Detection of Penicillin G and its Benzylpenicilloyl (BPO) - Derivatives in Cow Milk and Serum by means of an ELISA

Abstract

Pharmacokinetic characteristics of benzylpenicillin and its benzylpenicilloyl (BPO)-derivatives were studied in serum and milk of health cows, using a classical biological assay (Sarcina lutea test) and a competitive ELISA for BPO detection. The plasma level and passage into milk was determined after intramuscular administration of penethamate-hydroiodide and benzylpenicillin-procaine. In serum of cows receiving penethamate hydroiodide, BPO seemed to persist for a rather long time; the reason for this observation was not clarified. The effect of local (intramammary) application of penicillin G was followed with milk from cows having healthy and mastitic quarters. In all cases, it was found that BPO was not excreted any longer than active penicillin G in milk. In a further survey, 1015 bulk milk samples from two large dairy regions were examined with the ELISA and a biological assay using Bacillus stearothermophilus var. calidolactis. None of the samples showed detectable BPO or antibiotic residues. It is concluded that milk containing inactive penicillin derivatives, like BPO, is not an important source to cause allergies.