Search PubMed⌕ Search

Biomedical subjects

H Karch

Publications and source records attributed to H Karch.

At least 55 records · Page 3Linked to original sources
PubMed2000

Lyme arthritis in children and adolescents: outcome 12 months after initiation of antibiotic therapy.

OBJECTIVE: Lyme arthritis in children and adolescents due to infection with Borrelia burgdorferi responds well to intravenous and oral antibiotics, but nonresponders have been described with all antibiotic regimens tested and a standard therapy has not yet been established. We examined causes of the failure of antibiotic treatment in the presence of persistent organisms and autoimmune mechanisms. METHODS: A prospective multicenter study was carried out in 55 children and adolescents with Lyme arthritis. RESULTS: There were significant differences between younger and older patients with pediatric Lyme arthritis. Younger patients were more likely to have fever at the onset of arthritis and to have acute or episodic arthritis. Older patients were more likely to have chronic arthritis, higher levels of IgG antibodies to B. burgdorferi (by ELISA and immunoblot), and a longer interval between antibiotic treatment and the disappearance of arthritis. Of 51 patients followed for at least 12 months after initiation of antibiotic treatment, 24% retained manifestations of the disease including arthritis (8 patients) and arthralgias (4 patients). These patients were predominantly female (9/12) and were significantly older than patients without residual symptoms. Patients who had received intraarticular steroids prior to antibiotic treatment required significantly more courses of antibiotic treatment and the time required for disappearance of the arthritis was longer. CONCLUSION: Pediatric Lyme arthritis is more benign in younger children. Lyme arthritis should be excluded as a possible cause of arthritis prior to the administration of intraarticular steroids.

Acute Disease↗
PubMed1999

Evolution of bacterial pathogenesis.

The evolution of bacteria is associated with continuous generation of novel genetic variants. The major driving forces in this process are point mutations, genetic rearrangements, and horizontal gene transfer. A large number of human and animal bacterial pathogens have evolved the capacity to produce virulence factors that are directly involved in infection and disease. Additionally, many bacteria express resistance traits against antibiotics. Both virulence factors and resistance determinants are subject to intrastrain genetic and phenotypic variation. They are often encoded on unstable DNA regions. Thus, they can be readily transferred to bacteria of the same species or even to non-related prokaryotes. This review article focuses on the main mechanisms of bacterial microevolution responsible for the rapid emergence of variants with novel virulence and resistance properties. In addition, processes of macroevolution are described with special emphasis on gene transfer and fixation of adaptive mutations in the genome of pathogens.

Animals↗
PubMed1999

The ClpB protein from Campylobacter jejuni: molecular characterization of the encoding gene and antigenicity of the recombinant protein.

The ClpB heat-shock protein is necessary for the survival of Escherichia coli cells upon sudden increase of temperature. Using a PCR-based genomic walking method, the nucleotide sequence of a clpB homolog from Campylobacter jejuni was determined. The clpB gene encodes a protein of 857 amino acid (aa) residues, with a predicted molecular mass of 95.3kDa. Alignment of the deduced aa sequence with other known bacterial ClpB proteins revealed overall identity from 47% (E. coli) to 61% (Helicobacter pylori). Within the clpB promoter region, as indicated by primer extension analysis, we identified a sequence identical to the E. coli sigma70 consensus promoter. Northern blot analysis confirmed that clpB is heat-inducible in C. jejuni. The ClpB protein, fused to a 6xHis tag, was synthesized in E. coli and purified by metal-affinity and size exclusion chromatography. In ELISA studies, IgA levels reactive to recombinant ClpB were significantly higher in sera of patients with prior C. jejuni infections than in sera obtained from healthy control persons.

Amino Acid Sequence↗
PubMed1999

Shiga toxins even when different are encoded at identical positions in the genomes of related temperate bacteriophages.

The nucleotide sequence of an 11,142-bp region including the stx2 operon in the genome of the temperate bacteriophage 933W in the EDL933 strain of Escherichia coli O157 was determined and compared to the respective regions derived from other lambdoid bacteriophages. In phage 933W, a region of ORFs interlinked by overlapping start-stop codons (ATGA) was detected preceding the toxin gene. These ORFs show a high degree of sequence identity to genes of the nin region of phage lambda. Immediately downstream of these nin genes we identified an ORF that may code for an anti-terminator similar to the lambda Q protein. It is concluded that toxin expression is directly associated with the initiation of cell lysis. Downstream of the stx2 operon we identified an ORF that is homologous to the holin gene S of bacteriophage PA-2. PCR primers were designed, which, based on a comparison of the phage sequences, appeared to be common to both stx1- and stx2-harbouring phages. However, only seven of the 22 STEC strains investigated from serogroups O157, O26, O103 and O111 yielded the expected PCR amplification product. The data reported here may be useful in developing new strategies for inhibiting the expression of Stx and for developing universal diagnostic primers for use in tracking the origin and evolution of Shiga toxins and the phages that carry them.

