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PubMed2005

Salmonella in Black-headed gulls ( Larus ridibundus); prevalence, genotypes and influence on Salmonella epidemiology.

During a period of 3 years, 1998-2000, 1047 faecal swabs from Black-headed gulls were sampled at one location in Southern Sweden. Salmonella spp. was found in 28 individuals (2.7%) and the dominating serotype found was S. Typhimurium (83%). Twenty-five per cent of the Salmonella-infected gulls were later recaptured and re-sampled. We found that Salmonella infection in Black-headed gulls was of short duration, and that infection in this bird species was predominantly expressed as carriage without disease manifestations. All S. Typhimurium isolates were subjected to antibiotic resistance profiling and molecular characterization by pulsed-field gel electrophoresis and IS200 polymerase chain reaction. The S. Typhimurium gull isolates were compared to human and domestic animal isolates of the same serotype and phage type. We found genetic relatedness of S. Typhimurium DT195 isolates from gulls, domestic animals and humans, indicating that Black-headed gulls might play a role in the spread of S. Typhimurium in Sweden.

Animals↗
PubMed2000

Salmonella in sub-Antarctica: low heterogeneity in Salmonella serotypes in South Georgian seals and birds.

The number of human visitors to Antarctica is increasing rapidly, and with it a risk of introducing infectious organisms to native animals. To study the occurrence of salmonella serotypes in sub-Antarctic wildlife, faecal samples were collected from gentoo penguins, macaroni penguins, gray-headed albatrosses, black-browed albatrosses and Antarctic fur seals on Bird Island in the South Georgian archipelago during the austral summer of 1996 and 1998. In 1996, S. havana, S. typhimurium and S. enteritidis were isolated from 7% of gentoo penguins and 4% of fur seals. In 1998, however, 22% of fur seals were found to be infected with S. havana, S. enteritidis and S. newport. All isolates, except one, showed identical pulsed-field gel electrophoresis-patterns within each serotype, irrespective of sampling year and animal reservoir. No significant antibiotic resistance was found. The very low heterogeneity in the salmonella isolates found could either indicate a high genetic adaptation of the bacteria to the environment or a recent introduction of salmonella into the area.

Adaptation, Physiological↗
PubMed1965

Studies on the structure of lipopolysaccharides of Salmonella minnesota and Salmonella typhimurium R strains.

1. The composition of the lipopolysaccharides and the corresponding lipid-free polysaccharides from four R-mutants of Salmonella has been studied. All the lipopolysaccharides, from RI and RII serotypes contained d-glucose, d-galactose, heptose, N-acetylglucosamine and 3-deoxy-2-oxo-octonate. The polysaccharide obtained from the RII lipopolysaccharides also contained all these sugars. The polysaccharides from RI lipopolysaccharides lacked N-acetylglucosamine. 2. From partial hydrolysates of the lipopolysaccharides, a number of oligosaccharides have been isolated and partially characterized. Oligosaccharides containing N-acetylglucosamine or glucosamine were obtained only from RII lipopolysaccharides. Several oligosaccharides composed of glucose and galactose were common to RI and RII preparations. 3. A structural unit, based on the oligosaccharides found, is proposed for the RII lipopolysaccharide. It contains the sequence: alpha-N-acetylglucosaminyl- alpha-glucosyl-alpha-galactosyl-glucosyl.... A second alpha-galactosyl residue is bound to position 6 of the last glucosyl group. The complete unit is believed to to be attached to a polyheptose phosphate backbone in the RII antigen. 4. The RI lipopolysaccharide of Salmonella minnesota contains an analogous structure lacking the terminal N-acetylglucosamine residue. 5. A basal structure common to the lipopolysaccharides of several Salmonella species is proposed.

Chemical Phenomena↗
PubMed2000

Proposal of Salmonella paratyphi sp. nov., nom. rev. and request for an opinion to conserve the specific epithet paratyphi in the binary combination Salmonella paratyphi as nomen epitheton conservandum.

