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Helge Karch

Publications and source records attributed to Helge Karch.

At least 19 recordsLinked to original sources
PubMed2006

Structural and functional differences between disease-associated genes of enterohaemorrhagic Escherichia coli O111.

We analysed 72 clinical isolates of enterohaemorrhagic Escherichia coli (EHEC) O111 from patients with diarrhoea or haemolytic uraemic syndrome (HUS) isolated during the period from 1955 to 2005 and identified six motile strains (flagellar antigens 8, 10 and 11); the remaining 66 (92%) were nonmotile (NM) and could not be typed by conventional H serotyping. To improve subtyping methodologies, we determined genotypes of the flagellin-encoding fliC. Three fliC genotypes were found which were identical to those of motile EHEC O111 with H antigens 8, 10 and 11 and designated fliC(H8), fliC(H10) and fliC(H11). The IS629 insertion element was present, identically located, in six epidemiologically unrelated isolates with fliC(H8). The prevalence of the fliC genotypes in the 72 EHEC O111 strains were fliC(H8) (89%), fliC(H10) (7%) and fliC(H11) (4%). Within these fliC genotypes, a high degree of homogeneity for the presence of disease-associated genes was found. The adhesins-encoding genes eae and efa-1 were present in all strains with fliC(H8) and fliC(H11), but absent from strains with fliC(H10). The latter strains have not been reported previously. Strains with fliC(H10) and fliC(H11), but not those with fliC(H8), retained intact cadA and cadC loci and decarboxylated lysine. Three different stx genotypes including stx(1), stx(2) and stx(1)/stx(2) were determined among the 72 EHEC O111. We observed a significant increase over time in the frequency of strains harbouring both stx(1) and stx(2). The presence of stx(2) both alone and in combination with stx(1) was significantly (chi(2)=23.16, P<0.00001, CI(95) [2.29; 9.76]) associated with HUS. Therefore, the emergence of EHEC O111 should be monitored carefully. We conclude that EHEC O111 strains can be differentiated using specific loci required for motility, adherence, Stx production, and lysine decarboxylation. The divergence within EHEC O111 makes it possible to subtype these emerging pathogens in the laboratory thereby providing a basis for further investigations into their ecological niches and survival capabilities.

Adhesins, Bacterial↗
PubMed2006

Shiga toxin activatable by intestinal mucus in Escherichia coli isolated from humans: predictor for a severe clinical outcome.

BACKGROUND: Some Escherichia coli produce Shiga toxin (Stx) in which cytotoxicity is increased (activated) by intestinal mucus and elastase (Stx2d(activatable)). These strains are highly virulent in mice, but their association with human disease is poorly understood. We investigated the prevalence of Stx2d(activatable) among Stx-producing E. coli (STEC) isolated from humans and the association between production of this Stx and the clinical outcome of infection. METHODS: A total of 922 STEC isolates obtained from patients with hemolytic uremic syndrome or bloody or nonbloody diarrhea or from asymptomatic carriers were tested for the gene encoding Stx2d(activatable) by PCR and PstI restriction analysis. The toxin activatibility by human and mouse intestinal mucus and by an elastase was determined by quantifying the cytotoxicity using the Vero cell assay. RESULTS: The stx(2d-activatable) gene was identified in 60 (6.5%) of 922 STEC strains; in 31 of these strains, it was the sole stx gene. Thirty of these 31 strains produced Stx2d(activatable). All of them lacked the intimin-encoding eae gene. Among eae-negative STEC, which typically cause mild diarrhea or asymptomatic infection, production of Stx2d(activatable) was significantly associated with the ability to cause severe disease, including bloody diarrhea (P<.001), and with systemic complications, such as hemolytic uremic syndrome (P<.001). CONCLUSIONS: Production of Stx2d(activatable) by the infecting STEC may predict a severe clinical outcome of the infection, with progression to hemolytic uremic syndrome. A prompt and comprehensive subtyping of stx genes in STEC isolates is necessary to alert the treating physician that a patient is at risk of developing hemolytic uremic syndrome, even though the infecting STEC lacks eae.

Animals↗
PubMed2006

Complete sequence of the large virulence plasmid pSFO157 of the sorbitol-fermenting enterohemorrhagic Escherichia coli O157:H- strain 3072/96.