Amino Acid Sequence↗
PubMed1999

Incidence of Lyme borreliosis in the Würzburg region of Germany.

To assess the incidence of Lyme borreliosis in Central Europe, a 12-month, prospective, population-based surveillance study of Lyme borreliosis was conducted in the Wurzburg region of central Germany, following an aggressive awareness campaign. The diagnosis of Lyme borreliosis required the presence of (i) erythema migrans (diameter > or =5 cm); (ii) lymphocytoma; or (iii) another specific manifestation including Lyme arthritis, neuroborreliosis, carditis or acrodermatitis chronica atrophicans in conjunction with serological confirmation. A total of 313 cases of Lyme borreliosis was diagnosed, giving an incidence of 111 cases/100000 inhabitants, the highest rates occurring in children and elderly adults living in wooded as opposed to agricultural areas. The incidence in city dwellers and inhabitants of rural areas was not significantly different. Erythema migrans was the only manifestation in 279 (89%) patients. Of the 34 patients with manifestations other than erythema migrans alone, 15 had arthritis, nine neuroborreliosis, six lymphocytoma, four acrodermatitis chronica atrophicans and one carditis. Children were more likely than adults to have manifestations other than erythema migrans alone. Lyme borreliosis was very common in central Germany, and one of the most frequent bacterial infections. The observation of more cases of arthritis than neuroborreliosis was similar to that in the USA. These results may be representative for many parts of central Europe and suggest the need for development of a vaccine against borreliosis caused by European strains of Borrelia species.

Adolescent↗
PubMed1999

Epidemiology and diagnosis of Shiga toxin-producing Escherichia coli infections.

Shiga toxin-producing Escherichia coli (STEC) have been identified as a worldwide cause of serious human gastrointestinal disease and the life-threatening hemolytic uremic syndrome. The most common serotype implicated is E. coli O157: H7, but infections involving various non-O157 serotypes have been found with increasing frequency in many countries. Food-borne outbreaks caused by STEC can affect large numbers of people and cause serious morbidity, making the bacteria one of the most important emerging pathogens. Because there is no specific treatment of the disease currently available, there is an urgent need for effective preventive measures based on a detailed understanding of the epidemiology of STEC infections. Such measures will also be dependent on the availability of rapid, sensitive, and simple procedures for the detection of the pathogens both in human samples and in samples of nonhuman origin such as food. This review summarizes the current knowledge on the epidemiology of STEC infection and presents a survey of laboratory methods currently available for diagnosis of STEC. Special attention is given to new diagnostic procedures for the less readily detectable non-O157 STEC strains and to simple procedures, usually based on commercially available kits, that can be used in routine clinical microbiological laboratories.

Adult↗
PubMed1999

Protective effect of serum antibodies against a 110-kilodalton protein of Actinobacillus actinomycetemcomitans following periodontal therapy.

Thirty-four adult patients with untreated periodontitis were randomly assigned to receive full mouth scaling alone or scaling with an adjunctive antimicrobial therapy, both followed by supportive periodontal therapy. At 24 months, specific serum immunoglobulin A (IgA), IgG and IgG subclass antibody reactivities against a 110-kDa protein of Actinobacillus actinomycetemcomitans were assessed by Western blot. In patients harboring A. actinomycetemcomitans intraorally, the IgG4 antibody reactivity against the 110-kDa protein of A. actinomycetemcomitans was associated with significantly increased survival rates of teeth and of sites not exhibiting 2 mm or more of probing attachment loss. The same trend was found for IgG3 and IgG2 antibody reactivities, but it was statistically insignificant. No association with clinical treatment outcome was observed for IgA, IgG and IgG1 antibody reactivities. The results indicated that systemic IgG4 antibody reactivity against the 110-kDa protein of A. actinomycetemcomitans may have a protective effect against periodontal disease progression in patients harboring A. actinomycetemcomitans and receiving periodontal therapy.

Adult↗
PubMed1999

Efficacy and potential clinical applications of Pentaglobin, an IgM-enriched immunoglobulin concentrate suitable for intravenous infusion.

