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Category Archives: Listeria invanovi
Research – Virulence Characteristics and Distribution of the Pathogen Listeria ivanovii in the Environment and in Food
Listeria ivanovii and L. monocytogenes, are the only pathogenic species of the genus Listeria and share many virulence factors and mechanisms of pathogenicity. L. ivanovii shows host tropism towards small ruminants and rodents and much lower virulence for humans compared to L. monocytogenes. However, severe infections caused by L. ivanovii, resulting in bacteremia, abortion and stillbirth, occasionally occurred in immunocompromised persons and in pregnant women, while in immunocompetent hosts L. ivanovii can cause gastroenteritis. In this review, the updated knowledge on virulence aspects and distribution of L. ivanovii in the environment and in food is summarized. Recent research on its virulence characters at genome level gave indications on how pathogenicity evolved in this bacterial species. As for L. monocytogenes, L. ivanovii infections occurred after the ingestion of contaminated food, so an overview of reports regarding its distribution in food products was carried out to obtain indications on the categories of foods exposed to contamination by L. ivanovii. It was found that a wide variety of food products can be a source of this microorganism and that, like L. monocytogenes, L. ivanovii is able to persist in the food production environment. Studies on its ability to grow in enrichment and isolation media suggested that its occurrence in nature might be underestimated. Moreover, virulence varies among strains for differences in virulence character regulation, presence/absence of genetic regions and the possible instability of a Listeria pathogenicity genomic island, LIPI-2, which is unique to L. ivanovii. We can conclude that L. ivanovii, as a possible pathogen for animals and humans, requires more focused investigations regarding its occurrence in the environment and in food and on intra-species variability of pathogenic potential. View Full-Text
The use of active coatings is shown as an option to offer safe ready-to-eat fruits and respond the growing demand of consumers for fresh, environmentally friendly and products free from chemical preservatives. In this work, chitosan (Ch), chitosan + vanillin (Ch-V), and chitosan + geraniol (Ch-G) coatings were applied on apple cubes to evaluate their microbiological quality for 12 days of refrigerated storage. All combinations applied demonstrated significant bactericidal effects on native microbiota, resulting in number of mesophilics, psychrotrophics, and yeasts and molds under the detection limit (<2.00 log) immediately after coating and during 12 days for most of them. Moreover, Escherichia coli O157:H7 and Listeria innocua artificially inoculated on apple cubes showed great reductions after coating treatments, exerting vanillin or geraniol enriched coatings outstanding antimicrobial activity. In fact, after 12 days of refrigerated storage, apple cubes treated with vanillin and geraniol (>2.00 log CFU/g) showed reductions in E. coli O157:H7 counts greater than 2.00 log in comparison with the control (4.68 log CFU/g). The preliminary results of this study demonstrated that Ch, Ch-Va, and Ch-Ge could be an interesting alternative to improve the safety of apple cubes and, therefore, a novel option to offer safe, ready-to-eat apple to consumers.
Research – Distribution of Listeria spp. on Carcasses of Regularly Slaughtered Swine for Italian Dry Cured Ham
In recent years, the role of Listeria monocytogenes as a foodborne pathogen in public health has increased. Its presence poses a risk for humans, especially in ready-to-eat foods, such as ham. Understanding the presence and distribution of Listeria spp. on swine carcasses meant for Italian dry-cured hams can be a useful tool to improve food safety. This study assessed the distribution of Listeria spp. (as a marker of contamination with L. monocytogenes) on slaughtered pig carcasses intended for the production of high-quality, Italian, dry-cured ham and examined the roles of the site sampled on the carcass, farming cycle (open versus closed), farm-to-slaughterhouse distance, and time spent in lairage. Samples were collected from swine carcasses (n = 150) before refrigeration, from three different carcass locations (head, shoulder, and thigh), and assessed for the presence of listeriae. A total of 115 carcasses were contaminated with Listeria spp. in at least one location. In all, 178 listeriae were isolated and identified: 130 Listeria innocua, 28 Listeria welshimeri, 17 Listeria ivanovii, and 3 L. monocytogenes. Listeriae were detected on 62.7% of heads, on 25.3% of shoulders, and on 30.7% of thighs, with significant differences between heads versus shoulders and thighs. Animals reared in closed-cycle farms were more contaminated (P < 0.05) than were animals from open-cycle farms (90 versus 71.8%). The distance between farms and slaughterhouse was not related to the contamination rate. Carcasses of swine that stayed in lairage before slaughtering for more than 10 h showed a higher degree of contamination (90%) and were positive for Listeria spp. in more sample sites (55%) compared with those held for less than 2 h (73% of carcasses and 33.3% of samples). Our results show that heads should be detached from carcasses immediately after slaughter for meat-safety purposes and the amount of time animals stay in lairage should be limited. These results will be useful for a more-valid implementation of good manufacturing processes for slaughtering.