Antibiotic resistance genes and bacterial community distribution patterns in pig farms.

Antibiotic-resistant pathogens pose high risks to human and animal health worldwide. In recent years, many studies have been carried out to investigate the role of gut microbiota as a pool of antibiotic resistance genes (ARGs) in human and animals. Both the structure and function of the gut bacterial community and related ARGs in pig remain unknown. In this study, we characterized the gut microbiomes and resistomes of fecal samples collected from sixteen pig farms located in sixteen cities of Shandong Province by metagenomic sequencing. Alpha diversity indicated that fecal samples from Dezhou (DZ) and Jinan (J) showed higher alpha diversity, and the lowest was from pig farms of Rizhao (RZ). Other pig farms showed similar alpha diversity. Besides, we found that the composition of gut bacterial among these pig farms varied greatly. Helcococcus massiliensis was the dominant bacterial species in pig farms of RZ and Zibo (ZB), while Prevotella sp. P5-92 occupied a superior proportion in Binzhou (BZ) and Yantai (YT). The proportion of Lactobacillus johnsonii was similar among farms of Qingdao (QD), Linyi (LY), Taian (TA), Weifang (WF), Weihai (WH), and YT. In total, 1112 ARGs were obtained and classified into 69 groups from 48 fecal samples. ARG abundance was higher in farms of Dongying (DY) and WH than others, while the lowest farms in BZ and ZB. Interestingly, it is found that BZ pig farm was exclusive, so the tetQ gene showed a higher abundance. In contrast, the load of APH(3') - IIIa in fecal samples from DY, J-1, LC, WF, and WH was high. Meanwhile, the most relevant ARGs and the corresponding microbes were screened out. Our metagenomic sequencing data provides new insights into the abundance, diversity, and structure of bacterial community in pig farms. Meanwhile, we screened ARG-carrying bacteria and explored the correlation between ARGs and bacterial community, which provide a comprehensive view of the pig fecial ARGs and microbes in different farms of Shandong.