Search PubMed⌕ Search

Biomedical subjects

D A Stevens

Publications and source records attributed to D A Stevens.

At least 109 records · Page 6Linked to original sources
PubMed1998

Epidemiological investigation of vaginal Saccharomyces cerevisiae isolates by a genotypic method.

Saccharomyces cerevisiae is a ubiquitous, ascomycetous yeast, and vaginitis caused by this organism has been reported only very rarely. The aim of the present investigation was to assess the epidemiological relatedness of a group of vaginal and commercial S. cerevisiae isolates by a previously reported genetic typing method, which divided the isolates into two broad groups with numerous subtypes. Nineteen S. cerevisiae isolates obtained from patients suffering from vaginitis and four isolates from commercial products in the same city were analyzed. The cellular DNA from each isolate was digested with the restriction endonuclease EcoRI, and restriction fragment length polymorphisms were generated by horizontal gel electrophoresis. The results showed that although vaginal isolates did not cluster in any particular genetic subtype, multiple patients were infected with indistinguishable strains (there were nine distinct strains among 23 isolates). For two of three patients, all three with two episodes of S. cerevisiae vaginitis, different strains were isolated during the recurrence of this disease. Three other patients with indistinguishable isolates were epidemiologically related in that two were practitioners in the same clinic and the third was a patient at this clinic. We also found that one commercial strain was indistinguishable from the strain isolated from three different women at the time that they were suffering from vaginitis. The findings of the present study suggest that some S. cerevisiae strains may possess properties permitting persistence in the human host. Furthermore, person-to-person contact and the proliferation of the use of S. cerevisiae as a health-food product, in home baking, and in home brewing may be a contributing factor in human colonization and infection with this organism.

Adult↗
PubMed1998

Intergenic transcribed spacer PCR ribotyping for differentiation of Saccharomyces species and interspecific hybrids.

The taxonomy of the genus Saccharomyces has undergone significant changes recently with the use of genotypic rather than phenotypic methods for the identification of strains to the species level. The sequence of rRNA genes has been utilized for the identification of a variety of fungi to the species level. This methodology, applied to species of Saccharomyces, allows unknown Saccharomyces isolates to be assigned to the type strains. It was the aim of the present study to assess whether typing of the intergenic spacer region by using restriction fragment length polymorphisms of PCR products (intergenic transcribed spacer PCR [ITS-PCR] ribotyping) could distinguish among type strains of the 10 accepted species of Saccharomyces and further to assess if this method could distinguish strains that were interspecific hybrids. Cellular DNA, isolated after the lysis of protoplasts, was amplified by PCR using ITS1 and ITS4 primers, purified by liquid chromatography, and digested with restriction endonucleases. Ribotyping patterns using the restriction enzymes MaeI and HaeIII could distinguish all species of Saccharomyces from each other, as well as from Candida glabrata, Candida albicans, and Blastomyces dermatitidis. The only exception to this was the inability to distinguish between Saccharomyces bayanus and S. pastorianus (S. carlsbergensis). Furthermore, interspecific hybrids resulting from the mating of sibling species of Saccharomyces were shown to share the ITS-PCR ribotyping patterns of both parental species. It should now be possible, by this simple PCR-based technique, to accurately identify these strains to the species level, thereby allowing an increase in our understanding of the characteristics required by these interspecific hybrids for their particular ecological niches.

DNA, Fungal↗
PubMed1998

Species identification and virulence attributes of Saccharomyces boulardii (nom. inval.).

Saccharomyces boulardii (nom. inval.) has been used for the treatment of several types of diarrhea. Recent studies have confirmed that S. boulardii is effective in the treatment of diarrhea, in particular chronic or recurrent diarrhea, and furthermore that it is a safe and well-tolerated treatment. The aim of the present study was to identify strains of S. boulardii to the species level and assess their virulence in established murine models. Three strains of S. boulardii were obtained from commercially available products in France and Italy. The three S. boulardii strains did not form spores upon repeated testing. Therefore, classical methods used for the identification of Saccharomyces spp. could not be undertaken. Typing by using the restriction fragment length polymorphisms (RFLPs) of the PCR-amplified intergenic transcribed spacer regions (including the 5. 8S ribosomal DNA) showed that the three isolates of S. boulardii were not separable from authentic isolates of Saccharomyces cerevisiae with any of the 10 restriction endonucleases assessed, whereas 9 of the 10 recognized species of Saccharomyces could be differentiated. RFLP analysis of cellular DNA with EcoRI showed that all three strains of S. boulardii had identical patterns and were similar to other authentic S. cerevisiae isolates tested. Therefore, the commercial strains of S. boulardii available to us cannot be genotypically distinguished from S. cerevisiae. Two S. boulardii strains were tested in CD-1 and DBA/2N mouse models of systemic disease and showed intermediate virulence compared with virulent and avirulent strains of S. cerevisiae. The results of the present study show that these S. boulardii strains are asporogenous strains of the species S. cerevisiae, not representatives of a distinct and separate species, and possess moderate virulence in murine models of systemic infection. Therefore, caution should be advised in the clinical use of these strains in immunocompromised patients until further study is undertaken.

