Determining longitudinal and transverse elastic wave attenuation from zero-group-velocity Lamb waves in a pair of plates.

A method for the determination of longitudinal and transverse bulk acoustic wave attenuation from measurements of the decay-rate of two independent zero-group-velocity resonances in a couple of matched plates is presented. A linear relation is derived, which links the bulk-wave attenuation coefficients to the decay-rate of plate-resonances. The relation is used to determine the acoustic loss of tungsten at GHz frequencies from noncontact laser-ultrasonic measurements in plates with thicknesses of about 1 µm. The longitudinal and transverse attenuation was found to amount to 1918 m-1 and 7828 m-1 at 2.16 GHz and 3265 m-1 and 12181 m-1 at 2.46 GHz. The presented approach is validated with calculated responses to a thermoelastic source, and the accuracy of the obtained attenuation values is estimated to be in the range of 10%.

Enterococcus faecium NCIMB 10415 supplementation affects intestinal immune-associated gene expression in post-weaning piglets.

In a Salmonella challenge study of weaned piglets supplemented with the probiotic Enterococcus faecium NCIMB 10415 (SF68), we observed a delayed, post-infection proliferative response of purified blood mononuclear cell fractions towards Salmonella antigens. In order to clarify this observation, we examined the patterns of immune-associated gene expression in long-term feeding trials of both pre- and post-weaning piglets. Piglets supplemented with E. faecium NCIMB 10415 showed a post-weaning dysregulation in the expression patterns of both pro- and anti-inflammatory cytokine expression in intestinal tissues and spleen. Piglets of the supplemented group showed significantly reduced levels of IL-8, IL-10 and the co-stimulatory molecule CD86 mRNA expression in ileal Peyer's patches. The expression of CTLA4, an inhibitor of T-cell activation/proliferation, showed similar levels of expression in all tissues examined, particularly in ileal Peyer's patches post-weaning where IL-8, IL-10 and CD86 transcript levels were significantly reduced relative to control animals. Blood serum cytokine protein levels showed elevated TGFß in pre-weaning piglets which, together with IL-6, may have suppressed IFNγ production in the probiotic-fed animals. In a second Salmonella challenge study, post-weaning, E. faecium-fed animals showed significantly elevated levels of IL-8 gene expression in mesenteric lymph nodes, but reduced levels in the spleen. At early times post-infection, the probiotic-fed group showed similar levels of IL-10, CD86 and CTLA4 mRNA expression as the control animals in intestinal Peyer's Patches, despite high relative levels of IL-8 expression in mesenteric lymph nodes. The sum of the observations suggests that supplementation of pre-weaning piglets with E. faecium affects intestinal immune-associated gene expression, which is aggravated post-weaning when the animals receive increased levels of the probiotic in feed. We suggest the post-weaning reductions in gene expression may delay the host response to infections, and provide pathogenic bacteria such as Salmonella with a "window of opportunity", leading to the increased bacterial loads and shedding observed in challenge trials. Possible mechanisms explaining these effects of E. faecium NCIMB 10415 are discussed.

No protective effects of high-dosage dietary zinc oxide on weaned pigs infected with Salmonella enterica serovar typhimurium DT104.

Twenty-eight-day-old weaned pigs were fed diets with a low (LZn), medium (MZn), or high (MZn) Zn concentration (50 to 80, 150, or 2,500 mg Zn/kg of diet, respectively) provided as zinc oxide (ZnO)(24 pigs per group). They were infected orally with Salmonella enterica serovar Typhimurium DT104 on day 32. Salmonellae were cultivated from feces (up to 42 days postinfection [dpi]) and organs (2 and 42 dpi). Activation of the adaptive systemic and mucosal immune systems was investigated by recording anti-Salmonella IgG levels and levels of B and T lymphocyte subpopulations in blood and gut-associated lymphatic tissue. Growth performance was recorded as well. Salmonellae were shed at higher levels and for longer periods in the HZn group (P < 0.05), with no differences in the tissues. At 2 dpi, the relative percentages of CD4(+) T helper cells (P < 0.01) and of CD2(+) T and NK cells (P < 0.01) in blood were reduced from the relative cell counts obtained at 0 dpi, irrespective of the Zn group. The lowest percentage of cytotoxic T cells was found 14 dpi in the HZn group relative to the MZn (P < 0.05) and LZn (P < 0.01) groups. Supplementation of the feed with 2,500 mg Zn/kg of diet immediately after weaning could positively affect the immune responses of piglets infected with Salmonella Typhimurium, but for a short period only. After 2 weeks, all positive effects disappeared, and rather negative effects, such as higher shedding of salmonellae, lower T cell frequencies, and worse performance, occurred. Thus, supplementation with ZnO at high levels in the pig industry should be limited to 2 to 3 weeks.

