Example of<unk> . Thin paper discs containing an<unk>  have been placed on an agar plate growing bacteria. Bacteria are not able to grow around<unk> s to which they are sensitive. This is called "the zone of inhibition".|alt=See caption.<unk>  or<unk>  susceptibility<unk>  is the measurement of the susceptibility of bacteria to<unk> s. It is used because bacteria may have resistance to some<unk> s.<unk><unk>  results can allow a clinician to change the choice of<unk> s from empiric therapy, which is when an<unk>  is selected based on clinical suspicion about the site of an infection and common causative bacteria, to directed therapy, in which the choice of<unk>  is based on knowledge of the organism and its<unk> es.<unk><unk>  usually occurs in a medical laboratory, and uses culture methods that expose bacteria to<unk> s, or genetic methods that test to see if bacteria have genes that confer resistance. Culture methods often involve measuring the diameter of areas without bacterial growth, called zones of inhibition, around paper discs containing<unk> s on agar culture dishes that have been evenly inoculated with bacteria. The minimum inhibitory concentration, which is the lowest concentration of the<unk>  that stops the growth of bacteria, can be estimated from the size of the zone of inhibition.<unk>  susceptibility<unk>  has been needed since the discovery of the beta-lactam<unk>  penicillin. Initial methods were phenotypic, and involved culture or dilution. The Etest, an<unk>  impregnated strip, has been available since the 1980s, and genetic methods such as polymerase chain reaction (PCR)<unk>  have been available since the early 2000s. Research is ongoing into improving current methods by making them faster or more accurate, as well as developing new methods for<unk> , such as microfluidics.
Antibiotic sensitivity testing
Microbiological culture
Blood culture
Sputum culture
Culture conversion
Digital contact tracing
Empiric therapy
Bacteriology