Quantification of antibiotic resistance genes for environmental monitoring: Current methods and future directions

Various antibiotic resistance genes (ARGs) could be present in environments such as soil and water. This review and opinion article briefly summarizes on the current methods to quantify ARGs in these environments, with special emphasis on their application potentials for routine ARG monitoring. For routine ARG monitoring, methods should be rapid, specific, sensitive, and easy-to-use. Quantitative data are also important if removal efficiencies of ARGs during treatment processes or potential human health risks are evaluated/assessed. To meet these requirements, culture-independent, amplification-based methods are most promising, including quantitative polymerase chain reaction, high-throughput quantitative polymerase chain reaction, digital PCR, and loop-mediated isothermal amplification. Selection of target genes is also important for routine ARG monitoring. Future research may include the identification of ARG indicators that can predict the occurrence and the levels of various ARGs.