Structural correlations with cross-reactivity of beta-lactam antibiotics in delayed type hypersensitivity. Cross-allergenicity in hypersensitivity to cephems with a tetrazolyl group in the C-3 side chain.

Cross-reactivity associated with delayed type hypersensitivity (DTH) arising from cephem antibiotics with a tetrazolyl group in the C-3 side chain was investigated by clinical testing and animal experiments. Clinical cross-reaction testing was performed with the leucocyte migration inhibition test (LMIT) with respect to sixteen patients with hypersensitivity induced by cephems with a tetrazolyl group in the C-3 side chain. The proportion of positive LMIT cross-reactions to cephems with a tetrazolyl group in the C-3 side chain was 78% (25/32), to cephems without a tetrazolyl group, 5% (1/22), and to penams, 0% (0/12). The proportion of positives in tests performed with methyl-tetrazolethiol (MTT) and hydroxyethyl-tetrazolethiol (HTT), which essentially represent the structures of the C-3 side-chains in the allergenic drugs, was 29% (4/14), while the corresponding proportion for 7-aminocephalosporanic acid (7ACA), which represents the skeleton structure of the cephem antibiotics, was 33% (1/3). The animal experiments were performed with guinea pigs, with latamoxef, cefoperazone and MTT as the sensitizing agents and testing for cross-reactivity by means of delayed type intradermal reactions as well as the LMIT. The results of intradermal testing and the LMIT agreed almost completely, thus providing strong support for the clinical results. Latamoxef and cefoperazone displayed the same cross-reactivity, manifesting cross-reactions with MTT, HTT and 7ACA as well as with cephems having a tetrazolyl group in the C-3 side chain. Moreover, DTH induced by MTT displayed cross-reactivity with cephems possessing tetrazolyl groups in the C-3 side chain. The above results indicate that free MTT radicals, as well as the skeleton ring structure represented by 7ACA, are strongly involved in DTH arising from cephem antibiotics with a tetrazolyl group in the C-3 side chain.