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E Vilmer

Publications and source records attributed to E Vilmer.

At least 73 records · Page 4Linked to original sources
PubMed1997

Expansion of polyclonal B-cell precursors in bone marrow from children treated for acute lymphoblastic leukemia.

In a series of 12 patients (mean age: 3 years at diagnosis) receiving chemotherapy for acute lymphoblastic leukemia, bone marrow examinations performed during hematopoietic recovery following treatment-induced agranulocytosis or completion of maintenance treatment showed at least 15% of non malignant immature cells which were sometimes hardly distinguishable from leukemic cells. No comparable data was observed in patients treated with G-CSF. The cytological features of these cells as well as their immunophenotyping were defined. Results showed that the majority of cells expressed HLA-DR, CD19, CD10 and cytoplasmic IgM but not the CD34 markers. This predominant and homogeneous pre-B cell population which likely represents the expansion of a minor population detectable in normal bone marrow is phenotypically indistinguishable from leukemic cells. The pattern of IgH gene rearrangements studied by PCR amplification of the CDRIII region showed that these cells were polyclonal. Except in one patient, minimal residual disease was not detected using probes specific for IgH or TCR gene rearrangement of the malignant clone. In children during the hematopoietic recovery after chemotherapy, immature marrow cells in great numbers, even with an highly homogeneous immunophenotype identical to the malignant clone's, are not sufficient for the diagnosis of relapse.

Antigens, Surface↗
PubMed1997

[Elective phagocytosis of polynuclear neutrophils caused by medullary macrophages and autoimmune neutropenia in children].

UNLABELLED: Autoimmune neutropenia (AIN) is a frequent cause of chronic neutropenia especially in youngest children. Its diagnosis is established by immunological proof of the autoimmune mechanism. The aim of this study is to better describe this autoimmune process and to show the contribution of bone marrow smears to this diagnosis. PATIENTS AND METHODS: Ten children, six girls and four boys, were examined between 1990 and 1995. Eight of them had typical AIN, confirmed by the presence of antibodies against neutrophils. Two other patients were included on the basis of bone marrow pictures. Five non-neutropenic children with normal bone marrow smears were chosen as controls. Bone marrow analysis was always performed by the same cytologist according to a reproducible technique. RESULTS: Six out of ten patients had important features of elective phagocytosis of neutrophils by marrow macrophages (unlike controls) without signs of dysgranulopoiesis or hemophagocytosis. Antibodies against neutrophils were detected in six patients with phagocytosis and in four patients without these cytological features. In two other children presenting the same bone marrow picture and clinical profile, an autoimmune process was probable, even in the absence of antibodies against neutrophils. Some patients had several infections and were given immunoglobulins and/or granulocyte colony-stimulating factor (G-CSF) therapy. The efficacy of Immunoglobulin was not constant, whereas G-CSF was effective at low doses and shortened the duration of infections. CONCLUSION: Prolonged neutropenia in childhood must lead to look for phagocytosis by marrow macrophages in bone marrow smears, as a possible sign of autoimmunity. Growth factors may temporarily be used associated with antibiotics therapy in severe and prolonged infections.

Autoimmune Diseases↗
PubMed1997

[Transgenic human thymopoiesis from retrovirally transduced umbilical cord blood hematopoietic stem cells: experimental studies in the SCID-hu mouse].

The gene encoding the CD2 mouse cell surface antigen was retrovirally transduced into cord blood CD34+ cells. On infection by culture at the contact of retrovirus-packaging cells, the mCD2 marker was expressed by 30-40% CD34+ cells, that included the most primitive stem cell-enriched Thy-1+ and CD38- subsets. Accordingly, sorted cord blood CD34+Thy-1+ cells could be directly infected in the same conditions. mCD2- transgenic cord blood CD34+ cells were then used to reconstitute human fetal thymus implanted in SCID mice. Five to 8 weeks later, the mCD2 antigen was detected on approximately 10% of the human thymocytes repopulating the thymus grafts and the transgene genome was detected in graft cell DNA by Southern blot. These results demonstrate efficient gene transfer into primitive cord blood hematopoietic cells endowed with lymphoid potential and suggest gene therapy schemes in neonates suffering inherited or acquired-such as HIV infection-disorders of the T-cell lineage.

Animals↗
PubMed1997

Delineation of a 6 cM commonly deleted region in childhood acute lymphoblastic leukemia on the 6q chromosomal arm.

