Biomedical subjects

F Couture

Publications and source records attributed to F Couture.

At least 19 recordsLinked to original sources

PubMed2005

Prior red blood cell transfusions in cancer patients increase the risk of subsequent transfusions with or without recombinant human erythropoietin management.

Cancer patients often receive transfusions when their hemoglobin concentration falls to dangerously low levels due to chemotherapy or due to the disease itself. The availability of recombinant human erythropoietin (rHuEPO) has significantly reduced transfusion frequencies in cancer patients. However, the predictability of transfusions prior to the use of rHuEPO for future transfusions has not been evaluated. Data from five randomized, double-blind, placebo-controlled trials in cancer patients receiving chemotherapy and epoetin alfa were utilized to calculate the relative risk of subsequent transfusions in patients who were pretransfused. A meta-analysis with patient-level data was used to assess predictors of transfusion. Baseline data from an open-label study were used to compare quality-of-life (QOL) parameters between previously transfused and transfusion-naive patients. The mean relative risks (RR) of exposure to additional transfusion for pretransfused patients on placebo or epoetin alfa were 2.14 (95% confidence interval [CI]: 1.73, 2.65) and 2.51 (95% CI: 1.92, 3.27), respectively, compared with nontransfused patients. Data from the meta-analysis of patients on epoetin alfa showed that pretransfusion was the most significant predictor for subsequent transfusions (parameter estimate = -1.2628, p < 0.0001 from Logistic Regression Analysis). While epoetin alfa was similarly effective in reducing transfusion risks for patients with or without pretransfusions (compared with placebo), those who were pretransfused were more than twice as likely to be subsequently transfused, compared with those not pretransfused. QOL was significantly worse for pretransfused patients than for nontransfused patients, as measured by the Functional Assessment of Cancer Therapy -Anemia and the Linear Analogue Scale Assessment QOL instruments. The results suggest that transfusions prior to epoetin alfa therapy increase the risk of future transfusions, and early treatment with epoetin alfa might reduce the risk of subsequent transfusions.

Adolescent↗

PubMed2001

Epoetin alfa therapy increases hemoglobin levels and improves quality of life in patients with cancer-related anemia who are not receiving chemotherapy and patients with anemia who are receiving chemotherapy.

PURPOSE: To evaluate efficacy, safety, and quality of life (QOL) changes with epoetin alfa therapy for anemia in patients with nonmyeloid malignancies. PATIENTS AND METHODS: Anemic cancer patients were enrolled onto this prospective, open-label study from 34 centers across Canada. The trial had two cohorts: patients who were and were not receiving chemotherapy during the 16-week study. All patients initially received epoetin alfa 150 IU/kg subcutaneously three times per week. The dose was doubled after 4 weeks for patients who did not experience sufficient response. RESULTS: Of the 183 patients enrolled in the nonchemotherapy cohort, statistically significant and clinically relevant improvements in QOL were observed with epoetin alfa therapy using both the FACT-An questionnaire and linear analog scale assessment. Hemoglobin levels increased significantly (P <.001; mean increase 2.5 g/dL from baseline to end of study) and these increases were positively correlated with improved QOL and change in Eastern Cooperative Oncology Group (ECOG) scores. There was a significant reduction in the percentage of patients who required blood transfusions. The 218 patients in the chemotherapy cohort also experienced significant improvements in QOL, decreased transfusion use, and increased hemoglobin levels that correlated with QOL improvements and change in ECOG scores. Epoetin alfa was well-tolerated in both cohorts. CONCLUSION: Epoetin alfa administered to patients with cancer-related anemia for up to 16 weeks resulted in significantly improved QOL, increased hemoglobin levels, and decreased transfusion use. These benefits were observed in cancer patients who were not receiving chemotherapy as well as those who were.

Aged↗

PubMed2001

Epoetin alfa in cancer patients: evidence-based guidelines.

