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PubMed2005

Herd-level factors associated with isolation of Salmonella in a multi-state study of conventional and organic dairy farms I. Salmonella shedding in cows.

The objective of this study was to evaluate associations between herd characteristics and the isolation of Salmonella from dairy cows in Minnesota, Wisconsin, Michigan, and New York. Study farms were 129 conventional and organic farms enrolled without regard to previous history of Salmonella infection. Herds were sampled at 2-month intervals over a 1-year period. This is the largest study to date on Salmonella shedding in dairy cows and the only study evaluating herd-level risk factors using longitudinal sampling to characterize Salmonella shedding on dairy farms. Salmonella was isolated in fecal samples from 1026 (4.9%) of 20,089 cows. Over the course of the study, 113 (87.6%) of 129 farms had at least one positive cow sample. Multi-variable logistic regression using the generalized estimating equations approach was used to test the association between herd-level risk factors and the dependent variable of within-herd prevalence by visit (number of Salmonella-positive cows/number of cows sampled) after adjustment for effects of herd size, season, state of origin, and the multiple sampling occasions per herd. Factors retained in the final model included lack of use of tiestall or stanchion facilities to house lactating cows (OR=1.9; 95% CI: 1.1-3.3), not storing all purchased concentrate or protein feeds in an enclosed building (OR=2.5; 95% CI: 1.3-4.9), not using monensin in weaned calf or bred heifer diets (OR=3.2; 95% CI: 2.0-5.4), access of lactating or dry cows to surface water (e.g., lake, pond, river, or stream) (OR=2.3; 95% CI: 1.3-3.9), disposal of manure in liquid form (slurry or irrigation, as opposed to disposal of manure by broadcast/solid spreader only) on owned or rented land (OR=1.8; 95% CI: 1.3-3.9), and cows eating or grazing of roughage from fields where manure was applied in solid or liquid form and not plowed under during the same growing season (OR=1.8; 95% CI: 1.0-3.0). A seasonal association was also present as cows were more likely to be Salmonella-positive in summer, spring, and fall compared to winter. Herd size was not associated with Salmonella shedding in the final multi-variable model. The herd-level risk factors identified in this study could potentially be implemented in Salmonella control programs on dairy farms.

Animal Feed↗
PubMed1991

Anti-Salmonella lipopolysaccharide monoclonal antibodies: characterization of Salmonella BO-, CO-, DO-, and EO-specific clones and their diagnostic usefulness.

To facilitate the identification and serotyping of Salmonella species, we established a wide variety of murine monoclonal antibodies (MAbs) that were reactive with the lipopolysaccharides (LPSs) of Salmonella serogroups B to E. An effective approach for generating LPS-reactive hybridomas was used; this required immunization of mice with LPS-coated bacteria. To screen for diagnostically useful MAbs, the MAbs were tested by enzyme-linked immunosorbent assay against a set of purified LPSs from smooth and rough Salmonella strains. At least four major groups of antibody specificities were identified: Salmonella (i) BO specific, (ii) CO specific, (iii) DO specific, and (iv) EO specific. For a more detailed epitope analysis, a panel of eight different serogroup-specific MAbs which were shown to bind the O-antigenic polysaccharide chains, yielding characteristic ladder patterns in Western blots (immunoblots) against the LPS of Salmonella serogroups B to E, were selected. The availability of various chemically defined LPS structures and Salmonella O-antigen glycoconjugates permitted the definition of O-antigenic polysaccharide epitopes recognized by each MAb that serologically corresponded to factors O3, O4, O5, O6, O7, O8, O9, and O10 on the basis of the Kauffmann-White scheme for Salmonella classification. The diagnostic accuracy of these immunochemically defined O-specific MAbs for Salmonella serotyping was demonstrated by correct identification of all 167 salmonellae (including 72 serotypes from serogroups B to E) among the 294 bacterial strains in a slide agglutination test. No false-positive reactions were detected.

Animals↗
PubMed2002

PCR amplification of the Salmonella typhimurium fimY gene sequence to detect the Salmonella species.

