Streptococcus

Tiny germs live in your mouth.

Some grow in long chains. They look like little grains. These germs can be helpful. They help make Swiss cheese.

Some germs can make you sick. They can cause a sore throat. They can also cause pink eye. Some germs can even cause ear pain. Most of these germs are not bad. They live on your skin too. They are part of your body.

It is good to know about them.

Streptococcus is a type of tiny germ called bacteria.

Their name comes from Greek words. These words mean "twisted grain." This name fits how they grow. They divide in a way that makes long chains. These chains can look bent or twisted.

Many of these germs live in your mouth. They live on your skin too. These germs are often helpful. For example, they help make Swiss cheese.

But some types can make people sick. Scientists group them by how they act on blood. We call this hemolysis.

Some types are alpha-hemolytic. They turn blood a greenish color. Others are beta-hemolytic. These types break red blood cells apart completely.

One famous group is called Group A. It can cause strep throat. It can also cause scarlet fever. Some Group A germs cause very serious sickness. They can even cause skin infections. Another type is Group B. This can cause sickness in newborn babies. Scientists study these many groups to keep us healthy.

Streptococcus is a large group of tiny living things called bacteria.

Their name comes from two Ancient Greek words. The word "streptos" means twisted. The word "kokkos" means grain. These names describe how the bacteria look when they grow. They divide along a single line to form long chains. These chains often look bent or twisted.

This is different from other bacteria that grow in round clusters like grapes.

Scientists study these bacteria by seeing how they affect red blood cells. This process is called hemolysis.

Some types are alpha-hemolytic. They only partially break the cells. This makes the blood look greenish on a lab plate. Other types are beta-hemolytic. These bacteria use a tool called a streptolysin to break cells completely. This leaves clear or yellow areas on the blood agar. A third type is gamma-hemolytic, which does not change the blood at all.

People have studied these bacteria for a long time. A surgeon named Albert Theodor Billroth named them in 1877. Later, a scientist named Rebecca Lancefield created a way to group them. She used the different sugars on the cell walls to make groups. These are called Lancefield groups. They use letters from A to W to name them. This helps doctors know exactly which type of bacteria is present.

There are over 50 different species in this group today.

Some species are very helpful to us. For example, they are a necessary ingredient for making Emmentaler cheese. Many others live in our mouths and on our skin without causing harm. However, some can cause serious illness. Group A bacteria can cause strep throat or scarlet fever. They are estimated to cause more than 500,000 deaths every year. Group B bacteria are a common cause of meningitis in newborn babies.

Understanding these bacteria helps us stay healthy in many ways. Many of these germs are part of our natural microbiome. This is the collection of tiny living things that live in and on our bodies. Some bacteria live in our intestines or our respiratory tract. We can use medicine to stop the bad ones from spreading. Doctors even test pregnant women for Group B bacteria. This helps keep both the mother and the baby safe during birth.

Streptococcus is a large genus of gram-positive, spherical bacteria.

These microscopic organisms belong to the family Streptococcaceae. They are part of the order Lactobacillales, which includes many lactic acid bacteria. The name comes from Ancient Greek words meaning "twisted grain." This name describes their unique physical structure. Unlike staphylococci, which divide in many directions to form grape-like clusters, streptococci divide along a single axis. This specific way of dividing causes them to grow in long, bent, or twisted chains.

Scientists classify these bacteria using their hemolytic properties. Hemolysis describes how the bacteria affect red blood cells when grown on blood agar. There are three main types of hemolysis. Alpha-hemolytic species cause partial or incomplete hemolysis. They oxidize the iron in hemoglobin, which turns the agar a dark greenish color. This is why the viridans group is named after the Latin word for green. Beta-hemolytic species cause complete lysis, or the total rupture, of red blood cells. This creates clear or yellow transparent areas around the bacterial colonies.

Finally, gamma-hemolytic species cause no hemolysis at all.

Beta-hemolytic bacteria use specific tools called exotoxins to break down cells. One such enzyme is called streptolysin. There are two main types: Streptolysin O and Streptolysin S. Streptolysin O is an oxygen-sensitive cytotoxin. It interacts with cholesterol in the membranes of eukaryotic cells, such as red and white blood cells. Streptolysin S is an oxygen-stable cytotoxin. It affects immune cells like lymphocytes and helps the bacteria avoid being cleared by the host's immune system. Some species, like Streptococcus agalactiae, show special properties in the CAMP test when grown with Staphylococcus.

To organize these many species, scientists use the Lancefield grouping system. This method is a serotype classification based on specific carbohydrates found on the bacterial cell wall. Rebecca Lancefield developed this system while working at Rockefeller University. The groups are named with letters from A to W, though E, I, and J are excluded. In medical settings, doctors focus on specific groups. They look for alpha-hemolytic S. pneumoniae and the viridans group. They also watch for beta-hemolytic Lancefield groups A and B.

Group A streptococcus, or GAS, includes the species Streptococcus pyogenes. This bacterium is a major human pathogen. It can cause noninvasive infections like strep throat, impetigo, and scarlet fever. However, it can also cause invasive, severe infections. These include necrotizing fasciitis, which is sometimes called "flesh-eating" infection, and toxic shock syndrome. GAS is estimated to cause more than 500,000 deaths every year globally. Sometimes, the immune system's response to GAS can cause problems. For example, untreated infections can lead to rheumatic fever, where antibodies attack the body's own heart valves and joints.

Group B streptococcus, or S. agalactiae, presents different risks. It is a leading cause of meningitis and sepsis in newborns and the elderly. Because these bacteria can live in the female reproductive tract, they can be passed to a baby during birth. To prevent this, medical guidelines recommend testing pregnant women between 35 and 37 weeks of gestation. If a woman tests positive, doctors provide antibiotics during labor. This protocol can prevent 65% to 70% of early-onset sepsis cases in infants. Vaccines against Group III polysaccharides have also been shown to help prevent transmission.

Many streptococci are not harmful and are actually quite useful. Many species are part of the commensal human microbiota. This means they live naturally in our mouths, skin, intestines, and respiratory tracts without causing disease. They are even a necessary ingredient in making Emmentaler, or Swiss, cheese. Other groups, like Group C and Group G, are considered zoonotic pathogens. This means they can be passed from animals to humans. For example, S. equi can cause strangles in horses, while other species affect cattle. Understanding these diverse roles helps scientists manage both food production and public health.