Biosolids as a Source of Antibiotic Resistance Plasmids for Commensal and Pathogenic Bacteria.

Aaron Law,Matt Fagnan,Thibault Stalder,Olubunmi Solano,Celeste J Brown,Eva M Top,Samuel S Hunter

doi:10.3389/fmicb.2021.606409

Abstract

Antibiotic resistance (AR) is a threat to modern medicine, and plasmids are driving the global spread of AR by horizontal gene transfer across microbiomes and environments. Determining the mobile resistome responsible for this spread of AR among environments is essential in our efforts to attenuate the current crisis. Biosolids are a wastewater treatment plant (WWTP) byproduct used globally as fertilizer in agriculture. Here, we investigated the mobile resistome of biosolids that are used as fertilizer. This was done by capturing resistance plasmids that can transfer to human pathogens and commensal bacteria. We used a higher-throughput version of the exogenous plasmid isolation approach by mixing several ESKAPE pathogens and a commensal Escherichia coli with biosolids and screening for newly acquired resistance to about 10 antibiotics in these strains. Six unique resistance plasmids transferred to Salmonella typhimurium, Klebsiella aerogenes, and E. coli. All the plasmids were self-transferable and carried 3–6 antibiotic resistance genes (ARG) conferring resistance to 2–4 antibiotic classes. These plasmids-borne resistance genes were further embedded in genetic elements promoting intracellular recombination (i.e., transposons or class 1 integrons). The plasmids belonged to the broad-host-range plasmid (BHR) groups IncP-1 or PromA. Several of them were persistent in their new hosts when grown in the absence of antibiotics, suggesting that the newly acquired drug resistance traits would be sustained over time. This study highlights the role of BHRs in the spread of ARG between environmental bacteria and human pathogens and commensals, where they may persist. The work further emphasizes biosolids as potential vehicles of highly mobile plasmid-borne antibiotic resistance genes.

Highlights

Antibiotic resistance (AR) is a threat for modern medicine across the world (WHO, 2018; Centers for Disease Control and Prevention, 2019)
These previously reported plasmid sequences were used for a first round of annotations by aligning each pair of plasmids and transferring the annotations of the genes that showed at least 98% nucleotide identity and coverage, and an intact open reading frame (ORF)
Horizontal gene transfer facilitates the transit of antibiotic resistance genes (ARG) within microbiomes and between microbiomes of different habitats, to eventually end up in human pathogens and commensals

Summary

Introduction

Antibiotic resistance (AR) is a threat for modern medicine across the world (WHO, 2018; Centers for Disease Control and Prevention, 2019). Plasmids are important vectors of Biosolid Plasmids Transfer to Pathogens horizontal gene transfer and are capable of transferring multiple ARG simultaneously, providing multidrug resistance to the recipient bacteria in one event (Ochman et al, 2000; Martínez and Baquero, 2014; Mathers et al, 2015) This is true for self-transmissible plasmids that can transfer and replicate in a broad range of bacterial species (Datta and Hedges, 1972; Top et al, 1998; Jain and Srivastava, 2013). In many non-clinical environments, bacteria are reservoirs of plasmids and other mobile genetic elements that carry ARG This poses a crucial problem, as they drive the emergence of ARG in human pathogens from unpredictable and unknown sources (Allen et al, 2010; Wright, 2010; He et al, 2020).

Methods

Results

Conclusion