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Instructor/Advisor

Charlotte Berkes

Keywords

Antibiotic resistance, antibiotics, environmental safety

Abstract

The Merrimack River is an important source of drinking water and recreation for over 500,000 people including the communities of Lowell, Lawrence, Tewksbury, Methuen, and Andover, Massachusetts as well as Manchester and Nashua, New Hampshire. The safety of waters in the Merrimack River is regularly threatened by combined sewage overflows (CSOs), which contribute bacteria, debris, and other substances that may negatively impact public health and the health of the environment. The aim of this study is to detect and quantify antibiotic resistant bacteria in the Merrimack River. Water samples were collected at thirteen sites along the Merrimack River, between Manchester, NH and Newburyport, MA, throughout the summer of 2024. Additional samples were collected in association with combined sewage overflow events. To assay for the presence of antibiotic-resistant bacteria, a molecular approach was used in which total water DNA was isolated from microorganisms captured by filtration and antibiotic resistance genes (ARG) were quantified using qPCR. ARGs assayed included molecular markers of beta-lactam resistance (bla-TEM), sulfonamide resistance (sul2), and tetracycline resistance (tetA). ARG markers were normalized to a 16S rRNA control. Our results showed that baseline levels of ARG range from 10E-2 to 10E-7 ARG copies per 16S rRNA and increase several-fold following a CSO event, highlighting a potential environmental route by which ARB may spread. Monitoring will continue in 2025, and in addition, a high performance liquid chromatography/ mass spectrometry (LC/MS) method is being adapted to identify a variety of common antibiotics in the Merrimack River.

Antibiotic Resistance and Antibiotic Resistant Bacteria in the Merrimack River

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