AFNOR validation of Premi Test, a microbiological-based screening tube-test for the detection of antimicrobial residues in animal muscle tissue.

Premi Test contains viable spores of a strain of Bacillus stearothermophilus which is sensitive to antimicrobial residues, such as beta-lactams, tetracyclines, macrolides and sulphonamides. The growth of the strain is inhibited by the presence of antimicrobial residues in muscle tissue samples. Premi Test was validated according to AFNOR rules (French Association for Normalisation). The AFNOR validation was based on the comparison of reference methods (French Official method, i.e. four plate test (FPT) and the STAR protocol (five plate test)) with the alternative method (Premi Test). A preliminary study was conducted in an expert laboratory (Community Reference Laboratory, CRL) on both spiked and incurred samples (field samples). Several method performance criteria (sensitivity, specificity, relative accuracy) were estimated and are discussed, in addition to detection capabilities. Adequate agreement was found between the alternative method and the reference methods. However, Premi Test was more sensitive to beta-lactams and sulphonamides than the FPT. Subsequently, a collaborative study with 11 laboratories was organised by the CRL. Blank and spiked meat juice samples were sent to participants. The expert laboratory (CRL) statistically analysed the results. It was concluded that Premi Test could be used for the routine determination of antimicrobial residues in muscle of different animal origin with acceptable analytical performance. The detection capabilities of Premi Test for beta-lactams (amoxicillin, ceftiofur), one macrolide (tylosin) and tetracycline were at the level of the respective maximum residue limits (MRL) in muscle samples or even lower.

European Proficiency testing of national reference laboratories for the confirmation of sulfonamide residues in muscle and milk.

Two interlaboratory studies were organized in 2002-2003 in order to check the proficiency of laboratories in confirming the presence of sulfonamide residues in muscle and milk. These studies involved 25 EU National Reference Laboratories (NRLs) from 21 different European Countries in charge of statutory monitoring of antimicrobial residues in food of animal origin at a national level. The study was conducted according to international and national guidelines by the Community Reference Laboratory (CRL) in charge of antimicrobial substances. Four different test matrices of sheep muscle and four different test matrices of bovine milk containing different sulfonamide substances were prepared and sent to the participants. Each participant was asked to use his own routine confirmatory method and to analyse each sample in triplicate within a period of about six weeks during which the stability of the materials was checked by the organizer. The sulfonamide content of each material was determined by calculating the robust means of all the results and the deviation of the results from the assigned values was assessed by calculating Z-scores. Overall, results were satisfactory, particularly considering that it was the first proficiency test dealing with sulfonamides organised by the Community Reference Laboratory.