Beeinflussung des Stickstoffstoffwechsels wachsender Hähne durch die Jahreszeit

Although Enterococcus faecium is used as a probiotic feed supplement in animal production, feeding of the bacterium to piglets resulted in a more severe infection with Salmonella Typhimurium DT104 during a challenge experiment. To enlighten the mode of action by which E. faecium affected the piglets’ health, we investigated the influence of the probiotic bacterium on the development of intestinal and circulating immune cells during a challenge experiment with S.Typhimurium DT104. To minimise varying impacts of the maternal immunity on the course of infection, only piglets were implemented that descended from Salmonella-free sows. In addition, the potency of purified blood and intraepithelial immune cells to control the growth of Salmonella was tested in vitro. In animals treated with E. faecium, a reduction of intraepithelial CD8αβ T cells, reduced circulating CD8αβ T cells and a less efficient control of intracellular Salmonella growth, mediated by peripheral blood mononuclear cells, were observed.     

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.     

Influence of a Probiotic Strain of Enterococcus faecium on Salmonella enterica Serovar Typhimurium DT104 Infection in a Porcine Animal Infection Model

The beneficial effects of probiotic Enterococcus spp. in different hosts, such as mice and humans, have previously been reported in several studies. However, studies of large domestic animals, as well as challenge studies with pathogenic microorganisms, are very rare. Here, we investigated the influence of oral treatment of pigs with the probiotic bacterium Enterococcus faecium NCIMB 10415 on Salmonella enterica serovar Typhimurium DT104 infections in weaning piglets. Clinical symptoms, fecal excretion, the organ distribution of Salmonella, and the humoral immune response (immunoglobulin G [IgG], IgM, and IgA levels) in serum were examined. A pool of 89 piglets was randomly divided into probiotic and control groups. The probiotic group received a feed supplement containing E. faecium starting on day 14 postpartum prior to challenge with Salmonella serovar Typhimurium DT104 at 28 days postpartum. After challenge with Salmonella serovar Typhimurium DT104, piglets in both groups showed no severe clinical signs of salmonellosis. However, fecal excretion and colonization of Salmonella in organs were significantly greater in piglets fed E. faecium. Likewise, the humoral immune response against Salmonella (serum IgM and IgA levels) was significantly greater in the probiotic group animals than in control animals. The results of this study suggest that E. faecium NCIMB 10415 treatment enhanced the course of infection in weaning piglets challenged with Salmonella serovar Typhimurium DT104. However, the probiotic treatment also appeared to result in greater production of specific antibodies against Salmonella serovar Typhimurium DT104.The problem of increasing microbial resistance to antibiotics resulting from years of overuse and the resulting ban on the use of antibiotics in animal production have led to increased interest in alternatives to antibiotics in animal production. In recent years, probiotic bacteria have been considered as an alternative means of reducing pathogen loads in animal breeding and production units. However, while a number of studies have focused on the mode of action of probiotics, the mode of action these bacteria is not fully understood yet.A recent interdisciplinary research study of the modes of action of probiotics in swine showed that Enterococcus faecium NCIMB 10415 reduced the pathogenic bacterial load of healthy piglets (20, 26, 30, 36). In vitro studies further demonstrated that this E. faecium probiotic strain decreased the rate of invasion of a porcine intestinal epithelial cell line by Salmonella enterica serovar Typhimurium. To determine whether probiotics also provide a measure of protection during infections, experimental challenge studies with pathogenic bacteria at a defined infectious dose and under comparable conditions seem to be necessary. Field studies could be more representative of the real situation; however, the infection pressure is too low and difficult to define, and systematic sampling cannot be done.Studies of larger domestic and production animals are rare. Most such studies deal with the mode of action of probiotics in the healthy host, and only a few studies have investigated the mode of action in the context of infections with pathogenic bacteria, such as Salmonella.In a related study, weaned piglets were fed a mixture of five probiotic strains (one Pediococcus strain and four Lactobacillus strains) and challenged with Salmonella serovar Typhimurium (7). In that study, reduced incidence, severity, and duration of diarrhea and a reduced microbiological load of Salmonella were observed. Fedorka-Cray et al. (11) observed reduced numbers of Salmonella bacteria in cecal contents and at the ileocolic junction in S. enterica serovar Choleraesuis-challenged weaning piglets fed a competitive exclusion culture. In vitro investigations showed that Enterococcus strains have inhibitory effects on the growth of S. enterica serovar Enteritidis, and these effects were explained by both enterotoxin and nonenterotoxin factors (37). Other studies showed that E. faecium may be beneficial to the adhesion and colonization of Clostridium jejuni in the canine intestine (29) and reduced the rate of carryover infections with obligate intracellular pathogens from infected sows in piglets (26). E. faecium has also been shown to influence the composition of the bacterial community in the avian, swine, and canine gastrointestinal tracts (25, 29, 36).Infections with S. enterica are some of the most important sources of human gastroenteritis (39). In Germany, 52,563 human salmonellosis cases were reported in 2006 (http://www3.rki.de/SurvStat). The consumption of contaminated pork and pork products was found to be associated with 20% of human salmonellosis cases in Germany (33), indicating the importance of meat or meat products as a potential source of infection for consumers. Salmonella serovar Typhimurium, especially phage type DT104, is the Salmonella serotype most frequently isolated from pork (27), and it is of particular concern because of its acquisition of multiple antibiotic resistance (1, 38).In this study, we investigated the effect of E. faecium NCIMB 10415 on the infection dynamics of Salmonella serovar Typhimurium DT104, fecal shedding, and the patterns of Salmonella distribution in internal organs, as well as on the humoral immune response to Salmonella in weaning piglets. To the best of our knowledge, this is the first experimental study of the mode of action of a probiotic strain of E. faecium in which dissemination to different internal organs was investigated using weaned piglets experimentally infected with Salmonella.     

