RESUMO
Industrialized layer chicken feedlots harbor complex environmental microbial communities that affect the enrichment and exchange of gut bacteria and antibiotic resistance genes (ARGs). However, the contribution of different environmental sources to the gut ARGs of layer chickens is not clear. Here, layer chicken gut and environmental samples (air, water, feed, cage, feather, maternal hen feces, uropygial glands) were collected during the early 3 month period before the laying of eggs, and the source and characteristics of the gut microorganisms and ARGs were analyzed by performing 16S rRNA and metagenomic sequencing. The results showed that the abundances of Bacteroidetes and Actinobacteria in cecum of layer chickens gradually increased, while that of Proteobacteria decreased with age, and the number and relative abundance of ARGs decreased significantly with age. On day 5, 57% of the layer chicken cecal ARGs were from feather samples, and 30% were from cage samples. Subsequently, the contribution of cage ARGs became progressively more prominent over time. At days 30 and 57, the contribution of cage ARGs to the chick cecal ARGs reached 63.3 and 69.5%, respectively. The bacterial community composition (especially the abundances of Klebsiella pneumoniae and Escherichia coli) was the major factor impacting the ARG profile. K. pneumoniae and E. coli were mainly transmitted from feathers to the layer chicken cecum, and the contribution rates were 32 and 3.4%, respectively. In addition, we observed the transmission of ARG-carrying bacteria (Bacteroides fragilis) from the cage to the gut, with a contribution rate of 11.5%. It is noteworthy that B. fragilis is an opportunistic pathogen that may cause diarrhea in laying hens. These results can provide reference data for the healthy breeding of layer chickens and the prevention and control of ARG pollution.
RESUMO
To characterize the diversity and richness and explore the function and structure of swine gut microbiome and resistome in common pig-farming feedlots, we sampled and metagenomic sequenced the feces of pigs from four different industrialized feedlots located in four distant provinces across China. Surprisingly, more than half of the nonredundant genes (1,937,648, 54.3%) in the current catalogue were newly found compared with the previously published reference gene catalogue (RGC) of the pig gut microbiome. Additionally, 16 high-completeness draft genomes were obtained by analyzing the dominant species on each feedlot. Notably, seven of these species often appeared in the human body sites. Despite a smaller number of nonredundant genes, our study identified more antibiotic resistance genes than those available in the RGC. Tetracycline, aminoglycoside, and multidrug resistance genes accounted for nearly 70% of the relative abundance in the current catalogue. Slightly higher sharing ratios were shown between the industrialized feedlot pig gut microbiomes and human gut microbiomes than that between the RGC and human counterpart (14.7% versus 12.6% in genes and 94.1% versus 87.7% in functional groups, respectively). Furthermore, a remarkably high number of the antibiotic resistance proteins (n =141) were identified to be shared by the pig, human, and mouse resistome, indicating the potential for horizontal transfer of resistance genes. Of the antibiotic resistance proteins shared by pigs and humans, 50 proteins were related to tetracycline resistance, and 49 were related to aminoglycoside resistance.IMPORTANCE The gut microbiota is believed to be closely related to many important physical functions in the host. Comprehensive data on mammalian gut metagenomes has facilitated research on host-microbiome interaction mechanisms, but less is known about pig gut microbiome, especially the gut microbiome in industrialized feedlot pigs, compared with human microbiome. On the other hand, pig production, as an important source of food, is believed to exacerbate the antibiotic resistance in humans due to the abuse of antibiotics in pig production in various parts of the world. This study delineates an intricate picture of swine gut microbiome and antibiotic resistome in industrialized feedlots and may provide insight for the pig producing industry.