Streptococcus facts for kids

Quick facts for kids Streptococcus
Scientific classification
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Streptococcus are tiny living things called bacteria. The name comes from ancient Greek words meaning "twisted" and "grain," because these bacteria often grow in chains that look like twisted beads. They are round and usually grow in pairs or long chains. This is different from other bacteria like Staphylococcus, which grow in grape-like clusters.

Many Streptococcus bacteria can live with or without air. They are found all around us and even inside our bodies. Some types of Streptococcus are helpful, while others can cause illnesses. Scientists have identified over 50 different kinds of Streptococcus.

How Streptococcus Affects Us

Some Streptococcus bacteria are friendly and live in our bodies without causing harm. They are part of our natural microbiota in places like the mouth, skin, and gut. In fact, some are even used to make Emmental cheese!

However, other types of Streptococcus can cause various illnesses. These can range from common problems like strep throat and pink eye to more serious infections such as pneumonia (a lung infection) and meningitis (a serious infection of the brain and spinal cord lining). Some can also cause very serious skin infections.

How Scientists Classify Streptococcus

Scientists classify Streptococcus in different ways. One way is by how they affect red blood cells when grown in a lab:

• Alpha-hemolytic: These bacteria cause a partial breakdown of red blood cells, making the area around them look greenish.
• Beta-hemolytic: These cause a complete breakdown of red blood cells, leaving a clear area around the bacteria.
• Gamma-hemolytic: These do not affect red blood cells at all.

Another way to classify beta-hemolytic streptococci is called Lancefield grouping. This system looks at specific sugar molecules on the bacteria's cell walls. There are many Lancefield groups, named A through W. This system was created by a scientist named Rebecca Lancefield.

In medicine, the most important groups are:

• Alpha-hemolytic: Streptococcus pneumoniae and the Viridans streptococci group.
• Beta-hemolytic: Lancefield groups A and B (often called "group A strep" and "group B strep").

Common Streptococcus Species and What They Cause

Here are some important Streptococcus species and the conditions they can cause:

Alpha-Hemolytic Streptococcus

These bacteria cause a partial breakdown of red blood cells, making the area around them look greenish on a special dish in the lab. This is sometimes called "green hemolysis."

Streptococcus pneumoniae

Streptococcus pneumoniae is a common cause of pneumonia, which is a lung infection. It can also cause ear infections (otitis media), sinus infections, and sometimes meningitis.

Viridans Group Streptococcus

The Viridans streptococci are a group of bacteria often found in our mouths. Most of the time, they are harmless. However, if they get into other parts of the body, they can sometimes cause infections.

Beta-Hemolytic Streptococcus

These bacteria cause a complete breakdown of red blood cells. This makes the area around them look clear and transparent on a lab dish. This is also called "complete hemolysis."

Group A Streptococcus (GAS)

Group A S. pyogenes causes many common infections. These include strep throat, impetigo (a skin infection), and scarlet fever.

Sometimes, GAS can cause more serious infections if the bacteria spread to areas like the blood or organs. These can include severe illnesses like pneumonia or a serious body-wide infection called sepsis.

A serious problem that can happen after an untreated strep A infection is rheumatic fever. This happens when the body's immune system, while fighting the bacteria, gets confused and attacks parts of the body like the joints and heart valves.

Group B Streptococcus (GBS)

Streptococcus agalactiae, or group B Streptococcus, is a common cause of serious infections in newborns and older adults. It can cause pneumonia and meningitis in babies.

GBS can live in the intestines and the female reproductive system. This can increase the risk of passing the bacteria to a baby during childbirth. To prevent this, pregnant women are often tested for GBS. If they test positive, they receive antibiotics during labor to protect the baby.

Other Beta-Hemolytic Groups

• Group C Streptococcus: These bacteria, like Streptococcus equi, can cause infections in animals such as horses. Some types can also infect humans.
• Group D Streptococcus: Many bacteria once in this group are now called Enterococcus. These can cause infections in the urinary tract or heart.
• Group G Streptococcus: These are often found in animals but can also cause infections in humans.
• Group H Streptococcus: These bacteria mainly cause infections in dogs. They rarely cause illness in humans unless there is direct contact with a dog's mouth.

How Doctors Identify Streptococcus

Doctors use simple lab tests to identify common types of Streptococcus. One common method is the rapid strep test for group A strep. They can also use special kits that help tell the different groups apart.

Treatment for Streptococcus Infections

Most Streptococcus infections are treated with antibiotics, usually from the penicillin family. Common antibiotics include penicillin or amoxicillin. These medicines work by stopping the bacteria from building their cell walls. Treatment often involves taking antibiotics for about 10 days.

For people who are allergic to penicillin or have certain skin infections, other antibiotics like clindamycin can be used. Clindamycin works by stopping the bacteria from making proteins they need to survive.

Understanding Streptococcus DNA

Scientists study the DNA of Streptococcus to understand how they are related and how they cause illness. They have found that Streptococcus can be divided into several main groups based on their genetic information. This helps us learn more about these tiny organisms.

Scientists also study bacteriophages, which are viruses that infect bacteria. These phages can affect how Streptococcus bacteria behave. Bacteria can also share DNA with each other, which helps them adapt and survive in different environments.

Images for kids

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  Alpha-hemolytic S. viridans (right) and beta-hemolytic S. pyogenes (left) streptococci growing on blood agar

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  A chart showing how doctors might identify different bacterial infections, including Streptococcus.

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  A family tree showing how different Streptococcus species are related based on their DNA.

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  A diagram showing the different groups (subclades) within the Streptococcus family.

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  A diagram showing shared and unique genes among different Streptococcus species.

See also

In Spanish: Estreptococos para niños