Biomedical subjects

M A Ghannoum

Publications and source records attributed to M A Ghannoum.

At least 19 recordsLinked to original sources

PubMed2006

Interlaboratory study of quality control isolates for a broth microdilution method (modified CLSI M38-A) for testing susceptibilities of dermatophytes to antifungals.

The Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards, or NCCLS) M38-A standard for the susceptibility testing of filamentous fungi does not specifically address the testing of dermatophytes. In 2003, a multicenter study investigated the reproducibility of the microdilution method developed at the Center for Medical Mycology, Cleveland, Ohio, for testing the susceptibility of dermatophytes. Data from that study supported the introduction of this method for testing dermatophytes in the future version of the CLSI M38-A standard. In order for the method to be accepted by CLSI, appropriate quality control isolates needed to be identified. To that end, an interlaboratory study, involving the original six laboratories plus two additional sites, was conducted to evaluate potential candidates for quality control isolates. These candidate strains included five Trichophyton rubrum strains known to have elevated MICs to terbinafine and five Trichophyton mentagrophytes strains. Antifungal agents tested included ciclopirox, fluconazole, griseofulvin, itraconazole, posaconazole, terbinafine, and voriconazole. Based on the data generated, two quality control isolates, one T. rubrum isolate and one T. mentagrophytes isolate, were identified and submitted to the American Type Culture Collection (ATCC) for inclusion as reference strains. Ranges encompassing 95.2 to 97.9% of all data points for all seven drugs were established.

Antifungal Agents↗

PubMed2006

Determination of MICs of aminocandin for Candida spp. and filamentous fungi.

Candida and Aspergillus spp., as well as other filamentous molds, have increasingly been reported as the causes of severe invasive fungal infections. We evaluated the new echinocandin aminocandin (AMN) for its antifungal activities against a range of fungal pathogens by determination of the MICs for the organisms. The MICs of the comparator drugs amphotericin B, caspofungin, micafungin, and voriconazole were also determined. The MICs of AMN for 25 strains each of non-Candida albicans Candida spp. (including Candida parapsilosis, Candida krusei, Candida guilliermondii, and Candida tropicalis), Aspergillus fumigatus, Scedosporium spp., Fusarium spp., and zygomycetes (including Absidia, Mucor, and Rhizopus spp.) were determined by using the Clinical and Laboratory Standards Institute M27-A2 and M38-A methodologies for yeasts and filamentous molds, respectively. The MIC ranges of AMN for all yeasts were similar (0.03 to 4.0 microg/ml), while the MIC ranges of AMN for filamentous fungi were species specific. AMN demonstrated potent antifungal activity against A. fumigatus, limited activity against Scedosporium spp., and no activity against zygomycetes or Fusarium spp. Our data showed that AMN demonstrated potent antifungal activities against all of the yeasts and Aspergillus isolates tested, suggesting that AMN could be an important addition to our arsenal of antifungals for the treatment of invasive fungal disease.

Antifungal Agents↗

PubMed2006

Zygomycosis: the re-emerging fungal infection.

Invasive fungal infections are major medical complications in immunocompromised patients. The recent rise in the incidence of cancer and the increased use of newer medical treatment modalities, including organ transplantations, have resulted in growing numbers of highly immunosuppressed individuals. Although aspergillosis and candidiasis are among the most common invasive mycoses in such patients, there is evidence that the incidence of infectious diseases caused by Zygomycetes has risen significantly over the past decade. Patients with diabetes, malignancies, solid organ or bone marrow transplants, or iron overload and those receiving immunosuppressive agents, deferoxamine therapy, or broad-spectrum antimicrobial drugs are at highest risk for zygomycosis. This review details the emergence and importance of zygomycosis in current clinical practice and its manifestations and management. The etiologic species, pathogenesis and risk factors for zygomycosis are reviewed and updated. The clinical spectrum of zygomycosis is now broader, and it can be difficult to distinguish between mucormycosis and enthomophthoramycosis, both of which can manifest as disease ranging from a superficial infection to an angioinvasive infection with high mortality. Finally, the three-part treatment strategy (antifungal drugs, surgery, control of underlying diseases) is reviewed. Lipid formulations of amphotericin B are the antifungal agents of choice for treatment of zygomycosis. A novel antifungal triazole, posaconazole, has been developed and may become approved for treatment of zygomycosis. The clinical experience with adjunctive treatments like colony-stimulating factors, interferon-gamma, and hyperbaric oxygen therapy is still limited.

