Cephalosporin and penicillin cross-reactivity in patients allergic to penicillins

Background: Bata-lactam antibiotics are the most commonly used antibiotics which usually cause serious IgE-mediated allergic reactions. Of all bata-lactam antibiotics, penicillins have so far been the best-studied, but the studies of cephalosporins and their cross-reactivity with penicillins are rare. We sought to evaluate the IgE response in vitro and estimate cross-reactivity between penicillins and cephalosporins in patients allergic to penicillins. Methods: We studied 87 control subjects and 420 subjects allergic to penicillins. Radioallergosorbent test (RAST) was performed to detect eight types of specific-penicillin IgE and eleven types of specific-cephalosporin IgE. The cross-reactivity and different molecules recognition by IgE were studied with a radioallergosorbent inhibition test. Results: Of 420 patients allergic to penicillins, 95 patients (22.62%) showed specific-cephalosporin IgE positive, 73 patients (17.38%) showed IgEs positive to both penicillins and cephalosporins. In specific-penicillin IgE positive group, the positive rate of specific-cephalosporin IgE was significantly higher than in specific-penicillin IgE negative group (27.14% vs. 14.57%, p < 0.01). In urticaria group, the positive rate of specific-cephalosporin IgE was significantly higher than in other symptoms group (30.65% vs. 8.11%, p < 0.05). The analysis of drugs which have the same or similar side-chains showed that benzylpenicillanyl-IgE (BPA-IgE), ampicillanyl-IgE (APA-IgE), amoxicillanyl-IgE (AXA-IgE) were respectively related to cephalothanyl-IgE (CLA-IgE), cephalexanyl-IgE (CEXA-IgE), cephalexanyl-IgE (CEXA-IgE)in sera of penicillin-allergic patients we studied, and compared with patients who had negative amoxicillin-IgE, the positive rates of specific-ampicill in IgE and specific-cephalexin IgE were significantly higher in patients who had positive amoxicillin-IgE (14.43% vs. 3.72%, 14.00% vs. 2.96%, p < 0.01). Radioallergosorbent test and radioallergosorbent inhibition test confirmed that both nuclear structure and RI side-chain contribute to IgE recognition. Conclusions: There exists cross-reactivity between cephalosporins and penicillins; patients allergic to several penicillins are more likely to develop allergic reaction to cephalosporins; due to sensitization to the similar structural characteristics (nuclear and R1 side-chain), penicillin-allergic patients may develop cross-allergic reactions with not only first-generation but also third-generation cephalosporins.