Efficacy of a competitive exclusion culture against extended-spectrum β-lactamase-producing Escherichia coli strains in broilers using a seeder bird model

Background Administration of a competitive exclusion culture (CE culture) has the potential to induce protective effects in very young chicks against caecal colonisation by EEC (= extended-spectrum β-lactamases [ESBL] and AmpC-type [AmpC] beta-lactamases producing Escherichia coli). The study aimed to verify the protective capacity of a CE culture in broilers using the seeder bird model against EEC exposure of the chicks. Results Introduction of infected seeder birds resulted in rapid and strong caecal colonisation of four different EEC challenge strains tested in untreated contact broilers. Compared to controls the broilers pre-treated with the CE culture showed a considerable decrease in caecal load of different EEC challenge strains from about 3.0–3.5 log10 units (P < 0.05) on day 9 of life to 2.5–3.0 log10 units (P < 0.05) on day 37. A slightly higher protective level of the CE culture in layer birds than in broilers raises the question on reasons for possible differences in the efficacy of CE culture in broiler and layer breeds. Whether the diet’s protein content has an impact on both normal intestinal flora composition and the efficacy of CE cultures against EEC or other pathogens remains open and needs further elucidation. Conclusions Our findings suggest that CE cultures of undefined composition can be valuable to reduce the intestinal colonisation by EEC in newly hatched broilers

Comparing validation of four ELISAsystems for detection of Salmonella Derby- and Salmonella Infantis-infected pigs

The objective of this study was the comparative evaluation of four indirect Salmonella ELISA tests at study time approved in Germany to detect Salmonella infection in pigs. Three tests are based on a LPS-antigen mix and directed against specific IgG antibodies. The fourth test is based on a purified S. Typhimurium whole-cell lysate antigen and discriminates between Salmonella- specific IgM-, IgA-, and IgG- antibodies. In a longitudinal study, two groups of six weeks old hybrid piglets were orally infected with a porcine S. Infantis or S. Derby strain. Clinical and bacteriological parameters were monitored weekly during an observation period of 130 days after infection and serum samples were investigated in parallel with the respective ELISAs. Apparently, the LPS-based ELISA systems used in this study failed to recognize S. Infantis-infected pigs although those animals shed the pathogen in high amounts throughout the study until day 81 post infection (p. i.). In contrast, the isotype-specific Salmonella Typhimurium whole-cell-lysate based ELISA was capable of detecting Salmonella-infected pigs from day ten p. i. at all tested serotypes and revealed the highest sensitivity in detection of S. Infantis- infected pigs. Furthermore, it became apparent that the often used surveillance cut-off value of 40 OD% is not appropriate for intra-vitam detection of S. Infantis- and S. Derbyinfected pigs. In contrast, the cut-off values of the ELISAs given by the suppliers result in considerable higher detection rates

Studies on the influence of ochratoxin A administration on Salmonella typhimurium infection in pigs

The aim of the study was to assess whether immunomodulating effects produced by ochratoxin A (OTA) may influence the course of an experimental infection of pigs with Salmonella Typhimurium 27 Nat (STM 27 Nair). 8-week old pigs were administered 50 g OTA per kg body weight per day via feed. Either 7 or 14 days after beginning of OTA application, these pigs and untreated controls were challenged orally with STM 27 Nair. Different systemic immune parameters in blood and OT A concentration in serum and organs were examined. The number of STM 27 Nair was detected in faecal samples of the pigs. Despite high concentrations of OTA in sera and organs, systemic immune parameters were not modified compared with controls. Significant changes in these parameters were induced only by the Salmonella infection. Pigs pretreated with OTA excreted STM 27 Nair in slightly higher (not significant) concentrations than untreated controls. As the immunomodul ating effects produced by OT A after oral administration seem to be considerably lower than the effects induced by a challenge with Salmonella Typhimurium in a high dose, experiments using reduced doses for infection should give further information on the effect on Salmonella shedding

Occurrence and characterisation of Salmonella enterica subspecies diarizonae serovar 61: k: 1, 5, (7) in sheep in the federal state of Thuringia, Germany

Abstract Background The occurrence of Salmonella enterica subspecies diarizonae serovar 61: k: 1, 5, (7) (SASd) and other Salmonella organisms in sheep in the German federal state of Thuringia was examined for the first time. Pooled faecal samples from 90 flocks located in this state were monitored. Results Only SASd was detected in 74 (82.2%) out of the 90 sheep herds, other Salmonella serovars were not identified. A positive correlation was found between the flock size and the detection probability of SASd. Despite the agent’s high prevalence, clinical symptoms of a disease exclusively due to SASd have not been observed. The SASd strains were characterised by macrorestriction analysis, antimicrobial testing and the biochemical profile. All strains were sensitive to 13 out of 14 antimicrobial substances and resistant to only sulfamethoxazole. The high number of macrorestriction groups of SASd strains indicated a low clonality of the serovar. Conclusions Data from sheep derived foods and public health data in Germany strongly suggest that the significance of SASd for public health is considerably lower than that of serovars belonging to Salmonella enterica subspecies enterica. For this reason and because of the low disease-causing potential of SASd in sheep, it is worthwile to consider a reduction in ongoing activities from combating to monitoring serovar 61: k: 1, 5, (7) in the sheep population

Immune reaction and survivability of salmonella typhimurium and salmonella infantis after infection of primary avian macrophages.

