further degrades residue epitopes and reduces the potential for allergic response; and (4) sensitizing reactions are more directly related to intramuscular drug administration than to oral administration and the epitope distribution of protein-bound drug is so low as to be relatively insignificant as a potential cause for initiating and sensitizing responses when they are eaten. A summary of those rarely reported allergic reactions follows, with a commentary on conditions resulting in the adverse responses.

Four reports (two from the United States and two from England) of allergic reactions in persons previously sensitized to penicillin were identified between 1958 and 1969, when milk residues of penicillin were more prevalent. Vickers et al. (1958), Zimmerman (1958), Borrie and Barrett (1961), and Wicher et al. (1969) reported patients with dermatitis, urticaria, and subacute eczematous eruptions after drinking milk that contained residues of penicillin. Dewdney et al. (1991) cast doubt on (haptenized) penicillin residues as the causative factor in development of penicillin hypersensitivity. They argued that the immunogenicity, epitope density, and overall concentration were too low to contribute to allergy development. However, they did not point out that oral consumption of penicillin was less sensitizing than was parenteral administration. Questions still exist regarding the ability of parenteral administration to be the sensitizing stimulus and regarding the consumption of penicilloyl residues as a trigger for hypersensitivity reaction.

Other cases of allergic reactions reported between 1972 and 1980 were traced to consumption of penicillin-residue-containing meat. One reaction was to residues in pork, which originated from swine treated with penicillin 3 days before being butchered. Another reaction was to the beef in a frozen dinner, which subsequently was found to contain penicillin residues (Tscheuschner 1972; Schwartz and Sher 1984). Two patients experienced pruritus on the face and fingers, and one suffered an anaphylactic reaction. No deaths occurred.

Relative Risks: Residues versus Microbial Contamination

Microbial contamination of food is a major health problem worldwide. Great difficulty exists in ensuring that foods are free of microbial contamination, and there are many points in the chain of processing, storage, sale, and preparation that provide opportunities for microorganisms to proliferate in food. Initializing contamination events might be innocuous, but under conditions that permit these organisms to proliferate, the build-up of pathogenic bacteria and toxins will contribute significantly to food-borne illness (Altekruse et al. 1997). Surveillance and monitoring of contamination and disease outbreaks associated with microorganism-based food-borne illness is spread across several federal agencies, including FSIS, FDA, and the Centers for Disease Control and Prevention (CDC). There are now 10 organisms identified and tracked by the federal agencies under a collaborative interagency Pathogen Reduction Task Force that pro-



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