Anemia is a common cause of cancer-related fatigue. A systematic review of the literature was performed to establish guidelines on the use of epoetin alfa for the treatment of anemia. The evidence in support of these guidelines was selected, reviewed, and summarized by the members of the Canadian Cancer and Anemia Guidelines Development Group. The effects of epoetin alfa on quality of life (QOL) in patients with cancer were examined in 5 randomized, placebo-controlled trials and 2 large, open-label, nonrandomized, community-based studies. The effects of epoetin alfa on red blood cell transfusion requirements were examined in 19 randomized controlled trials (RCTs) with 21 comparisons. All trials compared epoetin alfa to a suitable control group, examined specified outcome measures that could be analyzed, and studied patients with cancer who were receiving chemotherapy. Trials involving patients with hematologic malignancies originating in the bone marrow were excluded. Outcome measures included 1) quality of life (QOL) (as measured by scales including the Linear Analogue Self-Assessment [LASA] and the Functional Assessment of Cancer Therapy [FACT] subscales), and 2) transfusion requirements (as measured by the proportion of patients requiring transfusion and amount of transfusion). The analysis confirmed that epoetin alfa produced statistically significant and clinically relevant improvements in QOL in patients with cancer. The overall relative risk ratio for transfusion among patients receiving epoetin alfa was calculated to be 0.60 (95% Cl, 0.53-0.69; P < 0.00001), representing a 40% reduction in the proportion of patients requiring transfusion. These results support recommendations for the use of epoetin alfa in patients with cancer-related anemia.

Anemia↗

PubMed2000

Candidate Neisseria meningitidis NspA vaccine.

The highly conserved NspA protein has been found in the outer membrane of every Neisseria meningitidis strain tested so far. Two monoclonal antibodies (MAbs) directed against this protein were used to demonstrate that biologically important epitopes of the NspA protein are exposed at the surface of serologically distinct meningococcal strains. Analysis of sera collected from mice that survived a deadly meningococcal challenge following immunization with recombinant NspA protein (rNspA) revealed the presence of cross-reactive antibodies which efficiently attached to and killed the four serogroup B strains tested. These data are additional proof that the NspA protein is exposed at the surface of intact meningococcal cells, which is an important characteristic for a vaccine candidate.

Amino Acid Sequence↗

PubMed2000

Intranasal immunization with gonococcal outer membrane preparations reduces the duration of vaginal colonization of mice by Neisseria gonorrhoeae.

Nasal immunization was studied to determine if it could elicit an immune response capable of preventing vaginal colonization by Neisseria gonorrhoeae or of reducing its duration in the estradiol-treated mouse model. Nasal administration of gonococcal outer membrane (OM) preparations induced the development of systemic and vaginal immune responses that were directed mainly against a limited number of gonococcal OM proteins. The impact of nasal immunization on vaginal colonization by N. gonorrhoeae was evaluated by use of an experimental model, in which mice were treated with estradiol to prolong the infection. Bacterial clearance was significantly faster for mice immunized intranasally with N. gonorrhoeae OM preparations (4.0+/-2.5 days) than for control mice (8.5+/-4.3 days). The estradiol-treated mouse model may serve as a useful tool for the evaluation of potential gonococcal vaccine candidates.

Administration, Intranasal↗

PubMed2000

Identification of group B streptococcal Sip protein, which elicits cross-protective immunity.

A protein of group B streptococci (GBS), named Sip for surface immunogenic protein, which is distinct from previously described surface proteins, was identified after immunological screening of a genomic library. Immunoblots using a Sip-specific monoclonal antibody indicated that a protein band with an approximate molecular mass of 53 kDa which did not vary in size was present in every GBS strain tested. Representatives of all nine GBS serotypes were included in the panel of strains. Cloning and sequencing of the sip gene revealed an open reading frame of 1,305 nucleotides coding for a polypeptide of 434 amino acid residues, with a calculated pI of 6. 84 and molecular mass of 45.5 kDa. Comparison of the nucleotide sequences from six different strains confirmed with 98% identity that the sip gene is highly conserved among GBS isolates. N-terminal amino acid sequencing also indicated the presence of a 25-amino-acid signal peptide which is cleaved in the mature protein. More importantly, immunization with the recombinant Sip protein efficiently protected CD-1 mice against deadly challenges with six GBS strains of serotypes Ia/c, Ib, II/R, III, V, and VI. The data presented in this study suggest that this highly conserved protein induces cross-protective immunity against GBS infections and emphasize its potential as a universal vaccine candidate.

