What is Streptococcus Group A?
Streptococcus pyogenes, a type of bacteria known as Group A streptococcus (GAS), is one of the most frequently found bacteria in our daily lives. This bacteria can cause a broad spectrum of infections in both adults and children, leading to an estimated 9,000-12,000 deaths in the U.S. per year. Group A streptococcus is a type of bacteria that is known for causing a variety of diseases.
This bacteria can be broken down into more than 100 different types, based on a surface element called ‘M-protein’. GAS infections often result in throatache (or acute pharyngitis), skin infections like impetigo, erysipelas and cellulitis. In some cases, these bacteria can cause more serious conditions, such as streptococcal toxic shock syndrome, an illness with sudden onset fever, low blood pressure and rash, and necrotizing fasciitis, a rapidly progressing and severe infection referred to commonly as “flesh-eating disease”.
Besides these immediate infections, GAS can also cause secondary or ‘nonsuppurative’ complications, including acute rheumatic fever, an inflammatory disease that can affect the heart, joints, skin, and brain, and post-streptococcal glomerular nephritis, a kidney disease that can occur following a throat or skin infection.
What Causes Streptococcus Group A?
Group A streptococci are common bacteria that exist normally on our skin and in our surrounding environment. One specific variety, Streptococcus pyogenes, grows well on a substance called blood agar. When kept at body temperature, they form smooth or damp greyish-white spots with clear edges. These spots are around the size of half a millimeter or larger and are encircled by an area of distinct color change, known as “beta-hemolysis”. Looking under the microscope, these bacteria would appear as small, Gram-positive (blue on a specific stain) bead-like structures arranged in a chain. One interesting fact about this bacteria is they test negative for substances known as catalase and oxidase.
Different illnesses can result from Group A streptococci infection, depending on how they’re introduced into the body. For example, a throat infection known as strep throat happens when the bacteria are passed from an infected person through contact with saliva or mucus. On the other hand, a skin infection called cellulitis occurs when the bacteria invade the body through injuries or wounds on the skin. If not contained, this infection can become worse and lead to a much severe condition known as necrotizing fasciitis. Likewise, skin conditions such as impetigo and erysipelas are caused when these bacteria gets under the skin through tiny breaks in our skin’s natural barrier.
Risk Factors and Frequency for Streptococcus Group A
GAS, a type of bacteria, only infects humans. The nature of infections caused by GAS varies based on the specific type of infection. For example, GAS causes throat infections, also known as pharyngitis, mainly in children between the ages of 5 and 15. It can also affect adults, although less commonly. Instances of this throat infection increase during winter and early spring. Out of all pharyngitis cases, between 15 to 30 percent in children and 5 to 10 percent in adults can be attributed to GAS.
GAS is also responsible for a number of skin infections. It causes around 10% of cellulitis and erysipelas cases, two types of skin infections involving different kinds of bacteria. Impetigo, another skin infection, is also caused by a variety of bacteria, but almost half of the cases are due to GAS.
Some of the less common infections caused by GAS include toxic shock syndrome and necrotizing fasciitis. The frequency of toxic shock syndrome is about 3 cases per 100,000 people each year, with no specific peak age or demographic. Necrotizing fasciitis, a severe skin infection, occurs at an estimated rate of 2.5 cases per 1,000,000 people per year in the United States.
- GAS bacteria only infect humans.
- It commonly causes throat infections primarily in children aged 5 to 15, and less commonly in adults.
- These throat infections occur most frequently in winter and early spring.
- GAS is responsible for 15 to 30 percent of throat infections in children and 5 to 10 percent in adults.
- Around 10% of skin infections like cellulitis and erysipelas are caused by GAS.
- Impetigo, another type of skin infection, is caused by a variety of bacteria, but almost half of the cases are from GAS.
- Toxic shock syndrome, a less common infection caused by GAS, affects about 3 out of every 100,000 individuals per year.
- Necrotizing fasciitis, a severe skin infection, occurs at an estimated rate of 2.5 cases per 1,000,000 people per year in the United States.
Signs and Symptoms of Streptococcus Group A
Group A streptococci can cause several types of infections, each with its own set of symptoms. For example, one common manifestation is pharyngitis or “strep throat.” Symptoms often appear suddenly and can include a fever and sore throat, along with headaches, stomach aches, and nausea. The disease tends to spread through close contact, hence it’s common during periods of high community prevalence.
