Supplementary tables to: In-vitro antimicrobial resistance of Escherichia coli, Serratia marcescens, Klebsiella oxytoca and Klebsiella pneumoniae on Bavarian dairy farms between 2014-2022 Lea H. Pirner, Wolfram Petzl, Armin Gangl, Reglindis Huber-Schlenstedt, Ulrike S. Sorge

The objective of this study was to describe the changes in antimicrobial resistance of the Gram-negative mastitis pathogens Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, and Serratia marcescens on Bavarian dairy farms between 2014 and 2022. Escherichia coli, Klebsiella oxytoca, and Klebsiella pneumoniae showed only few resistances from the beginning and their MIC decreased for most of the tested antimicrobials over the nine years. While Serratia marcescens isolates were intrinsically resistant to both amoxicillin/clavulanate and cefazolin, they showed only few resistances towards all other antimicrobials tested. There was an increase of numbers of isolates for all four pathogens, with a particularly steep incline in 2018, possibly related to a change of the regulation for veterinary drug prescriptions in Germany in 2018. In summary, the proportion of in-vitro resistances remained low for all pathogens.