ESBL-producing Escherichia coli in wastewater from German slaughterhouses

The increasing prevalence of ESBL-producing <i>Escherichia (E.) coli</i> (ESBL-<i>E. coli</i>) poses a significant threat to human and animal health, with livestock identified as a critical reservoir. This study examined the occurrence and diversity of ESBL-<i>E. coli</i> in wastewater from four German slaughterhouses (pig and poultry) over two sampling periods. The primary objective of the study was to determine whether these facilities have a persistent colonization of AMR bacteria or whether their presence fluctuates daily depending on which animals are processed. Using selective media and subsequent whole-genome sequencing, 47 wastewater samples were analyzed and 86 ESBL-<i>E. coli</i> strains were isolated, 40 of which were multidrug-resistant (MDR). Specifically, 27 out of 37 isolates from poultry and 13 out of 49 isolates from pig slaughterhouses were confirmed as MDR. In contrast to the expectation of a long-term persistent colonization of the abattoirs, our results indicate a daily introduction of ESBL-<i>E. coli</i> by the animals processed. The consistent detection of these strains in wastewater from slaughterhouses underlines the role of these facilities as important hotspots for the dissemination of AMR bacteria in the environment. This underscores the urgent need for enhanced surveillance and control measures to curtail the spread of antimicrobial resistance.