We propose Salmonella paratyphi sp. nov., nom. rev., by raising Salmonella choleraesuis subsp. choleraesuis serovar Paratyphi A to species status and request an Opinion to include the specific epithet paratyphi in the binary combination of Salmonella paratyphi in the list of epitheta specifica conservanda.

Salmonella↗
PubMed1985

Evidence for related virulence sequences in plasmids of Salmonella dublin and Salmonella typhimurium.

Transposon-insertion mutants were prepared from virulent field isolates of Salmonella dublin and Salmonella typhimurium. Detailed restriction-enzyme mapping of the single sites of TnA insertion in two mutants (M51 and M173) of S. dublin that showed diminished virulence in a mouse assay indicated that these sites were about 5 kbp apart on the approximately 70 kbp plasmid harboured by the isolate. A Tn10-insertion mutant (M242) of S. typhimurium that showed diminished virulence was also identified. A single copy of Tn10 was inserted into the approximately 90 kbp plasmid harboured by this isolate. Hybridization studies indicated that homology existed between the region encompassing the sites of TnA insertion in M51 and M173 and that encompassing the site of Tn10 insertion in M242. Restriction mapping indicated that the two regions were very similar and could even be identical and, if so, the Tn10 insertion in M242 could be mapped to a point 1.5 kbp from the TnA insertion in M51 and 6.5 kbp from that in M173. It appeared that the maximal extent of the putative similarity/identity was between 13 and 23 kbp. It is proposed that this stretch of high homology could represent a virulence sequence that has been conserved during the evolutionary divergence of the two Salmonella serotypes.

Animals↗
PubMed1988

Cell-surface properties of enterotoxigenic and cytotoxic Salmonella enteritidis and Salmonella typhimurium: studies on hemagglutination, cell-surface hydrophobicity, attachment to human intestinal cells and fibronectin-binding.

Thirteen Salmonella enteritidis and S. typhimurium strains with smooth or rough colony morphology were investigated for their surface properties based on hemagglutination (HA), hydrophobicity, and fibronectin-binding profiles. The strains showed 5 different patterns of HA which was mannose-sensitive. The rough strains possessed comparatively greater number of fimbriae than the corresponding smooth strains and also attached to human intestinal cells in greater numbers. The Salmonella strains used in this study interacted with fibronectin and its 29-kDa N-terminal fragment to varied extents. These properties may be helpful in broadening the prospective interaction capabilities of Salmonella organisms with the host surfaces.

Bacterial Adhesion↗
PubMed1994

Survival of Salmonella senftenberg and Salmonella typhimurium in glassy and rubbery states of gelatin.

Salmonella senftenberg and Salmonella typhimurium survived the production of gelatin sheets containing nutrient broth although there was some evidence of cell damage. Both strains survived but did not grow in glassy states with an a(w) of 0.45-0.28 and rubbery states with an a(w) of 0.93-0.96 for at least 28 d. Survival was less in intermediate states with an a(w) between 0.55 and 0.74. The results suggest that salmonellas should be excluded from glassy state products in order to prevent salmonellosis.

Colony Count, Microbial↗
PubMed1997

Salmonella enterica var Typhimurium and Salmonella enterica var Enteritidis express type 1 fimbriae in the rat in vivo.

In a series of experiments rats were dosed with purified type 1 fimbriae from Salmonella enterica var Enteritidis or with fimbriated cultures of either S. enterica var Typhimurium or S. enterica var Enteritidis. Paraffin-wax embedded histological sections of jejunal and ileal tissue were taken and stained by the streptavidin biotin complex (sABC) staining technique for the detection of salmonella and type 1 fimbriae. On oral infection with Enteritidis and Typhimurium both bacteria were shown to be closely associated with the rat ileal epithelium and expressed type 1 fimbriae, thus clearly demonstrating that type 1 fimbriae are expressed by salmonellae in vivo. Moreover, association with the ileum was also shown to occur when purified type 1 fimbriae were orally administered to rats. Our results suggest that type 1 fimbriae alone or in combination with other fimbriae may play an important role in the early stages of infection with these pathogenic bacteria.

