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D W Denning

Publications and source records attributed to D W Denning.

At least 109 records · Page 6Linked to original sources
PubMed1996

Rapid genotyping of Escherichia coli O157 isolates by random amplification of polymorphic DNA.

Although several typing methods have been described for Shiga-like toxin-producing Escherichia coli O157, the methods are somewhat cumbersome. Using 22 isolates of Escherichia coli O157 and five other Escherichia coli isolates, two primers (M13 core sequence and 970-11) were found to give excellent differentiation between isolates using random amplified polymorphic DNA (RAPD). Using only the presence or absence of variable bands, a matrix of 20 variable characters was identified. From these characters, similarity coefficients were calculated and a phenogram constructed. All of the Escherichia coli O157 isolates were easily distinguished from the non-O157 Escherichia coli isolates. Using a 95% similarity cutoff, we found 13 RAPD types among the 22 Escherichia coli O157 isolates. Isolates thought to be identical by toxin and phage typing as well as by epidemiological association were distinguished, and others thought to be distinct by lack of epidemiological association were identical. RAPD using M13 and 970-11 primers is a potentially useful typing tool for Escherichia coli isolates of serotype O157 and possibly other Escherichia coli isolates.

Bacteriophage Typing↗
PubMed1996

Aspergillus wound infection following laparostomy.

Wound infections with Aspergillus are surprisingly rare given the quantity of spores in hospital air. We report the first case of infection of abdominal viscera due to Aspergillus in a patient with a laparostomy for Crohn's disease. Amphotericin B effected a cure. Sampling of air from the patient's environment yielded one isolated of Aspergillus fumigatus that matched the patient's isolates. Other examples of surgical wounds being contaminated by Aspergillus are reviewed.

Adult↗
PubMed1996

Therapeutic outcome in invasive aspergillosis.

A review of series of > or = 4 cases of invasive aspergillosis (total, 1,223 cases) was undertaken to establish the crude mortality and rate of response to therapy with amphotericin B in the major at-risk host groups. In association with pulmonary, sinus, and cerebral aspergillosis in immunocompromised patients, the crude mortality rates were 86%, 66%, and 99%, respectively. No untreated patient survived. Among 84 patients treated for 1-13 days, only one survived. Among those with invasive pulmonary aspergillosis treated for > or = 14 days, the response rates to amphotericin B deoxycholate were 83% (in cases of heart and renal transplantation), 54% (leukemia), 33% (bone marrow transplantation) and 20% (liver transplantation). Patients with AIDS mostly received both amphotericin B and itraconazole, and 37% of those treated for > or = 14 days responded to therapy. Substantial variation in outcome from series to series was related to underlying disease status, site of disease, and management. Invasive aspergillosis remains a devastating opportunistic infection despite current treatment.

Amphotericin B↗
PubMed1996

Treatment of fungal infection in AIDS.

Fungal infections affect virtually all patients with the Acquired Immunodeficiency Syndrome (AIDS). Superficial infection (seborrheic dermatitis, tinea capitis, tinea corporis and tinea cruris) is more common than in the general population and can be difficult to eradicate. Mucosal disease (oropharyngeal, oesophageal and vaginal candidosis) is very common and often recurs. In advanced AIDS, patients usually fail to respond to topical therapy and often to systemic therapy and isolates of Candida spp. from these patients are frequently resistant in vitro to fluconazole and other azoles. Systemic fungal infection is less common but life threatening. The commonest such infection is Pneumocystis carinii pneumonia (PCP) although prophylaxis is usually successful in preventing either the first episode or recurrent episodes. Histoplasmosis, coccidioidomycosis and Penicillium marneffei infections are common in endemic areas. Cryptococcal meningitis and invasive aspergillosis occur worldwide. The prophylaxis and treatment of all these except PCP are discussed and reviewed.

AIDS-Related Opportunistic Infections↗
PubMed1996

Karyotyping of fluconazole-resistant yeasts with phenotype reported as Candida krusei or Candida inconspicua.

