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D W Warnock

Publications and source records attributed to D W Warnock.

At least 55 records · Page 3Linked to original sources
PubMed1998

Comparative evaluation of FUNGITEST and broth microdilution methods for antifungal drug susceptibility testing of Candida species and Cryptococcus neoformans.

The FUNGITEST method (Sanofi Diagnostics Pasteur, Paris, France) is a microplate-based procedure for the breakpoint testing of six antifungal agents (amphotericin B, flucytosine, fluconazole, itraconazole, ketoconazole, and miconazole). We compared the FUNGITEST method with a broth microdilution test, performed according to National Committee for Clinical Laboratory Standards document M27-A guidelines, for determining the in vitro susceptibilities of 180 isolates of Candida spp. (50 C. albicans, 50 C. glabrata, 10 C. kefyr, 20 C. krusei, 10 C. lusitaniae, 20 C. parapsilosis, and 20 C. tropicalis isolates) and 20 isolates of Cryptococcus neoformans. Overall, there was 100% agreement between the methods for amphotericin B, 95% agreement for flucytosine, 84% agreement for miconazole, 83% agreement for itraconazole, 77% agreement for ketoconazole, and 76% agreement for fluconazole. The overall agreement between the methods exceeded 80% for all species tested with the exception of C. glabrata (71% agreement). The poorest agreement between the results for individual agents was seen with C. glabrata (38% for fluconazole, 44% for ketoconazole, and 56% for itraconazole) and C. tropicalis (50% for miconazole). The FUNGITEST method misclassified as susceptible 2 of 12 (16.6%) fluconazole-resistant isolates, 2 of 10 (20%) itraconazole-resistant isolates, and 4 of 8 (50%) ketoconazole-resistant isolates of several Candida spp. Further development of the FUNGITEST procedure will be required before it can be recommended as an alternative method for the susceptibility testing of Candida spp. or C. neoformans.

Antifungal Agents↗
PubMed1998

Molecular epidemiological study of Aspergillus fumigatus in a bone marrow transplantation unit by PCR amplification of ribosomal intergenic spacer sequences.

We have developed a PCR-based method for the subspecific discrimination of Aspergillus fumigatus types by using two primers designed to amplify the intergenic spacer regions between ribosomal DNA transcription units. The method permitted the reproducible discrimination of 11 distinct DNA types among a total of 119 isolates of A. fumigatus collected from patients and from the environment of a bone marrow transplantation (BMT) unit over a three-year period. Ten DNA types of A. fumigatus were isolated from patients in the BMT unit; eight of these types were also found in the hospital environment, and six of these were present in the unit itself. Thirteen BMT patients developed infection with one of three DNA types some months after these had first been found in the environment of the unit. In other instances, the same DNA types of A. fumigatus were isolated from BMT patients that were later recovered from the environment of the unit. Several DNA types of A. fumigatus were found in the hospital environment over an 18-month period. Molecular typing of multiple isolates of A. fumigatus, obtained from postmortem tissue samples, showed that one patient was infected with a single DNA type, but two others had up to three different DNA types. Our findings suggest that A. fumigatus infection in BMT recipients may be nosocomial in origin and underline the need for careful environmental monitoring of units in which high-risk patients are housed.

Aspergillus fumigatus↗
PubMed1998

Itraconazole pulse: an overview of current use.

Traditionally, fungal infections of the fingernails and toenails have been difficult to treat. Itraconazole is an orally administered triazole antifungal agent with a wide spectrum of activity against dermatophytes, yeasts and some moulds. Pulse therapy with itraconazole is an effective new treatment which offers the shortest treatment course with the least total number of treatment days and lowest total dose.

Antifungal Agents↗
PubMed1998

Imported mycoses in Europe.

This article reviews the clinical manifestations, diagnosis and management of some of the more important systemic infections that are now being imported into Europe. It also considers the risks some of the causal organisms pose to European laboratory workers, many of whom are unfamiliar with the precautions that should be taken when handling these pathogens.

Adult↗
PubMed1997

Guidelines for the investigation of invasive fungal infections in haematological malignancy and solid organ transplantation. British Society for Medical Mycology.

