Competitive Exclusion Reduces Transmission and Excretion of Extended-Spectrum-β-Lactamase-Producing Escherichia coli in Broilers

Abstract

Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases (pAmpC) are enzymes able to hydrolyze a large variety of β-lactam antibiotics, including third-generation cephalosporins and monobactams. Broilers and broiler meat products can be highly contaminated with ESBL- and pAmpC-producing <i>Escherichia coli</i> strains, also known as extended-spectrum cephalosporin (ESC)-resistant <i>E. coli</i> strains, and can be a source for human infections. As few data on interventions to reduce the presence of ESC-resistant <i>E. coli</i> in broilers are available, we used transmission experiments to examine the role of competitive exclusion (CE) on reducing transmission and excretion in broilers. A broiler model to study the transmission of ESC-resistant <i>E. coli</i> was set up. Day-old chickens were challenged with an ESBL-producing <i>E. coli</i> strain isolated from healthy broilers in the Netherlands. Challenged and not challenged chicks were housed together in pairs or in groups, and ESBL-producing <i>E. coli</i> transmission was monitored via selective culturing of cloacal swab specimens. We observed a statistically significant reduction in both the transmission and excretion of ESBL-producing <i>E. coli</i> in chicks treated with the probiotic flora before <i>E. coli</i> challenge compared to the transmission and excretion in untreated controls. In conclusion, our results support the use of competitive exclusion as an intervention strategy to control ESC-resistant <i>E. coli</i> in the field.<b>IMPORTANCE</b> Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC β-lactamases are a primary cause of resistance to β-lactam antibiotics among members of the family <i>Enterobacteriaceae</i> in humans, animals, and the environment. Food-producing animals are not exempt from this, with a high prevalence being seen in broilers, and there is evidence pointing to a possible foodborne source for human contamination. We investigated the effect of administration of a commercial probiotic product as an intervention to reduce the amount of ESBL-producing <i>Escherichia coli</i> in broilers. Our results showed a substantial reduction in the level of colonization of broiler intestines by ESBL-producing <i>E. coli</i> after administration of commercial probiotic product. The protective effect provided by these probiotics could be implemented on a larger scale in poultry production. Reductions in the levels of ESBL-producing <i>Enterobacteriaceae</i> in the food chain would considerably benefit public health.