Properties of Ro 13-99041 as a substrate and inhibitor of beta-lactamases.

Ro 13-9904 is a novel semisynthetic and highly active parenteral cephalosporin. Its stability against hydrolysis by several beta-lactamases was studied. The enzymes were isolated from various Enterobacteriaceae or Staphylococcus aureus and several commercially available enzyme preparations were also included. Most of the penicillinases, cephalosporinases or the TEM-type beta-lactamase studied were unable to hydrolyze this novel cephalosporin. The cephalosporinases from Bacillus cereus 569/H9 and Proteus vulgaris 1028, however, were found to readily cleave all new cephalosporins like cefuroxime, cefotaxime and Ro 13-9904, but not cefoxitin. Ro 13-9904 was seen to be a potent inhibitor of several cephalosporinases, but had little or no affinity for penicillinases or the TEM lactamase.