Does the Disinfection of Public Water Supplies Increase Antibiotic Resistance Levels?

Abstract

Antibiotic resistance is a substantial threat to public health. Recently researchers have suggested that the disinfection of public water supplies increases antibiotic resistance levels. This study investigated the levels of antibiotic resistance genes prior to treatment and disinfection and from within the distribution system of 18 water utilities (14 systems used groundwater as a source; 4 used surface water as a source). Samples were analyzed by real-time qPCR and microfluidic qPCR targeting total bacteria, 19 antibiotic resistance genes, 3 genes encoding the integrase of 3 different classes of integrons, and a gene encoding for quaternary ammonium compound resistance. This study found that treatment and disinfection significantly (P < 0.05) reduced the concentration of 16S rRNA genes, tet(A) and intI1 by approximately 90 percent (1 log-unit reduction) in groundwater systems and approximately 99 percent (2 log-unit reduction) in surface water systems. In groundwater systems, there was no significant change (P < 0.05) in the relative abundance of intI1 or tet(A). In surface water systems, there was no significant change (P < 0.05) in the relative concentration of tet(A), but there was a significant increase in the relative abundance of intI1 (increase of 0.3 log-units, P < 0.01). In conclusion, this study suggests that disinfection of public water supplies decreases the total number of antibiotic resistance genes, thus supporting a century of research demonstrating the public health benefits of the disinfection of drinking water supplies.