After demonstrating the lack of effectiveness of standard antibiotics against the acquired antibiotic resistance of Bacillus cereus (NCTC 10989), Escherichia coli (NCTC 1186), and Staphylococcus aureus (ATCC 12715), we showed that the following natural substances were antibacterial against these resistant pathogens: cinnamon oil, oregano oil, thyme oil, carvacrol, (S)-perillaldehyde, 3,4-dihydroxybenzoic acid (beta-resorcylic acid), and 3,4-dihydroxyphenethylamine (dopamine). Exposure of the three pathogens to a dilution series of the test compounds showed that oregano oil was the most active substance. The oils and pure compounds exhibited exceptional activity against B. cereus vegetative cells, with oregano oil being active at nanogram per milliliter levels. In contrast, activities against B. cereus spores were very low. Activities of the test compounds were in the following approximate order: oregano oil > thyme oil approximately carvacrol > cinnamon oil > perillaldehyde > dopamine > beta-resorcylic acid. The order of susceptibilities of the pathogens to inactivation was as follows: B. cereus (vegetative) >> S. aureus approximately E. coli >> B. cereus (spores). Some of the test substances may be effective against antibiotic-resistant bacteria in foods and feeds.

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The effect of vacuum packaging on the microbial spoilage of 'ready-to-use' carrot slices and on the effect on shelf-life of the product is reported. The microbial development on vacuum packaged carrots was slower than that of non-vacuum packaged material. The predominant organisms present were Leuconostoc spp. in the vacuum packs as opposed to Erwinia spp. in the aerobic packs. Vacuum packaging of the sliced carrots significantly extended the shelf-life of the product when stored at 4°C from 5 to 8 days.

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ABSTRACT

beta 2-Adrenoceptor agonists (beta-agonists) are well known for their growth promoting and repartitioning effects in many species. Although the use of these compounds to increase muscle mass in stockfarming is prohibited within the EU, under directive 96/22/EC, significant illegal use still occurs. With legal and illegal synthesis of new structurally related compounds, the detection of traditional beta-agonists and new derivatives becomes increasingly problematical. This method describes the isolation and solubilisation of a beta 2-adrenoceptor from a transfected Chinese hamster ovary cell line, using the detergent digitonin. The solubilised receptor retained its activity and was isolated from the cell membrane at a concentration of 550 +/- 100 fmol mg-1 of solubilised protein. Competition analysis using the tritiated antagonist dihydroalprenolol revealed receptor affinity for five structurally different beta-agonists, with IC50 values ranging from 2.1 +/- 0.76 x 10(-7) M for salmeterol to 1.1 +/- 0.62 x 10(-5) M for ractopamine. This study has demonstrated that transfected cell lines with a high expression of beta 2-adrenoceptors are a convenient source of active receptor material. Solubilised beta 2-adrenoceptors could form the basis of a multi-analyte screening assay for use in routine screening.