16S rRNA Sequencing Analysis of the Gut Microbiota in Broiler Chickens Prophylactically Administered with Antimicrobial Agents

Abstract

In poultry production, gut microbiota (GM) plays a pivotal role and influences different host functions related to the efficiency of production performances. Antimicrobial (AM) use is one of the main factors affecting GM composition and functions. Although several studies have focused their attention on the role of AMs as growth promoters in the modulation of GM in broilers, the consequences of higher AM concentrations administered during prophylactic treatments need to be better elucidated. For this purpose, 16S rRNA gene sequencing was performed to evaluate the impact of different prophylactic AM protocols on the composition and diversity of the broiler GM. Diversity analysis has shown that AM treatment significantly affects alpha diversity in ileum and beta diversity in both ileum and caecum. In ileal samples, the Enterobacteriaceae family has been shown to be particularly affected by AM treatments. AMs have been demonstrated to affect GM composition in broiler. These findings indicate that withdrawal periods were not enough for the restoral of the original GM. Further studies are needed for a better elucidation of the negative effects caused by an altered GM in broilers.

Assessment of Antimicrobial Effects on Broiler Gut Barrier Through Histopathology and Immunohistochemistry of Tight-Junction Proteins

“…Normally, microbe-associated molecular patterns (MAMPs) of the gut microbiota do not induce any activation of the pattern recognition receptors and consequently do not initiate a pro-inflammatory response, keeping a controlled homeostasis of the intestine ( 4 , 6 ). As already demonstrated in our previous work ( 18 ), the AM treatments induced a dysbiosis status in the ileal and cecal microbiota, that was not recovered at the end of the rearing cycle. The presence of an altered microbiota in treated broilers may have led to break the balanced homeostasis between gut microbiota and host, inducing the activation of the pro-inflammatory cascade.…”

“…In poultry farming, gut health is considered of great importance for production performance, understanding the mechanisms of gut barrier dysfunction may allow future prevention of the serious sequelae of bacterial translocation and sepsis in veterinary medicine. The morphological alterations reported in this work are additional findings, that taken together with our previously published results on zootechnical parameters, transcriptional alterations and gut microbiota ( 17 , 18 ) will allow to better clarify the role of antimicrobial prophylaxes on the modulation of gut health. Thereby, further studies are needed to better understand the activity of AM against the intestinal barrier and TJ regulations.…”

“…However, also gut dysbiosis can induce the production of pro-inflammatory cytokines and initiate the inflammatory cascade ( 4 , 7 ). All administered AM have broad-spectrum activity and the gut microbiota in ileum and cecum were negatively affected in alpha and beta metrics by AM treatments ( 18 ). It is well-known that a healthy gut microbiota is a crucial part of the intestinal barrier and thus, for the defense of the host.…”

“…The broiler rearing conditions were previously described by Giannuzzi et al ( 17 ) and Cuccato et al ( 18 ). Concisely, 240 male broilers (Ross 308) were part of a zootechnical trial and they were reared under the same conditions in the chicken broiler farm facility of the Department of Veterinary Sciences of the University of Turin during 2018.…”

Impact of Antibiotic Therapies on Resistance Genes Dynamic and Composition of the Animal Gut Microbiota

“…Prophylactic administration of several antibiotics to Ross chickens resulted in modification of the ileum and caecum GIM. In particular, an increase of Enterococcaceae was observed in chickens treated with amoxicillin or thiamphenicol [110] (Table 3).…”