Certain bacteria isolated from raw and cooked shrimp displayed reduced sensitivity to tetracycline antibiotics in the presence of multivalent metallic cations or shrimp extracts; addition of a chelating agent resulted in reduction of the antagonism of such ions and extracts toward the antibacterial action of these antibiotics. In shrimp preservation, a dip in the chelating agent increased the efficacy of a subsequent tetracycline antibiotic dip when the product was judged by organoleptic observation or by viable bacterial counts.