THE CROSS-REACTIVITY AND IMMUNOLOGY OF BETA-LACTAM ANTIBIOTICS

Allergic reactions to beta-lactam antibiotics are well described; howe ver, only the immunochemistry of penicillin has been characterised. Al though the major determinant of benzylpenicillin (penicillin G) is com mercially licensed for diagnostic applications, minor determinants are only available at some centres to be used for identification of hyper sensitive individuals. Cephalosporins share a common bicyclic nuclear structure with penicillin and most cross-reactivity is generated to th e beta-lactam ring. It is not possible to determine the actual inciden ce of cross-reactivity between penicillins and cephalosporins, but evi dence suggests the true rate is lower than usually appreciated. In vit ro testing demonstrates extensive cross-reactivity between penicillin and the carbapenems. Although the rate of clinical cross-reactivity is not known, imipenem should not be given to patients with proven penic illin hypersensitivity. In contrast, aztreonam and the monobactams can be safely given to penicillin-allergic patients.