[Sensitivity of Proteus mirabilis to drugs in the presence of human blood serum].

For rational antibiotic therapy of patients with persisting bacterial infections, the routine determination of antibiotic resistance in the microorganisms may be insufficient. In this case estimation of the total bactericidal activity of the antibacterial drugs and sera against the causative agents is required. It was shown experimentally that in the presence of human blood sera sensitivity of the P. mirabilis strains to benzylpenicillin, ampicillin, gentamicin, kanamycin and cephaloridin increased, the sensitivity to rifampicin varied and the sensitivity to chloramphenicol and nalidixic acid lowered. The quantitative indices of the sensitivity depended on the biological properties of the strains. The bactericidal activity of the human blood sera lowered under the action of nalidixic acid, chloramphenicol and rifampicin, with the concentrations of the antibacterial drugs being equal to those attained in the blood of patients during chemotherapy. A method for determination of the bactericidal activity of human blood sera in the presence of the antibacterial drugs with the use of P. mirabilis is described. The method is relatively simple and provides satisfactory coincidence of the results indicative of the nonspecific resistance of the blood. This allows the physician to choose the rational antibiotic therapy.