The large virulence plasmid pSFO157 of sorbitol-fermenting E. coli O157:H(-) strain 3072/96 has a size of 121,239bp and contains 96 open reading frames >50bp. It is therefore 29,162bp larger (ca. 32%) than plasmid pO157 of E. coli O157:H7 strain EDL933. Major differences between the plasmids are the absence of katP, espP, and toxB in pSFO157 and, instead of these, the presence of the sfp fimbriae gene cluster and a large part of an F-plasmid transfer region, the latter accounting for most of the additional DNA. The differences in the order of the genes and their composition, as well as the presence of a number of replication-associated genes and mobile genetic elements suggests that the large E. coli O157 virulence plasmids have a complex evolutionary origin.

Bacterial Proteins↗
PubMed2006

New aspects in the pathogenesis of enteropathic hemolytic uremic syndrome.

Shiga toxin (Stx) subtyping suggests that the clinical outcome of infections caused by Shiga toxin-producing ESCHERICHIA COLI (STEC) depends, in large part, on the STX genotype of the infecting strain. Whereas the presence of the STX2 or STX2C genotype is associated with the ability of STEC to cause the hemolytic uremic syndrome (HUS), strains possessing STX2D or STX2E have been isolated from patients with less severe disease. In addition to the type of Stx, the level of Stx production might be critical for the pathogenicity of STEC. Control of Stx expression appears to be at the level of transcription. Injury to microvascular endothelial cells is the key event underlying the pathogenesis of HUS. We could show that in addition to Stx, STEC also produces other putative virulence factors, such as cytolethal distending toxin, which can contribute to the endothelial injury by interference with the cell cycle, which results in inhibition of cell proliferation and finally cell death.

Bacterial Toxins↗
PubMed2006

Epidemiology, clinical presentation, and pathophysiology of atypical and recurrent hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS) includes a heterogeneous group of hemolytic disorders. Among the identified causes of HUS are infections, particularly infections with Shiga toxin-producing ESCHERICHIA COLI (STEC), complement disorders, and disorders interfering with the degradation of von Willebrand factor (VWF). Other causes for atypical HUS include the cobalamin metabolism; pregnancy/hemolysis, elevated liver enzymes, and low platelets syndrome (HELLP); drugs; and other disorders (e.g., systemic diseases appearing as HUS, such as systemic lupus erythematosus and rejection after transplantation). The group not related to STEC is often also called atypical HUS. Most of the occurrences of infectious HUS have only one episode. Recurrent episodes (recurrent HUS) have strong relationships to diseases of the complement system. In these two subgroups the prognosis is poor, with severe renal insufficiency, together with the need for renal replacement therapy. Severe arterial hypertension is common. Treatment options are limited. To better define this group of patients, the European Society for Pediatric Nephrology supported an initiative to develop a European HUS registry. In this registry, 167 patients were acquired; 73 were female (43.8%). The year of onset of the disease ranged from 1974 to 2005. The prevalence of atypical HUS/recurrent HUS can be calculated as 3.3 per million child population (< 18 years). Underlying disorders included factor H, factor I, MCP-1, pneumococci, and von Willebrand factor disturbances. In 33 patients at least one renal transplantation was performed (total, 55 kidneys); 18% were successful and 73% demonstrated recurrence or thrombosis. Treatment options were plasma substitution or plasmapheresis. Despite continued efforts, transplantation is not recommended at present for these patients. Living-related transplantation should be abandoned. New therapeutic strategies are urgently needed.

Child↗
PubMed2006

Sex and virulence in Escherichia coli: an evolutionary perspective.

Pathogenic Escherichia coli cause over 160 million cases of dysentery and one million deaths per year, whereas non-pathogenic E. coli constitute part of the normal intestinal flora of healthy mammals and birds. The evolutionary pathways underlying this dichotomy in bacterial lifestyle were investigated by multilocus sequence typing of a global collection of isolates. Specific pathogen types [enterohaemorrhagic E. coli, enteropathogenic E. coli, enteroinvasive E. coli, K1 and Shigella] have arisen independently and repeatedly in several lineages, whereas other lineages contain only few pathogens. Rates of evolution have accelerated in pathogenic lineages, culminating in highly virulent organisms whose genomic contents are altered frequently by increased rates of homologous recombination; thus, the evolution of virulence is linked to bacterial sex. This long-term pattern of evolution was observed in genes distributed throughout the genome, and thereby is the likely result of episodic selection for strains that can escape the host immune response.

Alleles↗
PubMed2006

Chromosomal dynamism in progeny of outbreak-related sorbitol-fermenting enterohemorrhagic Escherichia coli O157:NM.

Sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:NM (nonmotile) is a unique clone that causes outbreaks of hemorrhagic colitis and hemolytic-uremic syndrome. In well-defined clusters of cases, we have observed significant variability in pulsed-field gel electrophoresis (PFGE) patterns which could indicate coinfection by different strains. An analysis of randomly selected progeny colonies of an outbreak strain after subcultivation demonstrated that they displayed either the cognate PFGE outbreak pattern or one of four additional patterns and were <89% similar. These profound alterations were associated with changes in the genomic position of one of two Shiga toxin 2-encoding genes (stx2) in the outbreak strain or with the loss of this gene. The two stx2 alleles in the outbreak strain were identical but were flanked with phage-related sequences with only 77% sequence identity. Neither of these phages produced plaques, but one lysogenized E. coli K-12 and integrated in yecE in the lysogens and the wild-type strain. The presence of two stx2 genes which correlated with increased production of Stx2 in vitro but not with the clinical outcome of infection was also found in 14 (21%) of 67 SF EHEC O157:NM isolates from sporadic cases of human disease. The variability of PFGE patterns for the progeny of a single colony must be considered when interpreting PFGE patterns in SF EHEC O157-associated outbreaks.

Animals↗
PubMed2006

Rapid identification and differentiation of clinical isolates of enteropathogenic Escherichia coli (EPEC), atypical EPEC, and Shiga toxin-producing Escherichia coli by a one-step multiplex PCR method.

Enteropathogenic Escherichia coli (EPEC), atypical enteropathogenic E. coli, and Shiga toxin-producing E. coli differ in their virulence factor profiles, clinical manifestations, and prognosis, and they require different therapeutic measures. We developed and evaluated a robust multiplex PCR to identify these pathogroups based on sequences complementary to escV, bfpB, stx1, and stx2.

DNA, Bacterial↗
PubMed2006

Cytolethal distending toxin in Escherichia coli O157:H7: spectrum of conservation, structure, and endothelial toxicity.

We identified the cytolethal distending toxin V (CDT-V) gene cluster in 19 (4.9%) of 391 enterohemorrhagic Escherichia coli O157:H7. cdt-V+ strains belonged to five phage types (PTs) and were most frequent within PTs 14 and 34. CDT-V was expressed in all but two cdt-V+ strains and was lethal to cultured endothelial cells. Subtyping schemes should include cdt-V as a marker to differentiate E. coli O157:H7 even within the same phage type.

Alleles↗
PubMed2006

Automated DNA sequence-based early warning system for the detection of methicillin-resistant Staphylococcus aureus outbreaks.

BACKGROUND: The detection of methicillin-resistant Staphylococcus aureus (MRSA) usually requires the implementation of often rigorous infection-control measures. Prompt identification of an MRSA epidemic is crucial for the control of an outbreak. In this study we evaluated various early warning algorithms for the detection of an MRSA cluster. METHODS AND FINDINGS: Between 1998 and 2003, 557 non-replicate MRSA strains were collected from staff and patients admitted to a German tertiary-care university hospital. The repeat region of the S. aureus protein A (spa) gene in each of these strains was sequenced. Using epidemiological and typing information for the period 1998-2002 as reference data, clusters in 2003 were determined by temporal-scan test statistics. Various early warning algorithms (frequency, clonal, and infection control professionals [ICP] alerts) were tested in a prospective analysis for the year 2003. In addition, a newly implemented automated clonal alert system of the Ridom StaphType software was evaluated. A total of 549 of 557 MRSA were typeable using spa sequencing. When analyzed using scan test statistics, 42 out of 175 MRSA in 2003 formed 13 significant clusters (p < 0.05). These clusters were used as the "gold standard" to evaluate the various algorithms. Clonal alerts (spa typing and epidemiological data) were 100% sensitive and 95.2% specific. Frequency (epidemiological data only) and ICP alerts were 100% and 62.1% sensitive and 47.2% and 97.3% specific, respectively. The difference in specificity between clonal and ICP alerts was not significant. Both methods exhibited a positive predictive value above 80%. CONCLUSIONS: Rapid MRSA outbreak detection, based on epidemiological and spa typing data, is a suitable alternative for classical approaches and can assist in the identification of potential sources of infection.

Algorithms↗
PubMed2005

Enterohemorrhagic Escherichia coli in human infection: in vivo evolution of a bacterial pathogen.