Amino Acid Sequence↗

PubMed1999

Two different schedules for integrating filgrastim as adjuvant therapy in the treatment of patients with advanced stage Hodgkin's lymphoma receiving MOPP/ABV hybrid chemotherapy.

PURPOSE: Management of advanced-stage Hodgkin's disease with a MOPP/ABV hybrid regimen (mechlorethamine, vincristine, procarbazine, prednisone, Adriamycin, bleomycin and vinblastine) has yielded a high complete response rate (75-85%). However, myelosuppression can limit delivery of treatment. Filgrastim has been shown to reduce chemotherapy-related neutropenia and allow for on-time administration of planned doses of chemotherapeutic agents. The objective of this study was to find the best way to integrate filgrastim with the MOPP/ABV hybrid regimen. METHODS: Enrolled in this study were 24 patients (aged 18-52 years) with newly diagnosed, histologically documented Hodgkin's disease. In schedule I, patients received filgrastim (5 microg/kg s.c. daily) beginning on day 9, 24 h after administration of ABV. In schedule II, patients received filgrastim concomitantly with procarbazine on days 2-7 (starting 24 h after day-1 MOPP administration and stopping 24 h before ABV administration) as well as after ABV beginning on day 9. Filgrastim after ABV administration was administered until two consecutive ANC readings of 10 x 10(9)/l were achieved. RESULTS: All patients were able to complete all six cycles of therapy. There was a trend to fewer dose reductions in schedule II (0.76%) as compared to schedule I (4.2%) with a P-value of 0.077 (chi-squared test). Specifically, 11.6% of MOPP courses and 5.5% of ABV courses were dose-reduced in schedule I versus 1.7% and 1.4%, respectively, in schedule II. CONCLUSION: In conclusion, filgrastim was effective in supporting the delivery of the MOPP/ABV chemotherapy. Concomitant administration of filgrastim with procarbazine (days 2-7) appears to be safe and allows the maximum dose intensity of this therapy.

Adolescent↗

PubMed1999

Combined results of two phase II studies of Taxol (paclitaxel) in patients with relapsed or refractory lymphomas.