Salmonella serovars are differentially able to infect chickens. The underlying causes are not yet fully understood. Aim of the present study was to elucidate the importance of Salmonella Pathogenicity Island 1 and 2 (SPI-1 and -2) for the virulence of two non-host-specific, but in-vivo differently invasive, Salmonella serovars in conjunction with the immune reaction of the host. Primary avian splenic macrophages were inoculated with Salmonella enterica sub-species enterica serovar (S.) Typhimurium and S. Infantis. The number and viability of intracellular bacteria and transcription of SPI-1 and -2 genes by the pathogens, as well as transcription of immune-related proteins, surface antigen expression and nitric oxide production by the macrophages, were compared at different times post inoculation. After infection, both of the Salmonella serovars were found inside the primary macrophages. Invasion-associated SPI-1 genes were significantly higher transcribed in S. Infantis- than S. Typhimurium-infected macrophages. The macrophages counteracted the S. Infantis and S. Typhimurium infection with elevated mRNA expression of inducible nitric oxide synthase (iNOS), interleukin (IL)-12, IL-18 and lipopolysaccharide-induced tumor necrosis factor alpha factor (LITAF) as well as with an increased synthesis of nitric oxide. Despite these host cell attacks, S. Typhimurium was better able than S. Infantis to survive within the macrophages and transcribed higher rates of the SPI-2 genes spiC, ssaV, sifA, and sseA. The results showed similar immune reactions of primary macrophages after infection with both of the Salmonella strains. The more rapid and stronger transcription of SPI-2-related genes by intracellular S. Typhimurium compared to S. Infantis might be responsible for its better survival in avian primary macrophages

Salmonella enterica subspecies enterica serovar Choleraesuis in a German wild boar population: occurrence and characterisation

Abstract Background The swine-adapted serovar Choleraesuis of Salmonella enterica subspecies enterica is found rarely in domestic pigs in Germany. However, a considerable and increasing number of S. Choleraesuis organisms have been isolated from wild boars in Germany in recent years. To investigate a possible epidemiological context, S. Choleraesuis strains from a regional German wild boar population and other hosts were characterised by genotyping methods. Results Macrorestriction analysis, biochemical differentiation and antimicrobial susceptibility typing enabled the identification of several clusters of S. Choleraesuis. Some clusters occurred almost permanently in a certain district, whereas other groups circulated among different wild boar herds in larger regions. Non-porcine hosts were infected with the same cluster as the wild boars. Conclusions The emergence of S. Choleraesuis in wild boars might be caused by a higher prevalence in the wild boar population, but also the higher awareness to infections with African swine fever may have resulted in a higher number of examined animals. Separation of wild boar populations and, as a result, also the diverse S. Choleraesuis organisms might be due to natural barriers and artificial barriers like arterial roads. The findings of S. Choleraesuis in domestic pigs emphasize the importance of strict biosecurity measures to prevent transmission from wild boars of this but also other pathogens. To avoid risks for humans by zoonotic pathogens regular inspections of meat from wildlife need to be conducted

Circulating γδ T Cells in Response to Salmonella enterica Serovar Enteritidis Exposure in Chickens

γδ T cells are considered crucial to the outcome of various infectious diseases. The present study was undertaken to characterize γδ (T-cell receptor 1(+) [TCR1(+)]) T cells phenotypically and functionally in avian immune response. Day-old chicks were orally immunized with Salmonella enterica serovar Enteritidis live vaccine or S. enterica serovar Enteritidis wild-type strain and infected using the S. enterica serovar Enteritidis wild-type strain on day 44 of life. Between days 3 and 71, peripheral blood was examined flow cytometrically for the occurrence of γδ T-cell subpopulations differentiated by the expression of T-cell antigens. Three different TCR1(+) cell populations were found to display considerable variation regarding CD8α antigen expression: (i) CD8α(+high) TCR1(+) cells, (ii) CD8α(+dim) TCR1(+) cells, and (iii) CD8α(−) TCR1(+) cells. While most of the CD8α(+high) TCR1(+) cells expressed the CD8αβ heterodimeric antigen, the majority of the CD8α(+dim) TCR1(+) cells were found to express the CD8αα homodimeric form. After immunization, a significant increase of CD8αα(+high) γδ T cells was observed within the CD8α(+high) TCR1(+) cell population. Quantitative reverse transcription-PCR revealed reduced interleukin-7 receptor α (IL-7Rα) and Bcl-x expression and elevated IL-2Rα mRNA expression of the CD8αα(+high) γδ T cells. Immunohistochemical analysis demonstrated a significant increase of CD8α(+) and TCR1(+) cells in the cecum and spleen and a decreased percentage of CD8β(+) T cells in the spleen after Salmonella immunization. After infection of immunized animals, immune reactions were restricted to intestinal tissue. The study showed that Salmonella immunization of very young chicks is accompanied by an increase of CD8αα(+high) γδ T cells in peripheral blood, which are probably activated, and thus represent an important factor for the development of a protective immune response to Salmonella organisms in chickens

