Specific infections are infections in which the causative microorganism has been identified. The only way to accomplish this is by performing a C&S, culture and sensitivity in the microbiology laboratory. Very commonly a C&S is not carried out because we know with a high degree of certainty which microorganisms cause which diseases. For example, say you had a wound infection on the leg. We know that only a few microorganisms can cause this so you are prescribed an antibiotic that covers those pathogenic microorganisms. In most cases, it is a waste of time and resources to perform a C&S on all locations of the body. Having said that, culture and sensitivity testing is performed when the exact pathogen needs to be identified.