Amphotericin B↗

PubMed2006

Correlation of MIC with outcome for Candida species tested against voriconazole: analysis and proposal for interpretive breakpoints.

Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between the in vitro activity and outcome from both in vivo and clinical studies. Using data generated by standardized broth microdilution and disk diffusion test methods, the Antifungal Susceptibility Subcommittee of the Clinical and Laboratory Standards Institute has now proposed interpretive breakpoints for voriconazole and Candida species. The MIC distribution for voriconazole was determined using a collection of 8,702 clinical isolates. The overall MIC90 was 0.25 microg/ml and 99% of the isolates were inhibited at < or = 1 microg/ml of voriconazole. Similar results were obtained for 1,681 Candida isolates (16 species) from the phase III clinical trials. Analysis of the available data for 249 patients from six phase III voriconazole clinical trials demonstrated a statistically significant correlation (P = 0.021) between MIC and investigator end-of-treatment assessment of outcome. Consistent with parallel pharmacodynamic analyses, these data support the following MIC breakpoints for voriconazole and Candida species: susceptible (S), < or = 1 microg/ml; susceptible dose dependent (SDD), 2 microg/ml; and resistant (R), > or = 4 microg/ml. The corresponding disk test breakpoints are as follows: S, > or = 17 mm; SDD, 14 to 16 mm; and R, < or = 13 mm.

Antifungal Agents↗

PubMed2004

Choices aplenty: antifungal prophylaxis in hematopoietic stem cell transplant recipients.

The incidence of invasive fungal infection (IFIs) in hematopoietic stem cell transplantation (HSCT) recipients ranges from 10 to 25% with an overall case fatality rate of up to 70-90%. Candida and Aspergillus genera remain the two most common pathogens. Although fluconazole prophylaxis in this population has been moderately effective in reducing mortality due to invasive candidiasis, this agent does not have activity against invasive aspergillosis (IA) and other mould. Several new agents such as voriconazole and caspofungin have enhanced potency and broad-spectrum antifungal activity and show promising results against yeasts and filamentous fungi when given as therapy and as chemoprophylaxis. Further, new diagnostic tools to detect circulating fungal antigens in biological fluids and PCR-based methods to detect species or genus-specific DNA or RNA have been developed. Incorporating these techniques along with clinical criteria appear to improve the accuracy of preclinical diagnosis of IFIs. Such approaches may alter the current treatment strategy from prophylaxis to pre-emptive therapy, thereby potentially decreasing cost and toxicity in high-risk patients.

Antifungal Agents↗

PubMed2004

Intra- and interlaboratory study of a method for testing the antifungal susceptibilities of dermatophytes.

The National Committee for Clinical Laboratory Standards (NCCLS) M38-A standard for the susceptibility testing of conidium-forming filamentous fungi does not explicitly address the testing of dermatophytes. This multicenter study, involving six laboratories, investigated the MIC reproducibility of seven antifungal agents tested against 25 dermatophyte isolates (5 blinded pairs of five dermatophyte species per site for a total of 300 tests), using the method of dermatophyte testing developed at the Center for Medical Mycology, Cleveland, Ohio. The dermatophytes tested included Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton tonsurans, Epidermophyton floccosum, and Microsporum canis. Seven antifungals with activity against dermatophytes were tested, including ciclopirox, fluconazole, griseofulvin, itraconazole, posaconazole, terbinafine, and voriconazole. Interlaboratory MICs for all isolates were in 92 to 100% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 88 to 99% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Intralaboratory MICs between blinded pairs were in 97% agreement at a visual endpoint reading of 50% inhibition as compared to the growth control and 96% agreement at a visual endpoint reading of 80% inhibition as compared to the growth control. Data from this study support consideration of this method as an amendment to the NCCLS M38-A standard for the testing of dermatophytes.

