Systematic Identification of Antibiotics in Muscle of Swine; Chloramphenicol and Polypeptolides

Abstract

Identification of residues of many antibiotics, including tetracyclines (TCs), macrolide antibiotics (Macs.) and aminoglycosides (Amgs), in swine can be carried out by microbioautography. In this study, we developed a method of identification for neutral antibiotics, i. e., chioramphenicol (CP), which can be extracted with diethylether independently of the pH following water extraction, and polypeptolides such as virginiamycin (VGM) and thiopeptin (TPT) by using the cup plating method with Escherichia coli NIHJ or Corynebacterium xerosis NCTC9755 as test bacteria. The detection limit and recovery were determined, and the results were confirmed by microbioautography.In the preliminary test, more than 50% of CP, VGM or TPT contained in an aqueous solution at pH 4 was transferred into the diethylether layer in the presence or absence of other antibiotics such as Macs. and TCs, whereas these other antibiotics were not transferred at all. However, the transferred amount of TPT was only 54% in the preliminary test and further, the residual amount in the water layer when TPT was added to muscle of swine was 16%. Further improvement of these results remains necessary.In the recovery test, CP or VGM alone in the presence muscle of swine gave 86% or 51% recovery, respectively and the detection limits were both 0.05ppm.When CP and other antibiotics (Macs. or TCs) coexisted in the presence of muscle of swine, 82-88% of CP was transferred into the diethylether layer, while 49-87% of Macs. or 54-73% of TCs remained in the water layer, indicating that this method affords satisfactory results. It was concluded that microbioautography is also available for the identification of CP and VGM, and the detection limit is 30-60ng/spot for either of the two antibiotics.