Animals↗
PubMed1998

Albuterol does not antagonize the inhibitory effect of dexamethasone on monocyte cytokine release.

Beta2-adrenoceptor agonists given by the inhaled route are the most effective bronchodilators known, yet high doses of these drugs may be associated with an increase in asthma mortality and morbidity. One theory for this paradox is that chronic use of beta2-adrenoceptor agonists compromises the anti-inflammatory action of glucocorticosteroids. This hypothesis derives from the ability of albuterol and fenoterol to inhibit the interaction of the glucocorticosteroid receptor (GR) with proinflammatory transcriptional activators acting on the promoter region of certain target genes that encode cytokines such as tumor necrosis factor-alpha (TNF alpha) and granulocyte/macrophage colony-stimulating factor (GM-CSF). However, the functional relevance of these results has not been formally investigated. We have tested the hypothesis that albuterol reduces the ability of dexamethasone to inhibit the generation of TNF alpha and GM-CSF from lipopolysaccharide (LPS)-stimulated human monocytes. Pretreatment of human monocytes with albuterol (1 and 100 microM) for 5 and for 180 min inhibited maximally TNF alpha generation by approximately 25%. However, regardless of the concentration of albuterol, or the time of preincubation, the inhibitory effect of dexamethasone was not significantly affected with respect to the EC50 or the maximal effect produced. Qualitatively identical data were obtained when GM-CSF release was used as an index of monocyte activation. We conclude that high concentrations of albuterol do not compromise the ability of dexamethasone to suppress the generation of TNF alpha and GM-CSF from LPS-stimulated human monocytes.

Adrenergic beta-Agonists↗
PubMed1998

Epidemiology of Candida albicans isolates from heroin addicts analysed by DNA typing.

Candida albicans is a ubiquitous commensal organism of humans. Several studies have examined outbreaks of candidiasis in heroin addicts utilizing a variety of methods to assess the epidemiological relatedness of the isolates and suggested the association of certain subtypes with disease in this patient population. The aim of the present study was to assess a separate group of isolates of C. albicans from heroin addicts in Spain using a DNA typing method. Results showed that, of the 34 isolates from heroin addicts, 20 were in subgroup IA, 10 were in subgroup IB and no isolates were of the subtype IA2. In addition, four isolates were in a recently described subgroup IC. Control isolates from the same geographical region (Spain) showed a distribution similar to the Spanish heroin addict isolates (12 subgroup IA, three subgroup IB, two subgroup IC and no isolates of the subtype IA2). In this study isolates from the same locality appeared similar irrespective of the patient population from which they were isolated. These results indicated that there may be differing geographical diversity of C. albicans than has previously been reported and that the newly described genotypic subgroup (IC) of C. albicans may be more widespread than previously shown.

Abscess↗
PubMed1998

Dermatophytes and host defence in cutaneous mycoses.

Dermatophytosis is the infection of keratinized tissues such as hair, nails and the stratum corneum of the skin by dermatophyte fungi. These fungi are onygenalean anamorphs and anamorphic species belonging to the genera Trichophyton, Microsporum and Epidermophyton. An important characteristic of the dermatophytes as parasites is their restriction to the dead keratinized tissues, except in rare cases where the patient is immunosuppressed. In contrast to many fungi, including normally non-pathogenic species, which can invade systemically in severely immunocompromised (e.g. neutropenic) patients, dermatophytes appear to be unable to cause systemic infection in this population. Thus, these fungi appear to have an unique interaction with the immune system. A better understanding of this interaction will contribute significantly to our knowledge of mammalian host defences.

