title: Fungal strains and the development of tolerance against natamycin.
abstract: 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.
authors: DSM Biotechnology Center, PO Box 1, 2600 MA Delft, The Netherlands.
authors: Hugo
authors: H
authors: Streekstra
authors: Applied and Industrial Mycology, CBS-KNAW Biodiversity Center, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
authors: Alex E E
authors: AE
authors: Verkennis
authors: Applied and Industrial Mycology, CBS-KNAW Biodiversity Center, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
authors: Robbert
authors: R
authors: Jacobs
authors: DSM Biotechnology Center, PO Box 1, 2600 MA Delft, The Netherlands.
authors: Angelina
authors: A
authors: Dekker
authors: DSM Biotechnology Center, PO Box 1, 2600 MA Delft, The Netherlands.
authors: Jacques
authors: J
authors: Stark
authors: Applied and Industrial Mycology, CBS-KNAW Biodiversity Center, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands. Electronic address: j.dijksterhuis@cbs.knaw.nl.
authors: Jan
authors: J
authors: Dijksterhuis
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology; D000935:Antifungal Agents / Q000494:pharmacology; D025141:Drug Resistance, Fungal; D005520:Food Preservatives / Q000494:pharmacology; D005658:Fungi / Q000187:drug effects* / Q000502:physiology; D005670:Fusarium / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D010866:Natamycin / Q000494:pharmacology*; D009761:Nystatin / Q000494:pharmacology
chemical_list: D000935:Antifungal Agents; D005520:Food Preservatives; D009761:Nystatin; D000666:Amphotericin B; D010866:Natamycin
keywords: Antifungal compounds; Antimicrobial resistance; Food additive; Natamycin; Polyene antibiotics