Animals↗
PubMed1998

A highly sensitive and fast non-radioactive method for the detection of polymerase chain reaction products from Salmonella serovars, such as Salmonella typhi, in blood specimens.

A polymerase chain reaction based test was developed for the detection of Salmonella spp. in blood specimens. After amplification of a 389 bp-polymerase chain reaction product from the invA gene, a microtiter plate hybridization assay was performed. The protocol described allowed the detection of six to seven copies of the Salmonella typhi genome, as determined by serial dilutions of DNA from S. typhi. Eighteen blood specimens from artificially infected rats and 22 blood specimens from patients were analyzed to validate the method. Considering that the most frequent Salmonella serovar isolated from blood in case of bacteremia is S. typhi, the polymerase chain reaction-microtiter plate hybridization technique could be used as a novel, rapid diagnostic method for typhoid fever, particularly when standard culture assays are negative.

Animals↗
PubMed1999

Survival of Salmonella enteritidis and Salmonella typhimurium in chicken manure at different levels of water activity.

Survival of Salmonella enteritidis and Salmonella typhimurium in chicken manure at different levels of water activity (aw) was determined. The aw was adjusted by means of saturated salts with defined equilibrium relative humidity and the manure samples were stored aerobically at 20 degrees C. At aw levels higher than 0.93, a moderate increase in colony-forming units over 8-9 h was found for both strains; at aw levels of 0.89-0.75, there was a thousand-fold reduction. Extended storage resulted in a million-fold reduction of Salmonella enteritidis in 8 days at an aw of 0.89. At higher and lower levels of aw, the reduction was less extensive.

Animals↗
PubMed1990

[O5-antigenic classification of Salmonella typhimurium isolated from outbreaks of Salmonella enteritis].

S. typhimurium (STM) were isolated from outbreaks of Salmonella enteritis and were studied for their reactivity to monoclonal antibody TMY1 specific for Salmonella O5-antigen with the following results; By using the bacterial agglutination test with TMY1, STM were classified into O5-antigenic molecule positive and negative (copenhagen type) strains, suggesting the usefulness of TMY1 as an exquisite epidemiologic tool for Salmonella enteritis.

Antigens, Bacterial↗
PubMed2006

SseL is a salmonella-specific translocated effector integrated into the SsrB-controlled salmonella pathogenicity island 2 type III secretion system.

Bacterial pathogens use horizontal gene transfer to acquire virulence factors that influence host colonization, alter virulence traits, and ultimately shape the outcome of disease following infection. One hallmark of the host-pathogen interaction is the prokaryotic type III secretion system that translocates virulence factors into host cells during infection. Salmonella enterica possesses two type III secretion systems that are utilized during host colonization and intracellular replication. Salmonella pathogenicity island 2 (SPI2) is a genomic island containing approximately 30 contiguous genes required to assemble a functional secretion system including the two-component regulatory system called SsrA-SsrB that positively regulates transcription of the secretion apparatus. We used transcriptional profiling with DNA microarrays to search for genes that coregulate with the SPI2 type III secretion machinery in an SsrB-dependent manner. Here we report the identification of a Salmonella-specific translocated effector called SseL that is required for full virulence during murine typhoid-like disease. Analysis of infected macrophages using fluorescence-activated cell sorting revealed that sseL is induced inside cells and requires SsrB for expression. SseL is retained predominantly in the cytoplasm of infected cells following translocation by the type III system encoded in SPI2. Animal infection experiments with sseL mutant bacteria indicate that integration of SseL into the SsrB response regulatory system contributes to systemic virulence of this pathogen.

Animals↗
PubMed1978

Cellular response in Salmonella typhimurium-infected mice: evaluation of Salmonella receptors of B lymphocytes.

