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PRECLINICAL TESTING We perform a variety of in vitro tests that help to characterize a new compound's antifungal activity against a range of filamentous fungi and yeasts. We have a very large collection of frozen fungal strains that cause both systemic and topical fungal disease from which to draw. Our basic in vitro test is the minimum inhibitory concentration (MIC), which we perform according to appropriate Clinical and Laboratory Standards Institute (CLSI) guidelines. Dr. Ghannoum has been actively involved in the development of all of the approved CLSI standards for the susceptibility testing of yeasts and filamentous fungi, including M27-A3, M38-A2, and the recently published M51 agar diffusion assay. Dr. Ghannoum currently serves as the Chair of the CLSI Subcommittee on Antifungal Susceptibility Testing. From this basic microdilution assay, we are also able to perform minimum fungicidal concentration (MFC) assays to determine whether a drug acts in a static or cidal manner. We also offer combination MIC testing which will determine whether addition of one antifungal to a second antifungal will have a synergistic, antagonistic, or no effect on its activity. In addition, we can perform agar diffusion assays to measure zones of inhibition when testing formulations that are incompatible with broth dilutions, such as creams and lotions. Other in vitro testing includes time kill assays to characterize cidal action and development of resistance assays to determine whether fungal isolates will develop resistance to a drug following repeated exposure. Morphological effects of drugs can be visualized through various microscopic techniques, including phase and fluorescent microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In Vivo Testing We also have several assays to assess the safety and efficacy of new antifungal agents in animal models. The Center offers murine models of hematogenously disseminated candidiasis, fusariosis, and aspergillosis, which can be immunocompetent or immunocompromised depending on the strain. Additionally, the Center has in place a murine cryptococcosis intracranial model that mimics HIV infection. Survival observations as well as tissue fungal burden can be assessed. Due to the importance of the increase in fungal biofilm infections, we have developed both in vitro and in vivo biofilm models. These prosthetic device biofilm (fungal and bacterial) models use a combination of fungal burden and SEM to evaluate efficacy. Biofilm models include murine subcutaneous disk implantation and rabbit intravenous catheter. In addition to the systemic models of invasive mycoses, the Center has developed a guinea pig dermatophytosis model that has utility in evaluating the efficacy of oral and topical antifungals for the treatment of superficial infections. Clinical Trials The Center boasts an experienced clinical trials team dedicated entirely to all aspects of central laboratory administration. We are certified by the College of American Pathologists and CLIA and are directed by outstanding administrators who are leaders in the field. Dr. Mahmoud Ghannoum, our Laboratory Director, is the serving Chairman of the Clinical and Laboratory Standards Institute, Antifungal Subcommittee, and the Chair of the clinical trial consortium funded by the National Institute of Dental and Craniofacial called OHARA (Oral HIV AIDS Research Alliance) that totally is focused on clinical trials in association with the AIDS Clinical Trials Unit (ACTG). The Center serves as the repository for all Candida isolates obtained from clinical trials conducted under the auspices of the ACTG and is responsible for the identification and susceptibility testing of all strains. Further, the Center is the sponsor of the ongoing international trial of oral candidiasis using Gentian Violet. The Center has a highly trained staff experienced in direct microscopy and identification of dermatophytes, non-dermatophyte nail pathogens, and yeast isolates. Additionally, we are uniquely qualified to perform antifungal susceptibility on clinical trial isolates, having developed the method for dermatophyte testing adopted as part of the CLSI M38-A2 standard. Onychomycosis, tinea pedis, tinea capitis, miscellaneous
dermatophyte trials The Center provides support for clinical trials through all phases (Phase I through Phase III), from site selection to final database lock. Our services include training of site personnel at Investigator Meetings, furnishing and replenishing supplies, direct microscopy, fungal culture and isolate identification and long-term storage, susceptibility testing, and data management. We are flexible and always responsive to the needs of our clinical trial Sponsors and can provide help to avoid common pitfalls encountered in such complex trials. Site Personnel
Training The Center will present a training module at the trial Investigator Meeting that will cover important points of sample collection and shipping. For example, the successful culturing of dermatophyte isolates from onychomycosis is dependent upon having an adequate amount of subungual debris. Equally important is the thorough cleaning of the nail before sample collection, as both bacteria and saprophytic moulds grow at a much faster rate than dermatophytes and will overgrow the culture plates, resulting in non-recovery of dermatophyte pathogens. Direct Microscopy Direct examinations are performed using a fluorescent calcofluor white stain in KOH visualized with ultraviolet light, which greatly increases the sensitivity of the test as compared to conventional KOH. The availability of fluorescent microscopic facility will ensure higher enrollment and a lower rate of false negatives. Susceptibility Testing In the process of approving a new antifungal, the Food and Drug Administration requires data about the susceptibility of fungal isolates to clinical trial study drug, as well as to comparators currently in use. Also required is a comparison of susceptibility to study drug in isolates obtained at screening as compared to those obtained at end of treatment. This is to determine the propensity of the study drug to develop resistance in relevant organisms following repeated exposure over time. To that end, the Center saves all isolates obtained from study samples in our culture collection, which currently numbers well over 25,000 clinical strains. If you need to perform studies involving any of the above, please feel free to contact us for more details. |
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The
Center for Medical Mycology provides a variety of services, including: