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The effects and specificity of dietary supplementation of EconomasETM (EcoE), mainly consisting of organic selenium (0.15 or 0.30 mg/kg feed; Se) or of vitamin E (100 or 200 mg/kg feed; VE), on lipid oxidation were evaluated in rabbit hamburgers during refrigerated storage. Oxidation data obtained by thiobarbituric acid-reactive substances (TBARS) spectrophotometric analysis and solid-phase microextraction (SPME) coupled with gas chromatography (GC) to determine hexanal content were compared. The relationships between oxidation levels, colour and pH and the discriminability of EcoE- or VE-treatment compared with control were also examined. TBARS content decreased in both VE and EcoE groups, while hexanal showed lower values only in the VE100 dietary group. The colour parameters were compatible with acceptable product quality and seemed to parallel the TBARS values up to the second day storage. Both VE and EcoE improved oxidative stability without affecting the sensory properties, but the VE effect appeared to more specifically hamper lipid oxidation, as evidenced by the determination and quantification of hexanal, a specific product of fatty acid peroxidation.

The essential oils (EOs) of Origanum compactum and Satureja montana chemotyped (CT) at carvacrol, two Thymus vulgaris CT at thujanol and thymol, and Hydrolates (Hys) of S. montana and Citrus aurantium var. amara were chosen for studying their bactericidal efficacy against few phytobacterial pathogens. The Minimal Inhibitory Concentration (MIC) and Bactericidal Concentration (MBC) were found by microdilution assay. The essential oils of O. compactum (MBC 0.06% v/v), T. vulgaris CT thymol (MBC 0.06% v/v), and Hy of C. aurantium (MBC 6.25% v/v) resulted in being the most effective against Erwinia amylovora; thus, they were used as starting concentrations for ex vivo assays. Despite the great in vitro effectiveness, the disease incidence and the population dynamic ex vivo assays showed no significant results. On the other hand, EO of O. compactum and Hy of C. aurantium (at 0.03% and 4.5% v/v, respectively) showed resistance induction in tomato plants against Xanthomonas vesicatoria infections; both treatments resulted in approximately 50% protection. In conclusion, EOs and Hys could be promising tools for agricultural defense, but further studies will be necessary to stabilize the EOs emulsions, while Hys application could be an effective method to prevent bacterial diseases when used as resistance inducer by pre-transplantation treatment at roots.

The purpose of this study was to investigate the effect of dietary vitamin E or EconomasE™ supplementation on the growth of several background/pathogenic bacteria on rabbit carcasses and hamburgers during refrigerated storage. For 51days, 270 New Zealand rabbits received either a basal diet, or experimental diets enriched with 100 or 200mg/kg of vitamin E or EconomasE™. The bacteria studied were Salmonella, Listeria monocytogenes, Pseudomonas, Enterobacteriaceae, Escherichia coli, coagulase-positive staphylococci, plus both mesophilic and psychrotrophic aerobes. The growth of Listeria monocytogenes on contaminated patties was evaluated through a challenge test. The potential protective or antimicrobial effect of vitamin E or EconomasE™ on Listeria monocytogenes or Pseudomonas aeruginosa was assessed in vitro. Diet did not influence the concentrations of bacteria found on rabbit carcasses and developing on hamburgers. Vitamin E (in vivo and in vitro) and EconomasE™ in vivo had a protective antioxidant role, while EconomasE™ in vitro had strong antibacterial activity against Listeria monocytogenes, but not against Pseudomonas aeruginosa.

During 1997, in occasion of the severe epidemic caused by Erwinia amylovora (Ea) on pear-tree in Emilia-Romagna, the first certified cases of fire blight were also reported in Veneto. Of the 14 ascertained foci, 11 were found in Rovigo province, ie. in areas facing the northern border of Emilia-Romagna and 2 were found in Padua and Verona provinces. In the following two years, the territorial distribution of the new foci in Verona, Padua and Venice provinces clearly pointed out that from Venetian areas close to the border with Emilia-Romagna the Ea was spreading mostly towards the north-west. In this study, the AFLP genomic analysis of 14 isolates from pear-tree showed that all Venetian isolates were referred to the same clone originally coming from Emilia-Romagna. After 1997 in Emilia-Romagna there has been a substantial increase in the official cases of fire blight on host plants other than pear-tree. From the clonal lineage of Ea, introduced in 1994, may originate secondary lines different for pathogenic traits selected by the new host plant or a new clonal lineage could have occurred. The AFLP of the Ea strains isolated from host plants other than pear-tree was carried out in order to study the genetic variability between the Emilian strains which were found to belong to the original clone. Moreover, to test the hypothesis of continuity of the original clonal lineage, the changes of the virulence grade among the strains was studied. The pathogenicity test on immature pear fruitlets was performed measuring the minimum/maximum axis of the lesion induced by each strain (14 Venetian and 47 Emilian strains). The strain OMP-BO1077/7, associated to the primary foci in Emilia-Romagna on pear during 1994, was used as a reference strain. For each strain the virulence index was calculated and statistical analysis was used to determine the significant difference with the reference strain

Infiltration of protein-lipopolysaccharide complexes (prLPS) (250 Cg/ml) of Pseudomonas syringae pv. aptata into tobacco leaves protected against subsequent elicitation of the hypersensitive response (HR) by Erwinia amylovora. The effect of prLPS on the expression of E. amylovora hrp (hypersensitive response and pathogenicity) genes was tested in protected tobacco leaves and in a defined medium in which hrp genes were highly expressed. Two E. amylovora hrp loci transcriptionally fused with the Escherichia coli β-glucuronidase (Gus) coding sequence were used as chromosomal reporter genes. The prLPS treatment did not affect hrp gene expression of Hrp − mutants both in planta and in vitro, so the effect of prLPS treatment on hrp gene expression of two E. amylovora Hrp + transformants was assayed during HR development in unprotected tissue and during the same time in prLPS protected tissue. A plasmid containing the same Gus fusions previously located in the chromosome was introduced into a wild-type strain of E. amylovora. Gus activity was significantly lower in protected tissue. We suggest that HR inhibition by prLPS treatment requires the entire hrp gene cluster in order for the bacteria to send a signal to the plant, which, in turn, inhibits the expression of hrp genes