Antifungal Agents↗

PubMed2004

Evaluation of antifungal efficacy in an optimized animal model of Trichophyton mentagrophytes-dermatophytosis.

Dermatophytoses are known to cause considerable discomfort, cosmetic problems and financial loss that have been recognized as a significant health concern worldwide. Since currently available antifungal agents have limitations in their efficacy, new agents are being developed. This study was undertaken to optimize an in vivo model of experimental dermatophytosis for evaluation of the efficacy of antifungal compounds. Guinea pigs were infected with different inocula of T. mentagrophytes to establish dermatophytosis. The optimal conditions for dermatophytosis in guinea pigs were found to be an inoculum size of 1 x 10(7) fungal cells applied on abraded skin. After optimization, animals were treated with oral or topical formulations of terbinafine. The optimized guinea pig model was found to be highly reproducible, and useful in the primary screening and evaluation of the anti-dermatophytic efficacy of topical and oral formulations of antifungal agents.

Administration, Cutaneous↗

PubMed2003

Indoor mold, toxigenic fungi, and Stachybotrys chartarum: infectious disease perspective.

Damp buildings often have a moldy smell or obvious mold growth; some molds are human pathogens. This has caused concern regarding health effects of moldy indoor environments and has resulted in many studies of moisture- and mold-damaged buildings. Recently, there have been reports of severe illness as a result of indoor mold exposure, particularly due to Stachybotrys chartarum. While many authors describe a direct relationship between fungal contamination and illness, close examination of the literature reveals a confusing picture. Here, we review the evidence regarding indoor mold exposure and mycotoxicosis, with an emphasis on S. chartarum. We also examine possible end-organ effects, including pulmonary, immunologic, neurologic, and oncologic disorders. We discuss the Cleveland infant idiopathic pulmonary hemorrhage reports in detail, since they provided important impetus for concerns about Stachybotrys. Some valid concerns exist regarding the relationship between indoor mold exposure and human disease. Review of the literature reveals certain fungus-disease associations in humans, including ergotism (Claviceps species), alimentary toxic aleukia (Fusarium), and liver disease (Aspergillys). While many papers suggest a similar relationship between Stachybotrys and human disease, the studies nearly uniformly suffer from significant methodological flaws, making their findings inconclusive. As a result, we have not found well-substantiated supportive evidence of serious illness due to Stachybotrys exposure in the contemporary environment. To address issues of indoor mold-related illness, there is an urgent need for studies using objective markers of illness, relevant animal models, proper epidemiologic techniques, and examination of confounding factors.

Air Microbiology↗

PubMed2003

Uses and limitations of the XTT assay in studies of Candida growth and metabolism.

Colorimetric tetrazolium assays are used increasingly in studies of fungi, often in the absence of standardization or correlation with other methods. We examined species- and strain-related tetrazolium metabolism in Candida albicans and Candida parapsilosis by using XTT [2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide] and WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphonyl)-2H-tetrazolium] and found marked variations. Also, significant signal was often missed in the absence of dimethyl sulfoxide extraction.

Candida↗

PubMed2003

Human hyalohyphomycoses: a review of human infections due to Acremonium spp., Paecilomyces spp., Penicillium spp., and Scopulariopsis spp.

Human infections due to opportunistic molds are on the rise. This is due to recent advances in medical technology that have led to increased numbers of patients who are immunosuppressed, receiving broad-spectrum antibiotics, or have indwelling medical devices. In this article, human infections caused by four hyalohyphomycoses, Acremonium spp., Paecilomyces spp., Penicillium spp., and Scopulariopsis spp., will be reviewed. Specific areas of focus will include the epidemiology, mycology, clinical presentations, and treatment options for each of these four hyaline molds.

