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Biomedical subjects

H Karch

Publications and source records attributed to H Karch.

At least 163 records · Page 9Linked to original sources
PubMed1992

DNA fingerprinting of Escherichia coli O157:H7 strains by pulsed-field gel electrophoresis.

Pulsed-field gel electrophoresis of genomic DNA was carried out on Escherichia coli O157:H7 strains from different geographic locations to determine its value in an epidemiological survey of O157 infections. Pulsed-field gel electrophoresis of XbaI-digested DNA fragments clearly separated E. coli O157:H7 strains from nontoxigenic E. coli O157:H19, O157:H43, and O157:H45 strains and from Shiga-like-toxin-producing E. coli strains of other serogroups. However, among the E. coli O157:H7 strains, the restriction patterns either were identical or differed only by a few fragment bands. In some cases, it was therefore impossible to distinguish among epidemiologically unrelated strains. Hybridization experiments with a DNA probe complementary to Shiga-like toxin II sequences revealed that the Shiga-like toxin II genes were located on DNA fragments of different lengths. Our data show that for a single highly conserved clone, such as E. coli O157:H7, other typing techniques may need to be performed in addition to DNA fingerprinting in epidemiological surveys.

Bacterial Toxins↗
PubMed1992

Screening of blood donors and recipients for Borrelia burgdorferi antibodies: no evidence of B. burgdorferi infection transmitted by transfusion.

In the study presented here, the prevalence of antibodies against Borrelia burgdorferi, the etiologic agent of Lyme borreliosis, was determined in a group of blood donors from the Würzburg area (Southern Germany). 13 of 472 donors (2.7%) tested were positive by immunoblotting (IB). These 13 donors were examined in more detail by physical examination, anamnesis and determination of inflammation parameters of the blood. All persons were asymptomatic for Lyme borreliosis. One of 5 who remembered a tick bite actually had suffered from an erythema chronicum migrans 5 years ago. Another one had been affected by fever, headaches and pain in the limbs, arthralgia and motoric disorder in both hands 6 months before examination. Analysis of the blood did not provide any evidence of an acute infection. Moreover, each of the 472 serum samples was analyzed by a hemagglutination test (HAT). 26 (5.5%) showed a positive test result. In order to investigate whether a seroconversion of the recipients by transfusion of B. burgdorferi antibody-positive blood had taken place, 9 recipients of blood products originating from the 13 IB-positive donors were serologically reexamined. All samples taken proved to be antibody-negative. Consequently, the transfusion did not produce any seroconversion in the patients thus treated.

Antibodies, Bacterial↗
PubMed1992

[Infections with Borrelia burgdorferi in Würzburg blood donors: antibody prevalence, clinical aspects and pathogen detection in antibody positive donors].

The prevalence of antibodies against Borrelia burgdorferi, the etiologic agent of Lyme borreliosis, was determined in a group of blood donors from the Würzburg area (Southern Germany). 26 of 472 donors (5.5%) tested positive in a hemagglutination test. When performing immunoblots only 13 donors (2.7%) gave rise to B. burgdorferi-specific antibodies. 9 of them were examined in more detail by anamnesis, physical examination, determination of inflammation parameters of the blood and polymerase chain reaction (PCR) analysis of urine. All persons were asymptomatic for Lyme borreliosis. One of 4, who remembered a tick bite, actually had suffered from an erythema migrans 5 years ago. Another one had been affected by fever, headaches and pains in the limbs, arthralgia and motoric disorder in both hands 6 months before examination. Analysis of the blood did not provide any evidence of an acute infection. In the urine of 2 donors we detected B. burgdorferi-specific DNA by PCR. No seroconversion due to blood transfusion could be observed, when 9 recipients of blood products provided by the 13 seropositive donors were serologically reexamined. PCR analysis of urine samples of 5 recipients was also negative.

Antibodies, Bacterial↗
PubMed1992

[The role of antibiotics in the management of verotoxin-associated hemolytic anemia syndromes].

Significant improvements of dialysis techniques and the supportive treatment of the hemolytic uremic syndrome (HUS) during the last three decades do not veil the fact that causal therapy is not yet feasible. This holds true for the classic HUS associated with infections by verotoxin-(VT-)producing E.coli (VTEC) as for the majority of the much less frequent "atypical" forms. The influence of antimicrobial agents on production of verotoxins produced by clinical VTEC isolates was examined. Co-trimoxazole significantly increased the total yield of toxin. In contrast, ciprofloxacin, lincomycin and gentamicin caused significant reduction in toxin yields. The pathogenetic and therapeutic relevance of this finding is not yet known. Analysis of the clinical literature for the postulated relation between antibiotic treatment and development of HUS or its impact on the severity of the disease reveals a controversial picture. Based on the dynamics of the disease, the in vitro findings, and reports on unfavourable outcomes after treatment, it is concluded that antibiotics are not indicated in most cases of the enteropathic HUS or other VTEC infections. Antibiotic prophylaxis has neither been proven to be efficacious nor safe for the prevention of secondary cases during VTEC outbreaks. Apart from the implementations of hygienic measures, prospective studies on the role of antibiotics seem clearly warranted. Possible future strategies may include the design of immunological therapeutic concepts.

