Inclusion Criteria:  ICU patients receiving tigecycline or polymyxin B treatment; Age 14-95, gender unlimited; there are clear infections and strains; The patient and/or his/her family agree to sign the informed consent voluntarily.  Exclusion Criteria:  Patients with treatment of less than 4 days; patients with abscission; Pregnant patients; Patients with age < 14 years or > 95 years.