Bacteria are often divided into different families and groups. This division is based in part on the physical appearance of the bacteria as well as some of their chemical and biological characteristics. Beta-hemolytic strep describe bacteria which all can destroy red blood cells under certain conditions and can cause a variety of different diseases.

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Strep stands for streptococci, which describes a class of strains of bacteria. Streptococci typically are found in pairs or in chains, the University of South Carolina School of Medicine explains 2. These bacteria are gram-positive, which means that they have an outer wall which can react with certain kinds of dyes and are facultatively anerobic, which means that they can grow without oxygen if necessary. Streptococci are divided into different groups based on the proteins which are found on the bacteria's surface.

Hemolysis Classification

The term "beta hemolytic" refers to a test which can be used to differentiate different kinds of streptococci, Todar's Online Textbook of Bacteriology explains 1. The hemolysis test is performed by culturing the bacteria on a special growth medium known as blood agar. Beta hemolysis occurs when the bacteria are able to break down the blood cells in the growth media, causing large clear circles to appear around the bacteria. Alpha hemolysis, another potential result, causes the surrounding blood cells to turn green. Gamma hemolysis means the blood cells are unaffected. Group A and B streptococci are beta hemolytic.

Group A Streptococci

Group A streptococci infections cause many different kinds of infections. These bacteria are responsible for causing strep throat, many different ear infections, bacterial pneumonia, meningitis, scarlet fever and cellulitis, the Family Practice Notebook states. These bacteria can also cause toxic shock syndrome and sinus infections. The most common type of group A streptococci is Streptococcus pyogenes.

Group B Streptococci

Group B streptococci cause far fewer diseases than Group A, the University of South Carolina Medical School notes 2. However, Group B Streptococci includes the bacterium Streptococcus galactiae. This organism normally lives in the vagina and can cause meningitis and sepsis in newborns if they are infected during the birthing process.


The body's immune system is naturally able to fight off most streptococcal infections. In some cases, however, antibiotics may still be needed. In general, group A and B streptococci are still susceptible to penicillin, so it or other beta-lactam antibiotics may be used. Doctors may perform a culture on a sample from the patient to determine the strain of streptococcus bacteria and the most appropriate treatment.