Arthrodermataceae↗
PubMed1998

Cytokines and mycoses.

Cell-mediated immunity (CMI) has been shown, over many decades of clinical observation and bench research, to be central to the outcome of invasive fungal infections. In recent years, understanding the role of messenger molecules (cytokines), in coordinating and augmenting cellular immunity has been ascendant. These studies have made it possible to consider using cytokines, now available in abundant quantities via recombinant DNA technologies, to treat fungal infections. In this symposium, the most important fungal pathogens that cause infections in humans, particularly in immunocompromised patients, are considered, with emphasis on how recent experimental work may lead to a better understanding of the role of cytokines and their use in therapy.

Animals↗
PubMed1997

Superinduction of COX-2 mRNA by cycloheximide and interleukin-1beta involves increased transcription and correlates with increased NF-kappaB and JNK activation.

Many primary response genes, including cyclooxygenase-2 (COX-2), exhibit mRNA superinduction following agonist stimulation in the presence of translational blockers such as cycloheximide. This is widely assumed to result from mRNA stabilisation. However, superinduction of IL-1beta-induced COX-2 mRNA levels by cycloheximide in pulmonary type II A549 cells occurred by increased transcription and not by mRNA stabilisation. Furthermore, equivalent effects were observed on NF-kappaB binding to COX-2 promoter kappaB sites and activation of the Jun N-terminal kinases (JNK), p54 and p46. These signalling pathways play important roles in COX-2 induction and may therefore account for the observed increases in COX-2 transcription. These data are consistent with negative feed-back involving down-regulation of NF-kappaB by de novo IkappaB alpha synthesis and suggest that JNK activation may also be down-regulated by a cycloheximide sensitive process.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Analysis of compassionate use itraconazole therapy for invasive aspergillosis by the NIAID Mycoses Study Group criteria.

BACKGROUND: Successful therapy of invasive aspergillosis is difficult, and the place of new drugs is evolving. Earlier studies, with fewer patients, suggest itraconazole, an oral azole, is effective for some patients. METHODS: Compassionate use data were analyzed by criteria applied previously in a multicenter trial as a reference point. The course of 125 patients was evaluated and their clinical settings and responses were categorized. RESULTS: Overall, 34 (27%) had a complete response, 45 (36%) improved, 20 (16%) were unchanged, and 26 (21%) worsened. The subset receiving less than 2 weeks of itraconazole therapy had a worse outcome than the remainder of the group as did patients with sinus, central nervous system, or widely disseminated disease. Prior therapy, age, underlying disease, other sites of aspergillosis, dose, or Aspergillus species did not correlate closely with outcome. In patients who responded, a period of months was commonly required before objective improvement was documented. Patients who underwent bone marrow transplantation fared better than in previous reports. CONCLUSIONS: Itraconazole is effective in many patients with aspergillosis. This large series supports earlier conclusions that response rates are similar to those reported for amphotericin B.

Antifungal Agents↗
PubMed1997

Results of transplanting bone marrow from genetically identical twins into patients with aplastic anemia.

BACKGROUND: Aplastic anemia is caused by several diverse factors, including a lack of or defective hematopoietic stem cells, immune abnormalities, and disorders of the bone marrow microenvironment. The outcome of transplanting bone marrow from genetically identical twins into patients with aplastic anemia may help define how frequently these factors play a role in this condition. OBJECTIVE: To determine the outcome of transplanting bone marrow from genetically identical twins into patients with aplastic anemia. DESIGN: Observational study. SETTING: 31 centers participating in the international Bone Marrow Transplant Registry. PATIENTS: 40 patients with aplastic anemia who received bone marrow transplants from their genetically identical twins between 1964 and 1992. INTERVENTION: 23 patients received their first bone marrow transplant without pretransplantation conditioning; 17 received it after pretransplantation conditioning with cyclophosphamide alone or combined with other drugs or radiation. Six patients received post-transplantation immunosuppressive therapy with methotrexate, cyclosporine, and corticosteroids, alone or in combination. MEASUREMENTS: Outcomes of transplantation, including hematologic recovery and survival. RESULTS: Seven of 23 patients who received their first transplant without receiving conditioning had sustained complete hematologic recovery. One of 16 patients who did not have complete recovery after the first transplantation recovered after a second transplantation, which was not preceded by conditioning. The other 15 patients had two to five transplantations that were preceded by conditioning; in 13 patients, sustained bone marrow function was recovered. Twelve of 17 patients whose first transplantation was preceded by conditioning had sustained complete hematologic recovery. The likelihood of hematologic recovery was greater in patients who had conditioning before the first transplantation (P = 0.033). The actuarial 10-year survival rate for the 40 patients was 78% (95% CI, 59% to 92%). The survival rate was higher in patients who did not have conditioning before the first transplantation (patients without conditioning, 87% [range, 65% to 99%]; patients with conditioning, 70% [range, 47% to 89%]; P = 0.037). CONCLUSIONS: Most patients with aplastic anemia recover bone marrow function after receiving a transplant from a genetically identical twin. Pretransplantation conditioning may increase the chance of bone marrow recovery but does not seem to improve survival.

