“We cannot live without bacteria, though sometimes we die because of bacteria.”

engineer and anesthesiologist Dr. Anthony Kaveh. The speed depends on a number of factors: the patient’s metabolism as well as the medicine’s concentration and its half-life—the length of time before half of it is no longer present in the body. Penicillin, for example, has a half life of 1.4 hours or less, and all of it is out of a patient’s system less than eight hours after the last dose is taken. That’s the reason penicillin must be taken multiple times per day. As with all antibiotics, if the treatment is discontinued before all harmful bacteria are eliminated, the ones that survive may start to exhibit resistance to the specific antibiotic.

HOW DO ANTIBIOTICS GIVE RISE TO RESISTANCE?