The study was aimed at the assessment whether foodstuffs contaminated with Bacillus cereus (B. cereus) may concurrently be vectors of spreading resistance. The contamination of foodstuffs with B. cereus strains was found in 31% of dairy and in 28% of meat products tested. Only one product from skimmed milk was contaminated. High-fat milk products that were heat-treated during the technological process (87 samples), as well as heat-treated meat products (65 samples), were contaminated significantly frequently (63% and 48% of the samples respectively) (P < 0.01). Almost all B. cereus isolates displayed low susceptibility to ampicillin, cephalothin, and to oxacillin. Except for streptomycin (STR) resistance, resistance to other 8 antimicrobial agents occurred sporadically. The STR resistant isolates came particularly from spreading buffer (8 samples) (P < 0.05). It was established that the same samples were contaminated with two subpopulations of B. cereus with different STR resistances. The frequent occurrence of B. cereus in foodstuffs with either fat content and/or subject to heat treatment in processing makes these products risky, however, our study did not confirm that foodstuffs contaminated with B. cereus are concurrently vectors of transmissible resistance genes.

An interlaboratory study in 12 laboratories was performed to prove the validation of the ELISA method developed for the quantitative determination of mustard protein in foods. The ELISA kit used for this study is based on rabbit polyclonal antibody. This kit did not produce any false-positive results or cross-reactivity with in-house validation for a broad range of food matrixes with no detectable mustard protein. All participants obtained the Mustard ELISA kit with standard operational procedures, a list of samples, samples, and a protocol for recording test results. The study included 15 food samples and two spiked samples. Seven food matrix samples of zero mustard content and four samples with mustard declared as an ingredient showed mustard protein content lower than that of the first standard (0.42 mg/kg). Four samples with mustard declared as an ingredient revealed mustard protein content above 12.5 mg/kg (the highest standard). The statistical tests (Cochran, Dixon, and Mandel) and analysis of variance were used to evaluate the interlaboratory study results. Repeatability and reproducibility limits, as well as an LOQ (1.8 mg mustard proteins/kg) and LOD (0.5 mg mustard proteins/kg), for the kit were calculated.

An interlaboratory study was performed in six laboratories to prove the validation of the ELISA method developed for quantitative determination of beta-lactoglobulin (BLG) in foods. The ELISA kit used for this study is based on rabbit polyclonal antibody. In-house validation of the kit did not produce false-positive results or cross-reactivity in a broad range of food matrixes containing no milk proteins. All participants obtained the BLG kit with a standard operational procedure, the list of the samples, samples, and a protocol for recording test results. The study included 14 food samples (extruded breakfast cereals, bread, two soy desserts, butter, chicken ham, chicken meat, wheat flour, long grain rice, jelly, two whey drinks, crackers, and bitter chocolate) and six spiked samples (two rice, two wheat flour, and two chicken meat). Nine samples of food matrixes containing no milk proteins showed BLG content lower than the first standard (0.15 mg/kg). Two samples of food matrixes with no milk proteins revealed BLG content higher than standard 3 (1.5 mg/100 g) and standard 4 (5.0 mg/100 g). Three food samples containing milk were tested as positive, and all spiked samples were evaluated as positive. The statistical tests (Cochran, Dixon, and Mandel) and analysis of variance were used to evaluate the interlaboratory study results. Repeatability and reproducibility limits, as well as LOQ (0.22 mg BLG/kg) and LOD (0.07 mg BLG/kg), for the kit were calculated.

A collaborative study in 10 laboratories was performed to validate an ELISA method developed for the quantitative determination of peanut protein in foods. The ELISA kit used for this study is based on rabbit polyclonal antibody. This kit does not produce any false-positive results or cross-reactivity with a broad range of peanut-free food matrixes. All participants obtained the peanut ELISA kit with standard operational procedures, a list of samples, the samples, and a protocol for recording test results. The study included 15 food samples. Three food matrix samples of zero peanut content showed peanut protein content lower than the first standard (0.10 mg/kg). Three samples with peanut declared as an ingredient revealed peanut protein content outside the calibration curve (absorbance was above the highest standard) in all laboratories, and three samples had the peanut content reported either above the highest standard or within the calibration curve, depending on the laboratory. Six samples with peanut declared as an ingredient gave the peanut protein content within the calibration curve. Only these six samples, together with a positive control sample (CS2), were used for statistical evaluation. The statistical tests (Cochran, Grubbs, and Mandel) and analysis of variance were used for the evaluation of the collaborative study results. Repeatability and reproducibility limits, as well as an LOQ (LOQcollaborative 0.22 mg peanut proteins/kg) and an LOD (LODcollaborative 0.07 mg peanut proteinslkg) for the kit were calculated.

Brychta J., Smola J., Pipek P., Ondráček J., Bednář V., Čížek A., Brychta T. (2009): The occurrence of enterotoxigenic isolates of B. cereus in foodstuffs. Czech J. Food Sci., 27: 284-292.Enterotoxigenic Bacillus cereus was detected in a variety of meat stuffs (36), ready-to-cook products (5), and swabs (7). The bacterial colonies isolated from PEMBA agar were identified as B. cereus. The 85 isolates were examined for the enterotoxin production using both TECRA-VIA and BCET-RPLA kits (ELISA -47, RPLA -38). Thirty two isolates (66%) were positive for enterotoxin using the ELISA test while only 15 isolates (39%) gave positive results in the RPLA test system. In total, 178 (91.8%) and 164 (84%) of the strains isolated in our laboratory (from various foods) were enterotoxigenic as determined using TECRA-VIA and BCET-RPLA, respectively. Parallel enterotoxin positive results obtained using both tests were demonstrated in only 9 isolates from 19 assessed (47.4%). Coincidental negative results from both kits were established for 3 isolates (15.8%) only. The isolates of B.cereus from meat were resistant to cephalothin (57%), clindamycin (14%), oxytetracycline (14%), and erythromycin (7%). The isolates from swabs were resistant to cephalothin (83%), erythromycin (16%), clindamycin (16%) and enrofloxacin (16%).