Fig. 5

The putative mechanisms of growth promotion by altering the foregut microbiota through CTC and MCE treatment. (Left) The antibiotic CTC as an exogenous pressure interfered with gut microbial competition and increased the Kitasatospora and Streptomyces, which are multi-antibiotic-resistant bacteria and antibiotic producers. The induced multi-antibiotics and antibiotic synergist (clavulanic acid) amplify the antimicrobial effects. Additionally, CTC enhanced microbial synthesis pathways of nutrients and secondary bile acids in the host. (Right) MCE increased Lactobacillus to benefit the host in many aspects, such as producing vitamins and generating lactate for anaerobic bacteria to produce butyrate, an anti-inflammatory compound and energy source for the intestine. Some bacteria were competitively inhibited by Lactobacillus. Additionally, MCE promoted the synthesis pathways of amino acids, vitamins, and secondary bile acids to provide nutrition for the host