Biomedical subjects

W Rabsch

Publications and source records attributed to W Rabsch.

At least 19 recordsLinked to original sources

PubMed2005

Catecholate receptor proteins in Salmonella enterica: role in virulence and implications for vaccine development.

Three outer membrane proteins of Salmonella enterica serovar Typhimurium function as catecholate siderophore receptors. IroN promotes uptake of enterobactin, salmochelins and 2,3-dihydroxybenzoylserine, FepA transports enterobactin and 2,3-dihydroxybenzoylserine, and Cir is a receptor for 2,3-dihydroxybenzoylserine. In addition, all three proteins are required for l-norepinephrine-facilitated iron uptake from transferrin as judged by failure of a fepA iroN cir triple mutant to grow in serum-containing medium in the presence of l-norepinephrine. Moreover, pre-treatment of mice with l-norepinephrine resulted in enhanced systemic spread of the parental strain, but had no effect on the fepA iroN cir mutant. Inoculation of mice with the triple mutant, which is significantly attenuated, elicited a significant protective effect against subsequent challenge with the parental strain.

Animals↗

PubMed2005

Molecular epidemiology of Salmonella enterica serovar Agona: characterization of a diffuse outbreak caused by aniseed-fennel-caraway infusion.

During 2002-2003 increased numbers of notified salmonellosis due to S. enterica serovar Agona were observed in Germany. In order to understand the recent spread of this serovar and to trace the route of infection to its source, a new phage-typing scheme and pulsed field gel electrophoresis (PFGE) were used to analyse these isolates. By using 14 bacteriophages, 52 phage types were distinguished among the S. Agona strains. PFGE also differentiated 52 different patterns. A combination of both methods generated 94 clonal types among 165 S. Agona strains originating from Germany and other countries including the United States, United Arab Emirates, Turkey, India, Austria and Finland, indicating a great biological diversity within this serovar. However, 36 recent S. Agona isolates from infantile gastroenteritis in Germany, from an untreated batch of aniseed imported from Turkey and from fennel-aniseed-caraway infusion (packed in tea bags) revealed clonal identity indicating their epidemiological relatedness as a new source of infection. It is suggested that strains of S. Agona will continue to be of public health concern, and that phage typing together with PFGE typing should be applied as reliable and rapid tools for epidemiological subtyping and future monitoring.

Apiaceae↗

PubMed2005

Pilot study to evaluate microarray hybridization as a tool for Salmonella enterica serovar Typhimurium strain differentiation.

In developed countries, Salmonella enterica subspecies 1 serovars Enteritidis and Typhimurium range among the most common causes of bacterial food-borne infections. The surveillance and typing of epidemic Salmonella strains are important tools in epidemiology. Usually, Salmonella enterica subspecies 1 serovars are differentiated by serotyping for diagnostic purposes. Further differentiation is done by phage typing as well as molecular typing techniques. Here we have designed and evaluated a prototype DNA microarray as a tool for serovar Typhimurium strain differentiation. It harbors 83 serovar Typhimurium probes obtained by differential subtractive hybridization and from the public database. The microarray yielded reproducible hybridization patterns in repeated hybridizations with chromosomal DNA of the same strain and could differentiate five serovar Typhimurium reference strains (DT204, DT104, DT208, DT36, and LT2). Furthermore, the microarray identified two distinct groups among 13 serovar Typhimurium DT104 strains. This correlated with observations from pulsed-field gel electrophoresis analysis. Twenty-three further serovar Typhimurium strains were analyzed to explore future directions for optimization of the simple 83-probe DNA microarray. The data presented here demonstrate that DNA microarrays harboring small numbers of selected probes are promising tools for serovar Typhimurium strain typing.

Bacterial Typing Techniques↗

PubMed2003

Salmochelins, siderophores of Salmonella enterica and uropathogenic Escherichia coli strains, are recognized by the outer membrane receptor IroN.

Members of a family of catecholate siderophores, called salmochelins, were isolated by reversed-phase HPLC from Salmonella enterica serotype Typhimurium and structurally characterized by Fourier transform ion cyclotron resonance-MSMS and GC-MS. The tentative structure of salmochelin 1 contained two 2,3- dihydroxybenzoylserine moieties bridged by a glucose residue, bound to the serine hydroxyl group of one moiety and the carboxylate of the second moiety. Salmochelin 2 contained in addition a second glucose residue linked to a third 2,3-dihydroxybenzoylserine moiety. Salmochelins were not produced by an iroBC mutant, which indicated that the IroB protein might be responsible for the glucosyl transfer predicted by sequence similarities to known glycosyltransferases. Uptake experiments with radiolabeled (55)Fe-salmochelin and growth promotion tests with salmochelins showed that the IroN outer membrane receptor, encoded in the iroA locus of S. enterica and uropathogenic Escherichia coli strains, was the main receptor for ferric salmochelin transport.