Deletion of the long arm of human chromosome 6 in acute lymphoblastic leukemia (ALL) has been shown by cytogenetic studies in 4-11% of cases. To characterize further the region of deletion and to precisely establish its frequency, we studied loss of heterozygosity (LOH) in 120 children with ALL using polymorphic markers located from the 6q14-15 chromosomal band to the telomere. LOH was detected in eight patients. A single region of LOH, flanked distally by D6S1594 and proximally by D6S301 was detected. These DNA markers are separated by 6 cM and are approximately located at the 6q21-22 band. Our present results delineate a region that is likely to contain a tumor-suppressor gene involved in a subset of childhood ALLs.

Adolescent↗
PubMed1997

ETV6 is the target of chromosome 12p deletions in t(12;21) childhood acute lymphocytic leukemia.

The presence of ETV6 deletions was investigated in 215 children with acute lymphoblastic leukemia (ALL) using the loss of heterozygosity (LOH) approach. We used four intragenic or juxtagenic microsatellite markers to detect allelic deletions. In this series of unselected patients, LOH of ETV6 markers was found in 23% of cases (6% of T-ALL and 26% of B lineage ALL) confirming that chromosome 12p12-13 deletions represent a major genetic alteration in childhood ALL, frequently missed by cytogenetic analysis. The presence of a t(12;21)(p13;q22) was studied by RT-PCR and/or FISH in a total of 134 patients (125 B lineage ALL, nine T-ALL) including 42 cases with LOH. Thirty-four out of 44 patients (77%) for whom a t(12;21) was observed displayed LOH of the ETV6 markers. When associated with a t(12;21), ETV6 is very likely to be the target of deletions as indicated by the detection of intragenic deletions in three patients. Although deletion of ETV6 and t(12;21) were associated in most patients, in eight cases (six B lineage and two T-ALL) LOH was detected at the ETV6 locus without ETV6-AML1 hybrid RNA. FISH studies conducted in five of these eight patients confirmed the absence of translocation involving ETV6. In such patients, the other allele of ETV6 could be disrupted by either a small deletion, a point mutation, or an epigenetic modification and it will be of interest to study the structure and expression of the remaining allele of ETV6 in these cases. Alternatively, a tumor suppressor gene located close to ETV6 and CDKN1B could be the target of deletions.

Adolescent↗
PubMed1997

Analysis of ETV6 and ETV6-AML1 proteins in acute lymphoblastic leukaemia.

The t(12;21) is a recurring chromosomal abnormality in acute lymphoblastic leukaemias (ALLs) which results in the production of an ETV6-AML1 fusion gene. The association between t(12;21) and the deletion of the untranslocated allele of ETV6 is among the most frequent abnormalities observed in B-lineage ALLs in children. In order to study the proteins encoded by ETV6 and ETV6-AML1, we raised polyclonal antibodies directed against a recombinant peptide corresponding to the junctional region of ETV6-AML1. Cell lysates from various leukaemic cell lines, and from children with B- and T-lineage ALLs, were studied by Western blot. Two isoforms of ETV6 protein were detected in normal bone marrow cells and in leukaemic cells without 12p alteration: a major form (apparent m.w. 63 kD) and a minor one (apparent m.w. 53 kD). In the REH cell line, which expresses the ETV6-AML1 fusion transcript and no normal ETV6 mRNA, the ETV6 isoforms were absent and two new bands were detected corresponding to ETV6-AML1 protein products (apparent m.w. 95 and 105 kD). A similar pattern was obtained with blast cells from patients with a t(12;21) and a deletion of ETV6. In two patients with a t(12;21) but no deletion of ETV6, four bands were detected corresponding to both the normal ETV6 and ETV6-AML1 proteins, suggesting that in these cases the second ETV6 allele was not inactivated. Surprisingly, the expression pattern of ETV6 differed widely from patient to patient. In three out of 13 patients without t(12;21), the relative intensity of the bands corresponding to ETV6 isoforms in blast cells from patients was completely different from normal cells, with a marked predominance of the 53 kD isoform. The pattern of ETV6 expression was normal in bone marrow from the same patients during remission. These finding suggest that ETV6 abnormalities are not restricted to patients with translocations or deletions involving this gene.

