Antibiotic residues methods

J. Kramer, G. Carter, B. Arret, J. Wilner, W. Wright, and A. Kirshbaum, Antibiotic Residues in Milk, Dairy Products, and Animal Tissues Methods, Reports, and Protocols,... 

The classical microbial assay approaches to measuring antibiotic residues, diffusion, turbidimetric and acid production were described and the advantages and limitations reviewed. Other systems so discussed and reviewed were the affinity or receptor methods and the immunological approach using ELISA or EMIT assay techniques. The classical systems, in general, could measure antibiotic residues at the fractional ppm to the ppb levels. The potentials of the receptor and immunological assay system were discussed. 

Physicochemical Methods for Identifying Antibiotic Residues in Foods... 

In 1997, the percentage of slaughterhouse samples found positive for antibiotics differed based on the method of sampling, being higher in the case of directed sampling (Table 13.12). An analogous trend has appeared in the evolution of antibiotic residues over the period 1992-1997 (Table 13.13). 

In Belgium, 0.1% of the slaughtered cattle and swine are screened for antibiotic residues each year. In the analytical strategy applied, meat samples are screened with a modified four-plate test followed by screening with a group-specific ELISA for the identification of the antibiotics and confirmation by specific LC methods. 

In recent years antibiotics residues have accumulated in different environmental compartments. Fluoroquinolone antibiotics are strongly adsorbed by soil, and therefore their extraction requires exhaustive procedures, leading to complex extracts due to coextraction. Despite this the authors succeeded in selectively detecting the fluoroquinolones from crude soil extracts directly injected onto an MIP HPLC column and using UV detection [Fig. 2 (Fig. 6 of the original)]. Recoveries close to 100% were obtained for five fluoroquinolones. The analysis time was only a few minutes, so this method was found suitable for screening soil samples for the presence of fluoroquinolones. The individual fluoroquinolones were not resolved on the column. 

Besides physicochemical methods, the use of microbiological growth-inhibition assays to test meat and milk for the presence of antibiotics residues is popular over a long period of time. These tests use antibiotic-sensitive bacterial reporter strains, such as Bacillus subtilis and Bacillus stearothermophilus var. calidolactis. These bacteria are inoculated under optimal conditions with and without sample. After culturing, results are read from visible inhibition zones or from the color change of the bacterial suspension in agar gels [6]. 

A high level of FFAs may cause minor errors in determination of the fat content of milk (e.g., a decrease of 0.01 0.03% fat per 1 meq/100 g increase in FFA), whether by older methods such as Rose-Gottlieb or turbidimetric or infrared methods (van Reusel, 1975 van de Voort et al., 1987). Lipolysis may also lead to false positives in testing for antibiotic residues in milk (Carlsson and Bjorck, 1992). 

Chico J, Rubies A, Centrich F, Companyo R, Prat MD, Granados M, High-throughput multi-class method for antibiotic residue analysis by liquid chromatography-tandem mass spectrometry, J. Chromatogr. A 2008 1213 189-199. 

De Alwis H, Heller DN, Multi-class, multi-residue method for the detection of antibiotic residues in distillers grains by liquid chromatography and ion trap tandem mass spectrometry, J. Chromatogr. A 2010 1217 3076-3084. 

A key performance factor for the evaluation of a screening method is demonstration that the chosen STC can be achieved. The STC should be low enough to provide confidence that the antibiotic residue can be detected at the appropriate RL in the sample, that is, that there is sufficient margin of difference between the STC and the RL. This implies that the CCP is equal to or less than the RL. It does not necessarily require an estimation of the numeric value of CCP depending on the capability of the screening assay. 

Rault A, Gaudin V, Maris P, Fuseher R, Ribouchon JL, Cadieu N, Validation of a microbiological method The STAR protocol, a five-plate test, for the screeiung of antibiotic residues in milk. Food Addit. Contam. 2004 21 422-433. 

Analytical methods for the detection and/or determination of antibiotic residues in food fall into two categories ... 

It is evident from this chapter that there are many examples of methods for the analysis of antibiotic residues in food that utilize mass spectrometry. As a result, the fragmentation patterns for different classes of antibiotics have been proposed and described in several multi-residue methods, as well as in procedures for specific groups of compounds. Table 6.4 and Figure 6.14 provide examples of the common product ions and expected neutral losses seen in MS/MS spectra for major classes of antibiotics. Specific examples, along with relevant citations, are also provided. As MS methods begin to search for and identify more non-targeted analytes, it will become more important to be familiar with the fragmentation patterns of common analytes. 

Nikolaidou K, Samanidou V, Papadoyannis I, Development and validation of an HPLC method for the determination of seven tetracycline antibiotics residues in chicken muscle and egg yolk according to 2002/657/EC, J. Liq. Chromatogr. Rel. Technol. 2008 31 2141-2158. 

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