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Biomedical subjects

H Karch

Publications and source records attributed to H Karch.

At least 37 records · Page 2Linked to original sources
PubMed2001

Antibody response to Shiga toxins Stx2 and Stx1 in children with enteropathic hemolytic-uremic syndrome.

A Western blot (immunoblot) assay (WBA) for the detection of immunoglobulin G antibodies to Shiga toxins Stx2 and Stx1 in sera from 110 patients with enteropathic hemolytic-uremic syndrome (53 culture confirmed to have Shiga toxin-producing Escherichia coli [STEC] infection) and 110 age-matched controls was established by using a chemiluminescence detection system. Thirty-nine (74%) of the 53 culture-confirmed cases were infections with STEC serotype O157, and 14 (26%) were associated with infection by other STEC serotypes. The frequency of an anti-Stx2 response following infection by a Stx2-producing strain (34 of 48 cases; 71%) was higher than that of an anti-Stx1 response following Stx1-producing STEC infection (4 of 10). Furthermore, the frequency of an anti-Stx2 response in 110 control sera (10%) was significantly higher than the frequency of an anti-Stx1 response (1.8%) (P = 0.0325). For STEC O157 culture-confirmed cases WBA for toxin detection had a diagnostic sensitivity of 71% and a specificity of 90%. Because of its high specificity the assay might be a helpful tool for diagnosing suspected STEC infection when tests of stool samples or serological tests against various lipopolysaccharide antigens are negative. Furthermore, the prevalence of anti-Stx antibodies in healthy controls probably reflects the population immunity to systemic Stx-associated disease. It can thus serve as a basis for comparing immunity levels in different populations and for considering future Stx toxoid immunization strategies.

Adolescent↗
PubMed2001

Escherichia coli O157 infections and unpasteurised milk.

We report on two children with Escherichia coli O157 infection, one of whom developed haemolytic uraemic syndrome (HUS). Both had drunk raw cows or goats milk in the week before their illness. Molecular subtyping identified a sorbitol fermenting Escherichia coli O157:H isolate from a dairy cow. This isolate differed from Shiga toxin producing O157:H strains isolated from the 6 year old boy with HUS. This result underlines the need to search for other causes of infection, despite documented consumption of unpasteurised milk. In the second patient, human sorbitol non-fermenting O157:H isolates and animal isolates from goats were indistinguishable. The isolation of indistinguishable sorbitol non-fermenting Escherichia coli O157:H from contact animals supports the association between HUS and consumption of raw goats milk, and re-emphasises the importance of pasteurising milk.

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

Intestinal infection due to enteroaggregative Escherichia coli among human immunodeficiency virus-infected persons.

To investigate the pathogenic role of enteroaggregative Escherichia coli (EAggEC) among human immunodeficiency virus-infected persons, 111 outpatients with and 68 without diarrhea were evaluated. Examination of stool samples included the HeLa cell adherence assay and an EAggEC polymerase chain reaction (PCR) assay using primers complementary for the plasmid locus CVD432. The pCVD432 genotype, adherence phenotype, and patient characteristics were correlated with occurrence of diarrhea by multivariate analyses. EAggEC PCR and adherence assays were positive in 7 (6%) and 24 (22%) patients with diarrhea and in 1 (1%) and 21 (31%) asymptomatic control patients, respectively. Clinical manifestations associated with EAggEC PCR-positive isolates were nonspecific; EAggEC infections were independent of CD4 lymphocyte counts. Of the pCVD432 genotype, 5 (71%) of 7 were resistant to cotrimoxazole and ampicillin, and 1 strain was resistant to ciprofloxacin. Overall, pCVD432 PCR-positive E. coli was the most prevalent intestinal organism associated with diarrhea. The adherence assay results did not correlate with diarrhea.

Adult↗
PubMed2000

Inflammatory and immunological parameters in children with haemolytic uremic syndrome (HUS) and gastroenteritis-pathophysiological and diagnostic clues.

The objective of this study was to identify parameters indicating a risk for developing typical haemolytic uremic syndrome (D+HUS) during the prodromal phase of diarrhea caused by enterohaemorrhagic Escherichia coli (EHEC). Forty-eight children were studied prospectively with regard to inflammatory serum factors on admission to hospital. Ten patients developed D+HUS (group I), 15 suffered from viral-gastroenteritis (group IIa) and 23 from other types of bacterial gastroenteritis (group IIb). Mean levels of IL-8 tended to be elevated in group I compared to groups IIa and IIb. Neopterin and IL-10 levels particularly were significantly decreased in HUS in comparison to both gastroenteritis groups. Low IL-10 levels indicate a substantial disregulation of the immune response in HUS, as IL-10 downregulates the pro-inflammatory response and suppresses pro-coagulant activity in experimental endotoxemia. Our results suggest low neopterin, high IL-8 and especially low IL-10 levels are indicators of a high risk for developing HUS.