Mucosal lymphatic-derived gammadelta T cells respond early to experimental Salmonella enterocolitis by increasing expression of IL-2R alpha

To better understand the roles of gammadelta T cells in mucosal infection, we utilized Salmonella enterica serovar Typhimurium (Salmonella serovar Typhimurium) infection in cattle as it closely approximates Salmonella serovar Typhimurium-induced enterocolitis in humans. Protein and gene expression in alphabeta and gammadelta T cells derived from lymphatic ducts draining the gut mucosa in Salmonella serovar Typhimurium-infected calves were analyzed. In calves with enterocolitis, general gene expression trends in gammadelta T cells suggested subtle activation and innate response, whereas alphabeta T cells were relatively quiescent following Salmonella serovar Typhimurium infection. An increase in IL-2R alpha expression on gammadelta T cells from infected calves and results from in vitro assays suggested that gammadelta T cells were primed by Salmonella serovar Typhimurium LPS to better respond to IL-2 and IL-15. Together with gene expression trends in vivo, these data support early priming activation of target tissue gammadelta T cells during Salmonella serovar Typhimurium infection.     

Genomic relationship of Salmonella enterica serovar typhimurium DT104 isolates from Korea and the United States

Salmonella enterica serovar Typhimurium DT104 (Salmonella Typhimurium DT104 or DT104) has been emerging as a common pathogen for human in Korea since 1997. In order to compare the genomic relationship and to search for the dominant strains in Korea, we conducted pulsed-field gel electrophoresis (PFGE) and IS200 fingerprinting of 25 epidemiological unrelated isolates from human and animals from Korea and cattle from America. Two Salmonella Typhimurium DT104 isolates from human in Korea and all 8 isolates from American cattle had indistinguishable patterns from the PFGE and IS200 fingerprinting but multidrug-resistant Salmonella Typhimurium isolates, including DT104, from Korean animals had diverse genetic patterns. The data suggest that a dominant DT104 strain might have circulated between Korean and American cattle and that it had a high level of clonality.     

