| Abstract: | The efficacy of antibiotics including some newly developed penicillins and cephems on clinically isolated Branhamella catarrhalis was evaluated in vitro. Among 44 strains of B. catarrhalis which were isolated from expectorated sputum of patients with respiratory tract infections 36 strains were proved to produce beta-lactamase. MICs of penicillins for beta-lactamase positive strains ranged from less than or equal to 0.05 to 3.13 micrograms/ml, while those for beta-lactamase negative strains were all less than 0.05 microgram/ml. MICs of cephems, on the other hand, ranged more variably, especially among beta-lactamase positive strains. The most effective cephem we tested was LMOX which could inhibit all the strains of B. catarrhalis at the concentration of 0.05 microgram/ml or less. Aminoglycosides as well as macrolides also showed sufficiently low MIC values. We therefore concluded that the confirmation of beta-lactamase production by B. catarrhalis seems to be indispensable for the determination of an antibacterial activity of beta-lactam antibiotics. |
