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M Bitzan

Publications and source records attributed to M Bitzan.

At least 19 recordsLinked to original sources
PubMed2005

Silencing of Bak ameliorates apoptosis of human proximal tubular epithelial cells by Escherichia coli-derived Shiga toxin 2.

BACKGROUND: Escherichia coli-derived Shiga toxin (Stx), the cause of the enteropathic hemolytic uremic syndrome, is a potent inducer of apoptotic cell death. The present study was performed to examine the hypothesis that Stx initiates apoptosis by activating the mitochondrial pathway involving mitochondrial-associated, pro-apoptotic Bcl-2 family proteins Bax and Bak. MATERIALS AND METHODS: To determine if Stx2-mediated apoptosis is dependent on Bax or Bak, a gene-silencing approach was employed using sequence-specific small interfering (si)RNA duplexes. Silencing of Bax and Bak protein expression in human renal proximal tubular epithelial (HK-2) cells and its effect on Shiga toxicity was assessed by immunofluorescence microscopy and Western blotting. RESULTS: Transfection of HK-2 cells, shown to be exquisitely sensitive to Stx, with siRNA duplexes successfully diminished Bak, but not Bax protein expression. In order to determine if silencing of pro-apoptotic gene expression affects Stx-induced apoptosis, HK-2 cells were transfected with Bak-specific or control siRNA, exposed to lethal concentrations of Stx2 and assessed for cleavage of poly(ADPribose) polymerase-1 (PARP) as a marker of apoptosis, using Western blot technology. We observed that siRNA-induced reduction of Bak expression levels correlated with decreased PARP cleavage. CONCLUSION: Results suggest that Stx-induced cell death involves pro-apoptotic Bak and that silencing of Bak gene expression affords partial protection against Stx-mediated apoptosis.

Apoptosis↗
PubMed2005

Peritonitis due to Neisseria mucosa in an adolescent receiving peritoneal dialysis.

Neisseria mucosa is part of the normal nasopharyngeal flora and rarely pathogenic in humans. Reports of serious infections associated with this pathogen are very unusual. A 17-year-old boy with end-stage renal disease due to IgA nephropathy presented with acute, spontaneous, symptomatic peritoneal dialysis-associated peritonitis without reported break in sterility or PD catheter exit site infection. beta-lactamase-negative N. mucosa was isolated from the dialysate effluent. Intraperitoneal antibiotic treatment with cephalothin/gentamicin for 5 days and subsequent ceftriaxone led to complete resolution of the infection. This case demonstrates that "non-pathogenic" Neisseria species can cause clinically severe peritonitis with high intraperitoneal neutrophil counts, elevated C-reactive protein levels in the peritoneal effluent (in the presented case, 27,600/mul and 3.6 mg/l, respectively) and impaired peritoneal membrane transport function. To our knowledge, this is the first case of N. mucosa peritonitis complicating chronic peritoneal dialysis in an adolescent patient.

Adolescent↗
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↗
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↗
PubMed1997

Outbreak of Escherichia coli O157:H7 infection in a large family.

An outbreak of bloody and nonbloody diarrhoea caused by Escherichia coli O157:H7 including one case of haemolytic uraemic syndrome (HUS) and two cases of haemolytic anaemia, in five siblings (aged 2.5 to 11.3 years) and their playmate was investigated. Using sorbitol-MacConkey agar, colony blot hybridisation, and immunomagnetic separation, Shiga toxin 2-producing Escherichia coli O157:H7 was isolated from all children but the HUS patient; however, this patient had high immunoglobulin M antibody titres against Escherichia coli O157 lipopolysaccharide. Escherichia coli O157 isolates from all patients were indistinguishable in serotype, virulence properties, and genomic background, indicating that the same strain caused the infections. These data confirm the importance of person-to-person transmission.

Anemia, Hemolytic↗
PubMed1996

Immune response to non-O157 Vero toxin-producing Escherichia coli in patients with hemolytic uremic syndrome.

