What is a Serotype? - Definition & Methods for Serotyping

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

Serotypes are separate groups within a species of microorganisms that all share a similar characteristic. Learn more about serotyping and methods for how is it determined.

Food Poisoning

Have you ever been told not to eat raw cookie dough? If you have, the main reason why raw cookie dough should not be consumed is because of salmonella. Salmonella is a bacteria that is often found in raw eggs and poultry that can cause severe food poisoning. However, did you know that there are over 2,500 different types of salmonella? These different types of salmonella bacteria are based on their serotype.

This is a magnification of salmonella, a type of bacteria that has over 2,500 different serotypes.

What is a Serotype?

Serotypes refer to separate groups within a species of a microorganisms that all share a similar characteristic. More specifically, each serotype has the same number of antigens on their surfaces. Antigens are molecules that can cause an immune response when they enter the human body. Therefore, each of the over 2,500 different serotypes of salmonella has different antigens found on their surfaces.

As it was just mentioned, antigens are molecules that can cause an immune response. Antigens are often found in viruses, bacteria, and other microogranisms that can cause infections and diseases. For example, when a person consumes raw chicken or eggs that contain the salmonella bacteria, they will likely get sick with food poisoning. The antigens found on the surface of this bacteria will cause an immune response. The immune response involves the body creating antibodies, which are proteins that kill and destroy infectious viruses and bacteria.

Methods for Serotyping

In order to determine a microorganism's serotype, you must determine which antigens are found on their surface. If you recall, an antigen on a virus or bacteria will cause a person's immune system to produce specific antibodies that will kill or destroy this infectious microorganism. If you take a sample of a microorganism and its antigen and mix it with blood that contains its antibodies, it will form clumps. Blood that contains specific antibodies is known as antiserum. The process of clumps forming when an antigen is mixed with its antibodies is known as agglutination.

Agglutination involves the formation of clumps when antigens and their antibodies are mixed together.

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