[Studies on the in vitro effects of cephalothin and gentamicin, alone and in combination, on proteus mirabilis and enterococci (author's transl)].

A combined antibiotic therapy is only useful in a few precisely defined clinical pictures where testing of the chemotherapeutics administered is required to determine their characteristics of action (antagonism, indifference, synergism) on the isolated organism. For the initial therapy of critical acute infections, simultaneous administration of cephalothin and gentamicin proved to be valuable. In the present study, the efficiency of these chemotherapeutics alone and in combination was investigated in a quantitative serial dilution test and with the membrane-filtration method. Thirty strains of Proteus mirabilis and enterococci showed only low sensitivity to the antibiotic alone. In combination, whereby gentamicin was at a constant level comparable to in vivo serum levels, an increase of bacteriostatic and bactericidal action could be demonstrated, especially for Proteus mirabilis. The antibacterial spectrum, the molecular-biological mode of action, clinical experience and possible side-effects of the cephalotin-gentamicin combination are discussed.