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Fungal strains and the development of tolerance against natamycin
- Streekstra, Hugo, Verkennis, Alex E.E., Jacobs, Robbert, Dekker, Angelina, Stark, Jacques, Dijksterhuis, Jan
- International journal of food microbiology 2016 v.238 pp. 15-22
- Aspergillus ochraceus, Fusarium, amphotericin B, antibiotic resistance, food preservatives, foods, fungi, minimum inhibitory concentration, natamycin, nystatin, selection pressure
- Antimicrobial resistance is a relevant theme with respect to both antibacterial and antifungal compounds. In this study we address the possible development of tolerance against the antifungal food preservative natamycin. A selection of 20 fungal species, originating from a medical as well as a food product context, was subjected to increasing concentrations of natamycin for prolonged time, a procedure designated as “training”. The range of Minimum Inhibitory Concentrations (M.I.C.) before (1.8–19.2μM) and after (1.8–19.8μM) training did not change significantly, but natamycin-exposure caused an increase of M.I.C. in 13 out of 20 tested strains. The average M.I.C. increased from 6.1 to 8.6μM and 4 strains showed a >2-fold increase of tolerance after training. One strain (of Aspergillus ochraceus) also showed increased tolerance to amphotericin B and nystatin. However, two Fusarium strains showed similar or even decreased tolerance for these other polyene antifungals.The work reported here shows that a continuous and prolonged increasing selection pressure induced natamycin tolerance in individual strains. This implies that such a selection pressure should be avoided in the technical application of natamycin to ensure its continued safe use as a food preservative.