Cell Membrane↗

PubMed2003

Role of receptor proteins for enterobactin and 2,3-dihydroxybenzoylserine in virulence of Salmonella enterica.

Single, double, and triple mutants of an enterobactin-deficient mutant strain of Salmonella enterica serovar Typhimurium were constructed that were defective in the expression of the iron-regulated outer membrane proteins (IROMPs) FepA, IroN, and Cir, which are proposed to function as catecholate receptors. Uptake of naturally occurring and chemically synthesized catecholate molecules by these mutants was assessed in standard growth promotion assays. Unique patterns of uptake were identified for each IROMP; specifically, FepA and IroN were confirmed to be required for transport of enterobactin, and all three proteins were shown to function as receptors for the enterobactin breakdown product 2,3-dihydroxybenzoylserine. The fepA, iroN, and cir alleles were transduced to enterobactin-proficient strains of S. enterica serovar Typhimurium and S. enterica serovar Enteritidis, and the resulting phenotypes were confirmed by analysis of outer membrane protein profiles, by sensitivity to KP-736, a catecholate-cephalosporin conjugate, and by growth promotion tests on egg white agar. Intragastric infections of mice with the S. enterica serovar Typhimurium strains indicated that the parental strain and the fepA iroN double mutant were similarly virulent but that the fepA iroN cir triple mutant was significantly attenuated. Moreover, in mixed infections, the fepA iroN mutant showed similar cecal colonization and invasion of the liver to the parental strain, while the triple mutant showed significantly reduced cecal colonization and no measurable spread to the liver. Infections of 4-day-old chicks with S. enterica serovar Enteritidis strains also indicated that mutation of the fepA iroN genes did not significantly reduce cecal colonization and systemic spread compared with those of the parental strain. The results indicate that, while enterobactin uptake is not essential for the virulence of S. enterica serovars in mouse and chicken infection models, the ability to take up 2,3-dihydroxybenzoylserine via any of the three catecholate siderophore receptors appears to play an important role, since the S. enterica serovar Typhimurium triple mutant was significantly attenuated in the mouse model. Salmochelins appear not to be involved in the virulence of S. enterica.

Animals↗

PubMed2003

The high-pathogenicity island is absent in human pathogens of Salmonella enterica subspecies I but present in isolates of subspecies III and VI.

In this study we tested 74 Salmonella strains of all eight Salmonella groups and were able to demonstrate the presence of two high-pathogenicity island types in strains of Salmonella groups IIIa, IIIb, and VI. Most high-pathogenicity island-positive isolates produced yersiniabactin under iron-limited conditions and were positive for the high-molecular-weight proteins HMWP1 and HMWP2.

3' Flanking Region↗

PubMed2002

Clonal diversity of Shiga toxin-producing Escherichia coli O103:H2/H(-) in Germany.

Shiga toxin producing Escherichia coli O103:H2/H(-) belong to the third most frequently isolated EHEC serotypes in Germany following isolates of O157:H7/H(-) and O26:H11/H(-). A total of 145 respective E. coli 103 isolates from single cases of diarrhoea and haemolytic uremic syndrome (HUS) in 1997-2000 were characterised by a range of molecular subtyping methods (PFGE, P-gene profiling, ribotyping, electrotyping) and phage typing in order to analyse their genetic relatedness and the practicability for new epidemiological tracing back. All isolates cluster into a distinct EHEC subgroup and reveal a high clonal diversity together with a considerable stability. Since strains of this serotype rank up to the third most frequently isolated EHEC in Germany a large population of this serotype, and therefore, a great supply of such strains may exist in this country.

Clone Cells↗

PubMed2002

Phage typing and PFGE pattern analysis as tools for epidemiological surveillance of Salmonella enterica serovar Bovismorbificans infections.

