Definition: Bacterial culture is simply a fancy way of saying "growing bacteria." When doctors are trying to determine if a patient has a bacterial infection - in a wound, as an STD, in their throat - they take a sample from the area they think is infected and put it in a special medium where the bacteria can grow. That medium is chosen based on what site the sample is taken from and which types of bacteria are most likely to be present.
This type of culture can be used to detect everything from strep throat to chlamydia, even when an infection has barely begun. In fact, bacterial culture is a useful tool in a doctor's arsenal for just that reason. Given a comfortable environment in which to do so, bacteria tend to grow. This means that, over time, an undetectable number of bacteria that a doctor has isolated from a cut or from someone's urethra will quickly multiply to a number that can be observed, identified, and treated.