Anti-Bacterial Agents↗
PubMed1991

High incidence of serum antibodies to Escherichia coli O157 lipopolysaccharide in children with hemolytic-uremic syndrome.

Because the classic hemolytic-uremic syndrome has been etiologically linked to intestinal infections by Escherichia coli O157 and other verotoxin-producing E. coli (VTEC), we examined 22 consecutive children with acute hemolytic-uremic syndrome for the presence of VTEC, using microbiologic methods, and for a specific immune response to O157 lipopolysaccharide in acute-phase and follow-up sera, using the indirect hemagglutination assay and the immunoblot procedure. Of 22 children with enteropathic hemolytic-uremic syndrome, 15 (68%) had evidence of VTEC infection by culture of the pathogen or detection of free verotoxin in the feces, or both. Significantly elevated titers of short-lived agglutinins and IgM class antibodies against the O157 lipopolysaccharide were found in 20 (91%) of 22 patients, but not in two of three patients with non-O157 E. coli isolates or in healthy children or children with diarrhea caused by other enteric pathogens (p less than 0.01). The combined microbiologic and serologic procedures provided evidence for VTEC infection in all 22 patients. The high incidence of anti-O157 lipopolysaccharide antibodies in these patients indicates the predominance and the pathogenic potential of this serogroup. Both serologic techniques proved to be valuable tools to further characterize this form of hemolytic-uremic syndrome. Future studies on the induction of protective immunity seem warranted.

Antibodies, Anti-Idiotypic↗
PubMed1991

Clinical and genetic aspects of Shiga-like toxin production in traditional enteropathogenic Escherichia coli.

Cell culture tests, DNA colony blot hybridization and polymerase chain reaction were used to examine classical enteropathogenic Escherichia coli (EPEC) for the presence of Shiga-like toxin (SLT). Fifteen of 155 strains from West Germany, originally identified as EPEC on the basis of serotyping, were shown to harbor either SLT-I or SLT-II genes. All strains that hybridized with the 20-base oligonucleotide probes which are complementary to slt-IA or slt-IIA sequences derived from the genomic DNA of enterohemorrhagic E. coli O157:H7 strain 933 produced moderate or high levels of cytotoxin in Vero and HeLa cell assays. Four additional strains of low to moderate cytotoxicity did not hybridize with either probe. Five different serogroups producing SLTs were identified: O26, O55, O111, O119 and O128. All three SLT-positive E. coli O26:H11 and four of five E. coli O111:H- isolates hybridized with a 3.4 kilobase fragment (CVD 419 probe) derived from the 60-megadalton plasmid of EHEC O157:H7. Seven of the 15 SLT-gene positive strains were associated with bloody diarrhea, six isolates were from patients with hemolytic uremic syndrome (HUS). Based on their clinical, epidemiological, pathogenic and genetic features SLT-producing E. coli among classical EPEC mimic enterohemorrhagic E. coli O157:H7 and might be considered as EHEC.

Adult↗
PubMed1991

[Microbiologic findings in protracted and chronic enterocolitis].

Novel diagnostic methods (immunoblotting, immunofluorescence test) have been proved to be very sensitive and specific for detecting enteropathogenic bacilli. 28 patients with chronic enterocolitis were investigated. In 50% (14/28) of these patients Yersinia enterocolitica could be visualized in biopsies by immunofluorescence. The serum of 8 patients also contained IgA-antibodies against plasmid encoded released proteins of Y. enterocolitica. This paper reports evidence for persistence of Yersinia bacilli in a group of patients with chronic enterocolitis. Further studies must show, if these results may have therapeutic implications.

Adolescent↗
PubMed1991

[Lyme arthritis in childhood: monarthritis of the knee joint, clinically indistinguishable from monarthritis of unknown origin].

Four children with monarthritis of the knee had no further manifestations of Lyme borreliosis, but a positive antibody titer against Borrelia burgdorferi as measured by Elisa. About 3 years after antibiotic therapy none of the children had arthritis, but one suffered from fibromyalgia and another child had still a vigorous reactivity against Borrelia burgdorferi antigens by Elisa and immunoblot. In this study 4 out of 20 children with recently recognized arthritis had Lyme arthritis which makes it a rather frequent disease. The clinical presentation could not distinguish these 4 children from 4 other children with monarthritis of the knee of unknown origin. In the absence of better diagnostic criteria, the association of monarthritis, not otherwise explained, with a positive Lyme serology seems to be sufficient evidence to establish a diagnosis of Lyme arthritis. After confirmation of the diagnosis children should be treated without delay.