The yeasts Candida krusei and Candida inconspicua have similar phenotypes, which may make discrimination of these organisms difficult. In this study we determined the karyotypes of 51 isolates of these two yeast species by contour-clamped homogeneous electric field electrophoresis. We found that the 43 isolates that had the C. krusei phenotype had three karyotype-specific characteristics. These isolates produced either two or three bands between 2,000 and 3,000 kb and no band between 1,300 and 2,000 kb, and there was either a single bright band at 1,300 or 1,200 kb or two separate bands at 1,300, 1,200, or 1,100 kb. Using this technique, we were able to distinguish 27 different C. krusei types on the basis of band variations. The seven isolates identified as C. inconspicua on the basis of phenotype differed in that they produced at least one band between 1,300 and 2,000 kb. These isolates produced six to nine bands, in contrast to C. krusei strains, which produced three to six bands. The MIC of fluconazole for all of the isolates was at least 12.5 mg/liter, as determined by a broth dilution method.

Antifungal Agents↗
PubMed1996

Reduced accumulation of drug in Candida krusei accounts for itraconazole resistance.

Due to intrinsic resistance Candida krusei is emerging as a systemic pathogen in AIDS patients undergoing fluconazole therapy, but acquired resistance to itraconazole has not been studied biochemically. We report here studies on the basis for azole resistance and sterol composition in C. krusei. An itraconazole-resistant isolate showed reduced susceptibility to azole drugs in in vitro growth inhibition studies. Accumulation of 14 alpha-methyl-3,6-diol under azole treatment was associated with growth arrest. In vitro ergosterol biosynthesis and type II binding studies suggested no alteration in the affinity to azole drugs of the target enzyme, the cytochrome P-450 sterol 14 alpha-demethylase, in the resistant isolate. Resistance was associated with a decreased intracellular content of drug in the resistant isolate.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Comparison of D0870, a new triazole antifungal agent, to fluconazole for inhibition of Candida albicans cytochrome P-450 by using in vitro assays.

D0870 was 12 to 15 times more active than fluconazole in experiments to determine the MIC for growth arrest for two isolates of Candida albicans. A biochemical comparison of in vitro sterol biosynthesis in cell extracts showed only a twofold superiority of D0870 over fluconazole. A large differentiation (10-fold) in 50% saturating concentrations obtained by examining the binding of the azoles to microsomal P-450 was observed in a type II binding spectrophotometric assay, possibly reflecting the differential affinity for more than one P-450 enzyme. Additional mechanisms besides affinity for the target enzyme sterol 14 alpha-demethylase, such as differential intracellular accumulation of drug, may contribute to the differences in antifungal activity.

Antifungal Agents↗
PubMed1996

In vitro activity of BMS-181184 compared with those of fluconazole and amphotericin B against various candida spp.

We compared the in vitro activity of BMS-181184, the first compound of a new class of antifungal agents, the pradimicins, with those of fluconazole and amphotericin B against 64 clinical isolates of Candida species. MICs were determined by a microdilution method with high resolution medium for BMS-181184 and fluconazole and antibiotic medium no. 3 with 2% glucose for amphotericin B. MICs of BMS-181184 for all yeasts were in the range of 0.78 to 12.5 micrograms/ml. BMS-181184 was active against isolates resistant to other antifungal agents, consistent with a novel mode of action. Minimum fungicidal concentrations for 16 isolates showed that BMS-181184 was fungicidal. Clinical studies are now required to confirm its activity.

Amphotericin B↗
PubMed1996

Evidence of multiple extracellular phospholipase activities of Aspergillus fumigatus.

Extracellular phospholipase activity has been implicated in the pathogenesis of several bacterial infections. Recently, extracellular phospholipase activity has been proposed as a virulence factor in the opportunistic yeast Candida albicans. Aspergillus fumigatus is the most pathogenic member of its genus, responsible for > 90% of infections. Previously, no specific virulence factors have been determined. We investigated the ability of A. fumigatus to produce extracellular phospholipases at 37 degrees C. Fast atom bombardment was used to compare lipid-containing media before and at 5-h intervals during shaking culture of A. fumigatus. Lipids were extracted and analyzed. Many anions corresponding to phospholipid breakdown products were identified. Specific anion species identified indicated phospholipase A, B, C (PLC), and D activities. PLC activity was further investigated by using the synthetic substrate p-nitrophenylphosphorylcholine. PLC activity was initially observed after 30 h of growth and accumulated in broth cultures up to 50 h. At 55 h, there was a sharp increase in PLC activity which coincided with cultures reaching the stationary phase. Activity of the PLC was measured at different temperatures, with greater activity occurring at 37 degrees C than at lower temperatures. Phospholipases could represent a virulence determinant in A. fumigatus.

Aspergillus fumigatus↗
PubMed1996

D-mannitol in cerebrospinal fluid of patients with AIDS and cryptococcal meningitis.