This study evaluated the suitability of fimY gene amplification by PCR as an effective means of detecting Salmonella species. Although fimY gene of Salmonella typhimurium is involved in regulating type 1 fimbrial expression, the amino acid sequence of FimY shares very little homology with other known prokaryotic proteins in the GenBank database. Therefore, fimY is a promising target gene to detect the presence of Salmonella species. Herein, two primers internal to the fimY gene of S. typhimurium are used to investigate the distribution of the fimY homologous sequence among 45 Salmonella serovars and 20 non-Salmonella species by using PCR. Experimental results indicated that only Salmonella species possessed the fimY homologous sequence, subsequently generating the specific 526-bp DNA fragments. The sensitivity of the fmY-specific primer set was demonstrated on a Salmonella-free swab sample from a pork carcass surface, which was then artificially contaminated with different concentrations of S. typhimurium. A combining of pre-enrichment step in buffered peptone water and PCR amplification of fimY allowed the detection of S. typhimurium at the concentration of 3.4 x 10(0) CFU/ml from the swab sample. With an additional enrichment step in Rappaport-Vassiliadis (RV) broth, this procedure can also detect pork carcass surface naturally contaminated with Salmonella species in a slaughterhouse. Results in this study demonstrate that fimY is unique to Salmonella species and is an appropriate PCR target for detecting these microorganisms.

Bacterial Proteins↗
PubMed2001

Salmonella host cell invasion emerged by acquisition of a mosaic of separate genetic elements, including Salmonella pathogenicity island 1 (SPI1), SPI5, and sopE2.

Salmonella spp. possess a conserved type III secretion system encoded within the pathogenicity island 1 (SPI1; centisome 63), which mediates translocation of effector proteins into the host cell cytosol to trigger responses such as bacterial internalization. Several translocated effector proteins are encoded in other regions of the Salmonella chromosome. It remains unclear how this complex chromosomal arrangement of genes for the type III apparatus and the effector proteins emerged and how the different effector proteins cooperate to mediate virulence. By Southern blotting, PCR, and phylogenetic analyses of highly diverse Salmonella spp., we show here that effector protein genes located in the core of SPI1 are present in all Salmonella lineages. Surprisingly, the same holds true for several effector protein genes located in distant regions of the Salmonella chromosome, namely, sopB (SPI5, centisome 20), sopD (centisome 64), and sopE2 (centisomes 40 to 42). Our data demonstrate that sopB, sopD, and sopE2, along with SPI1, were already present in the last common ancestor of all contemporary Salmonella spp. Analysis of Salmonella mutants revealed that host cell invasion is mediated by SopB, SopE2, and, in the case of Salmonella enterica serovar Typhimurium SL1344, by SopE: a sopB sopE sopE2-deficient triple mutant was incapable of inducing membrane ruffling and was >100-fold attenuated in host cell invasion. We conclude that host cell invasion emerged early during evolution by acquisition of a mosaic of genetic elements (SPI1 itself, SPI5 [sopB], and sopE2) and that the last common ancestor of all contemporary Salmonella spp. was probably already invasive.

Animals↗
PubMed1982

Incidence of Salmonella in fresh dressed turkeys raised under Salmonella-controlled and uncontrolled environments.

The incidence of salmonella in turkeys from experimental salmonella-controlled and uncontrolled, or normal, flocks processed at three turkey slaughter plants were compared. The results indicate that processing salmonella-controlled turkeys in a plant that routinely kills normal birds may result in the contamination of the salmonella-controlled birds, probably due to salmonella in the plant environment. The salmonella-controlled turkeys studied tended to have a lower incidence of salmonella than normal birds. These observation indicate that salmonella control practices in turkey raising can result in a salmonella reduction in market birds even under existing commercial slaughter, evisceration, and cooling procedures.

Abattoirs↗
PubMed2002

Surface plasmon resonance (BIACORE) detection of serum antibodies against Salmonella enteritidis and Salmonella typhimurium.

We have used a surface plasmon resonance biosensor (BIACORE 3000) to detect serum antibodies in chickens having current or recent infections. Three well-defined Salmonella flagellar recombinant DNA antigens reflecting Salmonella enteritidis (H:g,m flagellin) and Salmonella typhimurium (H:i and H:1,2 flagellins) expressed in Escherichia coli were each immobilized in a single flow cell of a biosensor chip. Glutathione-S-transferase was immobilized on the surface of another flow cell to monitor non-specific binding. Sera collected from chickens with no history of Salmonella infection, and from chickens infected with Salmonella serotypes infantis, pullorum, gallinarum were used to test the performance of the system. The sensitivity exhibited to a range up to 900 arbitrary response units (RU) for the most positive S. typhimurium serum at a dilution of 1/40. Sera from Salmonella infantis, Salmonella pullorum and Salmonella gallinarum infected birds gave responses less than the cut-off point, which was determined as the averaged response of sera from specific pathogen-free chickens plus three times the standard deviation. A positive response was obtained when these sera and whole blood were fortified with S. enteritidis and S. typhimurium positive serum. The sensitivity, specificity, precision and reproducibility obtained suggested that this approach could be used for detecting past or present infection with a range of pathogens in animals.