Epidemiological Analysis on the Occurrence of <i>Salmonella enterica</i> Subspecies <i>enterica</i> Serovar Dublin in the German Federal State Schleswig-Holstein Using Whole-Genome Sequencing

The cattle-adapted serovar Salmonella Dublin (S. Dublin) causes enteritis and systemic diseases in animals. In the German federal state Schleswig-Holstein, S. Dublin is the most important serovar in cattle indicating an endemic character of the infection. To gain information on dissemination and routes of infection, whole-genome sequencing (WGS) was used to explore the genetic traits of 78 S. Dublin strains collected over a period of six years. The phylogeny was analysed using core-genome single nucleotide polymorphisms (cgSNPs). Genomic clusters at 100, 15 and 1 cgSNPs were selected for molecular analysis. Important specific virulence determinants were detected in all strains but multidrug resistance in S. Dublin organisms was not found. Using 15 cgSNPs epidemiological links between herds were identified, clusters at 1 cgSNPs provided clear evidence on both persistence of S. Dublin at single farms in consecutive years and transmission of the organisms between herds in different distances. A possible risk factor for the repeated occurrence of S. Dublin in certain districts of Schleswig-Holstein might be the spreading of manure on pastures and grassland. Effective control of S. Dublin requires farm-specific analysis of the management supplemented by WGS of outbreak causing S. Dublin strains to clearly identify routes of infection

Characterization of Avian γδ T-Cell Subsets after Salmonella enterica Serovar Typhimurium Infection of Chicks ▿

Avian γδ T lymphocytes are frequently found in blood and organs and are assumed to be crucial to the immune defense against Salmonella infections of chicks. To elucidate the so-far-unknown immunological features of subpopulations of avian γδ T cells in the course of infection, day-old chicks were infected orally with Salmonella enterica serovar Typhimurium. Until 11 days after infection, the occurrence as well as transcription of the CD8 antigen and immunologically relevant protein genes of CD8α− and CD8α+high (CD8αα+ CD8αβ+) γδ cells were analyzed using flow cytometry and quantitative real-time reverse transcription-PCR (RT-PCR) with blood, spleen, thymus, and cecum samples. After infection, an increased percentage of CD8α+high γδ T lymphocytes was found in blood, in spleen, and, with the highest values and most rapidly, in cecum. Within the CD8α+high subset, a significant rise in the number of CD8αα+ cells was accompanied by enhanced CD8α antigen expression and reduced gene transcription of the CD8β chain. CD8αα+ and CD8αβ+ cells showed elevated transcription for Fas, Fas ligand (FasL), interleukin-2 receptor α (IL-2Rα), and gamma interferon (IFN-γ). While the highest fold changes in mRNA levels were observed in CD8αβ+ cells, the mRNA expression rates of CD8αβ+ cells never significantly exceeded those of the CD8αα+ cells. In conclusion, both CD8α+high γδ T-cell subpopulations (CD8αα+ and CD8αβ+) might be a potential source of IFN-γ in Salmonella-infected chicks. However, due to their prominent frequency in blood and organs after infection, the avian CD8αα+ γδ T-cell subset seems to be unique and of importance in the course of Salmonella Typhimurium infection of very young chicks

Relative quantification of mRNA expression of immune-related proteins in primary avian macrophages infected with <i>S</i>. Typhimurium or <i>S</i>. Infantis.

<p>Data were presented as fold change compared to non-infected macrophages. White columns—macrophages infected with <i>S</i>. Typhimurium (n = 6), Grey columns—macrophages infected with <i>S</i>. Infantis (n = 6) ** <i>P</i> ≤ 0.05 or * <i>P</i> ≤ 0.1 <i>S</i>. Typhimurium vs. <i>S</i>. Infantis; <b>a</b>) <i>P</i> ≤ 0.05 or a) <i>P</i> ≤ 0.1 <i>S</i>. Typhimurium vs. control; <b>b</b>) <i>P</i> ≤ 0.05 or b) <i>P</i> ≤ 0.1 <i>S</i>. Infantis vs. control.</p