OBJECTIVE: Characterisation of the antibodies against important human pathogens in two immunoglobulin preparations: Intraglobin F and IgM-enriched Pentaglobin. DESIGN: In vitro assay of antibody titre using bacterial outer-membrane proteins, lipopolysaccharides (LPS), and exotoxins of clinically relevant bacteria. METHODS: Antibody reactivities measured by ELISA and immunoblot techniques against antigens from bacteria that cause sepsis, antibiotic-resistant nosocomial pathogens, and enteric pathogens. RESULTS: IgG anti-LPS reactivity was present in both study drugs. Specific IgM antibodies against LPS of gram-negative bacteria that cause sepsis were also detected in the IgM-enriched Pentaglobin. IgG-reactivity against gram-positive multiresistant strains of Staphylococcus aureus (S. aureus) were detectable in both preparations. IgG and IgM antibodies present against Yersinia outer proteins and Campylobacter jejuni (C. jejuni) outer membrane proteins were detected in Pentaglobin. Both preparations reacted against alpha toxin of S. aureus and streptolysin of Streptococcus pyogenes. Pentaglobin showed a strong IgM-reactivity against alpha-haemolysin. CONCLUSION: Our data suggest that infusion of well characterised immunoglobulin preparations might be beneficial for patients with severe infections. This is highly relevant in view of the high pathogenicity of bacteria that cause infections in patients in hospital and the continually increasing antibiotic resistance (particularly methicillin-resistant S. aureus).

Antibodies, Bacterial↗
PubMed1999

Non-O157:H7 pathogenic Shiga toxin-producing Escherichia coli: phenotypic and genetic profiling of virulence traits and evidence for clonality.

The virulence profiles of most non-O157 Shiga toxin (Stx)-producing Escherichia coli (STEC) are unknown. STEC belonging to serogroups O26, O103, and O111 were characterized to determine clonality and to profile virulence traits. Isolates within STEC serogroups O26, O111, and O103 were >80% identical in their randomly amplified polymorphic DNA pattern, suggesting clonality in these serogroups. The serogroups were distantly related to each other and to E. coli O157:H7. stx restriction fragment length polymorphism differentiated some STEC with the same randomly amplified polymorphic DNA pattern. The hemolytic phenotype of STEC O103:H2 isolates resembled that of alpha- and not enterohemorrhagic E. coli hemolysin. Virulence gene (eae, E-hly, espP, etp, katP, stx) probing demonstrated serogroup-specific profiles. Pathogenic STEC O26, O103, and O111 belong to their own lineages and have unique profiles of virulence traits that are different from the virulence profile of E. coli O157:H7.

Bacterial Toxins↗
PubMed1999

A large outbreak of hemolytic uremic syndrome caused by an unusual sorbitol-fermenting strain of Escherichia coli O157:H-.

Escherichia coli O157:H7 does not ferment sorbitol, a factor used to differentiate it from other E. coli. From December 1995 to March 1996, 28 children with hemolytic uremic syndrome in Bavaria, Germany, were identified; many had a sorbitol-fermenting (sf) E. coli O157:H- cultured. A case-control study showed a dose-response relationship between sausage consumption and illness. A second case-control study showed a relationship between mortadella and teewurst consumption and illness, particularly during December (mortadella odds ratio [OR], 10.5, P=.004; teewurst OR, 6.2, P=.02). Twelve sf O157:H- were characterized to determine clonality and virulence traits. The strains possessed the Stx2, eae, and EHEC-hlyA genes but were nonhemolytic on blood agar plates. The O157:H- isolates belonged to phage type 88 and had identical pulsed-field gel electrophoresis patterns. This outbreak was caused by sf E. coli O157:H-, which is not detectable by culture on sorbitol MacConkey's agar. Consumption of two sausages, including a raw beef-containing sausage, was statistically related to illness.

Case-Control Studies↗
PubMed1999

Bovine colostrum ameliorates diarrhea in infection with diarrheagenic Escherichia coli, shiga toxin-producing E. Coli, and E. coli expressing intimin and hemolysin.

BACKGROUND: Diarrheagenic Escherichia coli may cause serious extraintestinal complications, but there is no specific treatment. METHODS: Patients with diarrhea caused by diarrheagenic E. coli, specifically Shiga toxin-producing E. coli and E. coli-expressing intimin and enterohemorrhagic E. coli-hemolysin were treated by administration of pooled bovine colostrum, rich in antibodies to Shiga toxin and enterohemorrhagic E. coli-hemolysin, in a placebo-controlled, double-blind study. Symptom resolution and fecal excretion of infecting strains were assessed. RESULTS: No side effects were attributable to colostrum. Stool frequencies in the group treated with bovine colostrum were significantly reduced compared with those in the placebo group. No effect of therapy on the carriage of the pathogens or on complications of the infection could be demonstrated. CONCLUSIONS: Bovine colostrum is well tolerated and diminishes frequency of loose stools in children with E. coli-associated diarrhea. A prospective study should be conducted among a larger number of children with Shiga toxin-producing E. coli identified early in illness, to determine the effectiveness of colostrum therapy.