Bacterial Infections↗
PubMed2000

Enterohemorrhagic Escherichia coli infections: following transmission routes.

Infections with enterohemorrhagic Escherichia coli (EHEC) are the major cause of hemolytic-uremic syndrome (HUS), the most-common cause of acute renal failure in childhood. The mortality rate of HUS (0%-5% in most recent series and 10%-30% in individual reports) and residual chronic renal sequelae (in up to 50% of patients in long-term follow-up studies) emphasize the seriousness of HUS for public health. Several studies have described possible sources of EHEC infection. However, in the majority of cases the pathogen cannot be identified in food or animals and the routes of transmission remain unclear. In this review article the hypothesized routes of transmission are summarized. The medical data bases "Medline" and "Current contents" were screened for the years January 1966 through November 1998. The difficulties in following the chain of EHEC infection are discussed. A precise evaluation of the environmental aspects of the patient is a precondition for further analysis.

Escherichia coli Infections↗
PubMed2000

Genome plasticity in Enterobacteriaceae.

The comparative analysis of multiple representatives of the genomes of particular species are leading us away from a view of bacterial genomes as static, monolithic structures towards the view that they are relatively variable, fluid structures. This plasticity is mainly the result of the rearrangement of genes within the genome and the acquisition of novel genes by horizontal transfer systems, e. g. plasmids, bacteriophages, transposons or gene cassettes. These mechanisms often act in concert thus generating a complex genetic structure. Genomic variations are not a phenomenon at the DNA level alone, they influence the phenotype of a bacterium as well and can render a formerly harmless organism into a hazardous pathogen. This review deals not only with the mechanisms of genome rearrangements and the horizontal transfer of genes in Enterobacteriaceae but also points out that mobile genetic elements themselves are subjected to variation.

Bacteriophages↗
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

Heterogeneity of the prtC gene of Porphyromonas gingivalis.

In this study, the nucleotide sequences of the prtC genes of six clinical Porphyromonas gingivalis isolates obtained from patients with periodontitis and from reference strain 53977 were determined. All analyzed genes were heterogeneous in their nucleotide composition and differed in up to 13 nucleotides. Moreover, substantial differences were found in comparison to prtC of reference strain 53977. The prtC genes of 45 Porphyromonas gingivalis isolates were amplified by polymerase chain reaction (PCR) and the PCR products were also digested with restriction endonucleases Tsp509I, NlaIII and DraII (PCR-restriction fragment-length polymorphism). Nine different restriction pattern combinations were observed, with four being most frequent (28.9%, 26.7%, 17.8% and 11.1%). The data presented here demonstrates that prtC genes are heterogeneous in their nucleotide sequence and therefore may be used as a target for molecular epidemiological studies. The observed heterogeneity of prtC genes may be a result of microevolution processes.

Bacterial Proteins↗
PubMed2000

Human antibody response during sepsis against targets expressed by methicillin resistant Staphylococcus aureus.

The identification of target structures is a prerequisite for the development of new treatment options, like antibody based therapy, against methicillin resistant Staphylococcus aureus (MRSA). In this study we identified immunodominant structures which were expressed in vivo during sepsis caused by MRSA. Using human sera we compared the immune response of humans with MRSA sepsis with the immune response of normal individuals and asymptomatically colonized individuals. We identified and characterized four staphylococcal specific antigenic structures. One target is a staphylococcal protein of 29 kDa that exhibited 29% identity to secreted protein SceA precursor of Staphylococcus carnosus. The putative function of this protein, which was designated IsaA (immunodominant staphylococcal antigen), is unknown. The second target is an immunodominant protein of 17 kDa that showed no homology to any currently known protein. This immunodominant protein was designated IsaB. The third and fourth antigens are both immunodominant proteins of 10 kDa. One of these proteins showed 100% identity to major cold shock protein CspA of S. aureus and the other protein was identified as the phosphocarrier protein Hpr of S. aureus. The identified immunodominant proteins may serve as potential targets for the development of antibody based therapy against MRSA.

Amino Acid Sequence↗
PubMed2000

A new Shiga toxin 2 variant (Stx2f) from Escherichia coli isolated from pigeons.