Physical symptoms of strep throat can involve inflamed tonsils, sore lymph nodes in the neck, a red and swollen uvula (the dangly bit at the back of your throat), tiny red spots on the roof of the mouth, and sometimes a scarlet fever rash. However, symptoms like a runny nose, cough, pink eye, or diarrhea are rare and usually suggest a viral, not bacterial, infection.
- Sudden onset
- Fever and sore throat
- Headaches, stomach aches, and nausea
- Inflamed tonsils, sore lymph nodes in the neck
- Red and swollen uvula
- Red spots on the roof of the mouth
- Possible scarlet fever rash
Impetigo, another infection caused by Group A streptococci, usually affects school-aged children who show up with ‘honey-crusted’ skin lesions on the face and extremities. The children otherwise appear well and do not show signs of distress or unusual vital signs, aside from the distinctive skin lesions.
A more severe condition caused by these bacteria is necrotizing fasciitis, a serious skin infection. It can start subtly, resembling a simple skin inflammation, but notably causes intense pain. The inflamed area expands quickly, and blisters or sores may form and leak bloody fluid. The skin may start to die and peel off, and there might be production of gas under the skin. As the disease progresses, the pain might decrease due to nerve damage surrounding the infected area. Other symptoms include fever and chills, and in severe cases, low blood pressure and a fast heart rate, signs of sepsis.
Another critical condition caused by Group A streptococci is toxic shock syndrome, a life-threatening complication of bacterial infections. This illness results from bacterial toxins entering the bloodstream, leading to broad symptoms of a systemic infection, like a rapid heart rate, low blood pressure, poor blood flow to the tissues, and signs of organ failure.
Testing for Streptococcus Group A
Some infections caused by a certain type of bacteria known as Group A Streptococcus (GAS) are diagnosed based only on symptoms and a physical exam. This is especially true for skin infections such as cellulitis, impetigo, and a life-threatening infection called necrotizing fasciitis. However, severe infections like toxic shock syndrome may require further testing like blood cultures. Blood cultures involve taking a sample of your blood and trying to grow the bacteria in the lab to identify what’s causing your infection and the best antibiotic to treat it.
One common infection caused by GAS is strep throat (also known as pharyngitis). The best way to test for strep throat is to swab the throat and grow any bacteria in the lab. However, results usually take at least 24 hours to come back. There are rapid tests available which are very specific – if they say you have strep, then you likely do. However, their sensitivity is a bit lower, meaning they might miss some cases of strep throat. In children, since strep throat is fairly common, a positive result on the rapid test is usually trusted, and no further testing is needed. In adults, strep throat is less common, so a negative result on the rapid test is usually trusted without further testing.
In the lab, GAS is notably easy to grow on sheep’s blood agar, a substance used to encourage bacteria growth. Its appearance under the microscope is as a Gram-positive coccus (round bacterium) arranged in chains. GAS doesn’t produce certain enzymes called catalase and oxidase. The bacteria’s type is confirmed using a method named Lancefield grouping or newer techniques such as the MALDI-TOF.
Treatment Options for Streptococcus Group A
Infections caused by Group A Streptococcus (GAS) bacteria are combated with antibiotics designed specifically to eliminate these bacteria. When a person has an infection that is believed to be caused by GAS, physicians often start the antibiotic treatment before having the lab confirm that it’s indeed a GAS infection. However, if lab results later reveal that GAS isn’t causing the infection, the use of those specific antibiotics is usually discontinued.
Several different types of antibiotics can effectively treat GAS infections. Penicillin-based antibiotics, like ampicillin and amoxicillin, are a good choice. Other types of antibiotics, including cephalosporins, macrolides, and clindamycin, also work well against GAS.
When treating a mild GAS throat infection or a simple skin infection (cellulitis), doctors often prescribe a course of oral antibiotics. For the throat infection, this usually lasts about ten days, and for the skin infection about 5 to 7 days. If a patient has a throat infection but can’t take pills regularly for some reason, they might receive a one-time injection of a type of penicillin instead.
For serious, life-threatening GAS infections like necrotizing fasciitis (a severe skin infection) or toxic shock syndrome, doctors usually don’t know what’s causing the infection right away. Because the patient’s life is a risk, they immediately start intravenous (IV) treatment with broad-spectrum antibiotics. These antibiotics fight a wide range of bacteria, including GAS, while waiting for lab results to identify the specific cause. For these severe infections, additional supportive treatments like fluids for hydration and medication to maintain blood pressure are also given.
