Xiaole Yin
Xi Chen
Xiao-Tao Jiang
Ying Yang
Bing Li
Marcus Ho-Hin Shum
Tommy T Y Lam
Gabriel M Leung
Joan Rose
Concepcion Sanchez-Cid
Timothy M Vogel
Fiona Walsh
Thomas U Berendonk
Janet Midega
Chibuzor Uchea
Dominic Frigon
Gerard D Wright
Carlos Bezuidenhout
Renata C Picão
Shaikh Z Ahammad
Per Halkjær Nielsen
Philip Hugenholtz
Nicholas J Ashbolt
Gianluca Corno
Despo Fatta-Kassinos
Helmut Bürgmann
Heike Schmitt 
Chang-Jun Cha
Amy Pruden
Kornelia Smalla
Eddie Cytryn
Yu Zhang
Min Yang
Yong-Guan Zhu
Arnaud Dechesne
Barth F Smets
David W Graham
Michael R Gillings
William H Gaze
Célia M Manaia
Mark C M van Loosdrecht
Pedro J J Alvarez
Martin J Blaser 
James M Tiedje 
Edward Topp
Tong Zhang

Surveillance of antibiotic resistance genes (ARGs) has been increasingly conducted in environmental sectors to complement the surveys in human and animal sectors under the "One-Health" framework. However, there are substantial challenges in comparing and synthesizing the results of multiple studies that employ different test methods and approaches in bioinformatic analysis. In this article, we consider the commonly used quantification units (ARG copy per cell, ARG copy per genome, ARG density, ARG copy per 16S rRNA gene, RPKM, coverage, PPM, etc.) for profiling ARGs and suggest a universal unit (ARG copy per cell) for reporting such biological measurements of samples and improving the comparability of different surveillance efforts.