If a pathogenic bacterium is sensitive to a certain antibiotic, that is, the application of conventional doses of antibiotics can inhibit or kill the pathogenic bacterium. The patient should be judged before using antibiotics, some patients have contraindications, such as vancomycin antibiotics, if the patient culture out positive, sensitive to vancomycin, but the patient’s renal function is not good, because vancomycin has nephrotoxicity, so the patient with poor renal function before applying vancomycin, need to be carefully considered.