The monograph is devoted to the causes of postoperative purulent-septic complications, the species composition (aerobic and anaerobic) of the microflora of the mucous membrane of the vermiform appendages and abdominal cavity exudate, the sensitivity of the microflora of the mucous membrane of the vermiform appendages and abdominal cavity exudate to antibacterial drugs, the prediction of the effectiveness of antibacterial therapy, the basic principles of antibacterial therapy, and the characteristics and classification of antibacterial drugs. The monograph will be of interest to surgeons, gastroenterologists, students of continuing professional development and postgraduate education programmes for medical professionals, family medicine specialists, general practitioners, clinical residents and medical students, as well as anyone interested in the history of medicine.