‘Flesh-eating’ bacteria: how it spreads and what its risks are

What is streptococcal toxic shock syndrome and what causes it?

Streptococcal toxic shock syndrome (STES) is a serious infection caused by group A streptococcus bacteria, specifically by the bacterium Streptococcus pyogenes, popularly known as flesh-eating bacteria or flesh-eating bacteria, which has triggered an alarm in Japan because health authorities have detected an increase in cases without being able to determine the reasons. Specifically, in 2023, 941 cases and 97 deaths were registered in this country due to this cause, and as of June 2 of this year, 977 new cases have been reported.

This syndrome is a medical emergency that has a high mortality rate (up to 30%) if not treated properly. We explain how it is contracted, what its symptoms and treatment are, whether it has also reached Europe and Spain and what measures to take to prevent infection.

Why is ‘Streptococcus pyogenes’ known as a ‘flesh-eating’ bacteria?

Streptococcus pyogenes is a common pathogen that usually colonizes the upper respiratory tract or the upper layers of the skin and usually causes mild illnesses such as strep throat, impetigo or scarlet fever, but in more severe cases it can trigger complications such as necrotizing fasciitis or toxic shock syndrome, as explained by Ignacio López-Goñi, member of the Spanish Society of Microbiology (SEM) and Professor of Microbiology at the University of Navarra, in The Conversation.

The nickname ‘carnivorous’ or ‘meat-eating’ is due, according to López-Goñi, to the destruction or necrosis of muscle and adipose tissue that occurs in necrotising fasciitis. This serious infection originates when some of the bacteria’s toxins stimulate immune system cells such as macrophages and T lymphocytes in an uncontrolled manner.

Has the flesh-eating bacteria reached Europe?

Although the Japanese origin of the flesh-eating bacteria has been mentioned, the truth is that it has been present in Europe for some time. Specifically, the M1UK strain, which was detected in 2008 and which in 2022 was responsible for an increase in cases of scarlet fever and invasive group A streptococcal infection in the United Kingdom. The M1UK strain of S. pyogenes is characterized by carrying a ‘hypertoxin’ called SpeA that makes it more virulent than other known variants.

This new, highly virulent variant has also been detected in Spain, although it has not yet been confirmed that it is dominant or more aggressive than other strains. However, it must be taken into account that S. pyogenes disease is not mandatory and this makes its monitoring more difficult.

The Spanish Society of Pediatric Infectology also reported in December 2022 on the alert in the United Kingdom and on “an apparently unusually high number of serious cases” in our country and the death of some children from this cause, for which it offered recommendations to prevent infection in minors.

Symptoms of streptococcal toxic shock syndrome

Symptoms of streptococcal toxic shock syndrome usually develop rapidly and may include:

• Sudden high fever with temperatures above 38.9°C.
• Low blood pressure (hypotension), which can lead to dizziness, fainting, or shock.
• Symptoms of damage to multiple organs: kidneys (acute renal failure), liver (liver failure), lungs (pulmonary edema and respiratory distress).
• Coagulation and bleeding problems.
• Severe pain in the affected area, often from a wound or injury.
• Skin rash. A red, sunburn-like rash may appear, which may then peel.
• Gastrointestinal problems: nausea, vomiting, diarrhea.
• Neurological symptoms: confusion, disorientation and, in severe cases, coma.

How you get streptococcal toxic shock syndrome

Streptococcal toxic shock syndrome (TSS) is contracted when group A streptococcus bacteria enter the body and produce toxins that trigger an excessive immune response. These bacteria are highly contagious, explains the Centers for Disease Control and Prevention (CDC) in the United States, and even some infected people who do not experience symptoms can transmit the bacteria to others, almost always through respiratory droplets or direct contact. TSS can develop under the following conditions:

• Wound infection. Bacteria can enter through wounds in the skin, such as cuts, scrapes, burns, insect bites, surgery, or traumatic injuries.
• Soft tissue infections. May occur in the context of necrotizing fasciitis, cellulitis, or deep soft tissue infections.
• Respiratory infections. Strep throat infections can rarely progress to TSS, especially if the bacteria spread to other parts of the body.
• Postpartum uterine infections can be an entry point for bacteria.
• Bloodstream infections. Bacteria can enter the bloodstream and spread to different parts of the body, causing systemic infections.

Risk factors for developing SSTE

In addition, there are factors or health problems that can increase the risk of developing streptococcal toxic shock syndrome, such as:

• Skin injuries or wounds: Any break in the skin, whether from cuts, surgery, burns or insect bites, can serve as an entry point for bacteria.
• Chronic diseases: Diabetes, heart disease, cancer, or chronic lung diseases can weaken the immune system and increase susceptibility to infections.
• Use of immunosuppressive medications: Treatments that suppress the immune system, such as corticosteroids, may increase the risk of this and other serious infections.
• Previous Streptococcus infections: Having had a recent or recurrent strep infection may increase your risk.
• Concurrent viral illnesses: Viral infections, such as influenza, can weaken the immune system and facilitate bacterial invasion.
• History of severe infections: People who have had severe infections with group A bacteria previously may be at higher risk.
• Conditions that compromise the integrity of the skin or mucous membranes: such as chickenpox, dermatitis or psoriasis can compromise the skin barrier and increase the likelihood of infection.

How to prevent infection with the bacteria ‘Streptococcus pyogenes’

There is no vaccine to prevent group A strep infections, and to reduce the risk of becoming infected with the Streptococcus pyogenes bacteria and avoid toxic shock syndrome, it is important to:

• Maintain good hygiene and wound care by properly cleaning and covering any cuts or injuries.
• Wearing a mask also helps prevent airborne transmission.
• Treat strep infections promptly with antibiotics as prescribed by a doctor.
• Monitor any wound or infection for signs of worsening, such as increasing pain, redness, swelling, or fever, and seek medical attention if this occurs.
• Avoid unnecessary use of immunosuppressive drugs and follow medical recommendations for the treatment of chronic diseases.
• Seek medical attention immediately if a serious infection is suspected or if symptoms consistent with SSTE occur.

How is streptococcal toxic shock syndrome treated?

If severe symptoms of infection occur, especially if associated with high fever and severe pain, it is crucial to seek immediate medical attention. Treatment for streptococcal toxic shock syndrome usually includes:

• Antibiotics, such as penicillin and clindamycin, which are often used in combination with penicillin to inhibit the production of bacterial toxins
• Intravenous fluid administration: to maintain blood pressure and hydration.
• Surgery when necessary to remove infected or dead tissue, especially in cases of necrotizing fasciitis or deep soft tissue infections.
• Support therapies, such as mechanical ventilation if the patient suffers from respiratory failure or dialysis if the patient has kidney failure.
• Intravenous immunoglobulin (IVIG): In some cases, this is administered to neutralize toxins produced by the bacteria.