60,322 research outputs found

    Salmonella Typhimurium resides largely as an extracellular pathogen in porcine tonsils, independently of biofilm-associated genes csgA, csgD and adrA

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    In European countries, Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) is the serovar most frequently isolated from slaughter pigs1. Porcine carcass contamination with Salmonella Typhimurium can largely be attributed to persistently infected pigs. Even though tonsils are a predilection site for Salmonella persistence in pigs, virulence mechanisms necessary for cell invasion and intracellular survival do not contribute to tonsillar colonization2, suggesting that Salmonella Typhimurium resides mainly extracellularly in porcine tonsils. Biofilm formation is a mechanism used by several bacteria to survive in an extracellular context or in hostile environments3. The role of biofilm formation in Salmonella Typhimurium persistence in pigs is still unknown. It was the aim of the present study to determine whether Salmonella Typhimurium persists intracellularly or extracellularly in tonsils of pigs. Additionally, the role of biofilm formation in persistence of Salmonella Typhimurium in porcine tonsils was determined

    Salmonella Typhimurium interferes with the humoral immune response in pigs

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    Foodborne salmonellosis is one of the most important bacterial zoonotic diseases worldwide. Salmonella Typhimurium is the serovar most frequently isolated from slaughter pigs in Europe. Circumvention of the host’s immune system by Salmonella might contribute to persistent infection of pigs. We found that Salmonella Typhimurium strain 112910a, which is able to persist in pigs, was capable of downregulating the expression of major histocompatibility class II (MHC II) molecules on porcine alveolar macrophages (PAM) in a Salmonella pathogenicity island 2 (SPI-2) dependent way and that MHC II downregulation was Salmonella strain dependent. The MHC II downregulation capacity was abolished when bacteria were opsonized with Salmonella-specific antibodies. Furthermore, intracellular proliferation of Salmonella Typhimurium opsonized with Salmonella positive pig serum was significantly impaired compared to that of the bacteria opsonized with negative pig serum. In a subsequent in vivo experiment, Salmonella Typhimurium strain MB2216 that did not induce MHC II downregulation in vitro, was shed less and persisted less but induced earlier seroconversion in pigs than strain 112910a. From the in vitro data, it is proposed that Salmonella Typhimurium downregulates the humoral immune response to promote intracellular survival inside porcine macrophages, contributing to long-term Salmonella persistence in pigs. The fact that the less persistent strain MB2216 induced earlier seroconversion than strain 112910a is of major interest for Salmonella-monitoring programs primarily based on serology, since this indicates that more persisting strains are more likely to escape serological detection

    The immunological relationship between filtrable agent, Salmonella and murine leukosis

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    Salmonella typhimurium was invariably isolated from our J strain murine leukosis. Immunization of D103 mice with either inactivated Salmonella typhimurium or the cell-free extract of leukosis inhibited the transplantation of leukosis. The adoptive immunization of D103 mice with spleen cells of Strong A mice immunized with either Salmonella or the cell-free extract of leukosis inhibited the transplantation of leukosis. The addition of either Salmonella or the cell-free extract of leukosis inhibited the migration of macrophages of leukosis spleen in tissue culture. Strong A mice is non-susceptible to J strain leukosis. However, inoculation of neonatal Strong A mice with the cell-free extract of leukosis produced a susceptibility to the transplantation of leukosis. These results suggest that both a filtrable agent and Salmonella typhimurium are present in cells of this leukosis and might be etiologically related to the leukosis.</p

    Tissue-specific Salmonella Typhimurium gene expression during persistence in pigs

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    Salmonellosis caused by Salmonella Typhimurium is one of the most important bacterial zoonotic diseases. The bacterium persists in pigs resulting in asymptomatic 'carrier pigs', generating a major source for Salmonella contamination of pork. Until now, very little is known concerning the mechanisms used by Salmonella Typhimurium during persistence in pigs. Using in vivo expression technology (IVET), a promoter-trap method based on Delta purA attenuation of the parent strain, we identified 37 Salmonella Typhimurium genes that were expressed 3 weeks post oral inoculation in the tonsils, ileum and ileocaecal lymph nodes of pigs. Several genes were expressed in all three analyzed organs, while other genes were only expressed in one or two organs. Subsequently, the identified IVET transformants were pooled and reintroduced in pigs to detect tissue-specific gene expression patterns. We found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes during Salmonella peristence in pigs. Furthermore, we compared the persistence ability of substitution mutants for the IVET-identified genes sifB and STM4067 to that of the wild type in a mixed infection model. The Delta STM4067::kanR was significantly attenuated in the ileum contents, caecum and caecum contents and faeces of pigs 3 weeks post inoculation, while deletion of the SPI-2 effector gene sifB did not affect Salmonella Typhimurium persistence. Although our list of identified genes is not exhaustive, we found that efp and rpoZ were specifically expressed in the ileocaecal lymph nodes of pigs and we identified STM4067 as a factor involved in Salmonella persistence in pigs. To our knowledge, our study is the first to identify Salmonella Typhimurium genes expressed during persistence in pigs