Some years ago, an increase in the number of sporadic cases and outbreaks of salmonellosis due to S. enterica serovar Bovismorbificans was observed in several European countries including Finland, Sweden, England/Wales, Austria, and Germany. In order to understand the recent spread of this serovar and to trace the route of infection back to its source, it was considered necessary to subtype S. Bovismorbificans isolates. Using phage typing (newly described here) and molecular fingerprinting (PFGE-pattern, plasmid profiles and ribotype) the isolates of European origin could be subtyped and compared to S. Bovismorbificans isolates that originated in overseas countries such as Australia, Thailand, India, etc. where this serovar was isolated more frequently. Significant clonal diversity was identified but some of the clonal types of S. Bovismorbificans dominated the epidemics and single cases in Europe as well as in overseas countries. The clonal identity among these isolates indicates an international distribution, new sources of infection, and highlights the urgent requirement for standardized laboratory based surveillance networks (e.g. Enter-Net). Moreover, it is suggested that strains of S. Bovismorbificans will continue to be of concern in public health and that phage typing together with PFGE typing can be applied as reliable and rapid tools for their future monitoring.

DNA Fingerprinting↗

PubMed2001

Transfer of the Salmonella type III effector sopE between unrelated phage families.

Salmonella spp. are pathogenic enterobacteria that employ type III secretion systems to translocate effector proteins and modulate responses of host cells. The repertoire of translocated effector proteins is thought to define host specificity and epidemic virulence, and varies even between closely related Salmonella strains. Therefore, horizontal transfer of effector protein genes between Salmonella strains plays a key role in shaping the Salmonella-host interaction. Several effector protein genes are located in temperate phages. The P2-like phage SopE Phi encodes SopE and the lambda-like GIFSY phages encode several effector proteins of the YopM/IpaH-family. Lysogenic conversion with these phages is responsible for much of the diversity of the effector protein repertoires observed among Salmonella spp. However, free exchange of effector proteins by lysogenic conversion can be restricted by superinfection immunity. To identify genetic mechanisms that may further enhance horizontal transfer of effector genes, we have analyzed sopE loci from Salmonella spp. that do not harbor P2-like sequences of SopE Phi. In two novel sopE loci that were identified, the 723 nt sopE gene is located in a conserved 1.2 kb cassette present also in SopE Phi. Most strikingly, in Salmonella enterica subspecies I serovars Gallinarum, Enteritidis, Hadar and Dublin, the sopE-cassette is located in a cryptic lambda-like prophage with similarity to the GIFSY phages. This provides the first evidence for transfer of virulence genes between different phage families. We show that such a mechanism can circumvent restrictions to phage-mediated gene transfer and thereby enhances reassortment of the effector protein repertoires in Salmonella spp.

Amino Acid Sequence↗

PubMed2001

Non-typhoidal salmonellosis: emerging problems.

Two major changes in the epidemiology of non-typhoidal salmonellosis have occurred during the second half of the 20th century. First, Salmonella typhimurium strains resistant to multiple antibiotics have emerged and spread within populations of food animals. Secondly, Salmonella enteritidis has emerged as a major egg-associated pathogen. This article reviews available data on the origins of the human epidemics.

Animals↗

PubMed2000

Nontoxigenic sorbitol-fermenting Escherichia coli O157:H- associated with a family outbreak of diarrhoea.

A recent study from Germany reported the isolation of E. coli O157:H7/H- from patients with non-bloody diarrhoea and hemolytic uremic syndrome, questioning the role of Shiga toxin as the main trait of virulence for human disease. We isolated 6 sorbitol-fermenting E. coli O157:H- strains that do not contain Shiga toxin genes. The isolates originated from an outbreak (3 patients, 3 asymptomatic contacts) of non-bloody diarrhoea affecting two families sharing one household. Two children (age 10 months and 2 years) suffered severe diarrhoea over 30 and 10 days, respectively. Their uncle had moderate diarrhoea for 2 weeks. In contrast to the other isolates, the uncle's strain (EH109) did not harbour a chromosomal eae gene encoding gamma-intimin nor the plasmid gene E-hly; it also showed a PFGE pattern that was different from the unique pattern of the other isolates. Employing PFGE, phage typing, and P-gene typing, five of the six stx negative isolates were indistinguishable from the stx 2 positive "Bavarian outbreak strain". The only human serum tested, obtained from one asymptomatic contact, contained antibodies to the O157 lipopolysaccharide antigen. Our finding of five stx negative sorbitol-fermenting E. coli O157:H- isolates (harbouring eae and E-hly) associated with an outbreak of non-bloody diarrhoea supports the hypothesis that Stx production is not obligatory for the pathogenicity of E. coli O157 for humans.

Adult↗

PubMed2000

Prevalence and polymorphism of genes encoding translocated effector proteins among clinical isolates of Salmonella enterica.

