Publikationsdatenbank

Varying susceptibilities for sulfamethoxazole-trimethoprim among Staphylococcus aureus isolates from horse origin (2019)

Art

Poster

Autoren

Scholtzek, Anissa D. (WE 7)

Klein, Katja-Sophia (WE 17)

Stöckle, Sabita D. (WE 17)

Eichhorn, Inga (WE 7)

Walther, Birgit

Feßler, Andrea T. (WE 7)

Hanke, Dennis (WE 7)

Gehlen, Heidrun (WE 17)

Lübke-Becker, Antina (WE 7)

Schwarz, Stefan (WE 7)

Kongress

8th Symposium on Antimicrobial Resistance in Animals and the Environment

Tours Val de Loire - France, 01. – 03.07.2019

Quelle

8th Symposium on Antimicrobial Resistance in Animals and the Environment : Abstracts book : 1-3 July 2019 — UMR 1282 Infectiologie et Santé Publique Institut National de la Recherche Agronomique (Hrsg.)

France: INRA Science & Impact, 2019 — S. 128

Sprache

Englisch

Verweise

URL (Volltext): https://symposium.inrae.fr/arae2019/Abstract-Book

Kontakt

Pferdeklinik

Oertzenweg 19 b
14163 Berlin
+49 30 838 62299 / 62300
pferdeklinik@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Background and objectives:
Antimicrobial susceptibility testing of Staphylococcus aureusisolates from veterinary routine diagnostics using an automated testing system and abroth microdilution method (BMD) showed deviating results with respect to sulfamethoxazole/ trimethoprim (SXT). This observation was in accordance with a previous study in which BMD, broth macrodilution and agar disk diffusion (DD)had been compared [1]. Reading of test results for this combination might be challenging, since bacterial growth in the presence of SXT often shows trailing end points. Currently, growth reduction of ≥ 80% is considered as the MIC [2]. The aim of this study was to further investigate different methods for SXT susceptibility testing.

Materials and methods:
Susceptibility of 19 S. aureusisolates from 17 horses to SXT was initially tested via a commercially available automated system. Since subsequent SXT susceptibility testing results obtained with BMD [2] lacked consistence, a second commercially available automated system was used and further CLSI-approved approaches [2] were employed: two additional BMD tests, including another commercially available plate and an in-house set-up testing the susceptibility against sulfisoxazole (SUL) and trimethoprim (TMP) separately and disk diffusion (DD) for SXT, SUL and TMP. The strains S. aureusATCC®29213 (BMD) and ATCC®25923 (DD) were used as quality controls. Whole genome sequences wereobtained (Illumina MiSeq) and investigated for the respective resistance genes.

Results:
The first automated system classified all isolates as resistant to SXT, whereas the initial BMD identified only three strains as resistant and 16 as susceptible. Thesecond automated system identified 17 as resistant and two as susceptible. The subsequent BMD plate setup classified only one isolate as susceptible and all others as resistant. DD for SXT identified three isolates as resistant, eleven as intermediate, and five as susceptible. BMD for SUL correlated well with the first BMD, classifying the same strains as susceptible (n = 16) and resistant (n = 3), whereas in DD all isolates were susceptible to SUL. For TMP, BMD and DD, classified all strains as resistant.Both reference strains were always within the acceptable range [3]. All isolates harbored a trimethoprim resistance gene (dfrG[n=3] or dfrS1[n=16]).

Conclusion:
Results regarding the classification of S. aureusas susceptible or resistant to SXT must be interpreted with caution, since substantial differences can occur with the different susceptibility testing methods.