Acremonium↗

PubMed2002

Antifungal susceptibility of Candida biofilms: unique efficacy of amphotericin B lipid formulations and echinocandins.

Biofilms, likely the predominant mode of device-related microbial infection, exhibit resistance to antimicrobial agents. Evidence suggests that Candida biofilms have dramatically reduced susceptibility to antifungal drugs. We examined antifungal susceptibilities of Candida albicans and Candida parapsilosis biofilms grown on a bioprosthetic model. In addition to conventional agents, we determined if new antifungal agents (triazoles, amphotericin B lipid formulations, and echinocandins) have activities against Candida biofilms. We also explored effects of preincubation of C. albicans cells with subinhibitory concentrations (sub-MICs) of drugs to see if they could modify subsequent biofilm formation. Finally, we used confocal scanning laser microscopy (CSLM) to image planktonic- and biofilm-exposed blastospores to examine drug effects on cell structure. Candida biofilms were formed on silicone elastomer and quantified by tetrazolium and dry weight (DW) assays. Susceptibility testing of fluconazole, nystatin, chlorhexidine, terbenafine, amphotericin B (AMB), and the triazoles voriconazole (VRC) and ravuconazole revealed resistance in all Candida isolates examined when grown as biofilms, compared to planktonic forms. In contrast, lipid formulations of AMB (liposomal AMB and AMB lipid complex [ABLC]) and echinocandins (caspofungin [Casp] and micafungin) showed activity against Candida biofilms. Preincubation of C. albicans cells with sub-MIC levels of antifungals decreased the ability of cells to subsequently form biofilm (measured by DW; P < 0.0005). CSLM analysis of planktonic and biofilm-associated blastospores showed treatment with VRC, Casp, and ABLC resulted in morphological alterations, which differed with each agent. In conclusion, our data show that Candida biofilms show unique susceptibilities to echinocandins and AMB lipid formulations.

Amphotericin B↗

PubMed2002

Comparison of biofilms formed by Candida albicans and Candida parapsilosis on bioprosthetic surfaces.

Little is known about fungal biofilms, which may cause infection and antibiotic resistance. In this study, biofilm formation by different Candida species, particularly Candida albicans and C. parapsilosis, was evaluated by using a clinically relevant model of Candida biofilm on medical devices. Candida biofilms were allowed to form on silicone elastomer and were quantified by tetrazolium (XTT) and dry weight (DW) assays. Formed biofilm was visualized by using fluorescence microscopy and confocal scanning laser microscopy with Calcofluor White (Sigma Chemical Co., St. Louis, Mo.), concanavalin A-Alexafluor 488 (Molecular Probes, Eugene, Oreg.), and FUN-1 (Molecular Probes) dyes. Although minimal variations in biofilm production among invasive C. albicans isolates were seen, significant differences between invasive and noninvasive isolates (P < 0.001) were noted. C. albicans isolates produced more biofilm than C. parapsilosis, C. glabrata, and C. tropicalis isolates, as determined by DW assays (P was <0.001 for all comparisons) and microscopy. Interestingly, noninvasive isolates demonstrated a higher level of XTT activity than invasive isolates. On microscopy, C. albicans biofilms had a morphology different from that of other species, consisting of a basal blastospore layer with a dense overlying matrix composed of exopolysaccharides and hyphae. In contrast, C. parapsilosis biofilms had less volume than C. albicans biofilms and were comprised exclusively of clumped blastospores. Unlike planktonically grown cells, Candida biofilms rapidly (within 6 h) developed fluconazole resistance (MIC, >128 microg/ml). Importantly, XTT and FUN-1 activity showed biofilm cells to be metabolically active. In conclusion, our data show that C. albicans produces quantitatively larger and qualitatively more complex biofilms than other species, in particular, C. parapsilosis.

