Assessing bacterial diversity and antibiotic resistance dynamics in wastewater effluent-irrigated soil and vegetables in a microcosm setting

Onthatile Onalenna,Teddie O. Rahube

doi:10.1016/j.heliyon.2022.e09089

Onthatile Onalenna, Teddie O. Rahube

Open Access

https://doi.org/10.1016/j.heliyon.2022.e09089

Copy DOI

Abstract

Water scarcity is one of the main challenges in sustainable agricultural development particularly in developing countries therefore, irrigation of food crops with wastewater effluent has become a common practice in order to meet the growing food demand. The aim of this study was to determine the impact of wastewater irrigation on bacterial community and antibiotic resistance dynamics in soil and vegetables in an agricultural setting. To determine bacterial diversity, occurrence and overall dynamics of antibiotic resistant genes (ARGs) in effluent irrigated soil and vegetables, 16S rRNA gene metagenomics, shotgun metagenomics and molecular PCR technique were utilized. A shift in bacterial community profile was observed as notable reduction in proteobacteria and increase in firmicutes phyla from the microcosm soil following wastewater effluent irrigation. Shotgun metagenomics revealed diverse ARGs belonging to at least nine different classes of antibiotics in the effluent wastewater. However, only blaTEM (beta-lactamase) and aadA (aminoglycoside) resistance gene sequences were identified in microcosm soil following irrigation and only blaTEM was detected on effluent irrigated vegetable surfaces (spinach and beetroots). From the study, only blaTEM gene was identified across all samples; effluent wastewater, effluent-treated soil, and vegetables. The data suggests a possible dissemination and persistence of the beta-lactamase blaTEM gene from effluent wastewater into agricultural soil and vegetables. This study enhances our understanding of antibiotic resistance spread and highlights the importance of monitoring antibiotic resistance in agro-systems, which is critical for informing policies aimed at sustainable use of wastewater effluent in water-stressed countries.

Highlights

The global use and misuse of antibiotics have resulted in the accumulation of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment which has become an inevitable global public health threat
Wastewater treatment processes are not aimed at removing ARB and antibiotic resistant genes (ARGs), so the effluent released may consist of antibiotic resistant determinants that are released into the environment (Berendonk et al, 2015)
Metagenomics sequencing of the16S rRNA gene was carried out to determine the diversity of bacterial phylogenetic groups in Palapye wastewater treatment plant (PWWTP) effluent, effluent-treated and untreated soil

Summary

Introduction

The global use and misuse of antibiotics have resulted in the accumulation of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in the environment which has become an inevitable global public health threat. WWTPs are considered propagation routes for antibiotic resistance determinants due to antibiotic residues, high bacteria density and nutrient content in sewage. WWTPs collects waste from different environments such as households, industries and health care services, this has resulted in them being involuntary accumulation points for antibiotics, ARB and ARGs. Though WWTPs differ in design and processes they assemble three successive steps; pre-treatment, primary treatment and secondary treatment (Grady et al, 2011). Wastewater treatment processes are not aimed at removing ARB and ARGs, so the effluent released may consist of antibiotic resistant determinants that are released into the environment (Berendonk et al, 2015).

Objectives

Methods

Results

Discussion

Conclusion