Blotting, Western↗
PubMed1997

Systemic effect of intrathecal methotrexate during the initial phase of treatment of childhood acute lymphoblastic leukemia. The European Organization for Research and Treatment of Cancer Children's Leukemia Cooperative Group.

PURPOSE: The in vivo response to prephase corticosteroid therapy for 1 week has been described as a major prognostic factor in childhood acute lymphoblastic leukemia (ALL). Patients with less than 1,000 blasts/microL at day 8 are considered responders and have a better prognosis. This prephase therapy is usually considered as an evaluation of glucocorticoid sensitivity. In fact, it also includes one intrathecal (IT) injection of methotrexate (MTX). In this study, we try to clarify the influence of this injection of IT MTX on the response to the prephase therapy. PATIENTS AND METHODS: This retrospective study analyzed the response to prephase therapy in 1,044 children with ALL entered onto the European Organization for Research and Treatment of Cancer (EORTC) trial 58881 of the Children's Leukemia Cooperative Group (CLCG). Analysis was restricted to 732 cases with an initial blast count greater than 1,000/microL. The following variables were tested to analyze response to prephase therapy: age, sex, evaluated risk factor (RF), blast count on day 0, actual dose of prednisolone administered, immunophenotype (T v non-T), and day of IT MTX. For statistical analysis, the variable day of IT MTX (D) was stratified into three groups: group 1 if D less than 2, group 2 if D > or = 2 but < or = 6, and group 3 if D greater than 6. RESULTS: All variables tested had a significant influence on response to the prephase therapy. This was especially true for IT MTX: 90.4% responders in group 1, 76.9% in group 2, and 70% in group 3 (P < .001). Immunophenotype was also a major predictor of response to the prephase: 88% responders in B-lineage ALL versus 56.2% in T-lineage ALL. IT MTX had a significant influence in B-lineage ALL (96% responders in group 1, 90% in group 2, and 79% in group 3; P < .001), whereas the influence could not be detected in T-lineage ALL. CONCLUSION: These results clearly demonstrate a therapeutic systemic effect of low doses of IT MTX in childhood ALL, and response to prephase therapy should not be considered as an in vivo test for cortico-sensitivity only. Earlier use of IT MTX leads to a higher percentage of responders.

Antimetabolites, Antineoplastic↗
PubMed1997

In vivo infusion of anti-LFA-1 and anti-CD2 antibodies prevents graft failure after HLA partially incompatible bone marrow transplantation in children with high risk acute lymphoblastic leukaemia.

Bone marrow transplantation (BMT) from matched sibling donors is the therapy of choice for children with high-risk acute lymphoblastic leukaemia in children. It is however not available to more than two-thirds of patients who lack a matched donor. Here, we review the outcome of 28 patients with high-risk ALL who were transplanted in France with alternative marrow sources such as HLA-phenoidentical unrelated volunteers and HLA-partially incompatible relatives. For these patients, we tested the possibility to prevent T-depleted marrow graft rejection by infusing in vivo two monoclonal antibodies directed against adhesion receptors i.e., LFA-1 and CD2. Two previous multicenter trials in children transplanted with partially incompatible bone marrow for inborn errors of metabolism showed their efficacy in this setting. Twenty eight patients were enrolled in this study and followed for a median of 4.4 years. Bone marrow engraftment occurred in 81% of the evaluable patients. Post-transplantation leukaemic relapse was the most frequent cause of death in this group of patients, and occurred in 39% of patients. The second most frequent complication was infectious disease, while an EBV-induced B-lymphocyte proliferative disorder occurred in four patients. In conclusion, T-cell-depletion combined with infusion of anti-LFA-1 and anti-CD2 antibodies is efficient in preventing graft failure and GVHD in this group of children with high-risk leukaemia undergoing partially incompatible BMT. The overall DFS is not improved in contrast to what has been previously observed in patients with immunodeficiencies transplanted with a similar rejection prophylaxis. Other approaches are therefore needed aiming either at preserving donor T-cell mediated immunity or accelerating immune reconstitution.

Antibodies, Monoclonal↗
PubMed1996

A cell surface marker gene transferred with a retroviral vector into CD34+ cord blood cells is expressed by their T-cell progeny in the SCID-hu thymus.