    Клінічні особливості сучасного сальмонельозу

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    В роботі досліджено клінічні та лабораторні особливості перебігу сальмонельозу, спричиненого Salmonella typhimurium і S. enteritidis.В работе исследованы клинические и лабораторные особенности течения сальмонеллеза, вызванного Salmonella typhimurium и S. enterіtіdіs.In work it was studied the clinical and laboratory features of the course of salmonellosis caused by Salmonella typhimurium and S. enterіtіdіs

    Bacteriological evaluation of vaccination against Salmonella Typhimurium with an attenuated vaccine in subclinically infected pig herds

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    Subclinical infections with Salmonella Typhimurium occur frequently in pigs. They constitute a risk for human salmonellosis and are difficult to control with currently available control measures. Vaccination against Salmonella Typhimurium in pigs can be an effective tool to control Salmonella infections at farm level. In the present study, the efficacy of an attenuated Salmonella Typhimurium vaccine (Salmoporc®, IDT Biologika) to control Salmonella infections in pigs was evaluated in three subclinically infected pig herds. The effect on Salmonella excretion and the number of pigs positive for Salmonella Typhimurium field and vaccine strains in ileocecal lymph nodes at slaughter were evaluated using five different vaccination strategies: 1. vaccination of sows, 2. vaccination of sows and piglets, 3. vaccination of sows and fattening pigs, 4. vaccination of piglets, 5. vaccination of fattening pigs, which were all compared to a non-vaccinated control group (experimental group 6). Each vaccination strategy was implemented in each farm, during two consecutive production cycles of the same sows. The prevalence of Salmonella Typhimurium field strain excretion was low; in total, 4% of the fecal and overshoe samples collected in the non-vaccinated control group were Salmonella Typhimurium field strain positive. The excretion of Salmonella Typhimurium field strain did not significantly differ between farms, production cycles and experimental groups. Applying vaccination in either sows and piglets, sows and fattening pigs, or in piglets only, resulted in a significantly reduced number of Salmonella Typhimurium field strain positive lymph nodes of slaughter pigs in the second production cycle, but not in the first production cycle. Vaccination of sows and piglets resulted in the most consistent reduction of Salmonella Typhimurium field strain positive lymph nodes at slaughter. The vaccine strain was detected in the lymph nodes of 13 pigs at slaughter, indicating the possible persistence of the vaccine strain until slaughter. Because of limitations in the study design, and the variability between farms and production cycles, the results of the current observational study should be extrapolated with care. Nevertheless, the results provide evidence that applying vaccination against Salmonella Typhimurium in sows and piglets (preferred), sows and fattening pigs, and piglets only can support the control of Salmonella Typhimurium infections by decreasing the prevalence of Salmonella Typhimurium field strain positive lymph nodes at slaughter

    Utjecaj fermentiranoga soka cikle na kemijski induciranu mutaciju sojeva Salmonella typhimurium TA98 i TA100