The incidence and time course of the immune response to Vero toxin-producing Escherichia coli (VTEC) other than O157 (O26, O55, O111, O128) were determined in 107 children with enteropathic hemolytic uremic syndrome (HUS) by ELISA and compared to antibody profiles of 125 healthy pediatric controls and 100 children with community-acquired uncomplicated diarrhea. Six of 8 HUS patients with non-O157 VTEC isolates exhibited a serologic response to the homologous lipopolysaccharide antigen similar to that of patients infected with E. coli O157. In addition, elevated IgM or IgG antibodies were demonstrated in 7 of 19 culture- and O157 serology-negative HUS patients. Serogroup-specific antibodies decreased below cutoff levels within several months after convalescence. Anti-non-O157 antibodies were found in 14% of the diarrheic controls. Unexpectedly, a high proportion (27/82) of anti-O157 lipopolysaccharide antibody-positive HUS samples reacted with LPS from E. coli O55:B5, suggesting shared epitopes with endemic VTEC O157 strains.

Adolescent↗
PubMed1994

Pediatric clinical use of the ketoconazole/cyclosporin interaction.

Ketoconazole is known to inhibit the metabolism of cyclosporin through inhibition of cytochrome P-450. This pharmacological interaction was used in an 8-year-old renal transplant patient to successfully achieve therapeutic cyclosporin blood concentrations. The addition of ketoconazole to the cyclosporin regimen should be considered when difficulties are encountered in attaining satisfactory cyclosporin levels.

Child↗
PubMed1994

Evidence that verotoxins (Shiga-like toxins) from Escherichia coli bind to P blood group antigens of human erythrocytes in vitro.

The interaction of verotoxins (VTs) with human erythrocytes (RBCs) in vitro was investigated, with particular reference to the role of P blood group glycolipids that are structurally related to the known VT receptors. RBC binding of purified VT1, VT2, VT2c, and VT2e was detected by direct and indirect immunofluorescence. Glycolipids were extracted from defined RBCs, separated by thin-layer chromatography, and assessed for VT binding in an overlay assay by adding toxin and specific antibodies. All VTs bound to P1 phenotype (Pk, P, and P1 antigens) and P2 phenotype (Pk and P antigens) RBCs but not to p phenotype (lacking the Pk, P, and P1 antigens) RBCs. Binding of VT1 and VT2 was approximately 10-fold greater to P1 and the rare Pk2 (Pk antigen but no P1 or P antigen) phenotype cells than to P2 phenotype RBCs, whereas VT2e bound equally well to P1 and P2 phenotype cells. The VT1 and VT2 immunofluorescence results correlated with the detection of P1 and/or increased amounts of Pk (globotriaosylceramide) antigen; VT2e immunofluorescence correlated with the detection of P (globotetraosylceramide) antigen. The Pk band pattern and VT binding observed in the thin-layer chromatogram of human P1 and P phenotype RBC extracts varied from that of human kidney and Pk1 phenotype (Pk and P1 antigens) RBCs. We conclude that each VT binds to human RBCs in vitro by utilizing specific P blood group glycolipids as receptors. On P1 and P phenotype RBCs, the accessibility of the Pk antigen for VTs appeared to be restricted. The occurrence of VT-RBC binding in natural VT-producing Escherichia coli disease and its relevance for the pathophysiology of hemolytic uremic syndrome remain to be established.

Bacterial Toxins↗
PubMed1993

The role of Escherichia coli O 157 infections in the classical (enteropathic) haemolytic uraemic syndrome: results of a Central European, multicentre study.

To assess the importance of infection by Verotoxin (VT) producing Escherichia coli (VTEC) in children with HUS in Central Europe, stool and/or serum samples obtained from 147 patients from 28 paediatric centres were prospectively examined for the presence of VTEC and the kinetics of faecal VT titres (FVT), and for VT neutralization titres and antibodies against E. coli O 157 lipopolysaccharide, respectively. Ninety-two percent of the patients had classic (enteropathic) HUS (E+ HUS). Evidence of VTEC infection was obtained in 86% of them. VTEC/FVT were identified in 55/118 E+ cases (47%). A prominent feature was the frequent isolation of sorbitol-fermenting, VT2-producing E. coli O 157.H-.VT1 (C600/H19) was neutralized by 9%, and VT2 (C600/933W) by 99% of the initial serum samples from E+ patients, compared to 3% (VT1) and 100% (VT2) from age-related controls. Fourfold titre rises against VT1 and/or VT2 were observed in 13/70 (19%), and significantly elevated O 157 LPS IgM and/or IgA antibodies in 106/128 (83%) of the E+ patients. The ubiquitous VT2 neutralizing principle in the serum of HUS patients as of healthy controls warrants further investigations.