Animals↗
PubMed1991

The prevalence of Salmonella enteritidis and other Salmonella spp. among Canadian registered commercial layer flocks.

A survey was conducted to estimate the prevalence of Salmonella enteritidis and other salmonellas among Canadian commercial egg producing flocks. Environmental (faecal and eggbelt) samples from 152 of 295 (52.9%) randomly selected flocks were contaminated with salmonellas. Thirty-five different salmonella serovars were isolated. Eggbelt samples were more often contaminated with salmonellas than faecal samples (25.7 v. 10.1%). The most prevalent serovars were S. heidelberg, S. infantis, S. hadar, and S. schwarzengrund; they were isolated from samples of 59/295 (20%), 18/295 (6.1%), 17/295 (5.8%), and 15/295 (5.1%) flocks, respectively. Feed samples of 21/295 (7.2%) flocks were contaminated with salmonellas. Salmonella enteritidis was isolated from the environmental samples of 8/295 (2.7%) flocks. Salmonella enteritidis phage type (PT) 8 was isolated from 5 flocks, PT 13a from 2 flocks, and PT 13 from 1 flock.

Animal Feed↗
PubMed1991

The prevalence of Salmonella enteritidis and other Salmonella sp. among Canadian registered commercial chicken broiler flocks.

A nation-wide survey was conducted to estimate the prevalence of Salmonella enteritidis and other salmonellas among Canadian commercial broiler flocks. Environmental (litter and/or water) samples from 226 of 294 (76.9%) randomly selected flocks were contaminated with salmonellas. Litter samples were more often contaminated with salmonellas than water samples (47.4 v. 12.3%). Fifty different salmonella serovars were isolated. The most prevalent serovars were S. hadar, S. infantis, and S. schwarzengrund; they were isolated from samples of 98/294 (33.3%), 26/294 (8.8%), and 21/294 (7.1%) flocks, respectively. Feed samples of 39/290 (13.4%) flocks were contaminated with salmonellas. Salmonella enteritidis was isolated from the environmental samples of 9/294 (3.1%) flocks. Salmonella enteritidis phage type (PT) 8 was isolated from seven flocks, and PT 13a from two flocks.

Animal Feed↗
PubMed1984

[Protection against experimental Salmonella typhimurium infection in mice. Immunostimulating activity of heterologous Salmonella S-forms, R-mutants, lipopolysaccharides and muramyl dipeptide in vaccines combined with S. typhimurium].

In vaccines consisting of acetone-killed Salmonella, 90% of the bacteria were replaced by: heterologous Salmonella S-forms, R-mutants of Salmonella or Escherichia coli, lipopolysaccharide from S. typhimurium (S-form) or from R-mutants of Salmonella or E. coli and by muramyl dipeptide. Active immunizations of NMRI mice with these vaccines were undertaken. Mice received two intraperitoneal injections of the vaccines at intervals of 14 days, and were challenged with various doses of S. typhimurium C5 10 days later. The protective capacity of the mixed vaccines was compared with that of monovaccines (S. typhimurium) and with the effectiveness of vaccines consisting of the supplementing component (relatively weak immunizing ability) alone. The LD50 served as criterion for protective capacity. The results showed that S. typhimurium S-form could be replaced by Salmonella R-mutants belonging to different chemotypes without a recognizable decrease in protective immunizing capacity of the vaccines. Effective vaccines were also attained when heterologous Salmonella S-forms, which exhibit no O-antigenic determinants in common with S. typhimurium, were used as supplements. Mixtures with E. coli R-mutants proved to be less effective. In addition, the diminished dose of S. typhimurium could be so effectively supplemented with lipopolysaccharide from S. minnesota R 595 that complete protection was achieved. In contrast, comparable doses of R lipopolysaccharides from E. coli were somewhat less effective. Vaccines of LPS-extracted bacteria exhibited a reduced protective capacity and were ineffective when used as supplements in mixed vaccines. Analogous results were obtained when R-mutants served as basic vaccines in place of the S. typhimurium S-form indicating that an immunogenic component is enhanced in these organisms too and that their immunogenic capacity is not brought about barely by general stimulation of the immune system. However, the full effectiveness of the R-monovaccines was often not attained with supplements. Immunization with mixed vaccines of S. typhimurium S-form and heterologous Salmonella S-forms or Salmonella R-mutants led to equally high agglutinin and haemagglutinin titers as those obtained with monovaccines of S. typhimurium S-form.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1990

A comparison of different enrichment media for the isolation of Salmonella dublin from livers, kidneys and muscles of Salmonella-positive veal calves.

