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Bicarbonate as an interference in B. stearothermophilus assays
A F Erasmuson1, E R Cairns, B O'Kane
1National Chemical Residue Laboratory, Ministry of Agriculture and Forestry, Upper Hutt, New Zealand.
The Analyst
|August 6, 1999
Summary
Excessive bicarbonate in animal urine interferes with antibiotic residue testing. A simple acetic acid treatment effectively removes this interference, ensuring accurate penicillin detection in meat products.
Area of Science:
- Food safety analysis
- Microbiological assays
- Veterinary drug residue detection
Background:
- Bacterial inhibition assays are standard for detecting antibiotic residues in meat.
- The inhibition of Bacillus stearothermophilus is sensitive to penicillins.
- Urine samples from slaughtered animals are used for residue screening, often containing penicillins and tetracyclines.
Purpose of the Study:
- To identify and resolve an interference in the B. stearothermophilus inhibition assay.
- To determine the cause of assay interference in urine samples.
- To develop a simple method for eliminating interference without compromising antibiotic detection.
Main Methods:
- Utilized bacterial inhibition assays, specifically B. stearothermophilus.
- Investigated urine samples from slaughtered animals for antibiotic residues.
- Applied a mild acetic acid treatment to urine samples to adjust pH to 5.5 and remove carbon dioxide via vortex mixing.
Main Results:
- Excessive bicarbonate in urine was identified as the cause of assay interference.
- The acetic acid treatment effectively removed bicarbonate interference.
- The method successfully eradicated interference without affecting penicillin detection sensitivity.
Conclusions:
- A simple, low-equipment method involving acetic acid treatment can resolve bicarbonate interference in urine-based antibiotic residue assays.
- This technique ensures the reliability of penicillin screening in meat products.
- The findings contribute to accurate food safety monitoring in animal products.