Interventions to reduce the spread of ESBL/pAmpC-producing E. coli in the broiler production pyramid

ESBL/pAmpC-producing bacteria are resistant against beta-lactam antibiotics, including (amino)penicillins and cephalosporins, which affects treatment options for infection with these bacteria. ESBL/pAmpC-producing bacteria are present in humans, animals, food and the environment and are therefore considered a One Health problem. A high prevalence of these bacteria can be found in broiler chickens. In this thesis the spread of ESBL/pAmpC-producing bacteria in the broiler production chain and potential interventions to reduce the spread of these bacteria were studied. ESBL/pAmpC-producing bacteria can spread throughout the broiler production chain from parents to offspring, at the hatchery, on or between farms, and between farms and their environment. Exposure of young broilers to only small numbers of ESBL/pAmpC-producing bacteria leads to rapid colonization of these young broilers, followed by fast transmission within the flock. Therefore, interventions to prevent colonization with ESBL/pAmpC-producing bacteria should be applied as soon as possible after hatching. Different interventions were tested in an animal model. Competitive exclusion, the supply of intestinal bacteria from adult birds, prevented colonization of young birds if supplied before exposure to ESBL/pAmpC-producing bacteria. Compartmentalization, subdividing the flock, reduced the transmission rate within a broiler flock but could not stop it. Ideally, combinations of interventions should be applied in the broiler production chain targeting different transmission routes. The animal model developed in this thesis is very useful to test potential interventions. Knowledge on the attribution of the different transmission routes to the occurrence of ESBL/pAmpC-producing bacteria will help to further design the most effective intervention strategies.