The attempt to improve barn hygiene of weaned pigs with the aim of reducing the spread of antimicrobial resistance

The spread of antimicrobial-resistant pathogens in animal husbandry is usually attributed to poor hygiene and biosecurity. We therefore conducted an experimental trial to improve hygiene management in weaned pig houses and assessed the impact on the spread of antimicrobial resistance. For each of the two groups, the so-called experimental group and the control group, three batches of piglets were taken from the same pig breeder and kept in pre-cleaned flat decks. Hygiene conditions (cleaning, disinfection, dust removal and fly control) were improved on the flat decks of the experimental group, while regular procedures were followed in the control groups. The extent and spread of antibiotic resistance (AMR) were determined in Escherichia coli (E. coli; resistance indicator) using cultivation-dependent (CFU) and -independent (qPCR) methods as well as genomic sequences in various samples, including feces, flies, food, dust and swab. Surprisingly, there were no significant differences in the prevalence of resistant E. coli between the flat decks managed with conventional hygiene management and those managed with improved methods. Ampicillin - and sulfonamide-resistant E. coli were common, while cefotaxime-resistant E. coli was detected in rare cases and ciprofloxacin was absent in both groups. Factors such as colonization of piglets with AMR E. coli before arrival at fattening farm and frequent treatment of bacterial infections with antibiotics overshadowed the impact of hygiene management. The biocide tolerance test also showed no development of resistance to the disinfectants regularly used for house cleaning. It became clear that further attempts at hygiene management alone could not lead to a reduction in AMR in the piglet house. The multifactorial nature of AMR prevalence in the piglet house highlights the need for a holistic approach to AMR control strategies.