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Published on: February 14, 2018
Susceptibility testing of Aspergillus niger strains isolated from poultry to antifungal drugs--a comparative study of
S Tokarzewski1, G Ziółkowska, A Nowakiewicz
1Sub-Department of Veterinary Microbiology, Faculty of Veterinary Medicine, University of Life Sciences in Lublin, Akademicka 12, 20-033 Lublin, Poland. statok.wet@gmail.com
Abstract:
The aim of this study was to determine the sensitivity of Aspergillus niger strains isolated from birds to available antifungal drugs using different in vitro assays--classical disk diffusion, Etest and broth microdilution NCCLS/CLSI M 38-A. The study material consisted of about 2.000 swabs and samples from different species of birds. A. niger (n=10) was accounted for 6.81% of the total pool of strains isolated. Determinations were made for 13 antifungal drugs using the disk diffusion method. The A. niger exhibited high susceptibility to enilconazole, terbinafine, voriconazole, tioconazole and ketoconazole, low susceptibility to clotrimazole, miconazole and nystatin, and resistance to amphotericin B, itraconazole, pimaricin, fluconazole and 5-fluorocytosine. Minimum inhibitory concentration (MIC) was determined for 9 antifungal drugs using the micromethod of duplicate serial dilutions in a liquid medium. A. niger strains were most susceptible to enilconazole and voriconazole. MIC ranged from 0.0625 to 0.5 microg/ml for enilconazole, with MIC90-0.5 microg/ml and MIC50-0.125 microg/ml. The corresponding values for voriconazole were 0.25-1 microg/ml, 1 microg/ml and 0.5 microg/ml. MIC for amphotericin B and terbinafine ranged from 0.5 to 4 microg/ml, while the values for the remaining drugs were highly varied. MIC was measured by the gradient diffusion method using Etest for 5 antifungal drugs: amphotericin B, fluconazole, itraconazole, ketoconazole and voriconazole. By far the highest susceptibility was obtained in the case of voriconazole, with MIC ranging from 0.0625 to 1 microg/ml. MIC for amphotericin B ranged from 0.25 to 4 microg/ml, for itraconazole and ketoconazole ranging from 0.5 to 16 microg/ml. Methods available for this purpose are not always applicable in field conditions. The present results indicate that the Etest technique, due to its high percentage of agreement with the M 38-A microdilution method, should find application in medical and veterinary practice.
Insights
This study assessed Aspergillus niger bird isolates
Area of Science:
- Veterinary Mycology
- Antimicrobial Susceptibility Testing
Background:
- Aspergillus niger is an opportunistic fungal pathogen affecting avian species.
- Understanding antifungal drug susceptibility is crucial for effective treatment and disease management in birds.
Purpose of the Study:
- To determine the in vitro sensitivity of Aspergillus niger strains isolated from birds to various antifungal drugs.
- To compare the efficacy of different antifungal susceptibility testing methods.
Main Methods:
- Isolation and identification of Aspergillus niger from avian samples.
- Antifungal susceptibility testing using disk diffusion, Etest, and broth microdilution (NCCLS/CLSI M 38-A).
- Determination of Minimum Inhibitory Concentrations (MICs) for 13 antifungal drugs.
Main Results:
- Aspergillus niger strains showed high susceptibility to enilconazole and voriconazole.
- Resistance was observed against amphotericin B, itraconazole, pimaricin, fluconazole, and 5-fluorocytosine.
- The Etest method demonstrated good agreement with the broth microdilution method.
Conclusions:
- Voriconazole and enilconazole are promising agents for treating Aspergillus niger infections in birds.
- The Etest offers a practical alternative for antifungal susceptibility testing in veterinary settings.
- Standardized susceptibility testing is vital for guiding avian aspergillosis treatment.