This study was performed to determine the clinical activity and safety of paclitaxel in the treatment of patients with refractory or relapsing aggressive Non-Hodgkin's lymphoma (NHL). Between May 3, 1994 and February 16, 1996, 39 patients with refractory or relapsing NHL consented to be enrolled in two, multicenter, open-labelled studies to evaluate the efficacy, safety, time to progression and overall survival of paclitaxel given at a dose of 175 mg/m2 by a 3-hour IV infusion every three weeks without G-CSF use. Data from the two studies is combined. One patient, although registered, did not receive treatment. Of the remaining 38 patients, 17 men and 21 women aged 26-82 years (median 60) were given 104 courses of paclitaxel [median 2 (range 1-6)]. Seventeen patients had stage IV, 7 stage III, 8 stage II, 5 stage 1 and 1 unknown stage of disease. Histologic grades included 1 low, 33 intermediate, and 4 high. Three patients had bone marrow involvement. Median time from diagnosis to study entry was 19 months (1-160). The median number of previous chemotherapy regimens was 2 (range 1-6). Three of the 35 (8.6%) patients evaluable for response had partial remission (PR) of their disease for 1-7 months (median 2) and 11/35 (31.4%) stable disease (SD) for 1 to 19 months (median 3). All three responders and 3 of the 11 SD patients had received paclitaxel after relapsing from a CR. At analysis, nine of the 38 patients were alive. Median duration of follow up at analysis was 6 months (3 days-29 months). The estimated survival rates for all patients at 1 and 2 years are 34% and 27%, respectively (Kaplan-Meier) from the start of paclitaxel treatment. The median survival time was 5.4 months (3 days to 28+ months). Febrile neutropenia occurred in two patients. Seven (18%) patients developed a neutrophil nadir of < 0.5 x 10(9)/L and 2 (5%) patients developed a platelet nadir of < 50 x 10(9)/L. Six patients received blood transfusions. Non-hematologic toxicity was generally mild to moderate with all patients experiencing some toxicity. Twenty-seven patients experienced grade III toxicity including: alopecia (n = 19), pain (n = 9), fatigue (n = 5), nausea/vomiting (n = 3), diarrhoea (n = 2), pulmonary/shortness of breath (n = 2), anorexia (n = 1) and fluctuating levels of consciousness and somnolence (n = 1). Two patients experienced grade IV toxicity (infection, peripheral neuropathy, pain). No patient discontinued paclitaxel for a severe hypersensitivity reaction. In summary, administered as a 3-hour infusion, paclitaxel 175 mg/m2 results in mild myelotoxicity but minimal antitumor activity in patients with refractory NHL.

Adult↗

PubMed1998

Inducible overexpression of a toxic protein by an adenovirus vector with a tetracycline-regulatable expression cassette.

We have constructed two new adenovirus expression cassettes that expand both the range of genes which can be expressed with adenovirus vectors (AdV) and the range of cells in which high-level expression can be attained. By inclusion of a tetracycline-regulated promoter in the transfer vector pAdTR5, it is now possible to generate recombinant adenoviruses expressing proteins that are either cytotoxic or that interfere with adenovirus replication. We have used this strategy to generate a recombinant adenovirus encoding a deletion in the R1 subunit [R1(delta2-357)] of the herpes simplex virus type 2 ribonucleotide reductase. Cell lines expressing the tetracycline-regulated transactivator (tTA) from an integrated vector or following infection with an AdV expressing tTA are able to produce deltaR1 protein at a level approaching 10% total cell protein (TCP) when infected with Ad5TR5 deltaR1 before they subsequently die. To our knowledge, this is the first report of the overexpression of a toxic gene product with AdV. We have also constructed a new constitutive adenovirus expression cassette based on an optimized cytomegalovirus immediate-early promoter-enhancer that allows the expression of recombinant proteins at a level greater than 20% TCP in nonpermissive cell lines. Together, these new expression cassettes significantly improve the utility of the adenovirus system for high-level expression of recombinant proteins in animal cells and will undoubtedly find useful applications in gene therapy.

Adenoviridae↗

PubMed1997

Microsatellite instability in childhood T cell acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is the most frequent cancer encountered in children. Little is known about the molecular pathology of childhood T cell ALL. Oncogenesis is a multistep process that involves alterations in proto-oncogenes and tumor suppressor genes. Recently, a mutator phenotype detectable by microsatellite instabilities was shown to be associated with predisposition to cancer. This new mechanism for human carcinogenesis is caused by defects in the DNA replication/repair system. To study the involvement of some of these mutational events in the development of T cell ALL, we have initiated a systematic search for losses of heterozygosity (LOH) and microsatellite instabilities in children affected with this disease. These patients were allelotyped by PCR using 56 microsatellite markers located near known or putative tumor suppressor genes. The microsatellite patterns were altered in more than 80% of the patients. LOH were detected in chromosomes 6p, 12p and 9p. Two third of the patients were deleted for chromosome 9p21, suggesting the involvement of a tumor suppressor gene, probably the p16 gene. The only patient refractory to chemotherapy was shown to be associated with a mutator phenotype. This is the first documented case of a childhood neoplasia associated with genomic instabilities. Our results suggest that defects in DNA replication/repair components are involved in the development of a subset of childhood T cell ALL.

