Assessment of Antibiotic Resistance Genes in Urban Wastewater Microbial Communities

Thesis Abstract

This study investigates the prevalence and diversity of antibiotic resistance genes (ARGs) within microbial communities in urban wastewater systems, addressing the rising global concern over the dissemination of antimicrobial resistance (AMR) through environmental pathways. The unchecked release of wastewater containing residual antibiotics and resistant bacteria poses significant public health risks by contributing to the horizontal transfer of ARGs among pathogenic and non-pathogenic bacteria in aquatic environments. The primary aim of this research is to quantify and characterize ARGs in urban wastewater, elucidate factors influencing their distribution, and assess potential implications for public health and antimicrobial stewardship. Specifically, the study aims to (1) identify and quantify prevalent ARGs using quantitative PCR (qPCR), (2) assess the microbial community composition through 16S rRNA gene amplicon sequencing, (3) evaluate the correlation between physicochemical parameters (e.g., pH, organic load, antibiotic residues) and ARG abundance, and (4) analyze temporal variations in ARG prevalence over a twelve-month cycle. The research adopts a quantitative, observational field design grounded in the Ecosystem Theory to understand how wastewater characteristics influence ARG dissemination, and the One Health framework to contextualize environmental findings within human and animal health interfaces. The population comprised wastewater samples collected from six strategically selected treatment plants serving densely populated metropolitan areas, with an overall sample size of 180 (30 samples per site), ensuring spatial and temporal representativeness. Sampling occurred monthly to capture seasonal dynamics. Data collection employed Sterivex filters for microbial biomass concentration, and molecular techniques included DNA extraction followed by qPCR targeting key ARGs such as blaCTX-M, mecA, tetM, and sul1. Microbial community profiling was performed via Illumina MiSeq sequencing of the 16S rRNA gene. Physicochemical parameters were measured in situ and through laboratory analysis using standard protocols. Data validity and reliability were established through duplicate analyses, spiked controls, and calibration standards. Data analysis involved descriptive and inferential statistics, with regression analyses to determine relationships between physicochemical variables and ARG abundance, and multivariate techniques such as principal component analysis (PCA) to explore microbial community variations. Statistical significance was assessed at p<0.05, with ANOVA employed to compare ARG abundances across sites and seasons. The study further utilized network analysis to investigate co-occurrence patterns between ARGs and microbial taxa. Anticipated findings include a high prevalence of clinically relevant ARGs, with seasonal fluctuations influenced by factors such as antibiotic residues, wastewater load, and microbial community shifts. The results are expected to reveal significant correlations between specific physicochemical parameters and ARG abundance, supporting the hypothesis that anthropogenic activities significantly shape resistance gene dissemination in urban wastewater ecosystems. These insights will contribute to understanding the environmental reservoirs of AMR and assist in developing targeted interventions for wastewater management and antimicrobial stewardship. The study’s primary contribution to knowledge lies in providing empirical evidence on the distribution, drivers, and potential risks associated with ARGs in urban wastewater, emphasizing the need for integrated strategies to curb environmental AMR spread. The conclusions advocate for enhanced wastewater treatment protocols, routine monitoring of resistance genes, and policies promoting prudent antibiotic use. Recommendations include implementing advanced oxidation processes, establishing regular genetic surveillance within wastewater systems, and fostering multisectoral collaborations aligned with the One Health approach. Further research is suggested to explore the horizontal transfer potential of ARGs and evaluate intervention efficacy in reducing resistance dissemination within urban aquatic environments.