Transferable Extended-Spectrum β-Lactamase (ESBL) Plasmids in Enterobacteriaceae from Irrigation Water

Enterobacterales Producing ESBLs and AmpC in Fresh Vegetables from Tebessa City, Algeria

This study aimed to evaluate the contamination levels of fresh products by ESBLs-producing Enterobacterales (ESBLs-E) or AmpC-producing Enterobacterales and characterize ESBLs genes. A total of 132 samples (67 vegetables and 65 fruits) were collected from markets in Tebessa, eastern Algeria. Among the samples, 16 third-generation cephalosporin-resistant Enterobacterales isolates were identified with a prevalence of 19.40% in vegetable samples, while there was no positive finding in fruit samples. Isolates showed resistance to most β-lactams, and all of them displayed multidrug resistance. Phenotypic tests for ESBLs detection, using double-disk synergy test and double-disk test were positive for 14 strains, including Klebsiella pneumoniae (n = 5), Klebsiella oxytoca (n = 4), Klebsiella terrigena (n = 2), Kluyvera spp. (n = 2), and Enterobacter cloacae (n = 1). Two AmpC-producing strains (Citrobacter freundii and E. cloacae) were identified through the AmpC disk test. Contamination rates of vegetables by ESBLs-E and AmpC-producing Enterobacterales were 19.40% and 2.98%, respectively. PCR results showed the presence of at least one ESBL gene in seven selected strains, with the dominance of blaCTX-M gene. Notably, K. pneumoniae strains showed the co-occurrence of two or three genes. Sequencing identified uncommon variants of ESBLs genes for the first time in Algeria, including blaCTX-M-79 (2/7), blaCTX-M-107 (2/7), blaCTX-M-117 (2/7), blaTEM-112 (1/7), blaTEM-125 (2/7), blaTEM-194 (1/7), and blaSHV-176 (3/7).

Extended-spectrum beta-lactamase (ESBL)- and non-ESBL producing Escherichia coli surveillance in surface water sources in Edo State, Nigeria: a public health concern

This research explores the antimicrobial resistance (AMR) profiles and prevalence of extended-spectrum beta-lactamase (ESBL) and non-ESBL-producing Escherichia coli in Ojerame Dam and Ovokoto Spring, Edo State, Nigeria. Over 12 months, water was systematically sampled to accommodate seasonal variations and analyzed by employing an ESBL-selective medium for bacterial species. Additionally, bacterial isolates underwent identification and characterization using polymerase chain reaction (PCR) and disk diffusion methods to evaluate their susceptibility to antimicrobials. Results indicated significant prevalence of ESBL-producing E. coli, which exhibited complete resistance to common antimicrobials like ceftriaxone, ceftazidime, cefotaxime, and ampicillin while demonstrating 100% sensitivity to ertapenem, imipenem, meropenem, and nitrofurantoin. Non-ESBL-producing E. coli were resistant to ampicillin but sensitive to other antimicrobials mentioned earlier. Furthermore, both ESBL and non-ESBL-producing E. coli displayed multidrug resistance to varying degrees. Specific ESBL genes, including blaTEM, blaCTX-M-1, and blaCTX-M-15, were identified, alongside resistance genes like tetA, tetM, sul1, sul2, sul3, qnrA, qnrB, and qnrS in E. coli. This study pioneers the documentation of ESBL-producing E. coli in surface water in the region. This signals impending health risks associated with water being a reservoir of resistant genes while emphasizing the urgency for further research and public awareness concerning the quality of surface water.