We have isolated Shiga toxin (Stx)-producing Escherichia coli (STEC) strains from the feces of feral pigeons which contained a new Stx2 variant gene designated stx(2f). This gene is most similar to sltIIva of patient E. coli O128:B12 isolate H.I.8. Stx2f reacted only weakly with commercial immunoassays. The prevalence of STEC organisms carrying the stx(2f) gene in pigeon droppings was 12.5%. The occurrence of a new Stx2 variant in STEC from pigeons enlarges the pool of Stx2 variants and raises the question whether horizontal gene transfer to E. coli pathogenic to humans may occur.

Alleles↗
PubMed2000

Typing of intimin genes in human and animal enterohemorrhagic and enteropathogenic Escherichia coli: characterization of a new intimin variant.

Enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) produce the characteristic "attaching and effacing" (A/E) lesion of the brush border. Intimin, an outer membrane protein encoded by eae, is responsible for the tight association of both pathogens with the host cell. Several eae have been cloned from different EPEC and EHEC strains isolated from humans and animals. These sequences are conserved in the N-terminal region but highly variable in the last C-terminal 280 amino acids (aa), where the cell binding activity is localized. Based on these considerations, we developed a panel of specific primers to investigate the eae heterogeneity of the variable 3' region by using PCR amplification. We then investigated the distribution of the known intimin types in a large collection of EPEC and EHEC strains isolated from humans and different animal species. The existence of a yet-unknown family of intimin was suspected because several EHEC strains, isolated from human and cattle, did not react with any of the specific primer pairs, although these strains were eae positive when primers amplifying the conserved 5' end were used. We then cloned and sequenced the eae present in one of these strains (EHEC of serotype O103:H2) and subsequently designed a PCR primer that recognizes in a specific manner the variable 3' region of this new intimin type. This intimin, referred to as "epsilon," was present in human and bovine EHEC strains of serogroups O8, O11, O45, O103, O121, and O165. Intimin epsilon is the largest intimin cloned to date (948 aa) and shares the greatest overall sequence identity with intimin beta, although analysis of the last C-terminal 280 aa suggests a greater similarity with intimins alpha and gamma.

Adhesins, Bacterial↗
PubMed2000

Characterization of a shiga toxin 2e-converting bacteriophage from an Escherichia coli strain of human origin.

An infectious Shiga toxin (Stx) 2e-converting bacteriophage (phiP27) was isolated from Stx2e-producing Escherichia coli ONT:H(-) isolate 2771/97 originating from a patient with diarrhea. The phage could be transduced to E. coli laboratory strain DH5alpha, and we could show that lysogens were able to produce biologically active toxin in a recA-dependent manner. By DNA sequence analysis of a 6,388-bp HindIII restriction fragment of phiP27, we demonstrated that the stx(2e) gene was located directly downstream of ileZ and argO tRNA genes. Although no analogue of an antiterminator Q encoding gene was present on this fragment, a lysis cassette comprising two holin genes which are related to the holin genes of Pseudomonas aeruginosa phage phiCTX and a gene homologous to the endolysin gene gp19 of phage PS3 were detected. The results of our study demonstrated for the first time that Stx2e can be encoded in the genome of an infectious bacteriophage.

Bacterial Toxins↗
PubMed2000

Molecular characteristics and epidemiological significance of Shiga toxin-producing Escherichia coli O26 strains.

Fifty-five Shiga toxin (Stx)-producing Escherichia coli (STEC) O26:H11 and O26:H(-) strains isolated from humans between 1965 and 1999 in Germany and the Czech Republic were investigated for their chromosomal and plasmid characteristics. All motile (n = 23) and nonmotile (n = 32) STEC O26 strains were shown to possess the identical flagellin subunit-encoding gene (fliC). We observed a striking recent shift of the stx genotype from stx(1) to stx(2) among the STEC O26 isolates. While stx(1) was the exclusive genotype identified in our collection until 1994, 94% of the isolates obtained after 1997 possessed stx(2) either alone (71%) or together with stx(1) (23%). Plasmid profiling demonstrated a remarkable heterogeneity with respect to plasmid sizes and combinations. Southern blot analysis of plasmid DNA with probes specific to potential accessory virulence genes revealed considerable additional variability in gene composition and arrangement. Pulsed-field gel electrophoresis (PFGE) differentiated 16 subgroups among the 55 STEC O26 strains. Using these techniques we demonstrate the emergence of a new clonal subgroup characterized by PFGE pattern A and a unique combination of virulence markers including stx(2) and a single, approximately 90-kb plasmid harboring the enterhemorrhagic E. coli hlyA and etp genes. The proportion of PFGE subgroup A strains among STEC O26 isolates rose from 30% in 1996 to more than 50% in 1999. Four clusters of infections with the clonal subgroup A were identified. We conclude that the STEC serogroup O26 is diverse and that pathogenic clonal subgroups can rapidly emerge during short intervals. The extensive genetic diversity of STEC O26 provides a basis for molecular subtyping of this important non-O157 STEC serogroup.