Invasive fungal infections are increasing in incidence and now affect as many as 50% of neutropenic/bone marrow transplant patients and 5 to 20% of solid organ transplant recipients. Unfortunately, many of the diagnostic tests available have a low sensitivity. The guidelines presented here have been produced by a working party of the British Society for Medical Mycology in an attempt to optimise the use of these tests. The yield of fungi from blood cultures can be increased by ensuring that at least 20 ml of blood are taken for aerobic culture, by using more than one method of blood culture, and by employing terminal subculture if continuous monitoring systems are used with a five-day incubation protocol. Skin lesions in febrile neutropenic patients should be biopsied and cultured for fungi. The detection of galactomannan in blood or urine is of value in diagnosing invasive aspergillosis only if tests are performed at least twice weekly in high-risk patients. Antigen detection tests for invasive candidiasis are less valuable. Computed tomography scanning is particularly valuable in diagnosing invasive pulmonary fungal infection when the chest radiograph is negative or shows only minimal changes. Bronchoalveolar lavage is most useful in patients with diffuse changes on computed tomography scan. The major advances in the diagnosis of invasive fungal infection in patients with haematological malignancy or solid organ transplantation have been in the use of imaging techniques, rather than in the development of new mycological methods in the routine laboratory.

Algorithms↗
PubMed1997

Disseminated infection due to Cylindrocarpon lichenicola in a patient with acute myeloid leukaemia.

We describe what is to our knowledge the first reported case of disseminated infection due to Cylindrocarpon. The presumed source was athlete's foot, a condition with which this fungus has previously been associated. Diagnosis was made by needle aspiration of a cutaneous lesion. Radiographic evidence of pulmonary involvement was present. The infection resolved following marrow regeneration and treatment with amphotericin B. Correct identification of Cylindrocarpon may be useful in guiding antifungal therapy.

Aged↗
PubMed1997

Correlation between in-vitro susceptibility testing to itraconazole and in-vivo outcome of Aspergillus fumigatus infection.

Given the increased choice of therapeutic agents and the rising incidence of serious invasive disease, it is important that reliable in-vitro methods for detecting antifungal drug resistance in Aspergillus spp. are developed. Six clinical isolates of Aspergillus fumigatus, obtained from patients in whom the clinical outcome was known, were selected for study. Each was used to examine a range of parameters affecting agar dilution and broth microdilution susceptibility test results. The in-vitro results were compared with outcome in a neutropenic mouse model of invasive aspergillosis. Groups of animals were treated with itraconazole at 25 mg/kg and 75 mg/kg and survival rates and organ burdens were determined. Itraconazole was efficacious against four isolates (susceptible) but failed for two (resistant) in the animal model of infection. Both the resistant isolates had been obtained from patients receiving itraconazole treatment with good serum concentrations of the drug. Conditions for the agar dilution test which produced results that correlated best with our in-vivo observations included the use of RPMI agar with L-glutamine buffered to pH 7 with MOPS, inoculated with 10(6)-10(7) conidia/mL and incubated for 48-72 h at 28 or 35 degrees C with a no-growth endpoint. Optimal conditions for the broth microdilution method included the use of RPMI medium with L-glutamine and 2% glucose buffered to pH 7 with MOPS, an inoculum of 2 x 10(5) conidia in 200 microL incubated for 48 h at 35 degrees C with a growth (or trace) endpoint. The MICs for the susceptible isolates were 0.12-1.0 mg/L and > or = 16 mg/L for the resistant isolates. With careful selection and standardization of test conditions it is possible to generate reproducible in-vitro susceptibility data for Aspergillus spp. that will predict clinical outcome.

Animals↗
PubMed1997

Molecular biological characterization of an azole-resistant Candida glabrata isolate.

Two isolates of Candida glabrata, one susceptible and one resistant to azole antifungals, were previously shown to differ in quantity and activity of the cytochrome P-450 14alpha-lanosterol demethylase which is the target for azole antifungals. The resistant isolate also had a lower intracellular level of fluconazole, but not of ketoconazole or itraconazole, than the susceptible isolate. In the present study a 3.7-fold increase in the copy number of the CYP51 gene, encoding the 14alpha-lanosterol demethylase, was found. The amount of CYP51 mRNA transcript in the resistant isolate was eight times greater than it was in the susceptible isolate. Hybridization experiments on chromosomal blots indicated that this increase in copy number was due to duplication of the entire chromosome containing the CYP51 gene. The phenotypic instability of the resistant isolate was demonstrated genotypically: a gradual loss of the duplicated chromosome was seen in successive subcultures of the isolate in fluconazole-free medium and correlated with reversion to susceptibility. The greater abundance of the amplified chromosome induced pronounced differences in the protein patterns of the susceptible and revertant isolates versus that of the resistant isolate, as demonstrated by two-dimensional gel electrophoresis (2D-GE). Densitometry of the 2D-GE product indicated upregulation of at least 25 proteins and downregulation of at least 76 proteins in the resistant isolate.

