Antimicrobial resistance in breeding pigs in Germany – differences between 2015 and 2023

Direct contact with their offspring during the first few weeks makes sows a potential source of resistant bacteria for fattening pigs and food products derived from pigs. Moreover, staff working with breeding pigs are exposed to their bacterial flora which also includes zoonotic pathogens and antimicrobial resistant bacteria. In this study we investigated the antimicrobial resistance of E. coli and the prevalence and the antimicrobial resistance of Salmonella enterica, cephalosporin-resistant Escherichia coli (CTXR-E. coli) and methicillin-resistant Staphylococcus aureus (MRSA) in breeding pigs in Germany in 2015 and 2023 to identify potential changes in the prevalence and resistance over time during a period of reduction of antimicrobial use in farm animals in Germany. Resistance in E. coli to tetracycline and sulfamethoxazole and the prevalence of CTXR-E. coli decreased in breeding herds between 2015 and 2023 in Germany. The proportion of E. coli that were susceptible to all tested substances increased. In contrast, there were no changes in the herd prevalence of Salmonella and MRSA. Resistance of E. coli to some antimicrobials was associated with the presence of MRSA in the herd and to herd size. Larger herds were more prone to harbour MRSA and CTXR-E. coli. Results demonstrate a minor decrease in AMR in E. coli from breeding pigs in Germany but no decrease in the prevalence of Salmonella or MRSA.