Adolescent↗

PubMed1995

Primary structure of OXA-3 and phylogeny of oxacillin-hydrolyzing class D beta-lactamases.

We determined the nucleotide sequence of the blaOXA-3(pMG25) gene from Pseudomonas aeruginosa. The bla structural gene encoded a protein of 275 amino acids representing one monomer of 31,879 Da for the OXA-3 enzyme. Comparisons between the OXA-3 nucleotide and amino acid sequences and those of class A, B, C, and D beta-lactamases were performed. An alignment of the eight known class D beta-lactamases including OXA-3 demonstrated the presence of conserved amino acids. In addition, conserved motifs composed of identical amino acids typical of penicillin-recognizing proteins and specific class D motifs were identified. These conserved motifs were considered for possible roles in the structure and function of oxacillinases. On the basis of the alignment and identity scores, a dendrogram was constructed. The phylogenetic data obtained revealed five groups of class D beta-lactamases with large evolutionary distances between each group.

Amino Acid Sequence↗

PubMed1995

Mini-BEAM as salvage therapy for relapsed or refractory Hodgkin's disease before intensive therapy and autologous bone marrow transplantation.

PURPOSE: To evaluate the efficacy of carmustine (BCNU), etoposide, cytarabine (Ara-C), and melphalan (mini-BEAM) as salvage therapy in patients with relapsed or refractory Hodgkin's disease who were potentially eligible to undergo intensive therapy and autologous bone marrow transplantation (ABMT). PATIENTS AND METHODS: Forty-four patients with refractory or relapsed Hodgkin's disease after front-line combination chemotherapy referred for consideration of ABMT were treated with mini-BEAM (BCNU 60 mg/m2 on day 1, etoposide 75 mg/m2 on days 2 to 5, Ara-C 100 mg/m2 twice per day on days 2 to 5, and melphalan 30 mg/m2 on day 6) to maximum response. Eleven patients were refractory to primary chemotherapy. Twenty-three patients were treated in first relapse and 10 in second or subsequent relapse; 21 received mini-BEAM as their first salvage regimen. Patients were restaged to determine disease status immediately before intensive therapy and transplant. RESULTS: The overall response rate was 84% (exact 95% confidence interval [CI], 70% to 92%), with a complete response (CR) rate of 32% (95% CI, 20% to 47%) and a partial response (PR) rate of 52%. No treatment-related deaths were observed. Myelosuppression was the major toxicity. Almost all patients required platelet transfusions. Eighty-four percent were given RBC transfusions, and 54% required intravenous antibiotics for fever while neutropenic. CONCLUSION: Mini-BEAM is a safe and effective regimen for treatment of refractory or relapsed Hodgkin's disease. Further studies are required to determine if responding patients have improved disease-free survival (DFS) after intensive therapy and ABMT.

Adolescent↗

PubMed1995

Effect of antimicrobial prophylaxis on hematopoietic recovery following autologous bone marrow transplantation: ciprofloxacin versus co-trimoxazole.

We evaluated the effect of oral ciprofloxacin on neutrophil recovery in 20 consecutive patients undergoing autologous bone marrow transplantation (BMT) for malignant lymphoma and compared the results with a control group of 20 patients receiving co-trimoxazole and folinic acid. Both groups started the prophylactic antibiotic as well as granulocyte-macrophage colony-stimulating factor (GM-CSF) the day after marrow infusion and continued the former until the onset of febrile neutropenia (median duration of treatment 6 days for co-trimoxazole and 7 days for ciprofloxacin). The time of attain an absolute neutrophil count > or = 0.5 x 10(9)/L was significantly shorter in patients receiving ciprofloxacin (16 days vs 22 days; P = 0.006). There was no difference in time to attain a platelet count > or = 20 x 10(9)/L independent of transfusion or in time to the first febrile episode or incidence of bacteremia. We conclude that antibiotic prophylaxis with ciprofloxacin results in more rapid neutrophil recovery than prophylaxis with co-trimoxazole. This may result from a myelosuppressive effect of co-trimoxazole or an enhancement of neutrophil recovery by ciprofloxacin, or both.