Amongst a herd of 250, approximately 22 weeks old, Dutch Friesian veal calves, 84 were condemned on meat inspection because of typical pathology of salmonellosis, confirmed by isolation of Salmonella dublin from spleens. From the condemned animals 15 carcasses were randomly selected for further investigation. Their livers, kidneys and samples of their longissimus dorsi muscles were examined for Salmonella using Rappaport-Vassiliadis' and Muller-Kauffmann's enrichment media. In addition, livers were macroscopically scanned for necrotic foci. Signs of (multiple) miliary liver necrosis were not consistently related to isolation of Salmonella from the three tissues examined. Although all spleens had been found positive for Salmonella, from only 53% of the livers, 33% of the kidneys and 27% of the muscles could salmonellae be isolated by one or both enrichment procedures. The Rappaport-Vassiliadis enrichment medium was found to be slightly superior for the isolation of salmonellae. All Salmonella-isolates were serotyped as Salmonella dublin. Their antibiograms showed the expected resistance to chloramphenicol and tetracyclines but, surprisingly, sensitivity to ampicillin, kanamycin, neomycin and streptomycin.

Animals↗
PubMed2004

Variation in the faecal shedding of Salmonella and E. coli O157:H7 in lactating dairy cattle and examination of Salmonella genotypes using pulsed-field gel electrophoresis.

AIMS: To examine the variability in faecal shedding of Salmonella and Escherichia coli O157:H7 in healthy lactating dairy cattle and to evaluate the genetic relatedness of Salmonella isolates. METHODS: Faecal samples were obtained from lactating Holstein dairy cattle on four commercial farms in the southwestern US. All farms were within an 8-km radius and were sampled in August 2001, January 2002 and August 2002 (60 cows per farm per sampling; n = 720 total samples). Samples were cultured for E. coli O157:H7 and Salmonella and a portion of the recovered Salmonella isolates were examined for genetic relatedness using pulsed-field gel electrophoresis (PFGE). RESULTS: Faecal shedding of E. coli O157:H7 and Salmonella varied considerably between farms and at the different sampling times. Large fluctuations in the percentage of positive animals were observed from summer to summer for both of these pathogens. Similarly, Salmonella serotype and serotype prevalence varied from farm to farm and within farm from one sampling time to another. Multiple Salmonella genotypes were detected for a number of serotypes and identical genotypes were found on different farms with one genotype of Salmonella Senftenberg identified on three of the four farms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated the wide variability in pathogen shedding within and among dairy farms all located in a small geographical region and highlights the complexity of pathogen control at the farm level.

Animals↗
PubMed2006

Intracellular Salmonella enterica redirect exocytic transport processes in a Salmonella pathogenicity island 2-dependent manner.

During intracellular life, Salmonella enterica proliferate within a specialized membrane compartment, the Salmonella-containing vacuole (SCV), and interfere with the microtubule cytoskeleton and cellular transport. To characterize the interaction of intracellular Salmonella with host cell transport processes, we utilized various model systems to follow microtubule-dependent transport. The vesicular stomatitis virus glycoprotein (VSVG) is a commonly used marker to follow protein transport from the Golgi to the plasma membrane. Using a VSVG-GFP fusion protein, we observed that virulent intracellular Salmonella alter exocytotic transport and recruit exocytotic transport vesicles to the SCV. This virulence function was dependent on the function of the type III secretion system encoded by Salmonella Pathogenicity Island 2 (SPI2) and more specifically on a subset of SPI2 effector proteins. Furthermore, the Golgi to plasma membrane traffic of the shingolipid C(5)-ceramide was redirected to the SCV by virulent Salmonella. We propose that Salmonella modulates the biogenesis of the SCV by deviating this compartment from the default endocytic pathway to an organelle that interacts with the exocytic pathway. This observation might reveal a novel element of the intracellular survival and replication strategy of Salmonella.

Animals↗
PubMed1992

[Clinical and epidemiological aspects of enteritis due to Salmonella hadar. II. Environmental contamination by Salmonella hadar in Shizuoka Prefecture--studies on the feasibility of reducing S. hadar infection].