Antibodies, Bacterial↗
PubMed1990

[Hemolytic-uremic syndrome in infants due to verotoxin-producing Escherichia coli].

Between September and November 1988, six children (aged 4-17 months) from a parish in Upper Bavaria fell ill with a haemolytic-uraemic syndrome. The illness had been preceded by a gastroenteritis with at times haemorrhagic stools. All patients needed peritoneal dialysis for acute renal failure. A 12-month-old girl was left with statomotoric developmental impairment due to cerebral involvement, but the other five children were cured. In the first four children to be admitted stool examinations for the common enteritis-causing microorganisms had been negative. But in the following two, specific gene probes demonstrated enterohaemorrhagic E. coli O157: H- with formation of verotoxin 2 (Shiga-like toxin II). This group of microorganisms must be taken into account in the diagnosis of haemorrhagic enterocolitis, because they can cause severe complications.

Bacterial Toxins↗
PubMed1990

[Morphologic changes in the intestine of swine after infection with verotoxin-producing Escherichia coli].

Spontaneous morphologic lesions are described in 12 of 66 pigs submitted for necropsy. All 12 pigs were culture positive for Verotoxin-producing E. coli (VTEC). 10 of them were weaned pigs, one a suckling piglet and one a fattening hog. In 6 cases E. coli serovar 0139:H1 and in one case each the serovars 0139:H40; 0138:H-; 0125ac:H27 and 0154:H- were isolated. From the fecal samples of 2 animals E. coli ONT (O-group non typable):H- were cultured. Macroscopically there were cyanosis, edema of the eye lids, catarrhal enteritis and/or colitis as well as edema of the mesentery, swelling of the mesenteric lymph nodes and congestion of the lung to varying degrees. Histopathologic examination of 5 animals was carried out. In 3 animals atrophy and edema of the villi in the jejunum and ileum were discovered. In one animal an additional infection with corona virus was confirmed electron microscopically. Furthermore there was disseminated necrosis of lymphocytes in Peyer's patches of the small intestine and in secondary follicles of the mesenteric lymph nodes. In one of the animals a hemorrhagic-necrotising ileitis, occurred characterized by necrosis of villi and thrombosis of blood vessels in the mucosa. The highest number of VTEC with seven out of twelve animals was found in weaned pigs in association with the E. coli serovar 0139.

Animals↗
PubMed1989

Synthetic oligodeoxyribonucleotide probes to detect verocytotoxin-producing Escherichia coli in diseased pigs.

Oligonucleotide probes constructed from the sequences published for Shiga-like toxin I (SLT-I) and Shiga-like toxin II (SLT-II) genes and antibody against the purified toxins were used to study the SLT (SLT-IIp) produced by porcine E. coli O138 and O139 strains. By DNA hybridization assays no homology was observed between SLT-I and SLT-IIp. By contrast the oligonucleotide probe derived from the slt-II A gene detected porcine strains of E. coli producing SLT-IIp and E. coli strains associated with human disease producing SLT-II. Homology of nucleotide sequences between SLT-IIp and SLT-II is reflected by serological cross-reactivity as demonstrated by a dot blot ELISA and neutralization of SLT-IIp with anti-SLT-II. The toxins were distinguishable in their ability to kill HeLa S-3 cells. The oligonucleotide probe and anti-SLT-II can facilitate identification of SLT-IIp producing E. coli to further clarify their role in diseased pigs.

Animals↗
PubMed1989

Genes coding for Shiga-like toxin and heat-stabile enterotoxin in porcine strains of Escherichia coli.

Besides diarrheagenic enterotoxigenic Escherichia coli (ETEC) that produce classical heat stable and/or heat labile enterotoxins (STs, LTs) and the class of Shiga-like toxin-producing entero-hemorrhagic E. coli (EHEC), a new category of E. coli is defined sharing similarities with ETEC and EHEC. DNA hybridization studies indicate that some E. coli serovars from porcine origin harbor genes encoding cytotonic ST and cytotoxic Shiga-like toxin. The presence of two potent toxins might contribute to the virulence of such strains and should be taken into consideration when bio-assays are performed.

Animals↗
PubMed1989

Single primer pair for amplifying segments of distinct Shiga-like-toxin genes by polymerase chain reaction.