Administration, Oral↗

PubMed1994

Peripheral neuropathy following high-dose etoposide and autologous bone marrow transplantation.

We investigated the incidence of peripheral neuropathy in 142 consecutive patients receiving high-dose etoposide between August 1988 and December 1991. A retrospective chart review was conducted. Six patients with hematologic malignancies presented with a new sensory polyneuropathy after receiving an intensive therapy regimen consisting of etoposide 60 mg/kg i.v. and melphalan 140-160 mg/m2 i.v. followed by autologous bone marrow transplantation. Neurologic symptoms began 2-8 weeks after transplant, were grade 2-3 in severity and pursued a chronic course with slow improvement over months. Electromyographic studies in three of the patients tested confirmed distal sensory polyneuropathy. All 6 patients had previously received vincristine 1-60 months prior to autotransplant. We conclude that peripheral neuropathy of moderate severity is a potential complication of high-dose etoposide therapy but appears to be self-limited.

Adolescent↗

PubMed1993

High-dose etoposide and melphalan, and autologous bone marrow transplantation for patients with advanced Hodgkin's disease: importance of disease status at transplant.

PURPOSE: To evaluate an intensive therapy regimen of high-dose etoposide and melphalan and autologous bone marrow transplantation (ABMT) in advanced Hodgkin's disease; and to determine possible prognostic factors that predict for long-term disease-free survival (DFS). PATIENTS AND METHODS: Seventy-three patients with advanced Hodgkin's disease who had failed to achieve remission with front-line chemotherapy (n = 16) or who had relapsed (n = 57) were treated with high-dose etoposide 60 mg/kg and melphalan 160 mg/m2 and ABMT. Previous therapy included mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) alternating with doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD), or hybrid MOPP/ABV. All patients received pretransplant cytoreduction with conventional-dose salvage chemotherapy and 40 also received pretransplant extended-field radiation to areas of bulky nodal disease (> 5 cm). RESULTS: Response to high-dose etoposide and melphalan was determined at 3 months post-ABMT. The complete response (CR) rate was 75% (95% confidence interval [CI], 64% to 84%), including 35 of 50 patients with measurable disease before ABMT (70%; 95% CI, 60% to 86%). There were three early deaths (septicemia) and four late deaths (three interstitial pneumonitis, one intracerebral hemorrhage). Actuarial DFS is 38.6% at 4 years. Multivariate regression analysis showed that disease status at the time of ABMT (no evidence of disease [NED], nonbulky residual disease [NBRD], or bulky disease) was the most important factor determining DFS: 68% of those transplanted with NED versus 26% for patients with NBRD and 0% for bulky disease (P = .0002, log-rank test). Relapse in a previous radiation field was the only other significant prognostic factor. CONCLUSION: Etoposide and melphalan is an effective and well-tolerated intensive therapy regimen in advanced Hodgkin's disease. Patients in complete remission after conventional-dose salvage therapy transplanted with this regimen enjoy superior long-term DFS.

Adolescent↗

PubMed1993

Interleukin-3 followed by GM-CSF for delayed engraftment after autologous bone marrow transplantation.

