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Comparison of susceptibility of fungal isolates to lufenuron and nikkomycin Z alone or in combination with itraconazole

Richard F. HectorDepartment of Epidemiology and Biostatistics, University of California, San Francisco, CA 94143.

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Autumn P. DavidsonDepartment of Medicine and Epidemiology, School of Medicine, University of California, Davis, CA 95616.

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Suzanne M. JohnsonDepartment of Microbiology and Immunology, School of Medicine, University of California, Davis, CA 95616.

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Abstract

Objective—To evaluate and compare the in vitro antifungal properties of lufenuron and nikkomycin Z against isolates of Coccidioides immitis and Aspergillus fumigatus when used singly and in combination with the azole antifungal agent itraconazole.

Sample Population—3 clinical isolates of A fumigatus and the Silveira strain of C immitis.

Procedure—The fungal isolates were tested in vitro for susceptibility to the single and combination of compounds by use of microtiter-format susceptibility methods. Minimum inhibitory concentration end points were determined visually, and the contents of representative wells were examined microscopically for evidence of morphologic effects on fungi.

Results—No evidence of inhibition, either by susceptibility testing or direct microscopic examination of treated cells, was obtained with lufenuron under experimental conditions. In contrast, nikkomycin Z, a known inhibitor of fungal chitin synthesis, had potent activity against C immitis when used singly. A synergistic interaction between nikkomycin Z and itraconazole was found against isolates of both species tested.

Conclusions and Clinical Relevance—On the basis of our in vitro data, lufenuron does not appear to possess antifungal properties. ( Am J Vet Res 2005;66:1090–1093)

Abstract

Objective—To evaluate and compare the in vitro antifungal properties of lufenuron and nikkomycin Z against isolates of Coccidioides immitis and Aspergillus fumigatus when used singly and in combination with the azole antifungal agent itraconazole.

Sample Population—3 clinical isolates of A fumigatus and the Silveira strain of C immitis.

Procedure—The fungal isolates were tested in vitro for susceptibility to the single and combination of compounds by use of microtiter-format susceptibility methods. Minimum inhibitory concentration end points were determined visually, and the contents of representative wells were examined microscopically for evidence of morphologic effects on fungi.

Results—No evidence of inhibition, either by susceptibility testing or direct microscopic examination of treated cells, was obtained with lufenuron under experimental conditions. In contrast, nikkomycin Z, a known inhibitor of fungal chitin synthesis, had potent activity against C immitis when used singly. A synergistic interaction between nikkomycin Z and itraconazole was found against isolates of both species tested.

Conclusions and Clinical Relevance—On the basis of our in vitro data, lufenuron does not appear to possess antifungal properties. ( Am J Vet Res 2005;66:1090–1093)