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PubMed1990

Mice vaccinated with a non-virulent, aromatic-dependent mutant of Salmonella choleraesuis die from challenge with its virulent parent but survive challenge with Salmonella typhimurium.

BALB/c mice given a live vaccine of an aroA mutant of Salmonella choleraesuis by intraperitoneal (i.p.) injection were not protected against i.p. challenge with its virulent parental strain but were protected against i.p. challenge with either of two virulent strains of Salmonella typhimurium (O [1], 4, [5], 12). Vaccination with a live vaccine of S. typhimurium aroA protected against challenge with S. typhimurium but not with S. choleraesuis. Intraperitoneal administration of either aroA strain evoked high levels of serum antibody against the homologous lipopolysacharide (LPS) as determined by an enzyme immunoassay. Sera from vaccinated mice also reacted with heterologous LPS but at dilutions at least seven-fold lower than homologous endpoint titres. The vaccination schedule employed with either live-vaccine strain conferred an equal degree of resistance to challenge with Listeria monocytogenes. After mixed infection of mice with equal numbers of virulent S. typhimurium and S. choleraesuis by the i.p. route, the former was isolated in numbers at least 50,000 times greater than the latter from the liver and spleen between days 1 and 5. When mice were vaccinated i.p. with S. choleraesuis aroA, L. monocytogenes or P. multocida before mixed infection, neither serotype showed more than a slight predominance in the liver and spleen during the same period. Thus, in relative terms, vaccination with S. choleraesuis aroA or inoculation with unrelated bacteria suppressed the growth of virulent S. typhimurium in mice but allowed virulent S. choleraesuis to multiply. These results clearly show that S. choleraesuis 38(1) can multiply to kill immunised BALB/c mice.

Animals↗
PubMed1992

Type 1 pili enhance the invasion of Salmonella braenderup and Salmonella typhimurium to HeLa cells.

The relationship between type 1 pili-associated adhesion and invasion to HeLa cells by Salmonella braenderup and S. typhimurium was studied. When the clinical isolates of these strains were grown in L-broth, they showed both type 1 pili formation and mannose-sensitive adhesion to HeLa cells. On the other hand, the type 1 pili-defective mutants, which were obtained either by repeated subcultures on L-agar plates or by the transposon Tn1-insertion mutagenesis of the S. braenderup and S. typhimurium strains, concomitantly lost mannose-sensitive adhesion to HeLa cells. When the HeLa cells were incubated with Salmonella, the type 1 piliated strains invaded the HeLa cells with much higher infection rate than did the type 1 pili-defective strains. The invasion of type 1 piliated strains to HeLa cells was markedly inhibited in the presence of D-mannose. The infectivity of the strain, which lost type 1 pili but still had mannose-resistant adhesion, was slightly higher than that of the strains defective in both mannose-sensitive and mannose-resistant adhesion. These results suggested that type 1 pili have a role in enhancing the invasion of S. braenderup and S. typhimurium to HeLa cells.

Acute Disease↗
PubMed1993

The XbaI-BlnI-CeuI genomic cleavage map of Salmonella enteritidis shows an inversion relative to Salmonella typhimurium LT2.

We have established the genomic cleavage map of Salmonella enteritidis strain SSU7998 using pulsed-field gel electrophoresis. The chromosome of 4600 kb was analysed by XbaI (16 fragments), I-CeuI (7 fragments) and BlnI (12 fragments); the genome also contains a plasmid of 60 kb. Cleavage sites of I-Ceul, in the large subunit ribosomal RNA gene, are conserved from Salmonella typhimurium and Escherichia coli K-12, and the XbaI and BlnI sites in glt-tRNA are also conserved, but other sites are less conserved. Transposon Tn10, located at 60 different positions in the chromosome of S. typhimurium, was transduced by bacteriophage P22 into S. enteritidis and the insertion mapped using the XbaI and BlnI sites on Tn10. Gene order in S. enteritidis is identical to S. typhimurium LT2 and similar to E. coli K-12 except for an inversion of 815 kb, which covers the terminus region including T1 and T2. Endpoints are in the NDZs, or non-divisible zones, in which inversion endpoints were not detected in experiments in E. coli K-12 and S. typhimurium LT2. This inversion resembles the inversion between S. typhimurium and E. coli, but is longer at both ends.

Chromosome Inversion↗
PubMed1996

Seasonal variations in the isolation of Salmonella typhimurium, Salmonella enteritidis, Bacillus cereus and Clostridium perfringens from environmental samples.

Calf carcasses contaminated with S. typhimurium, B. cereus and Cl. Perfringens were placed in either a decomposition pit or in a deep burial pit. Salmonella was isolated from the soil around the decomposition pit for 27 weeks and for 15 weeks around the burial site. Salmonella re-appeared in soil samples during cold winter weather after an apparent 9-week absence from the decomposition pit and after 68 weeks in the burial site (a total of 88 weeks after the start of the experiment). There was also an annual rise in the isolation rate of B. cereus from the soil during the colder winter months, but Cl. perfringens appeared to be more prevalent in samples taken during spring of the second year of the study. A similar apparent rise in the prevalence of S. enteritidis during a cold winter period occurred in an empty poultry house that had previously held a naturally infected broiler-breeder flock.

Animals↗
PubMed2005

Differentiation of Salmonella Gallinarum biovar Gallinarum from Salmonella Gallinarum biovar Pullorum by PCR-RFLP of the fimH gene.

In our studies on FimH adhesins expressed by different Salmonella serovars, we cloned and sequenced the fimH genes from Salmonella enterica ssp. Enterica ser. Gallinarum biovar Gallinarum and S. enterica ssp. Enterica ser. Gallinarum biovar Pullorum. Comparison of the nucleotide sequences revealed the presence of a single-nucleotide polymorphism (SNP) at position 544 bp from the A of the start codon of the fimH open reading frame (ORF). Further analysis of the restriction enzyme sites in fimH gene showed that the SNP at this position is responsible for a sequence specifically recognized by SacI in S. Gallinarum biovar Gallinarum only, making it possible to differentiate both biovars with the use of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Digestion of PCR amplicons of the fimH gene from S. Gallinarum biovar Gallinarum strains with SacI gave two DNA fragments of 554 and 472 bp and only one fragment of 1026 bp for S. Gallinarum biovar Pullorum. This allows a clear differentiation between these two biovars.

Animals↗
PubMed2006

Salmonella enterica serotype Virchow: epidemiology, resistance patterns and molecular characterisation of an invasive Salmonella serotype in Israel.

This study outlines the unique epidemiology of Salmonella enterica serotype Virchow in Israel. Between 1997 and 2002, the overall incidence of non-typhoid Salmonella enterica (NTS) decreased from 69.3 to 53.3 infections/100,000 population, but the incidence of S. Virchow increased (from 7.2 to 9.1 infections/100,000). Since 2000, S. Virchow has become the second-ranking NTS isolate, accounting for 17% and 27% of all stool and blood NTS isolates, respectively. Infants aged < 1 year had the highest incidence of isolation from stools (92.8/100,000). The incidence of isolation from blood was highest for infants aged <1 year (4.4/100,000). Only 6% of isolates were susceptible to all ten antibiotic agents tested; 34% were resistant to one agent, 54% to one to three agents, and 40% to four to six agents. A high proportion of the tested isolates were resistant to nalidixic acid (89%), streptomycin (56%), tetracycline (43%), trimethoprim-sulphamethoxazole (38%) and chloramphenicol (28%), but none to ciprofloxacin or ceftriaxone. Pulsed-field gel electrophoresis revealed two closely related clusters, each containing a predominant pulsotype. Coupled with its invasive propensity, the increasing incidence of highly resistant S. Virchow in Israel is of real concern. Future research should focus on the sources of S. Virchow in the food chain in order to institute effective control measures.

Adolescent↗
PubMed1989

Susceptibility of Salmonella typhimurium and Salmonella typhi to oxygen metabolites.

The susceptibility of Salmonella typhimurium LT2 and S. typhi 1079 to oxygen metabolites were compared. S. typhimurium LT2 and S. typhi 1079 were killed to an equal extent (about 40%) by the xanthine-xanthine oxidase (200 mU/ml) system. Among the various scavengers of oxygen metabolites, catalase alone inhibited the killing of S. typhimurium LT2 and S. typhi 1079 by the xanthine-xanthine oxidase system, indicating that hydrogen peroxide contributed to the killing of Salmonellae. The respiratory burst of murine macrophages was efficiently triggered by the ingestion of S. typhimurium LT2, S. typhimurium SL1102, and S. typhi 1079 and all to the same extent. However, in the range of the concentration of hydrogen peroxide produced by murine macrophages, neither S. typhimurium LT2 nor S. typhi 1079 were killed. Only S. typhimurium SL1102, a rough mutant of S. typhimurium LT2, was markedly susceptible under these conditions. The findings suggest that both S. typhimurium LT2 and S. typhi 1079 are resistant to oxygen-dependent killing mechanisms.

Animals↗
PubMed2006

Variant Salmonella genomic island 1-L antibiotic resistance gene cluster in Salmonella enterica serovar Newport.

We report a new Salmonella genomic island 1 variant antibiotic resistance gene cluster called SGI1-L in a Salmonella enterica serovar Newport isolate containing a dfrA15 gene cassette conferring resistance to trimethoprim. The isolate carried another class 1 integron containing the aacC5 and aadA7 gene cassettes conferring resistance to gentamicin and streptomycin/spectinomycin, respectively.

Anti-Bacterial Agents↗
PubMed2001

Salmonella excretion after cessation of tosufloxacin therapy in acute nontyphoid salmonella enterocolitis.

Symptomatic nontyphoid salmonella enterocolitis patients were treated with tosufloxacin (TFLX) at oral doses of 150 mg three times a day for 5 to 7 days, but bacterial relapse without symptoms occurred in 85% of the patients within 15 days after the cessation of therapy. Our study indicates that TFLX may not be an ideal drug against symptomatic salmonella enterocolitis from a bacteriological point of view.

Administration, Oral↗
PubMed2002

Antibiotic resistance genes and Salmonella genomic island 1 in Salmonella enterica serovar Typhimurium isolated in Italy.

Fifty-four epidemiologically unrelated multidrug-resistant Salmonella enterica serovar Typhimurium isolates, collected between 1992 and 2000 in Italy, were analyzed for the presence of integrons. Strains were also tested for Salmonella genomic island 1 (SGI1), carrying antibiotic resistance genes in DT104 strains. A complete SGI1 was found in the majority of the DT104 strains. Two DT104 strains, showing resistance to streptomycin-spectinomycin and sulfonamides, carried a partially deleted SGI1 lacking the flo(st), tetR, and tetA genes, conferring chloramphenicol-florfenicol and tetracycline resistance, and the integron harboring the pse-1 gene cassette, conferring ampicillin resistance. The presence of SGI1 was also observed in serovar Typhimurium strains belonging to other phage types, suggesting either the potential mobility of this genomic island or changes in the phage-related phenotype of DT104 strains.

Blotting, Southern↗
PubMed2004

Salmonella genomic island 1 multidrug resistance gene clusters in Salmonella enterica serovar Agona isolated in Belgium in 1992 to 2002.

Salmonella genomic island 1 (SGI1) harbors a multidrug resistance (MDR) gene cluster which is a complex class 1 integron. Variant SGI1 MDR gene clusters conferring different MDR profiles have also been identified in several Salmonella enterica serovars and classified as SGI1-A to -F. A retrospective study was undertaken to characterize MDR regions from serovar Agona strains harboring SGI1 isolated from poultry in Belgium between 1992 and 2002. A total of 171 serovar Agona strains, displaying resistance to at least one antibiotic, were studied for the presence of SGI1. SGI1 was detected in 94 serovar Agona strains. The most prevalent variant was SGI1-A (85%), which harbors within the SGI1 complex class 1 integron a common region (CR1) containing orf513, a putative transposase gene, adjacent to the dfrA10 trimethoprim resistance gene. A new variant SGI1 named SGI1-G was identified in two strains. It consisted of the pse-1 gene cassette, as in SGI1-B, but with additional insertion of the orf513/dfrA10 region structure. Seven strains displaying the typical SGI1 MDR profile (Ap Cm Ff Sm Sp Su Tc) showed genetic variation at the 3' end of SGI1. These strains harbored the insertion of the CR1 containing orf513 as in SGI1-A, -D, and -G. However, downstream the right end of CR1, they presented different 7.4- to 8.5-kb deletions of the SGI1 3' end that extended to the chromosomal genes yieE and yieF. These results suggest a possible role of CR1 in deletion formation, as has been reported for some insertion sequences. Pulsed-field gel electrophoresis analysis showed that all the serovar Agona SGI1-carrying strains belonged to a single clone. Thus, SGI1 is largely encountered in serovar Agona strains isolated from poultry in Belgium, the most prevalent variant being SGI1-A. SGI1 MDR region undergoes recombinational events resulting in a diversity of MDR gene clusters.

Anti-Bacterial Agents↗
PubMed1969

Effect of pH and chelating agents on the heat resistance and viability of Salmonella typhimurium Tm-1 and Salmonella senftenberg 775W in egg white.

Supplementation of egg white at pH 8.9 with 5 mg of disodium ethylenediaminetetraacetic acid (EDTA) per ml resulted in a kill of Salmonella typhimurium Tm-1 of greater than 10(6) per ml after 28 days at 2 C. While at 28 C, supplementation with 7 mg of EDTA per ml resulted in approximately a 10(6) kill in less than 24 hr. Kena supplementation at 40 mg/ml of egg white resulted in a kill of S. typhimurium Tm-1 of greater than 10(6) after approximately 60 hr of storage at 28 C. This is in contrast to no reduction in viable count in unsupplemented egg white stored at 2 C and a 100-fold increase in viable count in that stored at 28 C. Supplementation of egg white with EDTA at 7 mg/ml or with Kena at 10 mg/ml also affected the heat resistant characteristics of the two organisms at 52.5 C, reducing the time required to kill 90% of the population (D value) at any pH by a factor of 2 to 6. There was a synergistic effect between EDTA and lactic acid when lactic acid was used to adjust EDTA-supplemented egg white to an acidic pH (5.3) which greatly decreased the heat resistance of Salmonella senftenberg 775W (from 100D to D).

Chelating Agents↗
PubMed1974

Comparison of the chemical structure and biological activities of the glycolipids of Salmonella minnesota R595 and Salmonella typhimurium SL1102.

It has been assumed in the past that the lipid moieties of endotoxic lipopolysaccharides are quite similar if not identical. This has been tested in the reported work here, where the chemical composition and biological activities of the glycolipids of two heptoseless Re mutants, Salmonella minnesota R595 and Salmonella typhimurium SL1102, have been studied and compared. The two glycolipids, extracted with chloroform-methanol (4:1), showed identical thin-layer chromatographic patterns. The molar ratios for hexosamine, fatty acids, phosphorus, 2-keto-3-deoxyoctonate, total amines, and total nitrogen of the purified glycolipids were in the same range, but small differences could be established. Both glycolipids contained the same major fatty acids, i.e., lauric, myristic, palmitic, and 3-hydroxymyristic acids, in similar but not identical ratios. On paper electrophoresis, the acid hydrolysates of the two glycolipids showed analogous components. In the determination of molecular weight, whereas S. minnesota R595 glycolipid did not show concentration dependence, the molecular weight measured for S. typhimurium SL1102 increased with its concentration. The molecular weight of the fully endotoxic R595 glycolipid has been found to be 17,000 +/- 1,500. Both glycolipids showed similar activities in the Shwartzman skin reaction, Limulus-lysate clotting assay, mouse lethality, and enhancement of nonspecific resistance, but the R595 preparation appeared to be more active on a weight basis in some parameters than SL1102. Using passive hemagglutination, we observed cross-reactivity between the glycolipids. In the gel-diffusion test, they revealed clear identity. The antiserum against S. minnesota R595 neutralized the Shwartzman skin reactivity not only of R595 but also of SL1102 glycolipid. These results confirm that there are identical immunodeterminant group(s) in the two glycolipids. On the other hand, chemical analytical data for two glycolipids showed only similarities, indicating that although both glycolipids are of comparable chemical nature, differences between them exist.

Antibodies, Bacterial↗
PubMed1987

Antigenic and immunogenic properties of recombinants from Salmonella typhimurium and Salmonella minnesota rough mutants expressing in their lipopolysaccharide a genus-specific chlamydial epitope.

Rough mutants from Salmonella typhimurium and Salmonella minnesota were transformed with a plasmid containing a 6.5-kilobase insert of DNA from Chlamydia trachomatis assumed to encode a glycosyltransferase. Transformation resulted in the expression of a genus-specific chlamydial epitope on the lipopolysaccharide (LPS) of the recombinant strains. Proteinase K-digested whole-cell lysates of the recombinants and of controls were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by silver staining or Western blot analysis. Two LPS populations were detected in the recombinants, the parent LPS and a faster-migrating component. The latter stained with monoclonal antibody against the genus-specific chlamydial epitope and was not seen in the controls. LPS was extracted and purified from recombinants of S. minnesota R595 and R4 and characterized by the passive hemolysis and passive hemolysis inhibition assays and by hydrolysis kinetics. Different antigenic determinants could be distinguished from each other by the passive hemolysis inhibition test with monospecific antigen-antibody reactions. Rabbits were immunized with heat-killed recombinant bacteria to study the immunogenic properties of the recombinants. In all animals, antibodies were raised against the parent core specificity and against the chlamydia-specific epitope. The data show that the recombinant bacteria are useful as immunogens to prepare polyclonal antisera against chlamydiae and that LPS isolated from them exhibits the same antigenic determinants as chlamydial LPS and may thus be used as a substitute for chlamydial LPS in serological assays.

Animals↗
PubMed1992

Construction of a recombinant oral vaccine against Salmonella typhi and Salmonella typhimurium.

The viaB gene coding for the Vi antigen of Salmonella typhi Ty2 was subcloned into expression vector pYA248. The recombinant plasmid was termed SMM202 and transformed into Salmonella typhimurium chi 4072, an attenuated delta cya delta crp mutant. Recombinant S. typimurium Vi4072 had the ability to produce Vi capsular polysaccharide and also to invade and colonize the small intestine, mesenteric lymph nodes, and spleen of BALB/c mice. Mice orally immunized with Vi4072 developed serum and secretory antibody responses to the Vi antigen, as measured by a passive hemagglutination assay. Mice developed a delayed-type hypersensitivity following a footpad injection with Vi antigen after being sensitized orally with a suitable dose of Vi4072. Immunization of mice with Vi4072 afforded complete protection against fatal infection with virulent S. typhi Ty2. All data indicate that this route of antigen delivery is effective for stimulating antibody-mediated immunity and for inducing a cell-mediated immune response in BALB/c mice. Thus, S. typhimurium Vi4072 may serve as a vaccine for protection against typhoid fever and salmonellosis caused by S. typhimurium.

Administration, Oral↗
PubMed1994

Hybrid hepatitis B virus core-pre-S proteins synthesized in avirulent Salmonella typhimurium and Salmonella typhi for oral vaccination.

Avirulent salmonellae expressing foreign genes are attractive for use as oral vaccine carriers. To facilitate the stable expression of heterologous genes without conferring antibiotic resistance, a deletion of the asdA1 gene was introduced into Salmonella typhimurium and S. typhi delta cya delta crp mutant vaccine strains. An asd-complementing plasmid expressing hybrid hepatitis B virus nucleocapsid-pre-S (HBcAg-pre-S) particles was constructed. These hybrid HBcAg-pre-S particle genes were stably expressed in S. typhimurium and S. typhi delta cya delta crp mutant vaccine strains in this balanced, lethal host-vector combination. A single oral immunization of BALB/c mice with a recombinant S. typhimurium delta cya delta crp mutant synthesizing hybrid HBcAg-pre-S elicited potentially virus-neutralizing anti-pre-S serum immunoglobulin G antibodies. In addition, serum immunoglobulin G recognizing S. typhimurium lipopolysaccharide was induced. Distribution in tissue after oral immunization was analyzed in one plasmid-strain combination. The recombinant S. typhimurium colonized the gut-associated lymphoid tissue and the spleen and persisted for over 4 weeks, retaining the HBcAg-pre-S expression plasmid. An isogenic virulence plasmid-cured S. typhimurium delta cya delta crp strain expressing the same HBcAg-pre-S gene had reduced immunogenicity for the carried antigen after oral immunization.

Administration, Oral↗
PubMed1998

Identification and sequence analysis of a 27-kilobase chromosomal fragment containing a Salmonella pathogenicity island located at 92 minutes on the chromosome map of Salmonella enterica serovar typhimurium LT2.

Using a genomic approach, we have identified a new Salmonella pathogenicity island, SPI-4, which is the fourth Salmonella pathogenicity island to be identified. SPI-4 was located at 92 min on the chromosome map and was flanked by the ssb and soxSR loci. The DNA sequence covering the entire SPI-4 and both boundaries was determined. The size of SPI-4 was about 25 kb and it contains 18 putative open reading frames (ORFs). Three of these ORFs encode proteins that have significant homology with proteins involved in toxin secretion. Another five ORFs encode proteins that have significant homology with hypothetical proteins from Synechocystis sp. strain PCC6803 or Acinetobacter calcoaceticus. The rest of the ORFs encode novel proteins, one of which has five membrane-spanning domains. SPI-4 is likely to carry a type I secretion system involved in toxin secretion. Furthermore, a previously identified locus (ims98), which is required for intramacrophage survival, was also mapped within the SPI-4 region. These findings suggested that SPI-4 is needed for intramacrophage survival.

Amino Acid Sequence↗