The effects of competitive exclusion products on colonization and excretion of Extended Spectrum β-Lactamase-producing E. coli in Broilers

Abstract

ESBL-producing Enterobacteriaceae are frequently reported in broilers. ESBL-producing E. coli (ESBL-E. coli) is the most common ESBL-producing Enterobacterium in the Netherlands with a prevalence of 23% in broilers at slaughter in 2018. ESBL-producing bacteria show antibiotic resistance against β-lactam antibiotics and this can potentially spread to humans. Therefore, the poultry industry aims to reduce ESBL prevalence. For this, interventions have been investigated to make the broilers less susceptible to colonization of ESBL-producing bacteria after challenge and reduce excretion of colonized birds. Supply of competitive exclusion products results in early stabilization of the intestinal flora and is therefore considered as a promising intervention. Single administration of a competitive exclusion product before challenge with a high dose of ESBL-E. coli led to reduced colonization and excretion in previous studies, but could not prevent colonization. Therefore, in this study we evaluated the effects of prolonged administration of competitive exclusion products on colonization and excretion of ESBL-E. coli in broilers after challenge with a low dose of ESBL-E. coli at day 5. A total of 100 Ross 308 broilers were randomly distributed at day of hatch over 8 isolators. Four groups were included in this study: a negative control group (unchallenged, untreated), positive control group (challenged, untreated) and two treatment groups that received competitive exclusion products, i.e. Aviguard® (unselected fermented bacteria) or Poultrystar® (selection of prebiotics and probiotics). The treatments were supplied via drinking water at day 0 to 14. At day 5, broilers were orally inoculated with 0.5 mL 102.0 CFU/ml E. coli encoding the beta–lactamase gene blaCTX-M-1 on an IncI plasmid. Presence and concentration of ESBL-E. coli was determined using faeces from cloacal swabs (day 0-14, 16, 19 and 21) and caecal content (day 21). Time until colonization between groups was analyzed using cox proportional hazard model. Excretion levels were analyzed with a linear mixed-effects regression model. Aviguard® led to a prevention of colonization with ESBL-E. coli. Poultrystar® resulted in some isolators to delayed time until colonization and reduced excretion of ESBL-E. coli and caecal content. This study showed that colonization after a low dose challenge with ESBL-E. coli can be prevented or delayed and can reduce excretion. Prolonged administration of competitive exclusion products applied shortly after hatch may be applicable as an intervention to reduce ESBL prevalence in the poultry industry.