By using a single synthetic oligonucleotide primer pair in the polymerase chain reaction, we amplified specific Shiga-like-toxin (SLT) gene segments from DNAs of 20 clinical Escherichia coli isolates, irrespective of whether they produce SLT-I, SLT-II, or heretofore uncategorized SLTs. These segments were not detectable in any of 20 nontoxigenic E. coli strains. The primers deduced from a conserved region among SLT genes are so-called degenerate-sequence primers; i.e., they contain intentionally introduced sequence ambiguities to overcome minor sequence variations within different SLT genes. In direct gel hybridization with genomic DNA, both primers recognized SLT-I and SLT-II DNA sequences. Amplified sequences of target DNA obtained by polymerase chain reaction were visualized after gel electrophoresis by ethidium bromide staining, and definitive identification of the amplification product as an SLT gene segment was achieved by hybridization to SLT-I- and SLT-II-specific 20-base oligonucleotide probes complementary to a portion of the amplified sequences but not to the primers. The detecting oligonucleotide probes shared only 30% base homology and were shown to recognize specifically SLT-I or SLT-II sequences within genomic DNA. Moreover, they were used to distinguish whether the amplified sequence originated from SLT-I or SLT-II genes. The PCR system with the primers described here is a powerful technique to amplify SLT sequences in E. coli strains that produce serologically distinct SLTs and will facilitate identification of these pathogens, particularly among a multitude of nonpathogenic E. coli strains.

Animals↗
PubMed1989

Evaluation of oligonucleotide probes for identification of shiga-like-toxin-producing Escherichia coli.

Four synthetic oligonucleotide probes representing different regions of the Shiga-like toxin I (SLT-I) structural genes and one oligonucleotide derived from the SLT-II gene of Escherichia coli serotype O157:H7 strain 933 were examined for the identification of E. coli strains that produce cytotoxins for Vero or HeLa cells. E. coli strains that synthesize SLT-I alone or O157:H7 isolates that coexpress SLT-I and SLT-II hybridized with all four probes that were complementary to the SLT-I genes, suggesting that they have toxin genes with great homology in all the regions examined. In colony hybridization tests, these oligonucleotide probes did not react with E. coli strains that were nontoxigenic for Vero cells or that produced cytotoxins belonging to the SLT-II family. The probe derived from the slt-IIA gene distinguished E. coli strains that produced SLT-II alone from SLT-I-producing strains and hybridized to all E. coli O157:H7 strains that produced both SLT-I and SLT-II. Using two of these oligonucleotide probes that were complementary to slt-IA or slt-IIA sequences, we identified 50 of 52 cytotoxin-producing strains, whereas none of 416 nontoxigenic E. coli strains was reactive. The colony blot hybridization with the oligonucleotide probes described here can serve as a specific and sensitive test with potential diagnostic value.

Animals↗
PubMed1989

[Infections by enterohemorrhagic Escherichia coli (EHEC): a clinical and microbiologic problem and a challenge for the public health service].

Enterohaemorrhagic Escherichia coli (EHEC) is the cause of haemorrhagic colitis which may be complicated by subsequent haemolytic uraemic syndrome (HUS), thrombotic-thrombocytopenic purpura (TTP), and neurologic disorders. The organisms produce at least three biochemically and immunologically distinct cytotoxins which are designated as Shiga-like (SLT) or verotoxins and which are identified by immunological methods, cell culture tests, or gene-probes. According to present knowledge infections are primarily caused by consumption of contaminated milk and meat products and secondarily during outbreaks by human-to-human transmission. In North America cattle is considered as the main reservoir whereas in Europe sufficient information is lacking. EHEC produce different amounts of SLT; high toxin producers were identified in strains belonging to E.coli O157:H7, O157:H-, 026:H11, 0111:H8 and 0111:H-. Sporadic cases and two outbreaks due to EHEC have been identified in the Federal Republic of Germany. The life-threatening complications of the the disease, unknown reservoirs and vehicles of transmission of the organisms in Europe, and sophisticated diagnostic laboratory methods represent a clinical and microbiological problem and a challenge to the public health service.

Animals↗
PubMed1988

Purified verotoxins of Escherichia coli O157:H7 decrease prostacyclin synthesis by endothelial cells.

Two immunologically distinct verotoxins purified from Escherichia coli C600, lysogenized with distinct temperate phages from E. coli strain 933 of serotype O157:H7, were compared by SDS-PAGE and different biological assays. The two toxins termed verotoxin 1 (VT1) and verotoxin 2 (VT2) differing in molecular weight exhibited similar biological activities. Both preparations were toxic for HeLa cells and lethal for mice. Epidemiological evidence of verotoxinogenesis in some cases of hemolytic-uremic syndrome (HUS) and the recent observations of inadequate prostacyclin production by endothelial cells associated with HUS prompted us to study the effect of purified verotoxins on prostacyclin synthesis in rat aortic tissue. Our results demonstrate a significant reduction of prostacyclin by both toxins at picomolar levels. The suppression of prostacyclin release by a lower concentration of VT2 as compared with VT1 reflects the relative potencies of these toxins in HeLa cell toxicity and mouse lethality. The results suggest an effect of verotoxins on endothelial cells and support the concept of these toxins as virulence factors in E. coli.

Animals↗