Identification of novel Salmonella enterica serovar Typhimurium DT104-specific prophage and nonprophage chromosomal sequences among serovar Typhimurium isolates by genomic subtractive hybridization

Genomic subtractive hybridization was performed between Salmonella enterica serovar Typhimurium LT2 and DT104 to search for novel Salmonella serovar Typhimurium DT104-specific sequences. The subtraction resulted mainly in the isolation of DNA fragments with sequence similarity to phages. Two fragments identified were associated with possible virulence factors. One fragment was identical to irsA of Salmonella serovar Typhimurium ATCC 14028, which is suggested to be involved in macrophage survival. The other fragment was homologous to HldD, an Escherichia coli O157:H7 lipopolysaccharide assembly-related protein. Five selected DNA fragments-irsA, the HldD homologue, and three fragments with sequence similarity to prophages-were tested for their presence in 17 Salmonella serovar Typhimurium DT104 isolates and 27 non-DT104 isolates by PCR. All five selected DNA fragments were Salmonella serovar Typhimurium DT104 specific among the serovar Typhimurium isolates tested. These DNA fragments can be useful for better detection and typing of Salmonella serovar Typhimurium DT104.     

Transmission routes of Salmonella Typhimurium DT 104 between 14 cattle and pig herds in Denmark demonstrated by molecular fingerprinting

AIMS: Salmonella Typhimurium DT 104 is generally assumed to be spread by contact between live animals, e.g. by trading. The aim of the present study was to assess the importance of other routes of transmission in the dissemination of this bacterium. METHODS AND RESULTS: An outbreak among 14 cattle and pig herds located in a geographically narrow area in Denmark was investigated. Epidemiological information and disease history of the herds was obtained through interviews. Based on this, the hypothesis for horizontal spread was proposed, and these were confirmed by comparison of the pulsed field gel electrophoresis (PFGE) and the plasmid profiles of isolates obtained by continuous sampling over a period of almost 3 years. CONCLUSIONS: The study indicated that other routes might play an important role, than the trading of live animals, in the spread of S. Typhimurium DT 104 among livestock. SIGNIFICANCE AND IMPACT OF THE STUDY: Salmonella Typhimurium DT 104 infected herd might pose a significant risk to herds located within the same geographic area. In advising on how to avoid the spread of this bacterium, factors like person contacts, sharing of equipment and contaminated slurry should be focussed on in addition to infected animals.     

Adaptive responses of Salmonella enterica serovar Typhimurium DT104 and other S. Typhimurium strains and Escherichia coli O157 to low pH environments

AIMS: Cattle are a known main reservoir for acid-resistant Escherichia coli O157 and Salmonella enterica serovar Typhimurium DT104. We studied the response of S. Typhimurium DT104 to extreme low pH environments and compared their response to that of acid-resistant E. coli O157 and other S. Typhimurium phage types. METHODS AND RESULTS: Bacteria were grown in nutrient-rich medium and subsequently acid challenged at pH 2.5. We found that stationary phase cultures of various S. Typhimurium strains were able to survive a challenge for 2 h at pH 2.5. As in E. coli, the ability of S. Typhimurium to survive at pH 2.5 was shown to be dependent on the presence of amino acids, specifically arginine. The amount of proton pumping H+/ATPase, both in E. coli O157 and S. Typhimurium strains, was lower when grown at pH values <6 than after growth at pH 7.5. Cyclo fatty acid content of membranes of bacteria grown at pH values <6 was higher than that of membranes of bacteria grown at pH 7.5. CONCLUSIONS: Various S. Typhimurium strains, both DT104 and non-DT104, are able to survive for a prolonged period of time at pH 2.5. Their response to such low pH environment is seemingly similar to that of E. coli O157. SIGNIFICANCE AND IMPACT OF THE STUDY: Food-borne pathogens like S. Typhimurium DT104 and E. coli O157 form a serious threat to public health since such strains are able to survive under extreme low pH conditions as present in the human stomach. The emergence these acid-resistant strains suggests the presence of a selection barrier. The intestinal tract of ruminants fed a carbohydrate-rich diet might be such a barrier.     

Infection-induced expansion of a MHC Class Ib-dependent intestinal intraepithelial gammadelta T cell subset

Salmonella species invade the host via the intestinal epithelium. Hence, intestinal intraepithelial lymphocytes (iIELs) are potentially the first element of the immune system to encounter Salmonella during infection. In this study, we demonstrate, in a mouse model, the expansion of a CD8alphabeta(+)CD94(-)TCRgammadelta(+) T cell subset within the iIEL population in response to oral infection with virulent or avirulent Salmonella. This population can be detected 3 days following infection, represents up to 15% of the TCRgammadelta(+) iIELs, and is dependent on the MHC class Ib molecule T23 (Qa-1). Qa-1 is expressed by intestinal epithelial cells and thus accessible for iIEL recognition. Such cells may play a role in the early immune response to Salmonella.     

