Can chlorination co-select antibiotic-resistance genes?

Area of Science:

• Environmental microbiology
• Water treatment technologies
• Antimicrobial resistance

Background:

• Environmental pollutants can co-select for bacterial antibiotic resistance.
• The impact of chlorination on antibiotic-resistant bacteria in water treatment is debated.

Purpose of the Study:

• To investigate whether chlorination in wastewater treatment co-selects for antibiotic-resistant bacteria.
• To quantify the effect of chlorination on antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs).

Main Methods:

• High-capacity quantitative polymerase chain reaction (qPCR) was used.
• Analysis targeted 282 antibiotic resistance genes (ARGs) and 13 mobile genetic elements (MGEs).
• Samples were collected from secondary effluents of a municipal wastewater treatment plant before and after chlorination.

Main Results:

• Chlorination significantly reduced the number and abundance of ARGs.
• The relative abundance of most ARGs decreased, with only six showing potential enrichment.
• The relative abundance of mobile genetic elements (MGEs) also decreased after chlorination.

Conclusions:

• Chlorination is effective in reducing ARGs and MGEs in wastewater treatment.
• Chlorination does not appear to co-select for antibiotic-resistant bacteria; instead, it reduces their prevalence.