Recombinant human interleukin-3 (IL-3) is well-tolerated according to phase I studies, and produces trilineage hematologic responses in patients with normal bone marrow. In addition, promising results have been obtained in a variety of bone marrow failure states. We studied IL-3 in 7 patients with markedly delayed engraftment after autologous bone marrow transplantation (ABMT) for hematologic malignancies (acute myeloid leukemia 4, chronic myeloid leukemia 1, myeloma 1, non-Hodgkin's lymphoma 1). All patients were red blood cell- and platelet transfusion-dependent, had an absolute neutrophil count (ANC) < 0.7 x 10(9)/L and failed to achieve a sustained ANC > 1.0 x 10(9)/L after receiving granulocyte-macrophage colony stimulating factor (GM-CSF) for 28 days. IL-3 was given daily for 21 days at 2 micrograms/kg/d (2 patients) and 5 micrograms/kg/d (5 patients). Toxicity was mild and consisted mostly of low-grade fever and malaise. No changes in platelet, hemoglobin or reticulocyte levels were observed. Four patients had at least a 2-fold increase in ANC at the end of IL-3 treatment. Five patients received GM-CSF 10 micrograms/kg/d subcutaneously for 7 to 10 days immediately after IL-3 and 4 had a further increase in ANC (median 1.7-fold, range 1.6- to 5.8-fold), but no change in platelet transfusion requirements. Hematopoietic colony assays of bone marrow cells obtained before and after treatment showed that granulocyte-macrophage colony-forming cell (CFU-GM) and erythroid blast-forming cell (BFU-E) levels were severely reduced and multilineage progenitors (CFU-GEMM) absent in all patients, and remained low after IL-3 treatment for 21 days. Sequential IL-3 and GM-CSF produced a significant but transient increase in the neutrophil counts of some patients. IL-3 appears to be of limited benefit in patients who are severely aplastic after ABMT and have very low levels of bone marrow progenitors.

Acute Disease↗

PubMed1992

Phylogeny of LCR-1 and OXA-5 with class A and class D beta-lactamases.

The nucleotide sequences of blaLCR-1 and blaOXA-5 beta-lactamase genes have been determined. Polypeptide products of 260 and 267 amino acids with estimated molecular masses of 27 120 Da and 27,387 Da were obtained for the mature form of LCR-1 and OXA-5 proteins. A progressive alignment was used to evaluate the extent of identity between LCR-1 and OXA-5 with 29 other beta-lactamase amino acid sequences. The data showed that both belong to class D. We identified amino acids conserved in 24 positions for class A beta-lactamases and in 28 positions for five class D enzymes. The structural similarities between class A and class D beta-lactamases are more extensive than indicated by earlier biochemical studies with overall 16% identity between both classes. From the alignment, dendograms were constructed with a distance-matrix and parsimony methods which defined three major groups of proteins subdivided into clusters giving insight on beta-lactamase phylogeny and evolution.

Amino Acid Sequence↗

PubMed1990

Nucleotide sequence and phylogeny of SHV-2 beta-lactamase.

We determined the nucleotide sequence of the blaSHV-2(pBP60-1) gene from Klebsiella ozaenae which confers resistance to broad-spectrum cephalosporins. The structural gene encodes a polypeptide product of 286 amino acids, and the estimated molecular weight of the mature protein is 28,900. Amino acid sequence comparison of the SHV-2pBP60-1 enzyme with all known class A beta-lactamases and homology studies showed that the residues were highly conserved. Furthermore, SHV-2pBP60-1 was clearly related to SHV-1, LEN-1, and OHIO-1. The SHV-2pBP60-1 enzyme differed from SHV-1 isolated from Klebsiella pneumoniae by seven amino acid substitutions. One of these substitutions, the Gly----Ser substitution at position 234, is probably a key region for the novel activity of cefotaxime hydrolysis. A phylogenetic tree was constructed by using all class A beta-lactamases of known sequences by a progressive alignment method. The data suggested that the beta-lactamases of gram-positive Streptomyces, Staphylococcus, and Bacillus species appeared early in evolution, followed by the PSE and CARB enzymes of Pseudomonas species and, more recently, by the SHV-type and TEM-type enzymes found in enteric bacteria. Larger evolutionary distances separated clusters of the gram-positive beta-lactamases than separated clusters of the gram-negative enzymes. Results of this phylogenetic study suggested that extended-spectrum enzymes are recent derivatives that are selected by the use of new cephalosporins.

Amino Acid Sequence↗