The cellular response in the course of experimental infection with Salmonella typhimurium was studied in mice. T cells were detected by the presence of theta-antigen, B cells by the binding of fluorescent immunoglobulins, and cells with receptors by labeled Salmonella binding. Lymphocytes were from spleen and lymph nodes. Results have been divided into three groups: group A, including mice with slight symptomatology; group B, including those with serious infection symptomatology; and group C, including mice that died in the course of the experiment. In spleen and lymph nodes of group A mice, an increase in the percentage of T and B lymphocytes was observed. This increase reached a peak 10 days after experimental infection. In lymph nodes, the B-cell percentage was equal to the percentage of T cells, whereas in spleen lymphocytes the B-cell percentage was higher. In spleens of group B mice we observed the same response as in mice of group A, whereas in lymph nodes there was a low response of T and B lymphocytes. In group C mice, there was no significant response of T and B lymphocytes in either spleen or lymph nodes. In B lymphocytes prepared from spleens of surviving mice, a small number of Salmonella receptors was detected: 200 bacterial cells per 10(9) lymphocytes.

Animals↗
PubMed1978

Protective effects of a supernatant factor from Salmonella typhimurium on Salmonella typhimurium infection of inbred mice.

A supernatant factor prepared from 48-h cultures of Salmonella typhimurium has been used to immunize mice against subsequent challenge with normally lethal doses of S. typhimurium. The mouse strains used, C57BL and BALB/c, were sensitive to S. typhimurium with 50% lethal doses of less than 50 organisms. Two doses of supernatant factor, given intraperitoneally 20 days apart, protected mice against a subcutaneous challenge dose 10 days later of 100 50% lethal doses of S. typhimurium, resulting in 50 to 80% survival. The viable counts were reduced initially in organs of immunized mice compared with controls, and the multiplication of bacteria was delayed, although the final levels found in the organs would normally have been lethal. Protection obtained was specific for S. typhimurium in that no increased survival was shown after Salmonella enteritidis challenge of immunized mice. Although lipopolysaccharide was demonstrated in the supernatant factor, lipopolysaccharide alone did not protect challenged mice. Supernatant factor produced delayed-type hypersensitivity reactions in mice sensitized with nonlethal doses of Salmonella. The nature of the active factor, found to be partially protein, has yet to be elucidated.

Animals↗
PubMed1995

Host restriction phenotypes of Salmonella typhi and Salmonella gallinarum.

Salmonella typhi and Salmonella gallinarum phenotypes correlated with mouse host restriction have been identified by using in vitro and in vivo systems. S. typhi is capable of entering the murine intestinal epithelium via M cells, as is Salmonella typhimurium, which causes systemic infection in the mouse. But, unlike S. typhimurium, S. typhi does not destroy the epithelium and is cleared from the Peyer's patches soon after M-cell entry. S. gallinarum appears to be incapable of entering the murine Peyer's patch epithelium. Our in vitro evidence suggests that S. gallinarum is taken up in murine phagocytic cells by a mechanism different from that of S. typhimurium. S. typhimurium is taken up at a higher frequency and is maintained at higher viable counts throughout a 24-h time course in a murine macrophage-like cell line than are S. gallinarum and S. typhi.

Animals↗
PubMed1999

Genomic subtractive hybridization and selective capture of transcribed sequences identify a novel Salmonella typhimurium fimbrial operon and putative transcriptional regulator that are absent from the Salmonella typhi genome.