Evaluation of the pH-dependent,stationary-phase acid tolerance in Listeria monocytogenes and Salmonella Typhimurium DT104 induced by culturing in media with 1% glucose: a comparative study with Escherichia coli O157:H7

AIMS: To comparatively evaluate the adaptive stationary-phase acid tolerance response (ATR) in food-borne pathogens induced by culturing in glucose-containing media, as affected by strain variability and antibiotic resistance, growth temperature, challenge pH and type of acidulant. METHODS AND RESULTS: Antibiotic resistant or sensitive strains of Listeria monocytogenes, Salmonella including S. Typhimurium DT104, and Escherichia coli O157:H7 were cultured (30 degrees C for 24 h; 10 degrees C for up to 14 days) in trypticase soya broth with yeast extract (TSBYE) with 1% or without glucose to induce or prevent acid adaptation, respectively. Cultures were subsequently exposed to pH 3.5 or 3.7 with lactic or acetic acid at 25 degrees C for 120 min. Acid-adapted cultures were more acid tolerant than nonadapted cultures, particularly those of L. monocytogenes and Salmonella. No consistent, positive or negative, influence of antibiotic resistance on the pH-inducible ATR or acid resistance (AR) was observed. Compared with 30 degrees C cultures, growth and acid adaptation of L. monocytogenes and S. Typhimurium DT104 at 10 degrees C markedly reduced their ATR and AR in stationary phase. E. coli O157:H7 had the greatest AR, relying less on acid adaptation. A 0.2 unit difference in challenge pH (3.5-3.7) caused great variations in survival of acid-adapted and nonadapted cells. CONCLUSIONS: Culturing L. monocytogenes and Salmonella to stationary phase in media with 1% glucose induces a pH-dependent ATR and enhances their survival to organic acids; thus, this method is suitable for producing acid-adapted cultures for use in food challenge studies. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacterial pathogens may become acid-adapted in foods containing glucose or other fermentable carbohydrates. Low storage temperatures may substantially decrease the stationary-phase ATR of L. monocytogenes and S. Typhimurium DT104, but their effect on ATR of E. coli O157:H7 appears to be far less dramatic.     

Immunoassays to detect the serum antibody response of cattle to infection with Salmonella Typhimurium definitive type 104 and following vaccination with Bovivac S

AIMS: To use ELISA and immunoblotting assays to examine the serum antibody response of cattle infected with Salmonella Typhimurium DT104 and following vaccination with Bovivac S. METHODS AND RESULTS: Three hundred and twenty-nine cattle, including 16 shedding multiresistant Salmonella Typhimurium DT104, were screened for serum antibodies binding to O=1, 4, 5, 12 lipopolysaccharide (LPS) antigens before and after vaccination with Bovivac S. Sera with an ELISA reading of 0.9A405 or above were shown to contain antibodies, of the IgG-class only, to the LPS of Salmonella Typhimurium using immunoblotting. Prior to vaccination, only 11 cattle had serum IgG-class antibodies to the O=4, 5 LPS antigens, and of these one also had antibodies to outer membrane proteins and H=i flagellar antigens. Following vaccination, 87 out of 315 cattle developed serum antibodies to the LPS of Salmonella Typhimurium. CONCLUSIONS: Evidence of infection of cattle with Salmonella Typhimurium was readily obtained with an LPS-based ELISA in association with an immunoblotting procedure, supplementing existing bacteriological procedures. This enabled the detection of an increase in the number of cattle with serum antibodies to Salmonella Typhimurium LPS following vaccination with Bovivac S. SIGNIFICANCE AND IMPACT OF THE STUDY: The immunoassays described provided evidence of infection with Salmonella Typhimurium and served as a valuable adjunct to established bacteriology.     