Bacterial Toxins↗
PubMed2000

Enterohemorrhagic Escherichia coli (EHEC) strains of serogroup O118 display three distinctive clonal groups of EHEC pathogens.

A recent case report of a child infected with enterohemorrhagic Escherichia coli (EHEC) of serotype O118:H16 in Bavaria, in association with the isolation of a bovine O118 strain on the same farm (A. Weber, H. Klie, H. Richter, P. Gallien, M. Timm, and K. W. Perlberg, Berl. Muench. Tieraerztl. Wochenschr. 110:211-213, 1997), prompted us to investigate the relationship between bovine and human strains of serogroup O118. A total of 29 human O118 E. coli strains from Europe (21), Canada (4), and Peru (4) were compared by virulence typing and macrorestriction analysis with 7 bovine O118 EHEC strains isolated in Bavaria. Twenty-five of the human strains were characterized as EHEC. By serotyping and determination of the virulence-associated factors Shiga toxin (stx1 stx2 stx2 variants), intimin (eae), and EHEC hemolysin (Hly(EHEC)), three distinctive groups of O118 human pathogens were identified. Most of the strains belonged to serotype O118:H16, displaying the virulence traits Stx1, intimin, Hly(EHEC), and EspP/PssA (group 1). In addition, we identified strains of serotype O118:H12 (Stx2d only; group 2) and of serotype O118:H30 (Stx2 and intimin; group 3). Macrorestriction analysis with BlnI and XbaI revealed that all strains with a single O118 serotype profile (O118:H12, O118:H16, and O118:H30) belonged to one clonal cluster, irrespective of their origin. Group 1 strains clustered in the same clonal group as the bovine O118:H16 strains. Moreover, four pairs of strains of different origins and indistinguishable by all other methods applied were identified as group 1 strains. Our data support the direct transmission of an EHEC O118:H16 strain from a calf to a 2-year-old boy in the above-mentioned case report. Since bovine and human O118:H16 strains represent the same clones, they must be considered zoonotic EHEC pathogens. In contrast, EHEC strains of serotypes O118:H12 and O118:H30 have been isolated only from humans, indicating a reservoir for certain human O118 EHEC strains other than bovines.

Adhesins, Bacterial↗
PubMed2000

Molecular analysis of H antigens reveals that human diarrheagenic Escherichia coli O26 strains that carry the eae gene belong to the H11 clonal complex.

Fifty-seven Escherichia coli O26 strains isolated from patients in six countries were investigated by PCR restriction fragment length polymorphism (RFLP) analysis of the flagellin-encoding (fliC) gene (fliC RFLP analysis). The strains were determined by serotyping to belong to five different H types or were nonmotile. The fliC RFLP analysis revealed only two different patterns among the 57 strains. One fliC RFLP pattern was displayed by 54 strains and was identical to that of E. coli H11 reference strain Su4321-41. The other fliC RFLP pattern was observed for three strains and was identical to that for E. coli H32 reference strain K10. The 54 strains with the H11 fliC RFLP pattern included 22 strains of serotype O26:H11, 23 nonmotile strains, and 9 strains that were initially serotyped as H2, H8, H21, and H32 but that were confirmed to express H11 by repeat serotyping. All 54 strains with the H11 fliC RFLP pattern contained the attaching-and-effacing (eae) gene. The three strains with the H32 fliC RFLP pattern belonged to serotype O26:H32, and all were eae negative. The fliC genes of 14 selected E. coli O26:H11 strains isolated between 1964 and 1999 had identical nucleotide sequences. Our results demonstrate that E. coli O26 strains that carry the eae gene belong exclusively to the H11 clonal complex. Since there were no H11 fliC allelic variations among the O26 strains tested, E. coli O26:H11 may have emerged recently. The fliC PCR-RFLP test is a reliable, easy-to-perform, and rapid method for determination of the H types of E. coli O26 isolates.

Adhesins, Bacterial↗
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↗