FIELD : medicine.SUBSTANCE : group of inventions relates to the field of medicine, specifically to clinical pharmacology and infectology, and is intended for the treatment of a bacterial infection in an individual. Pharmaceutical composition for treating a bacterial infection in an individual contains (a) at least one antibacterial agent or a pharmaceutically acceptable derivative thereof, and (b) an enhancer compound or a pharmaceutically acceptable derivative thereof. Enhancer compound is (i) resistant to beta-lactamases and (ii) selective and high affinity penicillin-binding protein PBP-binder with IC50 equal to 1 mcg / ml or less, only to one of PBP, which is selected from the compound of formula (III) and mecillinam. Also provided are methods for treating a bacterial infection in an individual and a method for increasing the antibacterial efficacy of an antibacterial agent in an individual.EFFECT : use of a group of inventions makes it possible to increase the effectiveness of treatment of a bacterial infection in an individual due to the synergistic bactericidal effect of the constituents.16 cl, 14 tbl, 3 ex