CEFAZOLIN, A NEW SEMISYNTHETIC CEPHALOSPORIN ANTIBIOTIC. IV

The antigenicity of cefazolin and its cross reactivity with benzylpenicillin, ampicillin and cephaloridine were studied. Cefazolin showed a sensitizing activity, as evidenced by the elicitation of specific precipitin antibodies and of hemagglutinating antibodies in experimental animals immunized with protein conjugates of this antibiotic, as do conjugates of penicillins and cephalosporins. Cefazolin gave a minimal cross reactivity, not only with benzylpenicillin but also with ampicillin and cephaloridine. Quantitative hapten inhibition of precipitation, against anti-benzylpenicillin antibodies, by haptens of 7-aminocephalosporanic acid and 6-aminopenicillanic acid was only minimal. This finding suggests the possibility that the cross reaction between cephalosporin derivatives and related penicillins against benzylpenicillin is mediated mainly by the acyl side chain of the molecules.