Pathogenic Salmonella enterica strains are capable of causing local and/or systemic infections. They employ two type III secretion systems to translocate an array of virulence-associated proteins (effector proteins) directly into the cytosol of target cells of the host. Earlier data had shown that changes in the repertoire of translocated effector proteins may contribute to the adaptation of Salmonella strains to new hosts and to the emergence of epidemic strains. Using PCR and Southern blot techniques the presence of and the polymorphism among the genes encoding the translocated effector proteins SopB, SopD, SopE, SopE2, SipA, SipB, SipC, AvrA, and SptP was studied in 71 phylogenetically well characterised S. enterica subspecies I (subspecies enterica) strains of the SARB collection and in 209 clinical and epidemic isolates of S. enterica subspecies I belonging to various serovars, phage types, and genotypes. All these Salmonella strains harbour all these respective genes with the exception of sopE and avrA which have been identified in only some of them. Several of the studied genes display genetic polymorphisms (RFLP). These RFLP patterns did not show a strict correlation with the genetic distance, the grouping genes in order to understand their role in the evolution of Salmonella as a pathogen.

Actins↗

PubMed2000

Clonal diversity of Shiga toxin-producing Escherichia coli O157:H7/H- in Germany--a ten-year study.

Two hundred and ten E. coli O157:H7/H- strains isolated from single cases and outbreaks of diarrhoea and haemolytic uraemic syndrome (HUS) in Germany between 1988 and 1998 were characterised by a range of molecular subtyping methods and phage typing in order to analyse their clonal nature. A high clonal heterogeneity, together with a considerable clonal stability, has been identified among the bacterial isolates and no single clonal type appeared to be geographically dominant. It is recommended to apply pulsed-field gel electrophoresis (PFGE) together with P gene profile determination (number and genomic positions of lambdoid bacteriophages) as laboratory tools for an extended epidemiological surveillance of E. coli OOFF phage typing will remain helpful as a first line of analysis, particularly in outbreak situations.

DNA, Bacterial↗

PubMed2000

Phage types, antibiotic susceptibilities and plasmid profiles of Salmonella typhimurium and Salmonella enteritidis strains isolated in Istanbul, Turkey.

OBJECTIVE: To examine 13 Salmonella typhimurium and 22 S. enteritidis strains isolated from individual cases of gastroenteritis for their phage types, antibiotic susceptibilities and plasmid profiles. METHODS: The phage typing of S. typhimurium strains was done according to the method of Anderson et al, and the phage typing scheme of Ward et al was used for phage typing of S. enteritidis strains. Antibiotic susceptibility testing was performed by the Kirby-Bauer disk diffusion method. Extended-spectrum beta-lactamase production of the strains was determined by the three-dimensional method. Plasmid profiles of the strains were examined using the method described by Kado and Liu with some modification by Graeber et al. RESULTS: Two S. typhimurium strains were DT 193 and one was DT 22, whereas 10 strains were untypable. PT 4 was the predominant phage type among S. enteritidis strains. Four S. enteritidis strains were DT 6a, three strains were PT 1 and one strain was PT 8, whereas only one strain was untypable. Eleven of 13 S. typhimurium and three of 22 S. enteritidis strains were found to be multiresistant. Ten different resistance patterns among S. typhimurium and four different resistance patterns among S. enteritidis strains were detected. Extended-spectrum beta-lactamase production was detected in 10 of 13 S. typhimurium and in three of 22 S. enteritidis strains. All S. typhimurium strains but one were found to contain at least one plasmid, with molecular masses varying between 4 and 107 MDa, and 11 different plasmid patterns were determined. Plasmid pattern analysis permitted further differentiation of the S. enteritidis strains into nine groups. A serovar-specific virulence plasmid of 36 MDa was detected in 13 of 22 S. enteritidis strains. CONCLUSIONS: The results suggest that the majority of S. typhimurium strains were closely related.

Anti-Bacterial Agents↗

PubMed2000

Cattle can be a reservoir of sorbitol-fermenting shiga toxin-producing Escherichia coli O157:H(-) strains and a source of human diseases.

Using the immunomagnetic separation procedure, we isolated sorbitol-fermenting (SF) Shiga toxin-producing Escherichia coli (STEC) O157:H(-) strains from two patients, one with hemolytic-uremic syndrome and the other with diarrhea, and from a dairy cow epidemiologically associated with the patients. The phenotypic and genotypic characteristics of all isolates were identical or closely related. Moreover, the bovine isolate showed a clonal relatedness to SF STEC O157:H(-) strains isolated from patients in Germany and the Czech Republic from 1988 to 1998. This is the first evidence that cattle can be a reservoir of SF STEC O157:H(-) and a source of human diseases.