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    The ability of fresh and fermented beetroot juice to limit chemical mutations has been studied using the Ames test and the strains of Salmonella typhimurium TA98 and TA100. Beetroot juice was fermented in either spontaneous or controlled fermentation, with the use of selected cultures of lactic acid bacteria, three Lactobacillus paracasei strains designated as 0916, 0920, 0923, and one Lactobacillus brevis strain 0944. N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) was used as a standard mutagen for the induction of His+ revertants in mutations of Salmonella typhimurium TA98 and TA100. The ability to reduce mutations was studied using the Ames test and the doses of beetroot juice of 0.5, 1.0, 2.0, 5.0 and 10.0 mL per plate. The study showed that the fermented beetroot juice (10 µL/plate) reduced the level of MNNG-induced mutations by 64 % in Salmonella typhimurium TA98 and by 65 % in Salmonella typhimurium TA100. The beetroot juice obtained by spontaneous fermentation retained only 24–25 % of initial antimutagenic activity (in Salmonella strain and at the highest tested dose of the juice, i.e. 10 µL/plate). The doses of 10 µL/plate of the beetroot juice fermented by three L. paracasei cultures (0916, 0920 and 0923) decreased the intensity of mutations induced by MNNG by 61, 50 and 56 % in Salmonella typhimurium TA98 and by 65, 56 and 49 % in Salmonella typhimurium TA100, respectively. The juice (10 µL/plate) fermented by L. brevis 0944 strain reduced the number of mutations by 58 % in Salmonella typhimurium TA98 and by 55 % in Salmonella typhimurium TA100. Thus, the controlled lactic acid fermentation of beetroot juice conducted by selected Lactobacillus strains maintains its antimutagenic activity.Pomoću Amesova testa ispitana su svojstva svježega i fermentiranoga soka cikle kako bi se spriječila kemijski inducirana mutacija sojeva Salmonella typhimurium TA98 i TA100. Fermentirani sok cikle dobiven je prirodnom, te kontroliranom fermentacijom pomoću odabranih sojeva mliječno-kiselih bakterija, i to: Lactobacillus paracasei 0916, 0920 i 0923, te Lactobacillus brevis 0944. Kao standardni mutagen za indukciju His+ revertanta sojeva Salmonella typhimurium TA98 i TA100 upotrijebljen je N-metil-N’-nitro-N-nitrozogvanidin (MNNG). Amesovim testom ispitan je utjecaj soka cikle (u dozama od 0,5; 1,0; 2,0; 5,0 i 10,0 μL po ploči) na smanjenje učestalosti mutacije. Ispitivanje je pokazalo da fermentirani sok cikle u dozi od 10 μL po ploči smanjuje mutaciju induciranu s MNNG za 64 % u Salmonella typhimurium TA98, te za 65 % u Salmonella typhimurium TA100. Sok cikle dobiven prirodnom fermentacijom, u najvećoj dozi od 10 μL po ploči, zadržao je samo 24-25 % od početne antimutagene aktivnosti. Ista doza soka cikle dobivenog kontroliranom fermentacijom s pomoću 3 soja Lactobacillus paracasei (0916, 0920 i 0923) znatno je smanjila induciranu mutaciju sojeva Salmonella typhimurium TA98 i S. typhimurium TA100, i to za 61 odnosno 65 % (primjenom soja 0916), za 50 odnosno 56 % (primjenom soja 0920), te za 56 odnosno 49 % (primjenom soja 0923). Sok fermentiran s pomoću Lactobacillus brevis 0944, u dozi od 10 μL po ploči smanjio je broj mutacija Salmonella typhimurium TA98 za 58 %, a Salmonella typhimurium TA100 za 55 %. Zaključeno je da je sok cikle proizveden kontroliranom fermentacijom s pomoću odabranih sojeva mliječno-kiselih bakterija zadržao antimutagena svojstva

    Application of the DIVA principle to Salmonella Typhimurium vaccines in pigs avoids interference with serosurveillance programmes

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    Salmonellosis is one of the most important bacterial zoonotic diseases in humans and Salmonella infections are often linked with the consumption of contaminated pork. In order to reduce Salmonella Typhimurium infections in humans, minimization of the Salmonella intake into the food chain is important. Vaccination has been proposed to control Salmonella infections in pigs. However, pigs vaccinated with the current vaccines cannot be discriminated from infected pigs with the lipopolysaccharide (LPS) -based serological tests used in European serosurveillance programmes. We therefore examined which LPS encoding genes of Salmonella Typhimurium can be deleted to allow differentiation of infected and vaccinated pigs, without affecting the vaccine strain’s protective capacity. For this purpose, deletion mutants in Salmonella strain 112910a, used as vaccine strain, were constructed in the LPS encoding genes: ∆rfbA, ∆rfaL, ∆rfaJ, ∆rfaI, ∆rfaG and ∆rfaF. Inoculation of BALB/c mice with the parent strain, ∆rfaL, ∆rfbA or ∆rfaJ strains but not the ∆rfaG, ∆rfaF or ∆rfaI strains protected significantly against subsequent infection with the virulent Salmonella Typhimurium strain NCTC12023. Immunization of piglets with the ∆rfaJ or ∆rfaL mutants resulted in the induction of a serological response lacking detectable antibodies against LPS. This allowed a differentiation between sera from pigs immunized with the ∆rfaJ or ∆rfaL strains and sera from pigs infected with their isogenic wild type strain

    Host stress drives Salmonella recrudescence

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    Host stress is well known to result in flare-ups of many bacterial, viral and parasitic infections. The mechanism by which host stress is exploited to increase pathogen loads, is poorly understood. Here we show that Salmonella enterica subspecies enterica serovar Typhimurium employs a dedicated mechanism, driven by the scsA gene, to respond to the host stress hormone cortisol. Through this mechanism, cortisol increases Salmonella proliferation inside macrophages, resulting in increased intestinal infection loads in DBA/2J mice. ScsA directs overall Salmonella virulence gene expression under conditions that mimic the intramacrophagic environment of Salmonella, and stimulates the host cytoskeletal alterations that are required for increased Salmonella proliferation inside cortisol exposed macrophages. We thus provide evidence that in a stressed host, the complex interplay between a pathogen and its host endocrine and innate immune system increases intestinal pathogen loads to facilitate pathogen dispersal