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Dendritic cells (DCs) as professional antigen-presenting cells play an important role in the initiation and modulation of the adaptive immune response. However, their role in the innate immune response against bacterial infections is not completely defined. Here we have analyzed the role of DCs and their impact on the innate anti-bacterial host defense in an experimental infection model of Yersinia enterocolitica (Ye). We used CD11c-diphtheria toxin (DT) mice to deplete DCs prior to severe infection with Ye. DC depletion significantly increased animal survival after Ye infection. The bacterial load in the spleen of DC-depleted mice was significantly lower than that of control mice throughout the infection. DC depletion was accompanied by an increase in the serum levels of CXCL1, G-CSF, IL-1α, and CCL2 and an increase in the numbers of splenic phagocytes. Functionally, splenocytes from DC-depleted mice exhibited an increased bacterial killing capacity compared to splenocytes from control mice. Cellular studies further showed that this was due to an increased production of reactive oxygen species (ROS) by neutrophils. Adoptive transfer of neutrophils from DC-depleted mice into control mice prior to Ye infection reduced the bacterial load to the level of Ye-infected DC-depleted mice, suggesting that the increased number of phagocytes with additional ROS production account for the decreased bacterial load. Furthermore, after incubation with serum from DC-depleted mice splenocytes from control mice increased their bacterial killing capacity, most likely due to enhanced ROS production by neutrophils, indicating that serum factors from DC-depleted mice account for this effect. In summary, we could show that DC depletion triggers phagocyte accumulation in the spleen and enhances their anti-bacterial killing capacity upon bacterial infection.

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Yersinia enterocolitica is associated with human clinical manifestations. In this study, the bioserotype distribution, virulence potential, the antimicrobial susceptibility, and the genomic diversity of Y. enterocolitica isolates recovered from Argentina and Chile were assessed. Eight Chilean and 22 Argentine isolates recovered from human (7) and animal feces (3), foods (18) and wastewater (2) were analyzed. They belonged to the bioserotypes B2 O:9 (9), B1A O:5 (8), B1A O:41,42‐41,43 (8), B4 O:3 (3) and B1A O:7,8‐8‐8,19 (2). Autoagglutination (AA), Ca2+‐dependent growth at 37°C and yadA, inv and yst genes were observed in B2 O:9 and B4 O:3 strains. B1A strains exhibited the genotype yadA‐ inv‐ yst+. All strains were resistant to ampicillin, rifampicin and erythromycin. By XbaI‐PFGE, 11 genomic types (GTs) were demonstrated (D.I. 0.90). The characteristics of these Y. enterocolitica isolates highlight the importance to maintain active surveillance of this enteropathogen in both countries. Practical applications The trade exchange among Chile and Argentina includes 12–19% of agricultural goods and foodstuffs with fresh and processed vegetables, seafoods and meat products as the major commodities. Additionally, travel and tourism have increased in recent years with more than 2.5 million passengers moving from Argentina to Chile in 2017. In this context, the control of foodborne pathogens and diseases represents a challenge for both countries. The analysis of bioserotypes, virulence potential, antimicrobial susceptibility, and clonal relatedness of Argentine and Chilean Y. enterocolitica isolates encourages further studies to contribute to the knowledge of the epidemiology of this enteropathogen and the implementation of adequate sanitary measures to prevent Y. enterocolitica illness in both countries.

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Foodborne diseases have become a health issue worldwide, mainly due to the consumption of contaminated foods that are either raw, improperly heat treated or cross‐contaminated after adequate heat treatment foods. A group of alkaloids extracted from plants were tested to evaluate their antimicrobial effect against different strains of Yersinia enterocolitica and other foodborne bacteria. The results obtained reveal that oliveridine and pachypodanthine inhibited Y. enterocolitica growth, with MIC values of 25 μmol l−1 and 100 μmol l−1 respectively. The results indicated that both alkaloids are good growth inhibitors, but oliveridine showed greater inhibitory effect with lower MIC values. Inhibitory alkaloids can be developed as potential antimicrobials in food system to prevent or treat foodborne diseases, thus contributing to solve the global issue of contaminated food consumption. Significance and Impact of the Study Alkaloids are abundant secondary metabolites in plants and represent one of the most widespread class of compounds endowed with multiple and varied pharmacological properties. In this work, we propose two aporphinoid alkaloids extracted from plants as new antimicrobial agents. Oliveridine and pachypodanthine inhibited Yersinia enterocolitica growth for up to 96 h of culture. This is the first reported study of the activity of these alkaloids as antimicrobial compounds.