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This paper proposes an improved high throughput microbial method for the simultaneous performance of first and second level screening for antibacterial residues in meat. It is based on growth inhibition of B. subtilis on agar medium pH 6, 7.2 and 8, of B. cereus on agar medium pH 5.9, of M. luteus on agar medium pH 8 and of E. coli on agar medium pH 7.2 (research or first level screening) and on the use of confirmatory solutions (Pase, Paba, MgSO4) for the identification or second level screening. In kidney control samples, dialysis membranes were interposed between samples and the agar surface to both prevent the action of lysozyme and reduce false positive results. The proposed method detects beta-lactams, sulfonamides, tetracyclines, aminoglycosides, macrolides and quinolones at MRL concentrations and reliably indicates the inhibitor family. Results are obtained in 18-24 h.

A total of 1,017 mascarpone cheese samples, collected at retail, were analyzed for Clostridium botulinum spores and toxin, aerobic mesophilic spore counts, as well as pH, a(w) (water activity), and Eh (oxidation-reduction potential). In addition 260 samples from other dairy products were also analyzed for spores and botulinum toxin. Experiments were carried out on naturally and artificially contaminated mascarpone to investigate the influence of different temperature conditions on toxin production by C. botulinum. Three hundred and thirty-one samples (32.5%) of mascarpone were positive for botulinal spores, and 7 (0.8%) of the 878 samples produced at the plant involved in an outbreak of foodborne botulism also contained toxin type A. The chemical-physical parameters (pH, a(w), Eh) of all samples were compatible with C. botulinum growth and toxinogenesis. Of the other milk products, 2.7% were positive for C. botulinum spores. Growth and toxin formation occurred in naturally and experimentally contaminated mascarpone samples after 3 and 4 days of incubation at 28 degrees C, respectively.

A novel application of a hybrid biosensor is here employed as an analytical method for the detection and presumptive identification of beta-lactam residues in milk. The method is based on measurements of carbon dioxide (CO2), the production of which is related to the microbial growth of the test microorganism Bacillus stearothermophilus var. calidolactis. The presence of beta-lactams in milk inhibits microbial growth and, consequently, the CO2 production rate. The analysis is based on the variation of CO2 between a milk sample spiked with beta-lactams and a twin milk sample containing beta-lactams plus a broad spectrum beta-lactamase, using an electrochemical device of biosensor. A blank milk sample is included as control. The result is obtained starting from the first 120 min. Moreover, the ability to recognize all of the beta-lactams speeds the total time of analysis when chemical identification and quantification are required. The analytical method appears to be adequate for milk control for qualitative screening purposes, complying with the requirements stated in Decision 2002/657/EC.

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Mechanisms of tetracycline resistance were investigated in two recent Listeria monocytogenes isolates from food, with L. innocua 52P tet r as a control. Tetracycline resistance was transferred conjugatively from all three strains to L. ivanovii and from one isolate and the control to Enterococcus faecalis. Molecular analysis demonstrated a chromosomal location for the tet determinant, which was identified as tetM in all cases. These studies are the first to show that L. monocytogenes from food could be a source of tetracycline resistance genes able to spread to other micro-organisms.

The migration of formaldehyde and melamine monomers has been measured on 90 samples of plastic tableware in three different situations - new articles, already used articles and artificially aged articles - by using simulant, contact times and temperatures prescribed by Commission Regulation (EU) No. 10/2011. Formaldehyde was determined by ultraviolet spectroscopy analysis of the coloured complex obtained by reaction with chromotropic acid. Melamine was measured by an ultra high performance liquid chromatography method. Fourier Transformed - Infrared Analysis was applied to characterise the plastic. The results highlighted the presence of different amino resins based on formaldehyde-melamine, urea-formaldehyde or melamine-urea-formaldehyde with different migration behaviour. The migration of monomers was related to progressive degradation of the resins. Ageing studies demonstrated that the potential degradation of the resins and the consequent migration of the monomers may continue throughout the service life of the product. The specific migration limit (SML) of melamine was exceeded after ageing.

Ninety-two Vibrio strains isolated over a period of 9 years from different sources (national and imported fishery products, shellfish, seawater from aquaculture settings, etc.) and belonging mostly to two species relevant for human health and fish pathology, V. parahaemolyticus and V. alginolyticus, were tested for resistance to different antibacterials using the standard disk diffusion test (five antibacterials: ampicillin, sulfamethoxazole, tetracycline, trimethoprim/sulfamethoxazole and chloramphenicol) and the Minimum Inhibitory Concentrations method (six antibacterial families: β-lactams, tetracyclines, chloramphenicol, aminoglycosides, quinolones, trimethoprim/sulfamethoxazole) providing consistent results. The analysis performed by standard disk diffusion test showed resistance to ampicillin in 82% of the strains, whereas 7% were resistant to sulfamethoxazole, 3% to tetracycline, and 1% to trimethoprim/sulfamethoxazole; no strain was found to be resistant to chloramphenicol. The results obtained by the MIC tests, because of the absence of established breakpoints for some antibacterials, were not readily interpretable for all substances, but showed no statistically significant difference to the results obtained by the standard disk diffusion test. Beside these results, high MIC 90 values (128 μg ml −1 and above) were obtained for kanamycin and streptomycin, indicating that high concentrations of these antibacterials were required to inhibit the growth of the strains. Strains exhibiting resistance or intermediate resistance to two or more antibacterials represented 15% of the total and included, beside resistance to ampicillin, resistance to sulfamethoxazole or, for V. parahaemolyticus isolates, tetracycline. Interestingly, differences in the mechanism of resistance to β-lactams were detected between the species V. parahaemolyticus and V. alginolyticus.