Differential overlap in human and animal fecal microbiomes and resistomes in rural versus urban Bangladesh

Abstract

Background Low- and middle-income countries (LMICs) bear the largest mortality burden due to antimicrobial-resistant infections. Small-scale animal production and free-roaming domestic animals are common in many LMICs, yet data on zoonotic exchange of gut bacteria and antimicrobial resistance genes (ARGs) in low-income communities are sparse. Differences between rural and urban communities in population density, antibiotic use, and cohabitation with animals likely influence the frequency of transmission of gut bacterial communities and ARGs between humans and animals. Here, we determined the similarity in gut microbiomes, using 16S rRNA gene amplicon sequencing, and resistomes, using long-read metagenomics, between humans, chickens, and goats in rural compared to urban Bangladesh. Results Gut microbiomes were more similar between humans and chickens in rural (where cohabitation is more common) compared to urban areas, but there was no difference for humans and goats. Urbanicity did not impact the similarity of human and animal resistomes; however, ARG abundance was higher in urban animals compared to rural animals. We identified substantial overlap of ARG alleles in humans and animals in both settings. Humans and chickens had more overlapping ARG alleles than humans and goats. All fecal hosts carried ARGs on contigs classified as potentially pathogenic bacteria, including Escherichia coli, Campylobacter jejuni, Clostridiodes difficile, and Klebsiella pneumoniae. Conclusions While the development of antimicrobial resistance in animal gut microbiomes and subsequent transmission to humans has been demonstrated in intensive farming environments and high-income countries, evidence of zoonotic exchange of antimicrobial resistance in LMIC communities is lacking. This research provides genomic evidence of overlap of antimicrobial resistance genes between humans and animals, especially in urban communities, and highlights chickens as important reservoirs of antimicrobial resistance. Chicken and human gut microbiomes were more similar in rural Bangladesh, where cohabitation is more common. Incorporation of long-read metagenomics enabled characterization of bacterial hosts of resistance genes, which has not been possible in previous culture-independent studies using only short-read sequencing. These findings highlight the importance of developing strategies for combatting antimicrobial resistance that account for chickens being reservoirs of ARGs in community environments, especially in urban areas.