Adolescent↗
PubMed1992

Indirect hemagglutination assay for diagnosis of Escherichia coli O157 infection in patients with hemolytic-uremic syndrome.

An indirect hemagglutination assay consisting of sheep erythrocytes coated with lipopolysaccharide (LPS) from Shiga-like toxin-producing Escherichia coli O157 was used for the serological diagnosis of E. coli O157 infections in children with classical (enteropathic) hemolytic-uremic syndrome (HUS). One week after the onset of diarrhea (acute phase of the disease), the E. coli O157 antibody titer was greater than or equal to 1:4,096 in 22 of 27 patients with HUS, compared with 4 of 249 controls, the majority of whom had O157 antibody titers of between 1:4 and 1:256. This antibody response was observed in HUS patients with stool cultures positive and negative for E. coli O157. Selective absorption with homologous LPS and heterologous LPS showed that the antibody response was specific for E. coli O157. Because of its simplicity and ease of interpretation, the indirect hemagglutination assay described in this paper is recommended for the serological diagnosis of E. coli O157 infections in patients with HUS.

Antibodies, Bacterial↗
PubMed1992

Molecular detection of sorbitol-fermenting Escherichia coli O157 in patients with hemolytic-uremic syndrome.

Shiga-like toxin-producing Escherichia coli strains of serogroup O157 were identified in 26 of 104 patients with hemolytic-uremic syndrome and in 18 of 668 patients with diarrhea. All strains were identified by colony hybridization with DNA probes complementary to Shiga-like toxin I and Shiga-like toxin II gene sequences and characterized by biochemical tests and serotyping. Seventeen of these 44 patients had E. coli O157 strains which were unusual because they fermented sorbitol within 24 h of incubation and were positive for beta-glucuronidase activity. Culture filtrates of these sorbitol-fermenting strains were highly toxic to Vero cells in culture. Serological tests and DNA analysis performed by restriction endonuclease digestion of B-subunit toxin genes revealed that all 17 isolates produced Shiga-like toxin II. Although by using molecular probes we established a high frequency of sorbitol-fermenting E. coli O157 strains in the patients we examined, further studies on the prevalence of such isolates in other areas of endemic disease are clearly warranted.

Adolescent↗
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↗
PubMed1990

[Pregnancy following organ transplantation].

In 17 of 74 patients, in the 20-40 years of age group, who had undergone an organ transplantation (kidney or liver), the course and outcome of pregnancy were evaluated. In three cases, the pregnancies ended in premature miscarriage and in five cases they were terminated for medical reasons. Nine infants were born alive between the 32nd to the 40th week of gestation, six of them spontaneously, three of them by abdominal Caesarean section. One of these infants born in the 32nd week of gestation with a birth weight of 800 grams died on the second day after birth. One infant born in the 33rd week of gestation showed incidence of a persistent ductus arteriosis Botalli. Four of the nine newborns suffered from intrauterine dystrophy. The birth weight of four further infants corresponded to the 10th to 25th percentile. Neither the incidence of a maternal varicella zoster infection in the early stages of pregnancy nor the reactivation of a herpes simplex (HSV) and cytomegalia virus infection during the pregnancy resulted in any perceptible damage to the infant or transplant. During pregnancy, three of the mothers were treated with immunosuppressants, either with a combination of azathioprine and prednisone (conventional) or cyclosporine (CSA) and prednisone, or with a combination of all three drugs (triple therapy). As opposed to the newborn of those mothers, who had been treated conventionally, the newborn of those treated with CSA showed post partum a tendency towards hypocalcaemia. Two of the mothers gave birth to their infants outside the Federal Republic of Germany.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
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↗