Salmonella typhi, the etiologic agent of typhoid fever, is adapted to the human host and unable to infect nonprimate species. The genetic basis for host specificity in S. typhi is unknown. The avirulence of S. typhi in animal hosts may result from a lack of genes present in the broad-host-range pathogen Salmonella typhimurium. Genomic subtractive hybridization was successfully employed to isolate S. typhimurium genomic sequences which are absent from the S. typhi genome. These genomic subtracted sequences mapped to 17 regions distributed throughout the S. typhimurium chromosome. A positive cDNA selection method was then used to identify subtracted sequences which were transcribed by S. typhimurium following macrophage phagocytosis. A novel putative transcriptional regulator of the LysR family was identified as transcribed by intramacrophage S. typhimurium. This putative transcriptional regulator was absent from the genomes of the human-adapted serovars S. typhi and Salmonella paratyphi A. Mutations within this gene did not alter the level of S. typhimurium survival within macrophages or virulence within mice. A subtracted genomic fragment derived from the ferrichrome operon also hybridized to the intramacrophage cDNA. Nucleotide sequence analysis of S. typhimurium and S. typhi chromosomal sequences flanking the ferrichrome operon identified a novel S. typhimurium fimbrial operon with a high level of similarity to sequences encoding Proteus mirabilis mannose-resistant fimbriae. The novel fimbrial operon was absent from the S. typhi genome. The absence of specific genes may have allowed S. typhi to evolve as a highly invasive, systemic human pathogen.

Amino Acid Sequence↗
PubMed2000

Igh-6(-/-) (B-cell-deficient) mice fail to mount solid acquired resistance to oral challenge with virulent Salmonella enterica serovar typhimurium and show impaired Th1 T-cell responses to Salmonella antigens.

In the present study we evaluated the role of B cells in acquired immunity to Salmonella infection by using gene-targeted B-cell-deficient innately susceptible mice on a C57BL/6 background (Igh-6(-/-)). Igh-6(-/-) mice immunized with a live, attenuated aroA Salmonella enterica serovar Typhimurium vaccine strain showed impaired long-term acquired resistance against the virulent serovar Typhimurium strain C5. Igh-6(-/-) mice were able to control a primary infection and to clear the inoculum from the reticuloendothelial system. However, Igh-6(-/-) mice, unlike Igh-6(+/+) C57BL/6 controls, did not survive an oral challenge with strain C5 at 4 months after vaccination. Transfer of immune serum did not restore resistance in Igh-6(-/-) mice. Total splenocytes and purified CD4(+) T cells obtained from Igh-6(-/-) mice 4 months after vaccination showed reduced ability to release Th1-type cytokines (interleukin 2 and gamma interferon) upon in vitro restimulation with serovar Typhimurium soluble cell extracts compared to cells obtained from Igh-6(+/+) C57BL/6 control mice. Therefore, the impaired resistance to oral challenge with virulent serovar Typhimurium observed in B-cell-deficient mice, which cannot be restored by passive transfer of Salmonella-immune serum, may be in part due to a reduced serovar Typhimurium-specific T-cell response following primary immunization.

Administration, Oral↗
PubMed2001

Salmonella enterica serotype typhimurium elicits cross-immunity against a Salmonella enterica serotype enteritidis strain expressing LP fimbriae from the lac promoter.

The biological significance of fimbrial phase variation in Salmonella serotypes is currently unknown. Exposure to long polar (LP) fimbriae of Salmonella enterica serotype Typhimurium results in selection against lpf phase ON cells of serotype Enteritidis during a subsequent challenge, suggesting that fimbrial phase variation may be a mechanism to evade cross-immunity between Salmonella serotypes. This notion was tested by assessing the effect of an immune response against serotype Typhimurium LP fimbriae on colonization of mice with a serotype Enteritidis mutant in which the lpf promoter region was replaced with the Escherichia coli lac promoter. During a challenge with a serotype Enteritidis mutant carrying the lac promoter in front of the lpf operon, significantly lower numbers were recovered from organs and feces of mice previously immunized with an lpf phase ON culture of serotype Typhimurium than from mice not previously exposed to LP fimbriae. Immunization with the lpf phase ON culture of serotype Typhimurium elicited antibodies that cross-reacted with a purified gluthathione-S-transferase-LpfA fusion protein of serotype Enteritidis. These data suggested that cross-immunity against LP fimbrial proteins cannot be evaded if phase variation on the transcriptional level is prevented by expressing the lpf operon from the lac promoter. These data hence support the idea that phase variation of LP fimbriae is a mechanism to evade cross-immunity between serotypes Enteritidis and Typhimurium.

Animals↗