New fast and cost-effective gene test to get the ETEC F18 receptor status in pigs.

In many infection studies and approaches in breeding research it is of high importance to know the genetic predisposition of pigs for the susceptibility to the Escherichia coli (E. coli). Therefore, we developed a gene test to determine the status of the F18 receptor, as indicated by the FUT1 gene. A SNP in the FUT1 gene was first described by Vogeli et al. (1996) and a gene test was patented by Meijerink et al. (1997). Up until now, the gene test of Meijerink has been used in research. However, faster and cheaper genotyping techniques are now available, which led us to develop an easily applicable, fast and cost effective genetic test to determine the status of the F18 receptor. To check the accuracy of the new test, we genotyped 32 pigs with the established test as well as with our new test. All in all, we genotyped 430 German Landrace pigs. The test was successful. We suggest this allele specific test as a new standard genetic tool to determine the ETEC F18 receptor status in pigs.

Feeding of the probiotic bacterium Enterococcus faecium NCIMB 10415 differentially affects shedding of enteric viruses in pigs.

Effects of probiotic bacteria on viral infections have been described previously. Here, two groups of sows and their piglets were fed with or without feed supplementation of the probiotic bacterium Enterococcus faecium NCIMB 10415. Shedding of enteric viruses naturally occurring in these pigs was analyzed by quantitative real-time RT-PCR. No differences between the groups were recorded for hepatitis E virus, encephalomyocarditis virus and norovirus. In contrast, astrovirus was exclusively detected in the non-supplemented control group. Rotavirus was shedded later and with lower amounts in the probiotic piglet group (p < 0.05); rotavirus-shedding piglets gained less weight than non-infected animals (p < 0.05). Serum titres of anti-rotavirus IgA and IgG antibodies were higher in piglets from the control group, whereas no difference was detected between sow groups. Phenotype analysis of immune cell antigens revealed significant differences of the CD4 and CD8ß (p < 0.05) as well as CD8α and CD25 (p < 0.1) T cell populations of the probiotic supplemented group compared to the non-supplemented control group. In addition, differences were evident for CD21/MHCII-positive (p < 0.05) and IgM-positive (p < 0.1) B cell populations. The results indicate that probiotic bacteria could have effects on virus shedding in naturally infected pigs, which depend on the virus type. These effects seem to be caused by immunological changes; however, the distinct mechanism of action remains to be elucidated.

No beneficial effects evident for Enterococcus faecium NCIMB 10415 in weaned pigs infected with Salmonella enterica serovar Typhimurium DT104.

Salmonella enterica serovar Typhimurium DT 104 is the major pathogen for salmonellosis outbreaks in Europe. We tested if the probiotic bacterium Enterococcus faecium NCIMB 10415 can prevent or alleviate salmonellosis. Therefore, piglets of the German Landrace breed that were treated with E. faecium (n = 16) as a feed additive and untreated controls (n = 16) were challenged with S. Typhimurium 10 days after weaning. The presence of salmonellae in feces and selected organs, as well as the immune response, were investigated. Piglets treated with E. faecium gained less weight than control piglets (P = 0.05). The feeding of E. faecium had no effect on the fecal shedding of salmonellae and resulted in a higher abundance of the pathogen in tonsils of all challenged animals. The specific (anti-Salmonella IgG) and nonspecific (haptoglobin) humoral immune responses as well as the cellular immune response (T helper cells, cytotoxic T cells, regulatory T cells, γδ T cells, and B cells) in the lymph nodes, Peyer's patches of different segments of the intestine (jejunal and ileocecal), the ileal papilla, and in the blood were affected in the course of time after infection (P < 0.05) but not by the E. faecium treatment. These results led to the conclusion that E. faecium may not have beneficial effects on the performance of weaned piglets in the case of S. Typhimurium infection. Therefore, we suggest a critical discussion and reconsideration of E. faecium NCIMB 10415 administration as a probiotic for pigs.