Cephamycins, a New Family of β-Lactam Antibiotics: Antibacterial Activity and Resistance to β-Lactamase Degradation

Abstract

The susceptibility to some cephalosporin antibiotics and to cephamycin C, a member of a new family of β-lactam antibiotics, was evaluated for 466 cultures representing 11 different genera or species of gram-negative clinical isolates. The susceptibility of 39 gram-negative cultures known to produce β-lactamase was also determined. The β-lactamase activity of a representative group of the clinical isolates and the 39 enzyme producers was studied with the cephalosporins (cephalothin and cephaloridine) and cephamycin C as substrates and was related to the in vitro disc susceptibility to these same antibiotics. The significant resistance to β-lactamase displayed by the cephamycins is reflected in the kinetics of enzyme activity ( K _m and V _max ) that are reported for the cephalosporins and the cephamycins. Resistance to β-lactamase is probably one of the reasons that many cephalosporin-resistant cultures are susceptible to cephamycin C.