of scarlet fever for example.

Hospitalization in certain cases

In the event of a serious infection with complications (determined by the clinical condition of the patient) the person will be hospitalized during the first 2-3 days, or even longer, for the implementation of treatment, samples, identification of the bacterium.

If the child cannot take his treatment orally he will be hospitalized throughout the treatment, this time administered by infusion.

What prevention? Is streptococcus contagious?

Several prevention measures are possible.

Protective measures

Streptococcus A is a bacteria that can be transmitted, mainly through the oropharyngeal route by droplets or by direct contact with infected lesions (when it is on the skin). It is therefore necessary to protect yourself if you know that someone is infected with this bacteria.

Test and antibiotic therapy

“When there has been a severe streptococcal A infection, around the person it is necessary to find out if there are people at risk (pregnant woman or who has just given birth, infant, elderly personperson with a current viral infection such as chickenpox)”, indicates Doctor Asmaa Tazi. “In these people at risk we implement antibiotic prophylaxis, i.e. antibiotic treatment to prevent possible infection. This mainly involves amoxicillin as well.”

We also respect basic preventions in the event of proximity to a person who has angina. This means wearing a mask, not sharing towels or cutlery at the table, and washing your hands carefully and frequently.

Research into an anti-streptococcus A vaccine is currently underway throughout the world and in Europe. “They should produce a vaccine within 10 years.” hopes Doctor Asmaa Tazi.

Death rate

As the Pasteur Institute indicates, “The mortality rate of invasive streptococcal A infections is estimated at around 10% for all pathologies combined (the mortality rates are respectively 30% in the case of streptococcal toxic shock, 15% for necrotizing dermo-hypodermitis and 20% for meningitis).