title: Development of a method for the detection of beta-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 beta-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 beta-lactamase is defined as a difference between the inhibitory zones of the test samples (supplemented with 25 microg/mL sulbactam plus 0.5 microg/mL penicillin G) and control samples (supplemented only with 0.5 microg/mL penicillin G) > or = 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 beta-lactamase-positive. In 2 undiluted milk samples showing extremely high beta-lactamase activity, 25 microg/mL sulbactam could not inhibit penicillin G activity. Because there is a lack of safety data on beta-lactamases in milk products, these data indicated a potentially serious safety concern for the dairy industry in the PRC.
authors.affiliation: National Institute for the Control of Pharmaceutical and Biological Products, Department of Antibiotics, Beijing 100050, People's Republic of China.
authors.forename: Shenghui
authors.initials: S
authors.lastname: Cui
authors.forename: Jingyun
authors.initials: J
authors.lastname: Li
authors.forename: Changqin
authors.initials: C
authors.lastname: Hu
authors.forename: Shaohong
authors.initials: S
authors.lastname: Jin
authors.forename: Yue
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002417:Cattle; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D003612:Dairying; D005504:Food Analysis / Q000379:methods*; D005506:Food Contamination; D016982:Micrococcus luteus / Q000378:metabolism; D008892:Milk; D010400:Penicillin G / Q000494:pharmacology; D015203:Reproducibility of Results; D012107:Research Design; D013193:Stainless Steel; D013407:Sulbactam / Q000494:pharmacology; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000032:analysis*
chemical_list: D000900:Anti-Bacterial Agents; D065093:beta-Lactamase Inhibitors; D013193:Stainless Steel; D001618:beta-Lactamases; D010400:Penicillin G; D013407:Sulbactam