Abstract
Simple SummaryDuring the ripening process of the dry-cured fermented sausage “salchichón”, Listeria monocytogenes could fail to be eliminated. In addition, the food safety criterion for L. monocytogenes in the European Union sets up a maximum level of 100 units of this microorganism per gram in ready-to-eat products throughout their shelf-life. Thus, since L. monocytogenes could be present in this product, it is necessary to evaluate the impact of the dry-cured fermented processing in the potential virulence of this pathogen, even considering the possible effect of the usual microbiota (lactic-acid bacteria) of “salchichón”. In this work, the effect of the processing of “salchichón”, inoculated with a selected strain of Lactilactobacillus sakei, on the growth of L. monocytogenes and on the expression of its virulence genes, was evaluated. The processing of “salchichón” provoked a relevant reduction in L. monocytogenes, but this pathogen was not completely eliminated. However, a downregulation in the expression of the tested virulence genes was found, which could suppose a reduction in the pathogenic effect of this microorganism. These findings could be of great interest to consider the dry-cured ripening of “salchichón” as a safe process to control the pathogen L. monocytogenes.The effect of the dry-cured fermented processing of “salchichón” inoculated with a selected strain of Lactilactobacillus sakei (205) on the growth and transcriptional response of three virulence genes (plcA, hly, and iap) of Listeria monocytogenes was evaluated. For this, three different batches of “salchichón” were analyzed: batch B (inoculated only with L. sakei), batch L (inoculated only with L. monocytogenes), and batch L + B (inoculated with both microorganisms). Sausages were ripened for 90 days according to a traditional industrial process. The processing of “salchichón” provoked a reduction in L. monocytogenes counts of around 2 log CFU/g. The downregulation of the expression of the three genes was found at the end of ripening when the water activity (aw) of “salchichón” was <0.85 aw. The combined effect on the reduction in L. monocytogenes counts together with the downregulation in the expression of the virulence genes throughout the “salchichón” processing could be of great interest to control the hazard caused by the presence of this pathogenic bacterium.
Highlights
L. monocytogenes is a Gram-positive, facultative intracellular bacterium responsible for human listeriosis, one of the most significant foodborne diseases in industrialized countries [1] that has well-known adverse health effects [2]
The consumption of dry-cured fermented sausages is considered at low risk for foodborne listeriosis [9], the presence of this pathogenic bacterium has been reported in ripened sausages [10,11,12], and in some cases, it has been involved in listeriosis outbreaks [13]
Different superscript numbers denote significant differences for the same gene and batch at each ripening day (p ≤ 0.05). These results showed that the virulence gene expression values decreased at the end of the ripening period, likely due to the stress conditions created due to the processing and composition of “salchichón” mainly characterized by the decrease in aw throughout the ripening until values below 0.85 aw
Summary
L. monocytogenes is a Gram-positive, facultative intracellular bacterium responsible for human listeriosis, one of the most significant foodborne diseases in industrialized countries [1] that has well-known adverse health effects [2]. L. monocytogenes can pull through stressful environments, such as low temperature, high acidity, and salt contents [2,5,6]. This ability is a serious concern for the dry-cured fermented sausage industry. The consumption of dry-cured fermented sausages is considered at low risk for foodborne listeriosis [9], the presence of this pathogenic bacterium has been reported in ripened sausages [10,11,12], and in some cases, it has been involved in listeriosis outbreaks [13]
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