The prevalence of Salmonella spp. in bovine faecal,rumen and carcass samples at a commercial abattoir

AIMS: To determine the prevalence, serotype and antibiotic resistance profile of Salmonella isolates in cattle and on carcasses at a commercial Irish abattoir. METHODS AND RESULTS: Faecal, rumen and carcass samples were collected from a beef abattoir over a 12-month period and examined for the presence of Salmonella spp. Isolates were serotyped, phage typed (when serotype was found to be S. Typhimurium) and tested for susceptibility to a panel of antibiotics. Salmonella was isolated from 2% of faecal, 2% of rumen and 7.6% of carcass samples. Salmonella was most frequently isolated from samples taken during the period August to October. S. Dublin was isolated from 72% of positive samples. S. Agona and S. Typhimurium definitive type (DT)104 were each isolated from 14% of positive samples. All S. Typhimurium DT104 isolates were resistant to ampicillin, chloramphenicol, streptomycin, sulphafurazole and tetracycline (ACSSuT). On occasion, from a single animal, the same serotype was isolated from more than one sample (i.e. faeces and rumen; faeces and carcass; rumen and carcass; faeces, rumen and carcass). CONCLUSIONS: Salmonella is present in cattle at slaughter and on beef carcasses at an Irish abattoir, with a higher frequency of occurrence during the period August to October. Most isolates from the study are not commonly associated with human clinical infection, with the exception of S. Typhimurium DT104 (R-type ACSSuT). SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides epidemiological data that is necessary for the understanding of beef as a source of human Salmonella infection.     

Effect of the probiotic Enterococcus faecium NCIMB10415 on cell numbers of total Enterococcus spp., E. faecium and E. faecalis in the intestine of piglets

Sows and their piglets were fed a diet supplemented with or without the probiotic E. faecium NCIMB10415 (also known as SF68). Piglets were sacrificed 14, 28, 35 and 56 days after birth and DNA from intestinal segments was extracted and purified. A real time PCR assay was used to distinguish Enterococcus spp. (16s rDNA based), E. faecium (Efaafm gene), E. faecalis (Efaafs gene) as well as the probiotic strain (unique plasmid sequence). Extracts of autoclaved sow feces inoculated with E. faecium and E. faecalis cultures were used to calibrate real time PCR results. The probiotic strain was detected in 14 day old suckling piglets before the piglets had access to the starter diet. In piglets of the probiotic group, probiotic E. faecium cell counts were always a significant proportion of total E. faecium cells in stomach digesta (4-20%), however only a small fraction of the total Enterococcus spp. cell number on day 14 and 28 in all intestinal segments (0.1-0.7%). Compared to control samples, the probiotic E. faecium strain significantly (p < or = 0.05) decreased the amount of total Enterococcus spp. and E. faecalis cells in the colon of 14 day old suckling piglets as well as in jejunum and colon samples one week after weaning. E. faecium cell counts were not modified on any sampling day or intestinal segment. This study showed that the presence of probiotic E. faecium NCIMB10415 coincided with reduced total E. faecalis, but not total E. faecium cell numbers in the intestine of piglets. In view of unchanged cell numbers and ratios in sow feces, modifications must have taken place within the intestine of suckling piglets.     

The effect of chlortetracycline treatment and its subsequent withdrawal on multi-resistant Salmonella enterica serovar Typhimurium DT104 and commensal Escherichia coli in the pig

AIMS: To investigate the effect of a therapeutic and sub-therapeutic chlortetracycline treatment on tetracycline-resistant Salmonella enterica serovar Typhimurium DT104 and on the commensal Escherichia coli in pig. METHODS AND RESULTS: Salmonella Typhimurium DT104 was orally administered in all pigs prior to antibiotic treatment, and monitored with the native E. coli. Higher numbers of S. Typhimurium DT104 were shed from treated pigs than untreated pigs. This lasted up to 6 weeks post-treatment in the high-dose group. In this group, there was a 30% increase in E. coli with a chlortetracycline minimal inhibitory concentration (MIC) > 16 mg l-1 and a 10% increase in E. coli with an MIC > 50 mg l-1 during and 2 weeks post-treatment. This effect was less-pronounced in the low-dose group. PCR identified the predominant tetracycline resistance genes in the E. coli as tetA, tetB and tetC. The concentration of chlortetracycline in the pig faeces was measured by HPLC and levels reached 80 microg g-1 faeces during treatment. CONCLUSION: Chlortetracycline treatment increases the proportion of resistant enteric bacteria beyond the current withdrawal time. SIGNIFICANCE AND IMPACT OF THE STUDY: Treated pigs are more likely to enter abattoirs with higher levels of resistant bacteria than untreated pigs promoting the risk of these moving up the food chain and infecting man.     

