Biophotometric investigations on the influence of cephradine and related cephalosporins on the growth of beta-lactamase-producing staphylococi.

Biophotometric growth studies were conducted with clinical isolates of beta-lactamase-producing staphylococi in the presence and absence of cephradine, cephalexin, cefazolin and cephacetrile. Of the four antibiotics, cephradine was the most effective in prolonging the suppression of bacterial growth resulting from antibiotic action while cefazolin was the least effective. Cephalexin and cephacetrile were intermediate in effect. The superiority of cephradine over cephalexin was shown to be related to the more rapid destruction of cephalexin by beta-lactamase. On comparing the results of these studies with clinical experience it was concluded that biophotometric studies have clinical relevance and consequently should be used for evaluating the efficacy of beta-lactam antibiotics against pathogenic staphylococi.