Detection Limits of β-Lactam Antibiotics in Ewe Milk by Penzym Enzymatic Test

Abstract

The Penzym is an enzymatic test widely used for the detection of β-lactam antibiotic residuals in milk. It is a specific method with good sensitivity to this group of antibiotics and enables results to be obtained within a short time. In the present work, the detection limits of 10 β-lactam antibiotics were determined in ewe milk, given the lack of previous studies of the Penzym test in ovine milk. For each antibiotic, eight concentrations were tested on 20 ewe milk samples proceeding from individual ewes (160 analyses per drug). The limits of the Penzym test were determined by means of logistic regression models, as follows: 5 μg/kg amoxicillin, 4 μg/kg ampicillin, 33 μg/kg cloxacillin, 3 μg/kg penicillin “G,” 43 μg/kg ce-phadroxil, 10 μg/kg cephalosporin “C,” 16 μg/kg cephalexin, 900 μg/kg cephoperazone, 120 μg/kg Ceftiofur, and 77 μg/kg cephuroxime. The percentages of positive results for those antibiotics at the maximum residue limit (MRL) concentration established by the European Union (EU) were: 100% (penicillin “G”), 93.3% (ampicillin), 93.3% (cloxacillin), 56.7% (Ceftiofur), and 56.7% (amoxicillin).