Adolescent↗
PubMed1997

In vitro antifungal activity of novel azole derivatives with a morpholine ring, UR-9746 and UR-9751, and comparison with fluconazole.

Thirty-three patient fungal isolates were studied by broth macrodilution methods for susceptibility to novel azole derivatives with a morpholine ring, UR-9746 and UR-9751, and fluconazole. MICs (micrograms/ml) ranged widely, but none had lower MICs for Candida albicans or Cryptococcus neoformans than UR-9751. Fluconazole and UR-9751 had the most activity versus other Candida species. Activity was demonstrated versus endemic fungal pathogens. Aspergillus species were generally resistant, although modest activity was seen. UR-9746 and UR-9751 are active in vitro, with a potency comparable to that of fluconazole.

Antifungal Agents↗
PubMed1997

Effect of iron on fluconazole activity against Candida albicans in presence of human serum or monocyte-derived macrophages.

Human serum, transferrin, and apotransferrin are known to profoundly inhibit the growth of Candida albicans by iron deprivation. On the other hand, iron overload (iron saturated transferrin) is a serious risk factor for candidiasis in newborn and in leukemic patients. We tested the efficacy of fluconazole and the previously demonstrated synergy of fluconazole and effector cells against C. albicans under iron overload conditions where efficacy might be diminished. We confirm that exogenous iron completely reversed the inhibitory effect of human serum and report that the efficacy of fluconazole against C. albicans was not significantly compromised in a 24 h assay system. Although exogenous iron inhibited fungistatic activity of monocyte-derived macrophages, it did not interfere with the synergistic candidacidal activity of fluconazole and monocyte-derived macrophages. In 72 h assays, where fluconazole had candidacidal activity, exogenous iron did not compromise efficacy of fluconazole, and fluconazole activity was often increased. These in vitro results suggest that effectiveness of fluconazole therapy would not be compromised in iron overload situations in vivo.

Antifungal Agents↗
PubMed1997

Tastes, structure and solution properties of D-glucono-1,5-lactone.

D-glucono-1,5-lactone differs from D-glucopyranose only in that it has a C = O group instead of CHOH group at carbon atom number one. The molecule therefore possesses an intact 3,4 alpha-glycol group and is sweet. However, it autohydrolyses in water solution at room temperature, forming D-gluconic acid and D-glucono-1,4-lactone. As the solution pH falls it becomes sweet-sour and eventually almost completely sour as the generated hydronium ions dominate both the solution properties and the taste perceptions elicited. It is shown that the ratio of generated hydronium ions to unchanged lactone accords with anticipated taste quality during the first 28 min of autohydrolysis. Changes in both apparent specific volume and apparent isentropic compressibility illustrate increasing solute-solvent interaction and increasing disturbance of water structure during the course of autohydrolysis. These changes are consistent with the concurrent sweet to sour change, but do not explain the weak bitterness which also accompanies them.

Adult↗
PubMed1997

Efficacies of two novel azole derivatives each containing a morpholine ring, UR-9746 and UR-9751, against systemic murine coccidioidomycosis.

UR-9746 and UR-9751 are novel azole derivatives each containing a morpholine ring. They were examined for both in vitro and in vivo activities against Coccidioides immitis. In vitro, UR-9746 and UR-9751 were active, with MICs of 25 and 3.1 micrograms/ml, respectively, against C. immitis Silveira; minimum fungicidal concentrations were > 100 micrograms/ml, the highest concentration tested, for both compounds. Antifungal activity in serum showed the desirable characteristic of remaining severalfold above the MIC at all times. Against systemic murine coccidioidomycosis, UR-9746 and UR-9751 prolonged survival at dosages of > or = 10 mg/kg/day and showed increased reduction of infectious burden in the spleens, livers, and lungs of treated mice with escalating dosage. Both compounds lacked observable toxicity and on a milligram-per-kilogram of body weight basis were > or = 10-fold superior to fluconazole in prolonging survival and clearing infection with C. immitis.

