Characterization of persistent Listeria monocytogenes strains from ten dry-cured ham processing facilities.

The majority of cases of listeriosis are associated with the consumption of contaminated food. Some strains of Listeria monocytogenes can persist over months or years in meat processing plants increasing the risk of product contamination. The presence of L. monocytogenes was examined in 10 dry-cured ham processing facilities. A total of 1801 samples were collected from environment and equipment, during processing (1095) and after cleaning and disinfection (706). These samples were taken from non-food contact (736) and food contact (1065) surfaces. In addition, 204 samples from ham surfaces were also analysed. Prevalence varied from 6% to 34% among facilities, and was higher during processing than after cleaning and disinfection (24.8% vs 11.0%) and from non-food than from food contact surfaces (22.6% vs 17.4%). L. monocytogenes serotype 1/2a was predominant (53.9%), followed by 1/2c (26.0%) and 1/2b (15.3%) and less frequently 4b (4.8%). A total of 142 different pulsotypes were registered. Potential persistent L.monocytogenes strains were isolated in 9 out the 10 facilities, with no more than 6 pulsotypes in a given plant. Two pulsotypes were common in different installations, detected before and after cleaning and disinfection, highlighting the importance of monitoring the presence of this pathogen in dry-cured ham processing environments.

In vitro assays of the antibacterial and antioxidant activity of aqueous leaf extracts from different Prunus salicina Lindl. cultivars.

The growing interest in the substitution of synthetic food antioxidants and antimicrobial additives by natural ones has fostered research on vegetable sources and on the screening of raw materials, for identifying new antioxidants and antimicrobial natural agents. The aim of the present study was to assess total phenolic contents and determine polyphenolic composition, related antioxidative and antimicrobial properties of plum leaves extracts from six cultivars. It was observed that the content of total phenolic compounds was cultivar dependent. High antioxidant capacity has been observed and related to the relative amounts of polyphenolic compounds with good antioxidant properties. The antimicrobial activity was confirmed against Listeria innocua and Escherichia coli, and it has found to be related with the high phenolic contents. Our results suggest that the use of plum leaf extracts is a feasible alternative as antibacterial and antioxidant agents to prevent the deterioration of stored foods by bacteria and oxidation.