What else can Streptococcus Group A be?
As stated earlier, various bacterial and viral diseases can look very similar to each other and to infections caused by Group A Strep (GAS). To determine what’s causing the illness, bacterial cultures or swabs may be performed. Here, they’re checking for GAS or other bacterial or viral infections. But other, non-infectious conditions can also look like a GAS infection.
Cellulitis, in particular, can look very similar to changes in the veins due to poor blood flow (venous stasis) or to symptoms of a deep vein blood clot (DVT), especially when the issues are happening in the lower legs. So, when a patient comes in with pain, redness, or swelling in their lower leg, doctors have to consider these conditions.
In many cases, changes from poor blood flow will happen in both legs, which isn’t as common in cellulitis. This information can help point towards the correct diagnosis. On the other hand, if the redness, swelling, and/or pain is only in one leg, then it might be due to a DVT or cellulitis. To determine the correct cause, ultrasound scans might be necessary.
What to expect with Streptococcus Group A
In general, if you have a less severe infection caused by Group A Streptococcus bacteria (GAS), your chances of recovery are very good. This is true for conditions like a sore throat (pharyngitis), skin inflammation (cellulitis), and skin infection (impetigo). These mild infections can easily be treated with antibiotics that you take by mouth. Interestingly, in the majority of cases, they can even get better on their own without any treatment. Because the death and disease rates (mortality and morbidity rates) of these types of infections are extremely low, it’s hard to give an accurate number for how often they cause death each year.
However, when it comes to more serious and invasive infections caused by GAS, it’s a different story. These more severe cases often lead to significant illness and even death. For example, toxic shock syndrome (a serious, life-threatening complication of certain bacterial infections) has been found to cause death in around 5-10% of cases. This is even more likely in people at extreme ages (very young or very old) or in people with other health conditions.
Even more concerning, the death rate in people diagnosed with necrotizing fasciitis (a serious bacterial skin infection that spreads quickly and kills the body’s soft tissue) ranges between 25% and 35%. Almost everyone with this condition will need surgery to help treat the infection, which can also affect their health long-term. It’s even worse for those who are diagnosed with both toxic shock syndrome and necrotizing fasciitis at the same time. For these individuals, up to 60% of cases may result in death.
Possible Complications When Diagnosed with Streptococcus Group A
Severe infections caused by the Group A Streptococcus (GAS) bacteria can lead to significant health issues and even death. One major concern, even with minor infections, is the risk of developing acute rheumatic fever. This condition comes from an adverse reaction in the body, typically following a throat infection caused by GAS. It can lead to joint pain, swelling, fever, abnormal movements, skin changes, and damage to the heart’s valves. Acute rheumatic fever can severely impact a person’s daily activities due to extreme swelling from heart failure, severe joint pain, high fever, and uncontrollable body movements.
Diagnosing this condition often involves hospital admission for comprehensive assessment of symptoms, including use of special heart imaging tests known as echocardiograms. Treatment primarily involves removing the GAS bacteria from the body using antibiotics. If the disease is severe, patients may need anti-inflammatory medications or steroids. In cases of abnormal body movements, anti-epileptic drugs may be necessary. Intensive management of heart failure symptoms could be vital for individuals struggling with fluid overload due to valve leakage. Occasionally, the heart valve damage from acute rheumatic fever becomes chronic. In severe cases, it may require surgery to repair or replace the damaged valve.
Another potential difficulty following a GAS infection is a kidney condition called post-streptococcal glomerular nephritis.
Potential Complications of GAS Infection:
- Acute rheumatic fever
- Joint pain and swelling
- Fever
- Abnormal voluntary movements
- Skin changes
- Damage to heart valves
- Kidney disease (post-streptococcal glomerular nephritis)
- Potential death
Preventing Streptococcus Group A
As is the case with any infection caused by viruses or bacteria, staying away from others and not exposing them to the infection is critical to prevent its spread. This is especially important with conditions like impetigo and strep throat, which are usually seen in children. As a result, kids are more likely to spread these infections since they are often in close contact with their peers. This makes it crucial to keep children who have confirmed infections separated from others. This may mean keeping them home from places like school or daycare. However, because the bacteria that causes these infections (Group A streptococcus or GAS) is commonly found in our environment and even on our own skin, it’s nearly impossible to completely avoid exposure to GAS.