Animals↗
PubMed1997

Itraconazole resistance in Aspergillus fumigatus.

Invasive aspergillosis is an increasingly frequent opportunistic infection in immunocompromised patients. Only two agents, amphotericin B and itraconazole, are licensed for therapy. Itraconazole acts through inhibition of a P-450 enzyme undertaking sterol 14alpha demethylation. In vitro resistance in Aspergillus fumigatus to itraconazole correlated with in vivo outcome has not been previously described. For three isolates (AF72, AF90, and AF91) of A. fumigatus from two patients with invasive aspergillosis itraconazole MICs were elevated. A neutropenic murine model was used to establish the validity of the MICs. The isolates were typed by random amplification of polymorphic DNA. Analysis of sterols, inhibition of cell-free sterol biosynthesis from [14C] mevalonate, quantitation of P-450 content, and [3H]itraconazole concentration in mycelial pellets were used to determine the mechanisms of resistance. The MICs for the three resistant isolates were >16 microg/ml. In vitro resistance was confirmed in vivo for all three isolates. Molecular typing showed the isolates from the two patients to be genetically distinct. Compared to the susceptible isolate from patient 1, AF72 had a reduced ergosterol content, greater quantities of sterol intermediates, a similar susceptibility to itraconazole in cell-free ergosterol biosynthesis, and a reduced intracellular [3H]itraconazole concentration. In contrast, AF91 and AF92 had slightly higher ergosterol and lower intermediate sterol concentrations, fivefold increased resistance in cell-free systems to the effect of itraconazole on sterol 14alpha demethylation, and intracellular [3H] itraconazole concentrations found in susceptible isolates. Resistance to itraconazole in A. fumigatus is detectable in vitro and is present in wild-type isolates, and at least two mechanisms of resistance are responsible.

Adult↗
PubMed1997

Activity of the triazole SCH 56592 against disseminated murine coccidioidomycosis.

SCH 56592 (SCH) is a new triazole antifungal with a broad spectrum of activity. In vitro susceptibility testing against five strains of Coccidioides immitis revealed MICs from 0.39 to 3.13 microg/ml and minimal fungicidal concentrations from 1.56 to 3.13 microg/ml. A murine model of systemic coccidioidomycosis was established in female CD-1 mice. Groups received either no treatment or oral therapy with fluconazole at 10 or 100 mg/kg of body weight; itraconazole at 10 or 100 mg/kg; SCH at 0.5, 2, 10, or 25 mg/kg; or its methylcellulose diluent alone. Therapy began 2 days postinfection and continued once daily for 19 days. Surviving mice were euthanized 49 days postinfection, and infectious burdens were determined by culture. All drugs were superior to no-treatment or diluent-treatment controls (P < 0.001) in prolonging survival but were not significantly different from one another. Itraconazole at 100 mg/kg was superior to fluconazole in reduction of CFU in the spleen, liver, and lung (P < 0.01 to 0.001). SCH at 0.5 mg/kg was superior to either fluconazole or itraconazole at 10 mg/kg in reduction of CFU in all three organs (P < 0.05 to 0.001). SCH at 2 mg/kg was not significantly different from itraconazole at 100 mg/kg in all three organs. SCH at 10 and 25 mg/kg was superior to either dose of fluconazole or itraconazole in all three organs (P < 0.05 to 0.001). In terms of reduction of CFU, SCH was > or = 200-fold as potent as fluconazole and > or = 50-fold as potent as itraconazole. There was a clear dose-responsive relationship for SCH in each of the organs. It is noteworthy that SCH effected cures (no detectable C. immitis in any organ) in 1 of 9, 6 of 10, or 9 of 9 surviving mice in animals given 2, 10, or 25 mg/kg, respectively. Neither fluconazole nor itraconazole cured any survivor. SCH has potent, fungicidal activity in vivo against C. immitis. It should be considered for clinical trials in patients with coccidioidomycosis.

Amphotericin B↗