title: Development of a rapid multi-residue assay for detecting β-lactams using penicillin binding protein 2x*.
abstract: OBJECTIVE
  To develop a rapid multi-residue assay for detecting 16 demanded by the European Union (EU).
  
  
  METHODS
  A recombinant penicillin-binding protein (PBP) 2x* from Streptococcus pneumoniae R6 was expressed in vitro and six β-lactams were conjugated to HRP by four methods. A rapid multi-residue assay for β-lactams was established with PBP2x* and HRP-conjugate.
  
  
  RESULTS
  PBP2x* was expressed and purified successfully and the ideal HRP-conjugate was identified. The multi-residue assay was developed. After optimization, penicillin G, ampicillin, amoxicillin, cloxacillin, dicloxacillin, oxacillin, nafcillin, cephalexin, ceftiofur, cefalonium, cefquinome, cefazolin, cefoperazone, cephacetrile, and cephapirin can be detected at levels below MRL in milk with simple pretreatment.
  
  
  CONCLUSIONS
  This assay developed can detect all 16 β-lactams demanded by the European Union (EU). The whole procedure takes only 45 min and can detect 42 samples and the standards with duplicate analysis.
authors: Department of Veterinary Pharmacology and Toxicology, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
authors: Kun
authors: K
authors: Zeng
authors: Jing
authors: J
authors: Zhang
authors: Yang
authors: Y
authors: Wang
authors: Zhan Hui
authors: ZH
authors: Wang
authors: Su Xia
authors: SX
authors: Zhang
authors: Chong Ming
authors: CM
authors: Wu
authors: Jian Zhong
authors: JZ
authors: Shen
mesh_terms: D000818:Animals; D008892:Milk / Q000737:chemistry*; D046915:Penicillin-Binding Proteins / Q000378:metabolism*; D047090:beta-Lactams / Q000032:analysis* / Q000378:metabolism
chemical_list: D046915:Penicillin-Binding Proteins; D047090:beta-Lactams
keywords: Milk; Multi-residue; Penicillin-Binding Protein 2x*; β-lactam