Gene transduction into immature hematopoietic cells collected at birth from the umbilical cord could be useful for the treatment of genetic or acquired disorders of the hematopoietic system diagnosed during pregnancy. The SCID-hu mouse is a convenient model to investigate T-cell lineage gene therapy, since it allows replication of human intrathymic T-cell development. CD34+ cells isolated from cord blood were cocultured with CRIP MFG-murine CD2 (mCD2) cells that produce recombinant retroviruses encoding the mCD2 antigen, a cell surface marker easily detectable by flow cytometry. After 3 and 4 days in coculture, a mean of 19% and 39% human hematopoietic cells, respectively, expressed the mCD2 antigen. CD34+ cells cocultured for 4 days were used to reconstitute human fetal thymus implanted in SCID mice. Five to 10 weeks later, the mCD2 antigen was detected on approximately 10% of human thymocytes repopulating the thymic grafts in four of nine SCID mouse chimeras. Vector genomes were detected in graft cell DNA by Southern blot. Analysis of vector integration indicated that positive cells were of polyclonal origin in three animals and predominantly monoclonal in the other one. Our data show that foreign genes can be transduced into CD34+ cord blood cells endowed with T-cell differentiation potential, and suggest strategies for T-cell lineage gene therapy in the neonate.

Animals↗
PubMed1996

Factors influencing outcome in de novo myelodysplastic syndromes treated by allogeneic bone marrow transplantation: a long-term study of 71 patients Société Française de Greffe de Moelle.

We report on 71 consecutive patients with de novo myelodysplastic syndromes referred to physicians belonging to the Société française de greffe de moelle from 1982 through 1991 and transplanted with marrow from HLA-identical siblings. There were 16 cases of refractory anemia, 27 of refractory anemia with excess of blast cells, and 28 of refractory anemia with excess of blast cells in transformation. Seventeen patients had received cytoreductive chemotherapy before the graft. The disease progressed in 17 patients between diagnosis and grafting. Twenty-three patients are alive with a median follow-up of 6 years, whereas 24 died from relapse and 24 from transplant-related complications. Kaplan-Meier estimates of event-free survival, relapse and transplant-related mortality at 7 years were 32%, 48%, and 39%, respectively. The log-rank test and Cox's model revealed better outcome among young patients, patients in an early stage of the French-American-British (FAB) classification or with a low percentage of marrow blasts before transplantation, patients who did not undergo cytoreductive chemotherapy before transplantation, and patients conditioned with total body irradiation and cyclophosphamide. The high rate of relapse in advanced FAB stages has led us to graft patients earlier in the course of the disease, and we are currently conducting a multicenter, randomized study to determine the value of intensive chemotherapy before grafting in patients with an excess of marrow blasts.

Adult↗
PubMed1996

The 12;21 translocation involving TEL and deletion of the other TEL allele: two frequently associated alterations found in childhood acute lymphoblastic leukemia.

A recurrent t(12;21)(p13;q22) has recently been described in human acute lymphoblastic leukemias (ALLs). This translocation fuses TEL and AML1, two genes previously cloned from translocation breakpoints in myeloid leukemias. In addition, allelic loss of the TEL gene can be detected in 15% to 22% of childhood ALLs. In the present study, we have sought allelic deletions of TEL and the presence of the t(12;21) in 50 children with B-lineage ALL, using a combination of microsatellite typing, fluorescent in situ hybridization (FISH), and analysis of the fusion transcripts resulting from the TEL-AML1 gene fusion. Our results indicate that the association between the t(12;21) and the deletion of the nontranslocated allele of TEL is among the most frequent abnormalities observed in B-lineage ALLs. FISH analysis using several cosmid probes showed that, in one patient with a t(12;21) translocation involving TEL, the second allele had an intragenic deletion. This observation points to TEL as the actual target of 12p12-13 deletions in patients that associate a t(12;21) with a deletion. The TEL-AML1 fusion RNA was found in all patients with the t(12;21) whereas the reciprocal AML1-TEL transcript was only found in a subset of patients, suggesting that only the protein product encoded by TEL-AML1 is likely to play a role in leukemogenesis. The observation that, in two patients with the t(12;21), a deletion of TEL was only present in a subclone indicates that this deletion was a secondary event that occurred after the translocation. The frequent occurrence of TEL deletions in patients with t(12;21) suggests that the deletion of the normal TEL allele subsequent to the t(12;21) provides a further proliferative advantage to leukemic cells.

