Quantitative Assay of Beta-Lactam Residues in Raw Milk Using a Disc Assay Method

Area of Science:

• Food safety
• Microbiology
• Analytical chemistry

Background:

• Antibiotic residues in raw milk pose a food safety concern.
• Existing methods for detecting penicillin (beta-lactam) residues are often qualitative, lengthy, and technically demanding.
• The Sarcina lutea Cylinder Plate (CP) method is the only quantitative option but is time-consuming and requires significant expertise.

Purpose of the Study:

• To develop a simpler and faster quantitative method for detecting beta-lactam antibiotic residues in raw milk.
• To establish a reliable assay for estimating antibiotic levels relative to a fixed standard.

Main Methods:

• A disc assay test utilizing Bacillus stearothermophilus was employed.
• Quantitative estimates were made by comparing bacterial inhibition zones to a reference standard.
• Paired-t statistical analysis was used to compute results above or below the reference level.

Main Results:

• The new method provides quantitative estimates of beta-lactam residues.
• The assay can be completed within a 3-hour timeframe.
• The method offers a simpler and faster alternative to the existing CP procedure.

Conclusions:

• This Bacillus stearothermophilus disc assay offers a practical and efficient solution for quantifying beta-lactam residues in raw milk.
• The developed method addresses the need for a faster, simpler, and quantitative approach to antibiotic residue testing in dairy products.