Adhesins, Bacterial↗
PubMed1999

Molecular characterisation of verocytotoxin-producing Escherichia coli of serogroup O111 from different countries.

A collection of epidemiologically unrelated verocytotoxin (VT)-producing Escherichia coli (VTEC) strains of serogroup O111 isolated from human patients and cattle with diarrhoeal disease in five different countries were characterised by determination of their VT genotypes, the presence of other virulence factors such as the intimin-coding eae gene and the enterohaemorrhagic E. coli (EHEC) plasmid, and their antibiotic susceptibility patterns. The genetic relatedness among isolates was evaluated by genomic DNA fingerprinting techniques such as restriction fragment length polymorphism analysis of ribosomal RNA genes (ribotyping) and pulsed-field gel electrophoresis. The results indicated that the VTEC O111 examined belong to two distinct clonal lineages. The first group was constituted mainly of non-motile, eae-positive, EHEC plasmid-positive isolates from both man and cattle. The second lineage was represented by an O111:H2 epidemic strain, isolated during an outbreak of haemolytic uraemic syndrome in France and exhibiting an unusual combination of virulence factors: VT production and aggregative adhesion to HEp-2 cells associated with an enteroaggregative E. coli (EAEC) plasmid.

Adhesins, Bacterial↗
PubMed1999

Interleukin-1 haplotype and periodontal disease progression following therapy.

The purpose of this study was to assess the prognostic value of the IL-1 haplotype on the progression of periodontal disease following therapy. 48 adult patients with untreated periodontitis harboring Actinobacillus actinomycetemcomitans and/or Porphyromonas gingivalis were randomly assigned to receive full-mouth scaling alone (control) or in combination with systemic metronidazole plus amoxicillin and supragingival irrigation with chlorhexidine digluconate (test). All patients received supportive periodontal therapy at 3 to 6 months intervals. In 33 patients, lymphocyte DNA was analyzed for polymorphism in the IL-1A gene at position -889 and IL-1B gene at position +3953. Overall, 16 of 33 patients (7 of 17 test and 9 of 16 control) carried the IL-1 haplotype. 2 years following initial periodontal therapy, no differences in the survival rates of sites or teeth not exhibiting probing attachment loss of 2 mm or more compared to baseline, were found between patients who tested positive (85% sites, 53% teeth) and patients who tested negative (89% sites, 56% teeth) for the IL-1 haplotype. The results indicated that the IL-1 haplotype may be of limited value for the prognosis of periodontal disease progression following non-surgical periodontal therapy.

Adult↗
PubMed1999

Transduction of enteric Escherichia coli isolates with a derivative of Shiga toxin 2-encoding bacteriophage phi3538 isolated from Escherichia coli O157:H7.

We investigated the ability of a detoxified derivative of a Shiga toxin 2 (Stx2)-encoding bacteriophage to infect and lysogenize enteric Escherichia coli strains and to develop infectious progeny from such lysogenized strains. The stx(2) gene of the patient E. coli O157:H7 isolate 3538/95 was replaced by the chloramphenicol acetyltransferase (cat) gene from plasmid pACYC184. Phage phi3538(Deltastx(2)::cat) was isolated after induction of E. coli O157:H7 strain 3538/95 with mitomycin. A variety of strains of enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), Stx-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC), and E. coli from the physiological stool microflora were infected with phi3538(Deltastx(2)::cat), and plaque formation and lysogenic conversion of wild-type E. coli strains were investigated. With the exception of one EIEC strain, none of the E. coli strains supported the formation of plaques when used as indicators for phi3538(Deltastx(2)::cat). However, 2 of 11 EPEC, 11 of 25 STEC, 2 of 7 EAEC, 1 of 3 EIEC, and 1 of 6 E. coli isolates from the stool microflora of healthy individuals integrated the phage in their chromosomes and expressed resistance to chloramphenicol. Following induction with mitomycin, these lysogenic strains released infectious particles of phi3538(Deltastx(2)::cat) that formed plaques on a lawn of E. coli laboratory strain C600. The results of our study demonstrate that phi3538(Deltastx(2)::cat) was able to infect and lysogenize particular enteric strains of pathogenic and nonpathogenic E. coli and that the lysogens produced infectious phage progeny. Stx-encoding bacteriophages are able to spread stx genes among enteric E. coli strains.