Evaluation of methods for the identification of Salmonella enterica serotype Typhimurium DT104 from poultry environmental samples

An increase in the prevalence of Salmonella enterica serotype Typhimurium DT104 has been reported worldwide. This study examined the prevalence of this microorganism in poultry environmental samples from commercial layer flocks and pullet environments as well as the sensitivity and specificity of a PCR-based method, and multiple antibiotic resistance profile of Salmonella serogroup B isolates in relation to the serotype and phagetype reference method for the identification of Salmonella Typhimurium DT104. A total of 435 Salmonella isolates were obtained from poultry house environmental samples tested during a 20-month period representing a prevalence of 5.5%. Of these, 313 (72%) isolates were identified as Salmonella serogroup B isolates. These isolates were tested by a PCR-based assay, and for resistance to five antibiotics: ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT) for the rapid identification of Salmonella Typhimurium DT104. Upon comparing the antibiotic resistance and PCR results with serotype and phage type data, the sensitivity and specificity for the identification of Salmonella Typhimurium DT104 of both methods were found to be 100%, and 99.6%, respectively. Both methods can be completed within 24 h after obtaining an isolate, while serotyping and phagetyping required more than 5 days to complete.     

Restriction enzyme analysis of randomly amplified polymorphic DNA amplicons of Salmonella enterica ser. Enteritidis PT4 and Typhimurium DT104

Salmonella enterica serotype Enteritidis PT4 and Typhimurium DT104 isolates were characterized using a random amplification of polymorphic DNA (RAPD) protocol found previously to be highly discriminatory for isolates of Salmonella . Profiles generated with a single primer 1254, and independently 1283, successfully characterized an outbreak strain of Enteritidis PT4 but could not differentiate epidemiologically unrelated strains of Enteritidis PT4 from the outbreak strains. Primer 1254 differentiated one strain, and 1283 two strains of Typhimurium DT104 previously undifferentiated on the basis of biochemical and physical properties. Subsequent analysis using a combination of RAPD and restriction enzyme analysis could not provide additional differentiation of Enteritidis PT4 and Typhimurium DT104 isolates but did, however, exhibit the potential to be a useful combination of molecular techniques.     

The cytokine balance in the maintenance of a persistent infection with Salmonella enterica serovar Typhimurium in mice

ClpXP, serine protease-disrupted mutant of Salmonella enterica serovar Typhimurium chi3306 exhibits attenuated but persistent infection in mice. During infection with S. enterica serovar Typhimurium ClpXP-disrupted mutant, gamma interferon (IFN-gamma) produced by CD4+ cells was up-regulated on day 10 and tumor necrosis factor-alpha (TNF-alpha) produced by CD8+ cells was up-regulated on day 30 after infection. Treatment of monoclonal antibodies against cytokines showed that IFN-gamma and interleukin 10 (IL-10) were involved in maintenance of growth of S. Typhimurium mutant on day 10 after infection, and IFN-gamma, TNF-alpha and transforming growth factor-beta (TGF-beta) were involved in maintenance of growth of this bacterium on day 30 after infection. During persistent infection of S. Typhimurium mutant, IFN-gamma, TNF-alpha, IL-10 and TGF-beta may play different roles to maintain the persistent infection. The cytokine balance might be important in persistent infection with ClpXP-disrupted S. enterica serovar Typhimurium.     

