The Different Types of Streptococci (Strep Bacteria)

Although strep throat is a common form of infection from streptococcal bacteria, it is not the only kind. Streptococcal infections are any type of infection caused by the streptococcal, or “strep” group of bacteria.

There are a number of different streptococci, which create symptoms ranging from a mild throat infection to a life-threatening infection of the blood or organs. Anyone can be affected, from babies and small children to older adults.

Most strep infections can be treated with antibiotics.

Streptococci infections are divided into several groups: Group A streptococcus, Group B streptococcus, Group C streptococcus, and Group G streptococcus.

Group A Streptococcus

Group A strep, sometimes called GAS, tends to affect the throat and the skin. People may carry GAS in these areas yet not show any symptoms of illness. Most group A strep infections cause relatively mild illness, but on rare occasions, these bacteria can lead to severe and even life-threatening disease.

Group A strep infections spread through direct contact with mucus from the nose or throat of infected persons or through contact with infected wounds or sores. (1) Illnesses from group A strep infection include:

Strep Throat In general, strep throat is a mild illness, but it can be very painful. Symptoms include sore throat that comes on very quickly, pain when swallowing, fever, red and swollen tonsils (sometimes with white patches or streaks of pus), small red spots on the roof of the mouth, and swollen lymph nodes in the front of the neck. Strep throat may also be accompanied by headache, abdominal pain, nausea, or vomiting, especially in children. Illness typically manifests two to five days after exposure.

A doctor cannot tell if someone has strep throat just by looking, so a diagnostic test is needed. A rapid strep test involves swabbing the throat and running a lab test to see if GAS is the cause of the illness.

While most sore throats are caused by viruses, strep throat is caused by bacteria and therefore can only be treated with antibiotics.

While anyone can get strep throat, it’s more common among school-aged children 5 through 15. Parents and adults who are often in contact with children of these ages are more likely to get strep throat than adults who are not. (2)

Scarlet Fever Also referred to as scarlatina, scarlet fever is a relatively mild illness characterized by a very red sore throat, a red rash that has a sandpaper feel, and a “strawberry,” or red and bumpy, tongue. Other symptoms can include fever, swollen glands in the neck, whitish coating on the tongue, and bright red skin in the underarm, elbow, or groin.

The illness typically begins with a fever and sore throat. The rash — caused by a toxin made by group A strep bacteria — usually appears a day or two later, although it can begin before the illness or up to seven days later.

Scarlet fever is highly contagious. It can be spread from person to person when someone who is infected coughs or sneezes: the bacteria travels in small droplets in the air. You can get sick by breathing in those droplets or by touching something that the droplets have landed on and touching your nose or mouth. Drinking from the same glass or eating from the same plate as an infected person can also spread the illness. It is also possible to get scarlet fever sores on the skin caused by GAS.

Scarlet fever is treated with a course of antibiotics. Complications sometimes occur and can include abscesses around the tonsils, swollen lymph nodes in the neck, and sinus and ear infections. Other, more rare complications can affect the heart, including rheumatic fever and kidney disease.

Like strep throat, scarlet fever is more common in children than adults, particularly those ages 5 through 15. Close contact with someone who has the infection is the biggest risk factor for getting the illness. There is no vaccine for scarlet fever, but people can protect themselves by practicing good hygiene, including using a tissue to cover your mouth when sneezing or coughing, washing hands frequently, using alcohol-based hand sanitizer if soap and water are unavailable, and coughing or sneezing into your upper sleeve or elbow rather than your hands if a tissue is not available. (3)

Impetigo This is an infection of the top layers of skin that typically starts when bacteria gets into a cut, scratch, or insect bite. It is usually caused by the bacteria Staphylococcus aureus but can also be caused by group A strep. It is most common among children ages 2 to 6.

Symptoms begin as itchy red or pimple-like sores surrounded by red skin, usually on the face, arms, or legs, that are filled with pus. Impetigo is contagious and can be spread by contact with sores or nasal discharge of an infected person. It can be treated with a round of antibiotics. (4)

Post-Streptococcal Glomerulonephritis Also referred to as PSGN, this is a kidney disease that can develop after a GAS infection — but PSGN is not a GAS infection of the kidneys. It’s a result of the body’s immune system fighting off the group A strep infection. PSGN usually occurs 10 days after strep throat or scarlet fever and about three weeks after a GAS skin infection.

Symptoms of PSGN include dark, reddish-brown urine, swelling in the face, hands and feet, decreased amount of urine or decreased need to urinate, and fatigue.

The condition is treated by managing symptoms, including limiting salt and water intake or prescribing medication to reduce swelling. Antibiotics can also help kill any strep A bacteria left in the body.

Most people with PSGN recover within a few weeks, but in rare instances long-term kidney damage, including kidney failure, can occur. (5)

Group B Streptococcus

Group B streptococcus, also known as group B strep or GBS, is a type of bacteria that can cause illness in people of all ages, though it can be particularly severe in newborns, most commonly causing sepsis, pneumonia, and meningitis. In adults, the most common health issues caused by GBS include urinary tract infections, skin infections, bloodstream infections, pneumonia, skin and soft-tissue infections, and bone and joint infections.

In babies, group B strep infections occur as either early-onset or late-onset. Early-onset occurs in babies younger than 1 week old, and the infection is most often passed from mother to baby during labor. Symptoms of GBS infection in newborn babies usually develop within the first few hours or days of giving birth and include being floppy or unresponsive, poor feeding, grunting when breathing, and unusually fast or slow breathing and heartbeat.

Antibiotics given to the mother during labor can help prevent the spread of the infection to the baby.

Late-onset group B strep infection in babies can occur at 1 week through 3 months old. A GBS infection is sometimes passed from mother to baby, but it can also come from another source.

Early-onset used to be the most common type of group B strep infection in newborns, but because of prevention efforts, both early-onset and late-onset occur at similar low rates, according to the Centers for Disease Control and Prevention (CDC).

In adults, group B strep infection occurs less frequently than in babies, but it can affect anyone. The sources of disease caused by GBS in adults are unknown, but the bacteria are present in both the gastrointestinal and genitourinary tracts, and may be the source of infection.

If the infection leads to sepsis or pneumonia, it can be fatal. On average, 1 in 20 nonpregnant adults with an invasive strep B infection dies, the CDC reports. The chance of GBS infection increases with age. Younger adults who do not have any other medical conditions have a lower risk of death from GBS. (6)

Group C and G Streptococci

Group C and G streptococci are much less understood than strep A and B because the diseases caused by these bacteria are far less common.

Group C and G strep most commonly live in animals such as horses and cattle and can spread to humans through raw milk or contact with these animals. The bacteria can also live in people’s throats and on human skin, particularly in areas damaged by conditions like eczema or on mucous surfaces, such as the vagina or bowel.

Infections can be treated with antibiotics, but severe infections can be fatal, especially when they have entered the bloodstream. (7)

1. Centers for Disease Control and Prevention
2. Mayo Clinic
3. Cleveland Clinic
4. Familydoctors.org