Bacterial Toxins↗
PubMed1999

A genomic island, termed high-pathogenicity island, is present in certain non-O157 Shiga toxin-producing Escherichia coli clonal lineages.

Shiga toxin-producing Escherichia coli (STEC) strains cause a wide spectrum of diseases in humans. In this study, we tested 206 STEC strains isolated from patients for potential virulence genes including stx, eae, and enterohemorrhagic E. coli hly. In addition, all strains were examined for the presence of another genetic element, the high-pathogenicity island (HPI). The HPI was first described in pathogenic Yersinia species and encodes the pesticin receptor FyuA and the siderophore yersiniabactin. The HPI was found in the genome of distinct clonal lineages of STEC, including all 31 eae-positive O26:H11/H(-) strains and 7 of 12 eae-negative O128:H2/H(-) strains. In total, the HPI was found in 56 (27.2%) of 206 STEC strains. However, it was absent from the genome of all 37 O157:H7/H(-), 14 O111:H(-), 13 O103:H2, and 13 O145:H(-) STEC isolates, all of which were positive for eae. Polypeptides encoded by the fyuA gene located on the HPI could be detected by using immunoblot analysis in most of the HPI-positive STEC strains, suggesting the presence of a functional yersiniabactin system. The HPI in STEC was located next to the tRNA gene asnT. In contrast to the HPI of other pathogenic enterobacteria, the HPI of O26 STEC strains shows a deletion at its left junction, leading to a truncated integrase gene int. We conclude from this study that the Yersinia HPI is disseminated among certain clonal subgroups of STEC strains. The hypothesis that the HPI in STEC contributes to the fitness of the strains in certain ecological niches rather than to their pathogenic potential is discussed.

Amino Acid Sequence↗
PubMed1999

Cloning and expression of the dnaK gene of Campylobacter jejuni and antigenicity of heat shock protein 70.

Campylobacter jejuni is a leading cause of infectious diarrhea throughout the world. In addition, there is growing evidence that Guillain-Barré syndrome, an inflammatory demyelinating disease of the peripheral nervous system, is frequently preceded by C. jejuni infection. In the present study, the hrcA-grpE-dnaK gene cluster of C. jejuni was cloned and sequenced. The dnaK gene consists of an open reading frame of 1,869 bp and encodes a protein with a high degree of homology to other bacterial 70-kDa heat shock proteins (HSPs). The overall percentages of identity to the HSP70 proteins of Helicobacter pylori, Borrelia burgdorferi, Chlamydia trachomatis, and Bacillus subtilis were calculated to be 78.1, 60.5, 57.2, and 53. 8%, respectively. Regions similar to the Escherichia coli sigma70 promoter consensus sequence and to a cis-acting regulatory element (CIRCE) are located upstream of the hrcA gene. Following heat shock, a rapid increase of dnaK mRNA was detectable, which reached its maximum after 20 to 30 min. A 6-His-tagged recombinant DnaK protein (rCjDnaK-His) was generated in E. coli, after cloning of the dnaK coding region into pET-22b(+), and purified by affinity and gel filtration chromatography. Antibody responses to rCjDnaK-His were significantly elevated, compared to those of healthy individuals, in about one-third of the serum specimens obtained from C. jejuni enteritis patients.

Amino Acid Sequence↗
PubMed1999

Escherichia coli O157:H7 and O157:H(-) strains that do not produce Shiga toxin: phenotypic and genetic characterization of isolates associated with diarrhea and hemolytic-uremic syndrome.

We have isolated one sorbitol-nonfermenting (SNF) Escherichia coli O157:H7 isolate and five sorbitol-fermenting (SF) E. coli O157:H(-) isolates that do not contain Shiga toxin (Stx) genes (stx). Isolates originated from patients with diarrhea (n = 4) and hemolytic-uremic syndrome (HUS) (n = 2). All isolates harbored a chromosomal eae gene encoding gamma-intimin as well as the plasmid genes E-hly and etp. The E. coli O157:H7 isolate was katP and espP positive. Respective sera obtained from the patient with HUS contained antibodies to the O157 lipopolysaccharide antigen. The stx-negative E. coli O157:H7 isolate is genetically related to stx-positive SNF E. coli O157:H7. All stx-negative SF E. coli O157:H(-) isolates belong to the same genetic cluster and are closely related to stx-positive SF E. coli O157:H(-) isolates. Our data indicate that stx-negative E. coli O157:H7/H(-) variants may occur at a low frequency and cannot be recognized by diagnostic methods that target Stx.

Antibodies, Bacterial↗