Activity of cefotiam in combination with beta-lactam antibiotics on enterobacterial hospital strains

By using checkerboard titrations the effect of cefotiam combined with different beta-lactam antibiotics on fifty strains of Enterobacteriaceae moderately susceptible (minimal inhibiting concentration ⩾8 mg/l) or resistant (minimal inhibiting concentration ⩾64 mg/l) to cefotiam was evaluated. The following compounds were tested: cefamandole, cefazolin, cefmenoxime, cefotaxime, cefotiam, ceftazidime, cefuroxime, mecillinam and piperacillin. The synergistic effect varied markedly. The combination cefotiam—mecillinam showed the highest rate of synergistic activity. Antagonism was found in 1% of the combinations.