[Antigenicity tests of tazobactam/piperacillin, tazobactam and piperacillin]

The antigenicity tests of Tazobactam/piperacillin (TAZ/PIPC), tazobactam (TAZ:beta-lactamase inhibitor) and piperacillin (PIPC:penicillin antibiotic) were performed in mice and guinea pigs. The following results were obtained. 1. TAZ/PIPC, TAZ or PIPC had no immunogenicity and allergenicity in either passive cutaneous anaphylaxis (PCA) test using BALB/c and C3H/He mice or in PCA test using guinea pigs. 2. Guinea pigs sensitized with TAZ/PIPC, TAZ or PIPC showed no anaphylactic symptoms in active systemic anaphylaxis (ASA) test. 3. Guinea pig PCA tests using protein conjugates as sensitizing and challenging antigens showed positive reactions. Immunological cross-reactivity tests were performed by using these conjugates in guinea pig PCA reaction. Results showed that TAZ/PIPC and PIPC cross-reacted with penicillin G (PCG) and ampicillin (ABPC), but not with cephalothin (CET) and cephmetazol (CMZ). TAZ did not cross-react with PCG, ABPC, CET or CMZ. 4. From the results of the passive hemagglutination (PHA) test, no antibody against TAZ/PIPC, TAZ or PIPC was detected. 5. In direct Coombs' test using human blood, TAZ/PIPC, TAZ, PCG and CET showed positive reactions at 20-80, 5-20, 80 and 10-20 mg/ml, respectively. 6. The results of a test on in vitro covalent binding activity with human serum albumin indicated that the order of binding potency was CET > CMZ > ABPC > PCG = PIPC > TAZ under the physiological condition (pH 7.2-7.4), and was CMZ > CET > ABPC > PIPC > TAZ > PCG under the alkaline condition (pH 10.0-10.5), respectively.