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7th International Conference of the European College of Veterinary Microbiology (ECVM)

10–12 Sept 2025
Kaiserin-Friedrich-Stiftung, Berlin
Europe/Berlin timezone

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Oxytetracycline 30µg agar disk diffusion results for four QC strains

12 Sept 2025, 12:30
15m
Seminar Room

Seminar Room
Oral presentation Microbiological Diagnostics Diagnostics

Speaker

Andrea Feßler

Description

Antimicrobial susceptibility testing is important to predict the outcome of antimicrobial therapy. Therefore, the aim was to compare oxytetracycline 30µg disk and media lots for four reference strains as a pre-requisite to establish QC ranges. Eight laboratories tested Escherichia coli ATCC® 25922, Staphylococcus aureus ATCC® 25923, S. aureus ATCC® 29213, and Streptococcus pneumoniae ATCC® 49619 with 2 lots oxytetracycline 30µg disks 10 times on 3 lots agar according to CLSI and EUCAST. As quality control, one lot tetracycline 30µg disks was tested on one medium lot. The data was analyzed using the RangeFinder software. All tetracycline values were in range. For S. aureus ATCC® 25923 a range of 21-35mm (98.96% values included), mean values were 25.74mm, 30.63mm and 26.53mm for media und 28.12.mm and 27.15mm for disks. For S. aureus ATCC® 29213 the calculated. range was 20-33mm (96.88%; mean 24.45/28.22/25.54mm [media], 26.68/25.46mm [disks]). The E. coli ATCC® 25922 range is 17-29mm (99.79%; mean 21.47/25.76/21.78mm [media], 23.85/22.16mm [disks]). For S. pneumoniae ATCC® 49619 (CLSI) a range of 24-35mm (98.96 %; mean 28.57/30.49/28.87mm [media], 29.90/28.72mm [disks]) was determined. EUCAST method revealed a range of 24-37mm (100%; mean 29.19/31.60/29.85mm [media], 30.74/29.69mm [disks]). In conclusion, for media lot B the zone diameters seemed larger. When quality control data is out of range, the use of an alternative medium/disks lots might be an option.

Keywords

antimicrobial susceptibility testing, validation, CLSI, EUCAST, interlaboratory trial, RangeFinder software

Registration ID ECVM25-0114
Professional Status of the submitter, who is also the speaker Postdoc

Authors

Johanna Jahnen (Institute of Microbiology and Epizootics, Centre for Infection Medicine, School of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany) Erika Matuschek (EUCAST Development Laboratory, Växjö, Sweden) Dr Christiane Cuny (Robert Koch Institute, Wernigerode, Germany,) Camille Fleury (Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland) Dr Andrea Niehues (Farm Animal Clinic, School of Veterinary Medicine, Freie Universität Berlin) Kristina Kadlec (Dairy Herd Consulting and Research Company (MBFG), Wunstorf, Germany) Dr Heike Kaspar (Federal Office of Consumer Protection and Food Safety (BVL), Berlin, Germany) Maria Kluge (Federal Office of Consumer Protection and Food Safety (BVL), Berlin, Germany) Leonard Limpinsel (Bavarian Health and Food Safety Authority (LGL), Oberschleißheim, Germany) Chris Leisner (Farm Animal Clinic, School of Veterinary Medicine, Freie Universität Berlin, Germany) Kerstin Meyer (Dairy Herd Consulting and Research Company (MBFG), Wunstorf, Germany) Nicole Muff (Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland) Gudrun Overesch (Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Bern, Switzerland) Prof. Julia M. Riehm (Bavarian Health and Food Safety Authority (LGL), Oberschleißheim, Germany) Dr Paul Siller (Federal Office of Consumer Protection and Food Safety (BVL), Berlin, Germany,) Prof. Stefan Schwarz (Institute of Microbiology and Epizootics, Centre for Infection Medicine, School of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany) Andrea Feßler

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External references

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Peer reviewing

Paper

Accepted on by Inga Regling
abstract2894.pdf