Microbiological detection of 10 quinolone antibiotic residues and its application to artificially contaminated poultry samples

Abstract

To assess if microbiological inhibition tests for detection of antibiotic residues are suitable for routine screening for quinolone residues, the limit of detection (LOD) of 10 different quinolones and fluoroquinolones was determined. Two media were tested, one at pH 6 and the other at pH 8, each seeded with one of the following test strains: Bacillus subtilis, Escherichia coli or Bacillus cereus. LODs of the 10 substances were highest on plates seeded with B. cereus, intended for selective detection of tetracycline residues. The pattern of zones on the other four plates differed for the targeted quinolones: flumequine and oxolinic acid were detected at lower concentrations at pH 6, while the LODs of ciprofloxacin, enrofloxacin, danofloxacin, marbofloxacin, sarafloxacin and norfloxacin were lower at pH 8. Nine of the 10 quinolones were detected more easily with E. coli, but the LOD of difloxacin was lower with B. subtilis. Finally, the three most sensitive media were selected and fluid from chicken meat, spiked with eight quinolones near maximum residue limits (MRL), analysed on each plate. The plate seeded with E. coli at pH 8 detected five of eight quinolones at levels of interest, but an additional E. coli plate at pH 6 was necessary for detection of flumequine in species other than poultry and fish. None of the plates detected oxolinic acid and difloxacin at MRLs in muscle tissue.

A plate diffusion method for detecting fluoroquinolone residues in raw cow's milk

“…The study has evaluated and compared the sensitivity of the method with a strain of E. coli to quinolones and differences in the sensitivity of the medium at pH 6 and 8. The plate with E. coli at pH 8 was more sensitive and detected 5 quinolones out of 8 at levels ≤ MRL in poultry meat (Okerman et al 2007).…”

Microbial screening methods for detection of antibiotic residues in slaughter animals

“…For all these residues E. coli ATCC 128 appeared to be superiorly sensitive and this organism was recommended for supplementing the existing microbial screening tests. A third comparative study evaluated the susceptibility of the same organisms as in [39] for ten different quinolones [41]. Only difloxacin appeared to be detected more sensitively using B. subtilis as the test organism.…”

Performance of a New Microbial Test for Quinolone Residues in Muscle

“…Differences between tissue matrices could explain this disagreement since antimicrobial residue concentration in matrices such as kidney was reported to be higher than concentration in muscle samples. Therefore some authors (Okerman et al 2007) have concluded that it should be advisable to use kidney rather than muscle samples as the test material for analysis of residues in animals. However, muscular antimicrobial concentration is more relevant for consumer safety than kidney levels.…”

“…The suitability of E. coli for screening of different quinolone residues was also determined using standard solutions in media with different pH values (Okerman et al 2007). The lowest limits of detection observed for enrofloxacin, ciprofloxacin, marbofloxacin, norfloxacin, sarafloxacin, danofloxacin, difloxacin and flumequine were 0.625, 1.25, 2.5, 5, 5, 1.25, 40 and 5 µg/kg, respectively.…”