Antifungal Agents↗
PubMed1997

In vitro studies of activity of voriconazole (UK-109,496), a new triazole antifungal agent, against emerging and less-common mold pathogens.

The in vitro activity of voriconazole was compared with that of itraconazole. Eighty-six isolates of pathogenic molds belonging to 23 species were tested by an agar dilution method in High Resolution medium. Voriconazole was more active than itraconazole against a number of hyaline molds, including several Fusarium spp. and Scedosporium prolificans. Voriconazole and itraconazole showed comparable good activity against several hyaline molds, including Penicillium marneffei and Scedosporium apiospermum, and a number of dematiaceous molds, including Bipolaris australiensis, Cladophialophora bantiana, several Exophiala spp., and several Fonsecaea spp. Our results suggest that voriconazole could be effective against a wide range of mold infections in humans.

Antifungal Agents↗
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↗
PubMed1996

Fungal infections: a survey of laboratory services for diagnosis and treatment.

A questionnaire on the services provided and the methods used for the diagnosis of fungal infections and for the support of antifungal chemotherapy was sent to members of the British Society for Medical Mycology (BSMM) and the British Society for Antimicrobial Chemotherapy (BSAC). Ninety-five responses from general microbiology laboratories in the United Kingdom were analysed, and we compared services provided by laboratories that serve a transplant unit with those offered by other laboratories. We estimate that about 150 cases of cryptococcosis, 500 to 600 of candidaemia, and 300 to 400 of invasive aspergillosis are identified by laboratories in the United Kingdom (UK) each year. The clinical laboratories are aware of the importance of fungal infection, but rely heavily on reference services. In some laboratories, however, the degree of investigation of specimens and the procedures in use are inadequate for diagnosing systemic mycoses and determining the susceptibility of isolates to antifungal agents. The balance between reference and local services requires attention and external quality assurance needs to be applied effectively. In addition, effective methods for the diagnosis of systemic mycoses, and reliable and practicable methods for determining the susceptibility of isolates to antifungal agents, are needed urgently.

Antifungal Agents↗
PubMed1996

Fatal Candida tropicalis fungaemia in a leukaemic patient receiving fluconazole prophylaxis.

A 50-year-old man with newly diagnosed acute myeloid leukaemia developed breakthrough candidaemia while receiving fluconazole as antifungal prophylaxis during remission-inducing chemotherapy. Candida tropicalis was isolated; the strain was resistant to fluconazole on in vitro sensitivity testing, a phenomenon which has not been previously reported in this setting.

Antifungal Agents↗
PubMed1996

Chaetomium pneumonia in patient with acute myeloid leukaemia.

A patient with relapsed refractory acute myeloid leukaemia developed typical fungal lung lesions despite intravenous amphotericin B prophylaxis. Chaetomium globosum was cultured from the resected right lower lobe. Histology showed branching hyphae negative for common Aspergillus species by immunohistochemical staining. Previous reports of invasive disease caused by Chaetomium and some applications of immunohistochemical staining for Aspergillus are discussed.

Adult↗
PubMed1995

Toxic gas generation from plastic mattresses and sudden infant death syndrome.

Microbial generation of toxic gases from antimony, arsenic, or phosphorus in compounds used as fire retardants in cot mattresses has been proposed as a cause of sudden infant death. To test this hypothesis, 23 polyvinyl chloride mattress samples from cot death cases were incubated on malt agar plates until good microbial growth was obtained. Silver nitrate and mercuric chloride test papers were then inserted and the colour reactions recorded. The predominant organism, recovered from all mattresses tested, was not, as claimed in earlier work, the fungus Scopulariopsis brevicaulis, but a mix of common environmental Bacillus spp. Test paper colour changes occurred whenever bacterial growth was present, but these reactions also occurred in control tests in which no mattress material was present on the plates. Chemical and instrumental analyses of exposed test papers showed that the colour reactions were not due to deposits of antimony, arsenic, or phosphorus. Our findings do not support the hypothesis that toxic gases derived from antimony, arsenic, or phosphorus are a cause of sudden infant death. More sulphur was found in test papers exposed in plates containing bacterial growth than in those without such growth. This result suggests that the test paper reactions were due to the generation of sulphur-containing compounds during bacterial growth on the agar medium.

Bacillus↗