Antifungal Agents↗

PubMed2002

Effects of fluconazole singly and in combination with 5-fluorocytosine or amphotericin B in the treatment of cryptococcal meningoencephalitis in an intracranial murine model.

In this study we developed a highly reproducible intracranial murine model of cryptococcosis. Mice (Balb/c, 5-7 weeks old) were challenged intracranially and treated with intermediate (30 mg/kg) or high (90 mg/kg) dose fluconazole, and amphotericin B (0.75 mg/kg), administered singly or in combination with flucytosine (100 mg/kg). Survival and brain CFU analyses were performed. Effect of fluconazole prophylaxis was also determined. Our data show that the developed model mimics clinical signs of cryptococcal meningitis. In single treatment, fluconazole (30 mg/kg) was more efficacious than amphotericin B or flucytosine (P < 0.0001). Combination treatment led to significantly increased anticryptococcal activity, which was highest for high dose fluconazole + flucytosine (P < 0.0001). However, no significant difference was observed between high dose fluconazole treatment with and without flucytosine (P >0.05). Fluconazole prophylaxis led to a significant decrease in brain CFU. In conclusion, high dose fluconazole administered post-infection, or as prophylaxis, may be highly efficacious in the treatment and prevention of meningoencephalitis.

Amphotericin B↗

PubMed2001

Candida: a causative agent of an emerging infection.

Incidences of infections due to Candida have increased over the last 15-20 y. This increase in the incidence and the high associated mortality rate despite therapy has focused the attention on this disease and prompted investigators to undertake research aimed at understanding the pathogenesis of this disease as well as methods to treat it. This paper discusses recent developments in the Candida field and the impact they have on patient management.

Antifungal Agents↗

PubMed2001

Extracellular phospholipase activity is a virulence factor for Cryptococcus neoformans.

The human pathogenic fungus Cryptococcus neoformans secretes a phospholipase enzyme that demonstrates phospholipase B (PLB), lysophospholipase hydrolase and lysophospholipase transacylase activities. This enzyme has been postulated to be a cryptococcal virulence factor. We cloned a phospholipase-encoding gene (PLB1) from C. neoformans and constructed plb1 mutants using targeted gene disruption. All three enzyme activities were markedly reduced in the mutants compared with the wild-type parent. The plb1 strains did not have any defects in the known cryptococcal virulence phenotypes of growth at 37 degrees C, capsule formation, laccase activity and urease activity. The plb1 strains were reconstituted using the wild-type locus and this resulted in restoration of all extracellular PLB activities. In vivo testing demonstrated that the plb1 strain was significantly less virulent than the control strains in both the mouse inhalational model and the rabbit meningitis model. We also found that the plb1 strain exhibited a growth defect in a macrophage-like cell line. These data demonstrate that secretory phospholipase is a virulence factor for C. neoformans.

Acyltransferases↗

PubMed2001

Fungal phospholipase activity and susceptibility to lipid preparations of amphotericin B.

It has been postulated that phospholipases of fungal origin can affect in vitro susceptibility testing of amphotericin B lipid complex (ABLC). We used specific phospholipase-deficient mutants of Candida albicans and Cryptococcus neoformans in susceptibility testing and demonstrated that extracellular fungal phospholipase activity does not influence the in vitro susceptibilities of these two fungi to ABLC.

Amphotericin B↗

PubMed2001

Antifungal susceptibility testing: practical aspects and current challenges.

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

Animals↗

PubMed2001

Hyphae and yeasts of Candida albicans differentially regulate interleukin-12 production by human blood monocytes: inhibitory role of C. albicans germination.

The role of Candida albicans yeast-to-hyphae transition in interleukin-12 (IL-12) production by monocytes was investigated. Germinating C. albicans not only failed to induce IL-12 p70 but also suppressed IL-12 production induced by heat-killed C. albicans. Comparison of the abilities of germinating C. albicans and agerminating mutants to inhibit IL-12 production showed that germination of C. albicans plays a critical role in the inhibition of IL-12 production.

Candida albicans↗