A systematic examination was performed for environmental food contamination by Salmonella in poultry farms, broiler chickens, broiler processing plants and meat on the market. Salmonella was isolated from 219 of 1197 samples and the serotypes showed a wide distribution. (Table 1-1). S. hadar accounted for 37.1% (96) of all isolations (259). The contamination rate of broiler chickens on arrival at broiler processing plants is relatively low. However, in the broiler processing plants, containers, processing machinery, cooling water and slaughters were highly contaminated by Salmonella, S. hadar being the most prominent serotype in the plants. 64% of chicken meat on the market was contaminated by Salmonella, S. hadar being the second most prominent serotype. 11% of the pork and none of the beef or horseflesh was contaminated by Salmonella. These results indicate that poultry is the main source of S. hadar infection in humans. However, no S. hadar was isolated from cultures of 119 samples of feed for chickens from each delivery (Table 1-1). Thus, as the main source of infection by S. hadar of broiler chickens, an association with the feed seems to be ruled out. S. hadar was isolated at three of 18 poultry farms within Shizuoka Prefecture. Follow-up studies were performed at the three poultry farms which revealed that in two of them, Salmonella was completely eradicated on completion of disinfection. In the other one farm, which is still being disinfected, various strains of Salmonella including S. hadar still survived. We conclude that the main cause of the problem is the magnification of contamination of Salmonella-free material during the process at the broiler processing plants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1964

ISOLATION OF SALMONELLAE FROM FOOD SAMPLES. VI. COMPARISON OF METHODS FOR THE ISOLATION OF SALMONELLA FROM EGG PRODUCTS.

THE RECOVERY OF SALMONELLAE FROM EGG PRODUCTS WAS STUDIED, BY USE OF THREE DIFFERENT ENRICHMENT PROCEDURES: (i) selenite broth, (ii) selenite broth containing 10% sterile feces, and (iii) the lactose pre-enrichment procedure. Brilliant Green Agar was used throughout as the recovery medium. Although the lactose pre-enrichment methodology promoted Salmonella recovery from samples containing small numbers of dormant organisms, the efficiency of this enrichment method is adversely affected by unfavorable coliform-Salmonella ratios. Under such conditions, early subculture of lactose broth into selenite broth is indicated. Selenite broth containing 10% sterile feces was more efficient than the lactose pre-enrichment methodology in promoting the growth of "dormant" salmonellae. Albumen adversely affected recovery of salmonellae from selenite broth, whereas whole egg and egg yolk enhanced Salmonella recovery from this medium. The selenite-feces medium presents a solution to the major problems encountered in the detection of salmonellae in egg products and offers an approach to a single medium in which food-borne salmonellae will manifest themselves with a minimum of laboratory manipulation.

Agar↗
PubMed1996

Effect of vaccination of hens with an avirulent strain of Salmonella typhimurium on immunity of progeny challenged with wild-Type Salmonella strains.

The avirulent Salmonella typhimurium chi3985 was used to vaccinate white leghorn chickens at 16 and 18 weeks of age, and the effect of maternal antibody on Salmonella colonization of progeny of vaccinated hens was assessed with S. typhimurium F98 or chi3985. Progeny of hens that had been vaccinated at 1 and 3 or 2 and 4 weeks of age with chi3985 were used to determine the effect of maternal immunity on vaccine efficacy. Vaccination of hens induced long-lasting Salmonella-specific antibodies which were transferred into eggs and were detected as immunoglobulin G (IgG) in the egg yolk. Maternal antibody was detected in the progeny of vaccinated birds as IgG and IgA in serum and intestinal fluid, respectively. The titer of maternally transmitted IgG or IgA was highest in the first week of life of the progeny and declined with age. Maternal antibodies prevented colonization of the chicks by S. typhimurium chi3985 and reduced colonization by S. typhimurium F98. Overall, chicks from vaccinated hens had significantly higher antibody responses than did the progeny of nonvaccinated hens after oral infection with Salmonella strains. Maternal antibody reduced the efficacy of vaccination of progeny with chi3985 at 1 and 3 weeks of age. But vaccination at 2 and 4 weeks of age induced excellent protection against challenge with S. typhimurium F98 or S. enteritidis 27A PT 8 in birds from vaccinated hens and in specific-pathogen-free chickens. Vaccination of chickens at 2 and 4 weeks of age has been shown to protect the birds against challenge with homologous and heterologous Salmonella serotypes. A combination of vaccination of adult animals and use of the progeny of vaccinated birds will enhance effective control of Salmonella infections in the poultry industry. This will complement the present control of Salmonella-associated food poisoning caused by Salmonella enteritidis in eggs because the avirulent S. typhimurium vaccine strain chi3985 induced excellent protection against S. enteritidis in chickens.

Animals↗