CapE (capture, amplify, extract): A rapid method for detection of low level contamination of water with Verocytotoxigenic Escherichia coli (VTEC)

Multi-target assessment of advanced oxidation processes-based strategies for indirect potable reuse of tertiary wastewater: Fate of compounds of emerging concerns, microbial and ecotoxicological parameters

Two advanced oxidation processes (AOPs), namely ozone/H2O2 and UV/H2O2, were tested at pilot scale as zero-liquid-discharge alternative treatments for the removal of microbiological (bacteria and viruses), chemical (compounds of emerging concern (CECs)) and genotoxic responses from tertiary municipal wastewater for indirect potable reuse (IPR). The AOP treated effluents were further subjected to granular activated carbon (GAC) adsorption and UV disinfection, following the concept of multiple treatment barriers. As a reference, a consolidated advanced wastewater treatment train consisting of ultrafiltration, UV disinfection, and reverse osmosis (RO) was also employed. The results showed that, for the same electrical energy applied, the ozone/H2O2 treatment was more effective than the UV/H2O2 treatment in removing CECs. Specifically, the ozone/H2O2 treatment, intensified by high pressure and high mixing, achieved an average CECs removal efficiency higher than UV/H2O2 (66.8% with respect to 18.4%). The subsequent GAC adsorption step, applied downstream the AOPs, further improved the removal efficiency of the whole treatment trains, achieving rates of 98.5% and 96.8% for the ozone/H2O2 and UV/H2O2 treatments, respectively. In contrast, the ultrafiltration step of the reference treatment train only achieved a removal percentage of 22.5%, which increased to 99% when reverse osmosis was used as the final step. Microbiological investigations showed that all three wastewater treatment lines displayed good performance in the complete removal of regulated and optional parameters according to both national and the European Directive 2020/2184. Only P. aeruginosa resulted resistant to all treatments with a higher removal by UV/H2O2 when higher UV dose was applied. In addition, E. coli STEC/VTEC and enteric viruses, were found to be completely removed in all tested treatments and no genotoxic activity was detected even after a 1000-fold concentration. The obtained results suggest that the investigated treatments are suitable for groundwater recharge to be used as a potable water source being such a procedure an IPR. The intensified ozone/H2O2 or UV/H2O2 treatments can be conveniently incorporated into a multi-barrier zero-liquid-discharge scheme, thus avoiding the management issues associated with the retentate of the conventional scheme that uses reverse osmosis. By including the chemical cost associated with using 11-12 mg/L of H2O2 in the cost calculations, the overall operational cost (energy plus chemical) required to achieve 50% average CECs removal in tertiary effluent for an hypothetical full-scale plant of 250 m3/h (or 25,000 inhabitants) was 0.183 €/m3 and 0.425 €/m3 for ozone/H2O2 and UV/H2O2 treatment train, respectively.

Characterization of Shiga toxin-producing Escherichia coli presence, serogroups and risk factors from private groundwater sources in western Ireland

Over recent years, Ireland has reported the highest crude incidence rates of Shiga toxin-producing Escherichia coli (STEC) enteritis in Europe. Unregulated private groundwater sources have emerged as an important potential transmission route for STEC, with up to 750,000 Irish residents reliant on these sources for domestic waters. This study aimed to investigate the prevalence and serogroup profile of STEC contamination from domestic private wells in western Ireland. Fifty-two groundwater sources were analysed during two sampling campaigns in the autumn (September/October) of 2019 (n = 21) and 2021 (n = 31). Untreated groundwater samples (30 L) were collected and analysed using the "CapE" (capture, amplify, extract) method. Extracted DNA was tested using multiplex real-time PCR for Shiga toxin stx1 and/or stx2 and eae genes. STEC positive DNA samples were tested for clinically relevant serogroups by real-time PCR. Data relating to 27 potential groundwater contamination risk factors were geospatially linked to each well and assessed for association with E. coli, stx1 and/or stx2 and eae presence/absence. Overall, 20/52 wells (38.4 %) were positive for E. coli (median concentration 8.5 MPN/100 mL as assessed by Colilert-18 method). Stx1 and/or stx2 was detected in 10/52 (19.2 %) wells overall and 8/20 E. coli positive wells, equating to a STEC to "generic" E. coli detection ratio of 40 %. Six of these wells (30 %) were also positive for eae. One or more serogroup-specific gene targets were identified in all but one stx1 and/or stx2 positive sample, with O145 (n = 6), O157 (n = 5) and O103 (n = 4) most prevalent. STEC presence was significantly associated with decreasing well depth (U = -2.243; p = 0.024) and increasing 30-day mean antecedent rainfall (U = 2.126; p = 0.034). Serogroup O104 was associated with increased sheep density (U = 2.089; p = 0.044) and detection of stx1 and/or stx2 + eae with increased septic tank density (U = 2.246 p = 0.023). Findings indicate high detection rates of clinically relevant STEC in E. coli contaminated groundwater sources in Ireland.

A Longitudinal Survey of Antibiotic-Resistant Enterobacterales in the Irish Environment, 2019-2020

The natural environment represents a complex reservoir of antibiotic-resistant bacteria as a consequence of different wastewater discharges including anthropogenic and agricultural. Therefore, the aim of this study was to examine sewage and waters across Ireland for the presence of antibiotic-resistant Enterobacterales. Samples were collected from the West, East and South of Ireland. Two periods of sampling took place between July 2019 and November 2020, during which 118 water (30 L) and 36 sewage samples (200 mL) were collected. Waters were filtered using the CapE method, followed by enrichment and culturing. Sewage samples were directly cultured on selective agars. Isolates were identified by MALDI-TOF and antibiotic susceptibility testing was performed in accordance with EUCAST criteria. Selected isolates were examined for bla_CTX-M, bla_VIM, bla_IMP, bla_OXA-48, bla_NDM, and bla_KPC by real time PCR and whole genome sequencing (n = 146). A total of 419 Enterobacterales (348 water, 71 sewage) were isolated from all samples. Hospital sewage isolates displayed the highest percentage resistance to many beta-lactam and aminoglycoside antibiotics. Extended-spectrum beta-lactamase-producers were identified in 78% of water and 50% of sewage samples. One or more carbapenemase-producing Enterobacterales were identified at 23 individual sampling sites (18 water, 5 sewage). This included the detection of bla_OXA-48 (n = 18), bla_NDM (n = 14), bla_KPC (n = 4) and bla_OXA-484 (n = 1). All NDM-producing isolates harbored the ble-MBL bleomycin resistance gene. Commonly detected sequence types included Klebsiella ST323, ST17, and ST405 as well as E. coli ST131, ST38 and ST10. Core genome MLST comparisons detected identical E. coli isolates from wastewater treatment plant (WWTP) influent and nursing home sewage, and the surrounding waters. Similarly, one Klebsiella pneumoniae isolated from WWTP influent and the surrounding estuarine water were identical. These results highlight the need for regular monitoring of the aquatic environment for the presence of antibiotic-resistant organisms to adequately inform public health policies.

Evaluating the potential for exposure to organisms of public health concern in naturally occurring bathing waters in Europe: A scoping review

Globally, water-based bathing pastimes are important for both mental and physical health. However, exposure to waterborne organisms could present a substantial public health issue. Bathing waters are shown to contribute to the transmission of illness and disease and represent a reservoir and pathway for the dissemination of antimicrobial resistant (AMR) organisms. Current bathing water quality regulations focus on enumeration of faecal indicator organisms and are not designed for detection of specific waterborne organisms of public health concern (WOPHC), such as antimicrobial resistant (AMR)/pathogenic bacteria, or viruses. This investigation presents the first scoping review of the occurrence of waterborne organisms of public health concern (WOPHC) in identified natural bathing waters across the European Union (EU), which aimed to critically evaluate the potential risk of human exposure and to assess the appropriateness of the current EU bathing water regulations for the protection of public health. Accordingly, this review sought to identify and synthesise all literature pertaining to a selection of bacterial (Campylobacter spp., Escherichia coli, Salmonella spp., Shigella spp., Vibrio spp., Pseudomonas spp., AMR bacteria), viral (Hepatitis spp., enteroviruses, rotavirus, adenovirus, norovirus), and protozoan (Giardia spp., and Cryptosporidium spp.) contaminants in EU bathing waters. Sixty investigations were identified as eligible for inclusion and data was extracted. Peer-reviewed investigations included were from 18 countries across the EU, totalling 87 investigations across a period of 35 years, with 30% published between 2011 and 2015. A variety of water bodies were identified, with 27 investigations exclusively assessing coastal waters. Waterborne organisms were classified into three categories; bacteria, viruses, and protozoa; amounting to 58%, 36% and 17% of the total investigations, respectively. The total number of samples across all investigations was 8,118, with detection of one or more organisms in 2,449 (30%) of these. Viruses were detected in 1281 (52%) of all samples where WOPHC were found, followed by bacteria (865(35%)) and protozoa (303(12%)). Where assessed (442 samples), AMR bacteria had a 47% detection rate, emphasising their widespread occurrence in bathing waters. Results of this scoping review highlight the potential public health risk of exposure to WOPHC in bathing waters that normally remain undetected within the current monitoring parameters.

A Point Prevalence Survey of Antibiotic Resistance in the Irish Environment, 2018-2019

Water bodies worldwide have proven to be vast reservoirs of clinically significant antibiotic resistant organisms. Contamination of waters by anthropogenic discharges is a significant contributor to the widespread dissemination of antibiotic resistance. The aim of this research was to investigate multiple different anthropogenic sources on a national scale for the role they play in the environmental propagation of antibiotic resistance. A total of 39 water and 25 sewage samples were collected across four local authority areas in the West, East and South of Ireland. In total, 211 Enterobacterales were isolated (139 water, 72 sewage) and characterised. A subset of isolates (n=60) were chosen for whole genome sequencing. Direct comparisons of the water versus sewage isolate collections revealed a higher percentage of sewage isolates displayed resistance to cefoxitin (46%) and ertapenem (32%), while a higher percentage of water isolates displayed resistance to tetracycline (55%) and ciprofloxacin (71%). Half of all isolates displayed extended spectrum beta-lactamase (ESBL) production phenotypically (n = 105/211; 50%), with bla_CTX-M detected in 99/105 isolates by PCR. Carbapenemase genes were identified in 11 isolates (6 sewage, 5 water). The most common variant was bla_OXA-48 (n=6), followed by bla_NDM-5 (n=2) and bla_KPC-2 (n=2). Whole genome sequencing analysis revealed numerous different sequence types in circulation in both waters and sewage including E. coli ST131 (n=15), ST38 (n=8), ST10 (n=4) along with Klebsiella ST405 (n=3) and ST11 (n=2). Core genome MLST (cgMLST) comparisons uncovered three highly similar Klebsiella isolates originating from hospital sewage and two nearby waters. The Klebsiella isolates from an estuary and seawater displayed 99.1% and 98.8% cgMLST identity to the hospital sewage isolate respectively. In addition, three pairs of E. coli isolates from different waters also revealed cgMLST similarities, indicating widespread dissemination and persistence of certain strains in the aquatic environment. These findings highlight the need for routine monitoring of water bodies used for recreational and drinking purposes for the presence of multi-drug resistant organisms.

Detection of OXA-48-like-producing Enterobacterales in Irish recreational water

The rapid dissemination of carbapenemase-producing Enterobacterales (CPE) is a major public health concern. The role that the aquatic environment plays in this dissemination is underexplored. This study aimed to examine seawater as a reservoir for CPE. Seawater sampling took place at a bathing site throughout the 2017 bathing season. Each 30 L sample (n = 6) was filtered using the CapE filtration system. Wastewater samples (200 mL) (pre-treatment (n = 3) and post-treatment (n = 3)) were obtained from a nearby secondary wastewater treatment plant, during the same time period. All samples were examined for CPE. Whole genome sequencing of confirmed CPE was carried out using Illumina sequencing. Isolate genomes were hosted in corresponding BIGSdb databases and analyses were performed using multiple web-based tools. CPE was detected in 2/6 seawater samples. It was not detected in any wastewater samples. OXA-48-like-producing ST131 Escherichia coli (Ec_BM707) was isolated from a seawater sample collected in May 2017 and OXA-48-like-producing ST101 Klebsiella pneumoniae (Kp_BM758) was isolated from a seawater sample collected in August 2017. The genomes of the environmental isolates were compared to a collection of previously described Irish clinical OXA-48-like-producing Enterobacterales (n = 105). Ec_BM707 and Kp_BM758 harboured bla_OXA-48 on similar mobile genetic elements to those identified in the clinical collection (pOXA-48 fragment in Ec_BM707 and IncL(pOXA-48) plasmid in Kp_BM758). Genetic similarities were observed between Ec_BM707 and several of the clinical ST131 E. coli, with allele matches at up to 98.2% of 2513 core genome multilocus sequence type (cgMLST) loci. In contrast, Kp_BM758 and the 34 clinical K. pneumoniae were genetically distant. The source of the CPE at this site was not identified. The detection of OXA-48-like-producing ST131 E. coli and OXA-48-like-producing ST101 K. pneumoniae in Irish recreational water is a concern. The potential for contamination of the aquatic environment to contribute to dissemination of CPE in Europe warrants further study.

Activated charcoal as a capture material for silver nanoparticles in environmental water samples

Silver nanoparticles (AgNPs), due to their antibacterial activity, have been incorporated into numerous consumer products. Their environmental impact however, is currently unclear. Uncertainties surround the concentration, fate, and effects of AgNPs in aquatic environments. This study examined the suitability of activated charcoal as a capture material for AgNPs from water. Samples of 100 ppb AgNPs were initially generated and exposed to activated charcoal for 24 h to examine the ability of charcoal to capture AgNPs. The decrease in Ag concentration was measured using ICP-MS. Following initial investigations, the surface area of the charcoal was increased firstly with a pestle and mortar and secondly by milling the charcoal using a ball mill. The increased surface area of the milled charcoal increased the capture of the AgNPs from 11.9% to 63.6% for the 100 ppb samples. Further investigations were carried out examining the effect on the capture of AgNP concentration (with concentration ranging from 10 to 100 ppb), particle coating and the effect of exposure time to the activated charcoal. The capture of AgNP increased with decreasing concentration. A hydrochloric acid (HCl) leaching procedure was also developed which successfully removed the captured silver allowing the fraction captured by the charcoal to be quantified with an average of 94.8% recovery. The results show that milled activated charcoal, can successfully capture AgNPs from water samples, and that therefore, activated charcoal may prove to be a cost effective material for the remediation of waters impacted by AgNP or other nano-wastes.

Indistinguishable NDM-producing Escherichia coli isolated from recreational waters, sewage, and a clinical specimen in Ireland, 2016 to 2017

In this study, New Delhi metallo-beta-lactamase (NDM)-producing Enterobacteriaceae were identified in Irish recreational waters and sewage. Indistinguishable NDM-producing Escherichia coli by pulsed-field gel electrophoresis were isolated from sewage, a fresh water stream and a human source. NDM-producing Klebsiella pneumoniae isolated from sewage and seawater in the same area were closely related to each other and to a human isolate. This raises concerns regarding the potential for sewage discharges to contribute to the spread of carbapenemase-producing Enterobacteriaceae.