CFUs are used to measure bacterial growth and are often referred to as “colony-forming units”. A CFU represents one cell that grows into an independent bacterium after being placed on an appropriate medium. For example, suppose you wanted to know if there was enough S. aureus present to cause infection, you could take a swab from your wound scabs, plating out what’s left onto agar plates containing antibiotics, such as methicillin. If no colonies were found after incubation, then you would conclude that the amount of S. aureus in your sample was not high enough to infect you.
The term colony refers to small clumps of bacteria that grow on an agar plate after being inoculated with samples containing microorganisms. A single cell does not form colonies, but if you put many different kinds of cells into one dish, they will begin to cluster together by themselves to form a colony. This happens because each type of cell produces a kind of glue that helps them stick together so that they cannot easily separate from one another. The result is usually a flat surface covered with tiny dots called “clusters”. When these clusters become large enough, they are visible under the microscope. Read on to know how to calculate CFU.…
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