BACKGROUND: Enterohemorrhagic Escherichia coli (EHEC) cause most cases of the hemolytic uremic syndrome (HUS) worldwide. To investigate genetic changes in EHEC during the course of human infection, we analyzed consecutive stool samples and shed isolates from patients with HUS, focusing on the genes encoding Shiga toxin (stx) and intimin (eae). METHODS: Sequential stool samples from 210 patients with HUS were investigated for the persistence of E. coli strains harboring stx and/or eae. Initial stool samples were collected during the acute phase of HUS, and subsequent stool samples were collected 3-16 days later (median interval, 8 days). RESULTS: Organisms that were stx and eae positive (stx+/eae+ strains; n=137) or stx negative and eae positive (stx-/eae+ strains; n=5) were detected in the initial stool samples from 142 patients. Subsequently, the proportion of those who shed stx+/eae+ strains decreased to 13 of 210 patients, whereas the proportion of those who shed strains that were stx-/eae+ increased to 12 of 210 patients. Seven patients who initially excreted strains that were stx+/eae+ shed, at second analysis, stx-/eae+ strains of the same serotypes; they had no free fecal Shiga toxin at follow-up. Comparison of the initial and follow-up isolates from these patients with use of molecular-epidemiological methods revealed loss of stx genes and genomic rearrangement. CONCLUSIONS: We demonstrate the loss of a critical bacterial virulence factor from pathogens during very brief intervals in the human host. These genetic changes have evolutionary, diagnostic, and clinical implications. Generation of stx- mutants might contribute to subclonal evolution and evolutionary success.

Enterotoxins↗
PubMed2005

Lipooligosaccharide of Campylobacter jejuni prevents myelin-specific enteral tolerance to autoimmune neuritis--a potential mechanism in Guillain-Barre syndrome?

Campylobacter jejuni-induced enteritis is the most common infection preceding Guillain-Barre syndrome (GBS), an immune-mediated polyradiculoneuritis. The acute autoimmune attack is thought to be based on C. jejuni antigens which may mimick antigens of the peripheral nervous system. Additional pathomechanisms, like disturbance of natural T cell immunoregulation by C. jejuni, have not been evaluated so far. In experimental autoimmune neuritis (EAN), a T lymphocyte-mediated animal model of human GBS, tolerance to myelin-derived autoantigens can be induced by oral feeding of the respective antigen. Here we investigated whether the lipooligosaccharide (LOS) fraction of C. jejuni may directly alter immunologic tolerance through gastrointestinal pathways. While EAN, actively induced by immunization with bovine peripheral nerve myelin could be ameliorated by precedent feeding of myelin, feeding of C. jejuni LOS along with the myelin antigen not only prevented the tolerizing effects of oral myelin but even accelerated the onset of overt EAN and augmented the myelin-specific B cell response. These findings provide evidence that LOS of C. jejuni, as produced in the gut during C. jejuni-induced enteritis, can disturb natural tolerance to definite proteins which may be or may mimic peripheral nerve antigens. In human patients this may be one of the potential mechanisms to explain why C. jejuni enteritis is a common trigger of GBS.

Animals↗
PubMed2005

Application of combined high-performance thin-layer chromatography immunostaining and nanoelectrospray ionization quadrupole time-of-flight tandem mass spectrometry to the structural characterization of high- and low-affinity binding ligands of Shiga toxin 1.

Shiga toxin 1 (Stx1) represents an AB5 toxin produced by enterohemorrhagic Escherichia coli, which cause gastrointestinal diseases in humans that are often followed by potentially fatal systemic complications, such as acute encephalopathy and hemolytic uremic syndrome. The expression of the preferential Stx1 receptor, Gb3Cer/CD77 (Gal alpha1-4Gal beta1-4Glc beta1-1Cer), is one of the primary determinants of susceptibility to tissue injury. Due to the clinical importance of this life-threatening toxin, a combined strategy of preparative high-performance thin-layer chromatography (HPTLC) overlay assay and mass spectrometry was developed for the detection and structural characterization of Stx1-binding glycosphingolipids (GSLs). A preparation of neutral GSLs from human erythrocytes, comprising 21.4% and 59.1% of the high- and low-affinity Stx1-binding ligands Gb3Cer/CD77 and Gb4Cer, respectively, was separated on silica gel precoated HPTLC plates and probed for the presence of Stx1 receptors. Stx1 positive on the one hand and anti-Gb3Cer/CD77 and anti-Gb4Cer antibody positive bands from parallel reference runs on the other hand were extracted with chloroform/methanol/water (30/60/8, v/v/v). These crude extracts were used without any further purification for a detailed structural analysis by nanoelectrospray ionization quadrupole time-of-flight mass spectrometry (nanoESI-QTOF-MS) in the negative ion mode. In all extracts investigated, neutral GSLs were detected as singly charged deprotonated molecular ions, [M-H]-, and neither buffer-derived salt adducts nor coextracted contaminants from the overlay assay procedure or the silica gel layer were observed. For the structural characterization of Stx1- and antibody-binding GSLs low-energy collision-induced dissociation (CID) was applied to high and low abundant receptor species of the crude extracts. All MS/MS spectra obtained contained full series of Y-type ions, B-type ions and additional ions generated by ring cleavages of the sugar moiety. Only analytical quantities in the microgram scale of a single GSL species within the complex GSL mixture were required for the structural MS characterization of Stx1 ligands as Gb3Cer/CD77 and Gb4Cer. This effective combined HPTLC/MS procedure offers a broad range of applications, not only for toxins of bacterial origin, but also for any GSL-binding agents such as plant-derived lectins or human proteins with yet unknown binding specificities.

