Abstract
Widespread antibiotic use increases the risk of livestock acting as potential reservoirs of antimicrobial resistance genes (ARGs) that may be transferred to human and animal pathogens. Particularly, maternal-infant transmission of antibiotics via breastmilk represents a great concern regarding infant health. In this study, we investigated the effects of 4-week low-dose antibiotic (LDA) treatment on the host immunity and antibiotic resistomes in weaned piglets. Transcriptomic analyses of ileum tissues revealed that the affected genes were largely enriched in innate immunity-related pathways. Significantly reduced protein expression of inflammatory factors, i.e., IFN-γ, IL-6 were observed. In addition, analyses of antibiotic resistomes identified a total of 1,021 ARGs related to 39 classes of antibiotics. The samples exhibited highly individual-specific diversity and no significant difference in the structure and diversity of ARGs and mobile gene elements (MGE) after LDA exposure for both colon and ileum samples. Despite of that, there were significant changes in the abundance of two transferrable ARGs [Erm(T) and tcr3] related to the antibiotics administered, implying an increased risk of transferrable antibiotic resistance. There was a significant change in the abundance of one pathogenic species after LDA exposure in the colon samples and one in the ileum samples, but there were no significant differences in the matched ARGs. Collectively, our findings reveal considerable changes in intestinal immunity-related genes, but minimal effects on gut antibiotic resistomes (ARGs and MGEs) in weaned piglets after 4 weeks LDA exposure. Our study provides a foundation for evaluating the longer-term cumulative effects of LDA use, especially the effects of maternal–infant LDA transmission, on antibiotic resistance and risks to infant health.
Highlights
In-feed antibiotics have been widely used in livestock production to prevent and treat infectious diseases and to control the gut microbiota [1, 2]
Considering that low-dose antibiotic (LDA) exposure induced significantly reduced total bacterial load in the ileum content, we focused on the transcriptomics analyses of the ileum tissues by RNA-seq technology
The results showed that the LDA group had significantly decreased levels of IFN-γ, IL-6, and TLR4, suggesting that LDA exposure for 4 weeks may induce an early anti-inflammatory response
Summary
In-feed antibiotics have been widely used in livestock production to prevent and treat infectious diseases and to control the gut microbiota [1, 2]. Non-therapeutic low-dose antibiotics (LDA) are commonly used as feed additives for piglets during the difficult weaning transition period to increase growth, promote gut health, and improve feed efficiency [3]. Antibiotic Resistomes and Immunity of Low-Dose-Antibiotics resistance is a worldwide public health concern and multidrug antibiotic resistance is partly related to excessive use of antibiotics for livestock. It is important to understand the potential negative side effects of LDA, especially as this preventive antibiotic-related approach is currently being banned in many countries around the world
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