Antibiotic resistance in pathogenic bacteria has been presenting an increasing threat to human health during the last decade, and it is widely accepted that the antibiotic resistance development and spread in microbes can be largely attributed to the abuse and misuse of antibiotics.

The human gut is inhabited by a large bacterial population, and this microbiota has a profound influence on human physiology and nutrition. However, there has been increasing attention paid to the gut microbiota as a reservoir for antibiotic resistance genes, but little is known about their diversity and richness within the gut.

Recently, HU Yongfei, et al. from Prof. ZHU Baoli’s laboratory in Institute of Microbiology, Chinese Academy of Sciences, analyzed the antibiotic resistance genes of gut microbiota from 162 individuals of three different populations (Denmark, Spain, and China). A total of 1,093 antibiotic resistance genes were identified in this study.

The authors find that Chinese individuals harbor the highest number and abundance of antibiotic resistance genes, followed by Danish and Spanish individuals. Single-nucleotide polymorphism-based analysis indicates that antibiotic resistance genes from the two European populations are more closely related while the Chinese ones are clustered separately. High abundance of tetracycline resistance genes in human gut is obviously observed, and is then confirmed by screening of fosmid library constructed from 3 Chinese healthy volunteer’s fecal samples.

In China, the overuse of antibiotics and antibiotic resistance are severe. Approximately 75% of patients with seasonal influenza are estimated to be prescribed antibiotics. In addition, China exhibits the most rapid growth rate of drug resistance compared with Kuwait and the United States.

These factors may partly explain why Chinese people harbor the highest number of resistance genes in their gut, though we do not know exactly how these resistance genes were acquired and transmitted. On the other hand, the relation between antibiotic resistance genes and the usage of antibiotics is very complex. The contribution to the enrichment of antibiotic resistance genes may not be only by the antibiotic abuse.

It is noteworthy that the batch effect of sampling could be factors that may influence the outcome of studies on entire populations owing to the sequencing capability and affordability. Therefore, large-scale study is needed to have a better understanding of antibiotic resistance genes in human gut microbiota. These would help to determine whether antibiotic resistance genes carried by human gut commensals pose a risk, for example, of horizontal transfer to potentially pathogenic microbes.

This work has been published in Nature Communications.