Confirmatory test results on milk from commercial sources that tested positive by beta-lactam antibiotics screening tests.
Fifty-four milk samples from commercial sources that tested positive for beta-lactam antibiotics were analyzed by a multiresidue liquid chromatographic (LC) procedure based on LC fractionation. Penicillin G and cephapirin were the beta-lactam antibiotics found most frequently. Some samples did not contain detectable beta-lactam antibiotics. In a few, the presence of a beta-lactam antibiotic was suspected because certain LC fractions tested positive for antimicrobial activity, which was no longer present in a replicate treated with beta-lactamase. However, the unknowns could not be identified by LC analysis.
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U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705, USA.
D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D003132:Commerce; D004350:Drug Residues / Q000032:analysis*; D005506:Food Contamination; D008892:Milk / Q000737:chemistry*; D015203:Reproducibility of Results; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams