Occurrence of Antibiotic-Resistant Genes and Bacteria in Household Greywater Treated in Constructed Wetlands

Abstract

There is a growing body of knowledge on the persistence of antibiotic-resistant genes (ARGs) and antibiotic-resistant bacteria (ARB) in greywater and greywater treatment systems such as constructed wetlands (CWs). Our research quantified ARGs (sul1, qnrS, and blaCTXM32), class one integron (intI1), and bacterial marker (16S) in four recirculating vertical flow CWs in a small community in the Negev desert, Israel, using quantitative polymerase chain reaction (qPCR). The greywater microbial community was characterized using 16S rRNA amplicon sequencing. Results show that CWs can reduce ARG in greywater by 1–3 log, depending on the gene and the quality of the raw greywater. Community sequencing results showed that the bacterial community composition was not significantly altered after treatment and that Proteobacteria, Epsilonbacteraeota, and Bacteroidetes were the most dominant phyla before and after treatment. Pseudomonas, Citrobacter, Enterobacter, and Aeromonas were the most commonly identified genera of the extended spectrum beta lactamase (ESBL) colonies. Some of the ESBL bacteria identified have been linked to clinical infections (Acinetobacter nosocomialis, Pseudomonas fulva, Pseudomonas putida, Pseudomonas monteilii, and Roseomonas cervicalis). It is important to monitor intI1 for the potential transfer of ARGs to pathogenic bacteria.

Transmission of tetracycline resistance genes and microbiomes from manure-borne black soldier fly larvae frass to rhizosphere soil and pakchoi endophytes

“…Similarly, although the network analysis plots showed that pakchoi endophytes were less associated with TRGs, we still used the same method to target Roseomonas as the host bacteria of tet Q in the pakchoi endophyte sample, although the abundance of this bacteria was not high. Roseomonas was detected in a constructed wetland as an extended-spectrum beta-lactamase bacterium associated with a clinical infection and is a potential host of intl1 ( Henderson et al, 2022 ). Roseomonas is reportedly a clinical pathogenic microorganism ( Church et al, 2020 ), and even if the relative abundance of this microorganism is less than 0.1%, it is a threat to public health.…”

“…Roseomonas was detected in a constructed wetland as an extended-spectrum beta-lactamase bacterium associated with a clinical infection and is a potential host of intl1 (Henderson et al, 2022). Roseomonas is reportedly a clinical pathogenic microorganism (Church et al, 2020), and even if the relative abundance of this microorganism is less than 0.1%, it is a threat to public health.…”

Heterogeneous Antibiotic Resistance Gene Removal Impedes Evaluation of Constructed Wetlands for Effective Greywater Treatment

“…In the winter season, most of the genes of interest significantly decreased after treatment, specifically tetG (p = 0.027), sul1 (p = 0.005), and blaTEM (p = 0.002). Overall, the RFVCW system removes most ARGs efficiently during the winter season, which may be attributed to multiple factors [47], such as the anaerobic and aerobic processes within the treatment system [53] or the removal of biomass or solids [54]. In treated samples, a significantly higher abundance after treatment was detected for genes sul1, blaTEM, and fabVAS2 during summer.…”

“…Once in the soil, the fate and behavior depend on various chemical, physical, and biological processes [45], which may affect the soil microbial community [46]. Nevertheless, recent studies demonstrated that irrigation with treated greywater does not seem to impact ARG levels in the soil microbiome [7,47].…”