Cryptococcal meningitis (CM) is associated with raised intracranial pressure which is linked with serious neurological sequelae. Cryptococcus neoformans produces D-mannitol in vitro and in experimental meningitis in rabbits. Mannitol present in the cerebrospinal fluid (CSF) of CM patients could exacerbate raised intracranial pressure and contribute to neurological damage. To link CSF mannitol to cryptococcal infection, levels of mannitol in the CSF of AIDS patients with CM were measured by gas-liquid chromatography. Mannitol was detected in 19 of 21 samples (range, 1.5 to 26.2 mg/liter), but there was no quantitative correlation between the mannitol concentration and the cryptococcal antigen titer.

AIDS-Related Opportunistic Infections↗
PubMed1996

Molecular typing by random amplification of polymorphic DNA and M13 southern hybridization of related paired isolates of Aspergillus fumigatus.

Three forms of DNA-based typing procedures for Aspergillus fumigatus isolates have been developed over the last five years. The procedures are random amplification of polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP) detection, and Southern hybridizations with various repetitive sequence-based probes. Using two of these procedures, we compared 16 selected isolates, grouped into eight pairs on the basis of epidemiology or previously assigned RFLP types. RAPD with four primers (R108, RC08, 2, and 4), including three previously used with A. fumigatus, showed that one primer, R108, gave the best discrimination (8 types). Southern hybridization of total genomic DNA digested with HindIII and probed with the total bacteriophage M13 genome resulted in the highest overall level of discrimination. Combination of the RAPD and Southern hybridization with the previously assigned RFLP types discriminated 10 isolates of 16. Isolates closely linked epidemiologically could not be distinguished from each other. In addition, three pairs of isolates previously unlinked by epidemiology had the same overall types. Two pairs were obtained from the same hospital within 2 years of each other, whereas the third pair were isolated from California and Germany. A full understanding of the epidemiology and ecology of A. fumigatus requires multiple discriminatory typing procedures.

Aspergillosis↗
PubMed1995

Resistance to fluconazole in Candida albicans from AIDS patients correlated with reduced intracellular accumulation of drug.

Mucosal candidosis is an almost inevitable consequence of AIDS. Resistance to fluconazole therapy associated with enhanced tolerance, detectable in microbiological estimation of sensitivity, occurs in up to 10% of cases with late-stage AIDS. We report here our biochemical analysis of the basis of resistance in a study of two susceptible and two resistant isolates. Resistance was not associated with a change in the target enzyme sterol 14 alpha-demethylase, as indicated by equivalent levels of fluconazole inhibition of activity in extracts from all four isolates, or by mutations in sterol delta desaturase as previously observed in Saccharomyces cerevisiae and Ustilago maydis. Reduced cellular content of fluconazole in the resistant isolates of between six to ten-fold was observed which could account for their resistant phenotype.

AIDS-Related Opportunistic Infections↗
PubMed1995

Liposomal amphotericin B (AmBisome) therapy in invasive fungal infections. Evaluation of United Kingdom compassionate use data.

BACKGROUND: Invasive fungal infections in the immunocompromised patient are associated with substantial mortality. The use of conventional amphotericin B, the main-stay of treatment, has often been limited by its adverse effects. The incorporation of amphotericin B into liposomes enables more drug to be given without an increase in adverse reactions. We examined the efficacy of AmBisome (Vestar Inc, San Diego, Calif), a small unilamellar liposomal formulation of amphotericin B, in the treatment of mycologically proven systemic fungal diseases. METHODS: A retrospective analysis of the "Compassionate Use of AmBisome" in 58 patients who were treated in 34 centers throughout the United Kingdom between July 1990 and August 1992, before licensure of the drug. RESULTS: Thirty patients had a definite or probable mycologic diagnosis, including 17 who had invasive aspergillosis, nine with Candida infections (three with mucosal disease only), three with zygomycosis, and one with cryptococcal meningitis. The overall response rate was 59% for patients with aspergillosis (80% for those who had had no prior therapy with amphotericin B) and 56% for those with candidosis. More than 40% of those in whom AmBisome was used as "salvage therapy" responded. A daily dose of up to 5 mg/kg was tolerated with minimal side effects. CONCLUSIONS: AmBisome is efficacious in the treatment of invasive fungal infections and provides an alternative therapy for those who fail to respond or become intolerant to conventional amphotericin B therapy.

Adolescent↗
PubMed1995

When to use fluconazole.

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AIDS-Related Opportunistic Infections↗