Development of a Method for the Detection of -Lactamases in Milk Samples
Abstract:With the rapid growth of the dairy industry and the establishment of strict antimicrobial residue limits in the People's Republic of China's (PRC) milk supply, a -lactamase product known as antimicrobial destroyer was introduced into dairy production without regulatory review. We developed a method for detecting this product in milk samples based on a modified cylinder plate method. The presence of -lactamase is defined as a difference between the inhibitory zones of the test samples (supplemented with 25 g/mL sulbactam plus 0.5 g/mL penicillin G) and control samples (supplemented only with 0.5 g/mL penicillin G) 3 mm. Using this method, 77 individually packaged milk samples were randomly collected from 5 retail stores in 3 cities over a 4-month period (May to August 2006). Of the 77 samples, 49 were found to be -lactamase-positive. In 2 undiluted milk samples showing extremely high -lactamase activity, 25 g/mL sulbactam could not inhibit penicillin G activity. Because there is a lack of safety data on -lactamases in milk products, these data indicated a potentially serious safety concern for the dairy industry in the PRC.
Document Type: Research Article
Affiliations: National Institute for the Control of Pharmaceutical and Biological Products, Department of Antibiotics, Beijing 100050, People's Republic of China.
Publication date: July 1, 2007
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