Semester of Graduation

May 2025

Degree

Master of Science in Civil Engineering (MSCE)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

Antimicrobial resistance (AMR) is a growing public health concern, especially with the spread of extended-spectrum beta-lactamase (ESBL) producing Escherichia coli. This study examined the prevalence and abundance of antibiotic-resistant E. coli in Yellow Water (YW) and Natalbany River (NR) in Tangipahoa Parish, Louisiana, which receive effluent from decentralized wastewater treatment systems. Monthly surface water grab samples were collected at four sites on each river from February 2023 to July 2024 and screened for generic and antibiotic-resistant E. coli using membrane filtration with ceftriaxone and cefotaxime as screening agents per the WHO Tricycle Protocol. We evaluated resistance patterns of the resulting isolates within and between the two rivers and assessed the potential role of precipitation and aerobic treatment units as potential AMR input sources. Our results showed that there was no significant difference in using ceftriaxone or cefotaxime to screen for ESBL phenotype (p = 0.7160), in estimating AMR prevalence (p = 0.4929), or abundance (p = 0.5613). The abundance of generic E. coli was significantly greater in YW (p = 0.0079), but the abundance of antibiotic-resistant E. coli was not (p > 0.050 for CTX and CRO). During testing of effluent from two treatment systems, antibiotic-discharge was detected in their discharge. Further CRO- and CTX-resistant E. coli prevalence was positively correlated with increased river discharge (r = 0.6743 and r = 0.7185, respectively), suggesting that precipitation-mobilized treatment system effluent may contribute to the spread of AMR. Our findings highlight the potential role of non-point source fecal pollution as a source of AMR in coastal waterways.

Date

3-26-2025

Committee Chair

Aaron Bivins

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Available for download on Thursday, March 26, 2026

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