Adolescent↗
PubMed1996

Mitoxantrone-containing regimen for treatment of childhood acute leukemia (AML) and analysis of prognostic factors: results of the EORTC Children Leukemia Cooperative Study 58872.

The objective of this study was to evaluate the feasibility, the toxicity and the efficiency of a BFM-like treatment protocol for acute nonlymphoblastic leukemia (ANLL) of children in which mitoxantrone was substituted for conventional anthracycline. The chemotherapy called for induction (mitoxantrone, cytosine arabinoside, etoposide), consolidation (mitoxantrone, cytosine arabinoside, 6 thioguanine), followed by two intensification courses with cytosine arabinoside plus, respectively, mitoxantrone during the first and etoposide during the second courses. Maintenance therapy consisted of daily 6 thioguanine, four-weekly courses of cytosine arabinoside (s.c. daily during 4 days) and eight-weekly courses of mitoxantrone. The latter drug was pursued up to a total cumulative dose of 150 mg/sqm. Maintenance therapy was stopped at 2 years of diagnosis. Out of 108 patients, 84 (77%) achieved a complete remission, 10 died during induction of hemorrhage, sepsis or pulmonary infiltration by leukemic cells. A total of 32 relapses occurred. The median follow-up was 3.5 years. Actuarial event-free survival, disease-free survival and overall survival at 3 years as 41%, 52%, 56%, respectively. These results compare favorably with most reported data, and cytogenetic findings appear to be the most important prognostic factor.

Adolescent↗
PubMed1996

[Lysinuric dibasic protein intolerance: characteristic aspects of bone marrow involvement].

BACKGROUND: The marrows of patients with lysinuric protein intolerance (LPI) are generally considered as normal, even though autoerythrophagocytosis has been observed in some of them. CASE REPORTS: Lysinuric protein intolerance was recognized in two 12 and 15-year-old brothers who had been diagnosed following an immuno-hematological investigation. Clinical history had been characterized by a neonatal macrophage activation syndrome (hepatosplenomegaly, pancytopenia, hypofibrinogenemia and hypertriglyceridemia). A putative diagnosis of familial lymphohistiocytosis had been ruled out because of unusual clinical and immunological course. Both brothers had displayed chronic aversion to high-protein foods, failure to thrive, osteoporosis and developmental delay. Metabolic investigations had revealed chronic hyperammonemia while cationic aminoaciduria (lysine, arginine and ornithine) was only present during L-citrulline supplementation. Bone marrow examinations had been performed during the neonatal period and during later metabolic investigations. They both displayed a peculiar red cell and granulocytes phagocytosis by histiocytes and granulocytes precursors. CONCLUSIONS: This aspect of bone marrow could be considered as a specific sign of LPI. This report suggests that appropriate metabolic investigations should be performed in any unexplained macrophage activation syndrome.

Amino Acid Metabolism, Inborn Errors↗
PubMed1996

A phase II trial of partially incompatible bone marrow transplantation for high-risk acute lymphoblastic leukaemia in children: prevention of graft rejection with anti-LFA-1 and anti-CD2 antibodies. Société Française de Greffe de Moelle Osseuse.

Bone marrow transplantation (BMT) from matched sibling donors has been useful for the treatment of acute lymphoblastic leukaemia in children with a poor prognosis but is not available to more than two-thirds of patients who do not have a matched allogeneic donor. This study was undertaken to assess one strategy of marrow graft rejection prevention when alternative marrow sources such as HLA-phenoidentical unrelated volunteers and HLA-partially incompatible relatives were used. Results have been compared with two matched groups of children with the same risks factors and disease status who underwent HLA-genoidentical or autologous BMT. The conditioning regimen was the same for the three groups of patients; in the study group anti-LFA-1 and anti-CD2 monoclonal antibodies combined with T-cell depletion of the marrow was added to prevent graft rejection and graft-versus-host disease. Nineteen patients were included and followed for a median of 25 months (14 months to 3 years). Bone marrow engraftment occurred in 83% of the evaluable patients. Post-transplantation infectious diseases were the most frequent causes of death in the study group, occurring in 31% of patients. No fatal infections occurred in the two control groups. Post-transplantation relapse of leukaemia occurred in 26% of study group's patients, in 58% of autologous BMT control group's patients and 5% of HLA-genoidentical allogeneic group's patients. The event-free survival was 83% in the HLA-genoidentical control group, and 30% and 24% in the study group and in the autologous control group, respectively. In conclusion, a high rate of engraftment was achieved by the use of anti-LFA-1 and anti CD2 antibodies. Occurrence of a long-lasting immunodeficiency, however, led to a high incidence of lethal infections and relapses. Combined approaches are therefore to be investigated accelerating immune reconstitution after transplantations of T-depleted HLA partially incompatible marrow.

