Antibiotic/Antimicrobial Residues in Milk ¹

Area of Science:

• Food safety
• Analytical chemistry
• Microbiology

Background:

• Antibiotic and antimicrobial residues in milk pose a potential public health risk.
• Monitoring milk for these residues is crucial for ensuring consumer safety.
• Previous surveys have indicated the presence of residues, but regional data is valuable.

Purpose of the Study:

• To assess the prevalence of antibiotic and antimicrobial residues in commercially available milk.
• To identify the types of residues most frequently detected in the surveyed region.
• To validate qualitative findings with confirmatory microbial assays.

Main Methods:

• A qualitative receptor assay was employed to screen commercial milk samples.
• Samples were collected over a 3-month period from various brands and bottling plants in the eastern Pennsylvania, Central New Jersey, and New York City area.
• Presumptive positive samples were further analyzed using microbial assays for confirmation.

Main Results:

• 63% of the 64 milk samples tested contained one or more residues.
• 27% of samples had two residues, and 11% had three or more.
• Tetracyclines and sulfonamides were the most predominant residues detected.
• Confirmatory assays confirmed 100% of presumptive tetracycline-positive samples and 75% of presumptive streptomycin-positive samples.

Conclusions:

• A significant percentage of commercial milk in the surveyed region contains antibiotic and antimicrobial residues.
• Tetracyclines and sulfonamides are the primary residues of concern.
• The qualitative assay demonstrated good reliability when confirmed by microbial assays.