Evaluation and validation of two microbiological tests for screening antibiotic residues in honey according to the European guideline for the validation of screening methods

Abstract

Two microbiological kits based on Bacillus stearothermophilus (Eclipse 50® and Premi®Test) have been evaluated and validated according to the European guideline for the validation of screening methods (January 2010) and in relation to the concentrations recommended by the EU-RL in 2007. Both tests are robust, a fast method and easy to implement. Both tests are applicable to a very large variety of honeys from different floral and geographical origins (rosemary, lavender, scrub, heath, alder, forest, lemon, acacia, chestnut, raspberry, mountain and flowers) as well as honey of different colours (from blank honey to brown honey, including yellow and orange honey). A satisfactory false-positive rate of 5% was obtained for the Eclipse 50® test. The observed detection capabilities CCβ of the Eclipse 50® kit were: chlortetracycline (>75 µg kg−1), oxytetracycline (≤200 µg kg−1), tetracycline (>100 µg kg−1), cloxacillin (≤40 µg kg−1), tylosin (≤200 µg kg−1), desmycosin (>400 µg kg−1), sulfadiazine (≤300 µg kg−1), sulfadimethoxine (≤250 µg kg−1), sulfamerazine (>300 µg kg−1), sulfamethazine (>1000 µg kg−1), sulfamethizole (>75 µg kg−1), sulfamethoxazole (≤25 µg kg−1), sulfanilamide (≫1000 µg kg−1), sulfaquinoxaline (>75 µg kg−1), sulfathiazole (≤250 µg kg−1) and lincomycin (>1500 µg kg−1). These levels were all higher than the recommended concentrations where they exist. Due to its lack of sensitivity, it cannot be recommended for reliable routine use. The observed CCβ of the Premi®Test kit were: chlortetracycline (10 µg kg−1), oxytetracycline (>10 µg kg−1), tetracycline (≤10 µg kg−1), cloxacillin (≤5 µg kg−1), tylosin (≤10 µg kg−1), desmycosin (≤15 µg kg−1), sulfadiazine (≤25 µg kg−1), sulfadimethoxine (≤25 µg kg−1), sulfamerazine (≤25 µg kg−1), sulfamethazine (≤25 µg kg−1), sulfamethizole (≤25 µg kg−1), sulfamethoxazole (≤10 µg kg−1), sulfanilamide (≤25 µg kg−1), sulfaquinoxaline (≤10 µg kg−1), sulfathiazole (25 µg kg−1) and lincomycin (≤25 µg kg−1). The Premi®Test kit could be recommended for reliable use in routine control due to its low detection capabilities (except for aminoglycosides), but the disadvantage is a high false-positive rate of 14%.