Adolescent↗
PubMed1996

Deletion mapping indicates that MTS1 is the target of frequent deletions at chromosome 9p21 in paediatric acute lymphoblastic leukaemias.

Recent reports have indicated a high frequency of deletions of MTS1 (CDKN2, p16ink4, CDKI4) in acute lymphoblastic leukaemias (ALLs). This gene is located at chromosome 9p21 and encodes an inhibitor of cyclin D-dependent kinases. In contrast with the observations in some other malignancies, no inactivation of MTS1 by intragenic mutation was demonstrated in leukaemias. A contribution of MTS1 alterations to leukaemogenesis therefore remains questionable. In order to test for the implication of MTS1 as a tumour suppressor gene in paediatric ALLs we have explored the 9p21 chromosomal region of 46 children with this disease. The copy number of the MTS1 gene in blasts from the patients was determined using a quantitative PCR assay enabling us to precisely detect mono- and bi-allelic deletions. Rearrangements of the gene were sought by Southern blot analysis. The extent of the deletions was studied using microsatellite markers spanning the 9p21 chromosomal region. Point mutations were sought in exon 1 and exon 2 of the MTS1 gene in patients with a mono-allelic deletion in addition, exon 2 of MTS1, which contains two-thirds of the coding region, was sequenced in all patients who had no deletion of the gene. Altogether, our data are consistent with the view that MTS1 is the target of 9p21 deletions. Either one or two alleles of the gene were deleted in 36% of non-selected children with B-lineage ALL and both alleles were deleted in all seven patients we studied with T-lineage ALL. The absence of any point mutation implies that the major mechanism of inactivation of MTS1 in ALLs is deletional.

Adolescent↗
PubMed1996

Prospective sandwich enzyme-linked immunosorbent assay for serum galactomannan: early predictive value and clinical use in invasive aspergillosis.

BACKGROUND: The delay between the onset of invasive aspergillosis and the start of antifungal therapy is crucial for the patient's recovery. Early diagnosis is difficult in cancer patients through lack of precocious specific signs. We have investigated the clinical usefulness of circulating Aspergillus antigen monitoring in pediatric hematology patients with a new sensitive sandwich enzyme-linked immunosorbent assay. METHODS: A prospective study was conducted by assessing circulating galactomannan levels in high risk patients. Thirty-seven patients studied during an 18-month period were evaluated twice weekly during neutropenic phases with the sandwich enzyme-linked immunosorbent assay for serum Aspergillus galactomannan. RESULTS: Twelve patients had one or more episodes of positive circulating galactomannan detection, 10 of whom developed presumptive invasive aspergillosis. The clinical and radiologic signs occurred at a mean of 13.4 days (range, 0 to 48) after circulating galactomannan detection and reversed in 6 patients treated with amphotericin B at the same time circulating galactomannan detection became negative. Reappearance of circulating galactomannan was observed during subsequent neutropenic periods in 3 patients. CONCLUSIONS: The detection of galactomannan at concentrations as low as 1 ng/ml can be useful for the early initiation of antifungal therapy and monitoring treatment in clinically documented lung aspergillosis. This technique coupled with chest computed tomography could help to restrict the need of invasive diagnostic procedures in fragile patients.

Adolescent↗
PubMed1996

Molecular epidemiology provides evidence of genotypic heterogeneity of multidrug-resistant Pseudomonas aeruginosa serotype O:12 outbreak isolates from a pediatric hospital.

Ribotyping randomly amplified polymorphic DNA analysis, and pulsed-field gel electrophoresis were used for the epidemiologic evaluation of eight Pseudomonas aeruginosa O:12 isolates obtained from eight children and two P. aeruginosa O:12 environmental isolates from a hematology ward. Randomly amplified polymorphic DNA analysis and pulsed-field gel electrophoresis were able to discriminate isolates that were indistinguishable by biochemical typing, O serotyping or ribotyping.

Adolescent↗