Antibiotic/Antimicrobial Residues in Milk ¹

A qualitative receptor assay for antibiotic and antimicrobial residues in milk was used in a survey of commercial milk samples obtained in the eastern Pennsylvania, Central New Jersey, New York City area. Sixty-four milk samples were obtained over a 3-month period, representing different brands and bottling plants. Sixty-three percent of milk samples contained one or more residues; 27% contained 2 residues; 11% contained 3 or more residues. Tetracyclines and sulfonamides were the most predominant residues detected. A subsample of milk was used to confirm the qualitative presence of residues, using microbial assays. Of 9 presumptive tetracycline-positive samples, 9 were confirmed. Of 4 presumptive streptomycin-positive samples, 3 were confirmed.