Precision Parameters for AOAC Bacillus stearothermophilus Disc Assay Based on FDA Milk Laboratory Quality Assurance...

Area of Science:

• Veterinary microbiology
• Food safety analysis
• Antimicrobial resistance detection

Background:

• Accurate detection of inhibitory substances in milk is crucial for public health and the dairy industry.
• Standardized methods are essential for reliable antibiotic testing in milk.
• Evaluating different agar media impacts the sensitivity and accuracy of these tests.

Purpose of the Study:

• To estimate precision parameters for inhibitory substance testing in milk.
• To compare the performance of antibiotic medium 4 (A4) and PM indicator (PM) agars.
• To assess the efficacy of these agars in detecting specific antibiotics.

Main Methods:

• Utilized State Split Milk Samples for inhibitory substance testing.
• Tested five common antibiotics: ampicillin, cephapirin, erythromycin, neomycin, and penicillin-G.
• Calculated repeatability relative standard deviations (RSDr) and reproducibility relative standard deviations (RSR).
• Compared zone sizes produced by antibiotics on A4 and PM agars.

Main Results:

• Repeatability relative standard deviations (RSDr) ranged from 1.0% to 4.8%.
• Reproducibility relative standard deviations (RSR) ranged from 4.8% to 10.4%.
• PM agar yielded significantly larger inhibition zones (α = 0.05) for erythromycin, neomycin, and penicillin-G compared to A4 agar.
• Cephapirin showed larger zones on A4 agar, while ampicillin showed no significant difference between the two agars.

Conclusions:

• Both A4 and PM agars provide reliable precision for antibiotic testing in milk.
• PM agar demonstrates superior performance for detecting erythromycin, neomycin, and penicillin-G.
• Agar choice can influence the detection efficacy of specific antibiotics, necessitating careful selection for accurate milk quality control.