Effects of storage and the presence of a beef microflora on the thermal resistance of Salmonella Typhimurium DT104 in beef and broth systems

AIMS: To investigate the effects of storage and the presence of a beef microflora on the thermal resistance of Salmonella serotype Typhimurium DT104 on beef surfaces and in a broth system during subsequent heat treatments after extended low-temperature storage (4 degrees C for 14 days) or mild temperature abuse (10 degrees C for 7 days). METHODS AND RESULTS: Surviving Salm. Typhimurium DT104 cells were estimated after heating in a water bath (55 degrees C) by plating beef and broth samples on tryptone soya agar and overlaying with xylose-lysine-deoxycholate agar. In beef and broth systems, D(55) values for Salm. Typhimurium DT104 stored at 4 degrees C or 10 degrees C in the presence or absence of a beef microflora were significantly lower (P < 0.01) than the D values for this organism heat-treated immediately after inoculation. In beef systems, the D(55) values were significantly lower (P < 0.05) in the presence of a beef microflora than the D(55) values obtained in 'pure' culture under all temperature/storage combinations. However, in broth systems, there was no significant difference between the D(55) values obtained in 'pure' culture and the D(55) values obtained from systems containing beef microflora. CONCLUSIONS: Storage of Salm. Typhimurium DT104 significantly reduced the thermal resistance of the pathogen in beef and broth systems. In the presence of high numbers of a Gram-negative beef microflora, the heat sensitivity of the pathogen was further increased on beef surfaces but not in broth. SIGNIFICANCE AND IMPACT OF THE STUDY: Studies investigating the survival of Salm. Typhimurium DT104 in different food systems will help define safe food preservation processes and will aid in the elimination this pathogen from the food production environments.     

National survey for Salmonella in pigs, cattle and sheep at slaughter in Great Britain (1999-2000)

AIMS: The objective of these surveys was to estimate the prevalence of faecal carriage of Salmonella in healthy pigs, cattle and sheep at slaughter, and of pig carcase contamination with Salmonella. These data can be used as a baseline against which future change in Salmonella prevalence in these species at slaughter can be monitored. METHODS AND RESULTS: In this first randomized National Survey for faecal carriage of Salmonella in slaughter pigs, cattle and sheep in Great Britain, 2509 pigs, 891 cattle and 973 sheep were sampled in 34 pig abattoirs and 117 red meat abattoirs in England, Scotland and Wales. Carriage of Salmonella in 25 g caecal contents was identified in 578 (23.0% pigs) but in only 134 (5.3%) of carcase swabs. The predominant Salmonella serovars found in both types of sample were S. Typhimurium (11.1% caeca, 2.1% carcases) and S. Derby (6.3% caeca, 1.6% carcases). The main definitive phage types (DT) of S. Typhimurium found were DT104 (21.9% of caecal S. Typhimurium isolates), DT193 (18.7%), untypable strains (17.6%), DT208 (13.3%) and U302 (13.3%). Three isolates of S. Enteritidis (PTs 13A and 4) and one enrofloxacin-resistant S. Choleraesuis were also isolated. A positive 'meat-juice ELISA' was obtained from 15.2% of pigs at 40% optical density (O.D.) cut-off level and 35.7% at 10% cut-off. There was poor correlation between positive ELISA results or carcase contamination and the caecal carriage of Salmonella. The ratio of carcase contamination to caecal carriage rates was highest in abattoirs from the midland region of England and in smaller abattoirs. In cattle and sheep 1 g samples of rectal faeces were tested. Two isolates (i.e. 0.2%) were recovered from cattle, one each of S. Typhimurium, DT193 and DT12. One sheep sample (0.1%) contained a Salmonella, S. Typhimurium DT41. In a small subsidiary validation exercise using 25 g of rectal faeces from 174 cattle samples, three (1.7%) isolates of Salmonella (S. Typhimurium DT104, S. Agama, S. Derby) were found. CONCLUSIONS: The carriage rate of Salmonella in prime slaughter cattle and sheep in Great Britain was very low compared with pigs. This suggests that future control measures should be focused on reduction of Salmonella infection on pig farms and minimizing contamination of carcases at slaughter. SIGNIFICANCE AND IMPACT OF THE STUDY: This work has set baseline figures for Salmonella carriage in these species slaughtered for human consumption in Great Britain. These figures were collected in a representative way, which enables them to be used for monitoring trends and setting control targets.