ALLERGIC REACTIONS TO BETA-LACTAMS - STUDIES IN A GROUP OF PATIENTS ALLERGIC TO PENICILLIN AND EVALUATION OF CROSS-REACTIVITY WITH CEPHALOSPORIN

A group of 34 penicillin-allergic patients was studied to determine sk in test reactivity to the different penicillins involved in inducing t he allergic reaction and the cross-reactivity with side-chain-related and side-chain-unrelated cephalosporins. All the subjects selected for the study had to be skin test positive to at least one of the followi ng determinants: benzyl-penicilloyl-polylysine (BPO-PLL), minor-determ inant mixture (MDM), amoxicillin (AX), or ampicillin (AMP), or to poss ess in vitro IgE to the following conjugates: benzyl-penicilloyl-human -serum albumin (BPO-HSA), ampicilloyl-human-serum albumin (AMP-HSA), a nd amoxicilloyl-human-serum albumin (AX-HSA). Cephalexin (CE) and ceft azidime (CEF) were used to assess cross-reactivity. If skin tests to a ny of these compounds were positive, the patient was considered to be allergic; if negative, a challenge test was performed. Sixteen patient s (47%) were skin test positive to BPO and/or MDM, and nine (26%) excl usively to AX and/or AMP. In three cases (8%), the RAST was positive a lthough the skin test was negative; one to BPO-HSA and two to AX-HSA a nd AMP-HSA. Six patients (17%) needed to be challenged with the penici llin involved to establish the diagnosis. In five patients (14%) the s kin tests were positive to CE and in none to CEF. In all the others, t he skin tests were negative to both cephalosporins, and the patients t olerated the drugs when challenged. These results indicate the relevan ce of side-chain-specific minor determinants in betalactams allergy an d provide support for the role of this chemical structure in the evalu ation of cross-reactivity between penicillins and cephalosporins.