Antibodies↗
PubMed2005

Enterohaemorrhagic Escherichia coli in human medicine.

Enterohaemorrhagic Escherichia coli (EHEC) are the pathogenic subgroup of Shiga toxin (Stx)-producing E. coli. EHEC can cause non-bloody and bloody diarrhoea, and the haemolytic uraemic syndrome (HUS). HUS is a major cause of acute renal failure in children. E. coli O57:H7 is the predominant, but far from being the only, serotype that can cause HUS. The cascade leading from gastrointestinal infection to renal impairment is complex, with the microvascular endothelium being the major histopathological target. EHEC also produce non-Stx molecules, such as cytolethal distending toxin, which can contribute to the endothelial or vascular injury. Because there are no specific therapies for EHEC infections, efficient reservoir and human preventive strategies are important areas of ongoing investigations. This review will focus on the microbiology, epidemiology, and pathophysiology of EHEC-associated diseases, and illustrate future challenges and opportunities for their control.

Escherichia coli Infections↗
PubMed2005

Immune responses to Campylobacter and serum autoantibodies in patients with complex regional pain syndrome.

We hypothesised that some complex regional pain syndromes (CRPS) may have a postinfectious and/or autoimmune basis. Sera from 92 patients with CRPS and 92 controls were investigated for immunoreactivity to Campylobacter strains and to rodent tissues. Both IgA-antibodies to Campylobacter and tissue-specific reactivity were often present in patients with short disease duration (< or = 1.5 years). Patients with minimal preceding trauma had stronger nervous tissue-specific reactivity than other patients, regardless of disease duration. These results provide preliminary evidence for immune activation early in CRPS and, additionally, that patients with minimal trauma may comprise an autoimmune subgroup.

Adult↗
PubMed2005

Shiga toxin 2e-producing Escherichia coli isolates from humans and pigs differ in their virulence profiles and interactions with intestinal epithelial cells.

Thirteen Escherichia coli strains harboring stx2e were isolated from 11,056 human stools. This frequency corresponded to the presence of the stx2e allele in 1.7% of all Shiga toxin-producing E. coli (STEC) strains. The strains harboring stx2e were associated with mild diarrhea (n = 9) or asymptomatic infections (n = 4). Because STEC isolates possessing stx2e are porcine pathogens, we compared the human STEC isolates with stx2e-harboring E. coli isolated from piglets with edema disease and postweaning diarrhea. All pig isolates possessed the gene encoding the F18 adhesin, and the majority possessed adhesin involved in diffuse adherence; these adhesins were absent from all the human STEC isolates. In contrast, the high-pathogenicity island encoding an iron uptake system was found only in human isolates. Host-specific patterns of interaction with intestinal epithelial cells were observed. All human isolates adhered to human intestinal epithelial cell lines T84 and HCT-8 but not to pig intestinal epithelial cell line IPEC-J2. In contrast, the pig isolates completely lysed human epithelial cells but not IPEC-J2 cells, to which most of them adhered. Our data demonstrate that E. coli isolates producing Shiga toxin 2e have imported specific virulence and fitness determinants which allow them to adapt to the specific hosts in which they cause various forms of disease.

Animals↗
PubMed2005

Presence and characterization of a mosaic genomic island which distinguishes sorbitol-fermenting enterohemorrhagic Escherichia coli O157:H- from E. coli O157:H7.

A mosaic genomic island comprising Shigella resistance locus (SRL) sequences flanked by segments of Escherichia coli O157:H7 strain EDL933 O islands 43, 81, and 82 was identified in sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:H(-) strain 493/89. This mosaic island is absent from strain EDL933. PCR targeting the SRL-related sequence is a useful tool to distinguish SF EHEC O157:H(-) from EHEC O157:H7.

Bacterial Typing Techniques↗