Carbenicillin plus cefazolin with or without mecillinam as an early treatment of bacteremia caused by gram-negative organisms: randomized double-blind study.

Mecillinam or a placebo was added to a combination of cefazolin and carbenicillin as an early therapy of septicemia caused by gram-negative organisms in patients with serious underlying diseases, none of whom was neutropenic, however. Patients in whom infection was caused by pathogens against which mecillinam and cefazolin or mecillinam and carbenicillin were synergistic might have responded more often than patients treated with nonsynergistic combinations. However, overall results did not show any benefit from combining mecillinam with cefazolin and carbenicillin. This study suggests that in nonneutropenic patients with septicemia caused by gram-negative organisms, there is no need to intensify antimicrobial therapy beyond a certain point of efficacy. The measurement of the bactericidal activity in the serum of treated patients might serve as guide for adequate therapy.