Animals↗

PubMed1999

Isolation of a temperate bacteriophage encoding the type III effector protein SopE from an epidemic Salmonella typhimurium strain.

Salmonella typhimurium employs the specialized type III secretion system encoded in pathogenicity island 1 (SPI1) to translocate effector proteins into host cells and to modulate host cell signal transduction. The SPI1 type III system and the effector proteins are conserved among all salmonellae and are thought to be acquired by horizontal gene transfer. The genetic mechanisms mediating this horizontal transfer are unknown. Here, we describe that SopE, a SPI1-dependent translocated effector protein, is present in relatively few S. typhimurium isolates. We have isolated a temperate phage that encodes SopE. Phage morphology and DNA hybridization, as well as partial sequence information, suggest that this phage (SopEPhi) is a new member of the P2 family of bacteriophages. By lysogenic conversion this phage can horizontally transfer genes between different S. typhimurium strains. Strikingly, most of the isolates harboring SopEPhi belong to the small group of epidemic strains of S. typhimurium that have been responsible for a large percentage of human and animal salmonellosis and have persisted for a long period of time. Our data suggest that horizontal transfer of type III dependent effector proteins by lysogenic infection with bacteriophages (lysogenic conversion) may provide an efficient mechanism for fine-tuning the interaction of Salmonella spp. with their hosts.

Bacterial Proteins↗

PubMed1999

Clonal relationship of Salmonella enterica serovar typhimurium phage type DT104 in Germany and Austria.

A new epidemic clone of Salmonella enterica serovar Typhimurium designated definitive phage type (DT) 104 has been emerging since 1990 to become most common type among S. Typhimurium isolates in Germany and Austria. Molecular fingerprinting (PFGE-pattern, plasmid profiles, IS200 pattern, ribotype, ERIC-type, OMP and MLE patterns) revealed the majority of the DT104 isolates to have clonal identity; they were designated as type 1 (about 95%). Moreover, clonal type 1 of DT104 was found to occur in sensitive as well as in a range of multiply drug-resistant variants and in a variety of plasmid profile types (in particular with small cryptic plasmids in the range of 1.0 to 5.0 Md). Since the clonal type 1 of DT104 has been identified among isolates from other countries, too, including such from the United Kingdom, the United Arab Emirates, the Philippines, and the Netherlands, its pandemic spread in man indicates that the import/export of this pathogen continues. About 5% of the DT104 isolates have been identified as genetically diverse indicating the independent appearance of the same multiple drug resistance and phage pattern phenotype among different Salmonella ancestor strains.

Animals↗

PubMed1999

Ferrioxamine-mediated Iron(III) utilization by Salmonella enterica.

Utilization of ferrioxamines as sole sources of iron distinguishes Salmonella enterica serotypes Typhimurium and Enteritidis from a number of related species, including Escherichia coli. Ferrioxamine supplements have therefore been used in preenrichment and selection media to increase the bacterial growth rate while selectivity is maintained. We characterized the determinants involved in utilization of ferrioxamines B, E, and G by S. enterica serotype Typhimurium by performing siderophore cross-feeding bioassays. Transport of all three ferric siderophores across the outer membrane was dependent on the FoxA receptor encoded by the Fur-repressible foxA gene. However, only the transport of ferrioxamine G was dependent on the energy-transducing protein TonB, since growth stimulation of a tonB strain by ferrioxamines B and E was observed, albeit at lower efficiencies than in the parental strain. Transport across the inner membrane was dependent on the periplasmic binding protein-dependent ABC transporter complex comprising FhuBCD, as has been reported for other hydroxamate siderophores of enteric bacteria. The distribution of the foxA gene in the genus Salmonella, as indicated by DNA hybridization studies and correlated with the ability to utilize ferrioxamine E, was restricted to subspecies I, II, and IIIb, and this gene was absent from subspecies IIIa, IV, VI, and VII (formerly subspecies IV) and Salmonella bongori (formerly subspecies V). S. enterica serotype Typhimurium mutants with either a transposon insertion or a defined nonpolar frameshift (+2) mutation in the foxA gene were not able to utilize any of the three ferrioxamines tested. A strain carrying the nonpolar foxA mutation exhibited a significantly reduced ability to colonize rabbit ileal loops compared to the foxA+ parent. In addition, a foxA mutant was markedly attenuated in mice inoculated by either the intragastric or intravenous route. Mice inoculated with the foxA mutant were protected against subsequent challenge by the foxA+ parent strain.

Amino Acid Sequence↗