Atwill E, Jeamsripong S. Antimicrobial resistance, virulence profile, and genetic analysis of ESBL-producing Escherichia coli isolated from Nile tilapia in fresh markets and supermarkets in Thailand

This study investigated the prevalence and antimicrobial resistance (AMR) of Escherichia coli (E. coli) in Nile tilapia from fresh markets and supermarkets. A total of samples (n = 828) were collected from Nile tilapia including fish flesh (n = 276), liver and kidney (n = 276), and intestine (n = 276). Overall prevalence of fecal coliforms (61.6%) and E. coli (53.0%) were observed. High prevalence of E. coli was found in the intestine (71.4%), followed by the liver and kidney (45.7%). The highest prevalence of resistance was commonly found against tetracycline (78.5%), ampicillin (72.8%), and sulfamethoxazole (45.6%) with resistance to only tetracycline (15.2%) as the most common antibiogram. The prevalence of multidrug resistance (MDR) (54.4%) and Extended-spectrum beta-lactamases (ESBLs) (5.7%) were examined. The predominant virulence genes (n = 158) were st (14.6%), followed by eaeA (0.6%). The blaTEM (73.4%), tetA (65.2%), and qnrS (57.6%). There is statistical significance between Nile tilapia from fresh markets and supermarkets. Based on logistic regression analysis, ampicillin-resistant E. coli was statistically associated with the phenotypic resistance to tetracycline and trimethoprim, and the presence of blaTEM and tetA (p < 0.05). Further investigation of AMR transference and their mechanisms is needed for AMR control.

Fresh produce as a reservoir of antimicrobial resistance genes: A case study of Switzerland

Antimicrobial resistance (AMR) can be transferred to humans through food and fresh produce can be an ideal vector as it is often consumed raw or minimally processed. The production environment of fresh produce and the agricultural practices and regulations can vary substantially worldwide, and consequently, the contamination sources of AMR. In this study, 75 imported and 75 non-imported fresh produce samples purchased from Swiss retailers were tested for the presence of antimicrobial resistant bacteria (ARB) and antimicrobial resistance genes (ARGs). Moreover, the plasmidome of 4 selected samples was sequenced to have an insight on the diversity of mobile resistome. In total, 91 ARB were isolated from fresh produce, mainly cephalosporin-resistant Enterobacterales (n = 64) and carbapenem-resistant P. aeruginosa (n = 13). All P. aeruginosa, as well as 16 Enterobacterales' isolates were multidrug-resistant. No differences between imported and Swiss fresh produce were found regarding the number of ARB. In 95 % of samples at least one ARG was detected, being the most frequent sul1, blaTEM, and ermB. Abundance of sul1 and intI1 correlated strongly with the total amount of ARGs, suggesting they could be good indicators for AMR in fresh produce. Furthermore, sul1 correlated with the fecal marker yccT, indicating that fecal contamination could be one of the sources of AMR. The gene sulI was significantly higher in most imported samples, suggesting higher anthropogenic contamination in the food production chain of imported produce. The analyses of the plasmidome of coriander and carrot samples revealed the presence of several ARGs as well as genes conferring resistance to antiseptics and disinfectants in mobile genetic elements. Overall, this study demonstrated that fresh produce contributes to the dissemination of ARGs and ARB.

Presence of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Food-Producing and Companion Animals and Wildlife on Small-Holder Farms of Floreana Island, Galápagos Islands

Background: Antimicrobial resistance (AR) has led to increasing human and animal morbidity and mortality and negative consequences for the environment. AR among Escherichia coli (EC) is on the rise, with serious concerns about extended-spectrum β-lactamase-producing E. coli (ESBL-EC). In the Galápagos Islands, where antimicrobials are available without a prescription, growing demands for food production can drive antimicrobial use. Food producing animals are at the interface of wildlife and environmental health on the smallest human-inhabited Galápagos Island, Floreana. We sought to determine if ESBL-EC were present in Floreana Island farm animal species and nearby wildlife and the relatedness of ESBL-EC isolates identified. Materials and Methods: During July 4-5, 2022, we visited 8 multispecies farms, representing 75% of food-producing animal production on Floreana, and collected 227 fecal samples from farm animals and wildlife. Each sample was plated on MacConkey agar supplemented with cefotaxime (4 μg/mL). Results: ESBL-EC was isolated from 20 (9%) fecal samples collected from pigs (N = 10), chickens (N = 6), wildlife (N = 3), and dog (N = 1). All ESBL-EC isolates were from samples taken at three (38%) of the eight farms. Fifteen (75%) of the ESBL-EC isolates were from a single farm. All ESBL-EC isolates were multidrug resistant. The most prevalent ESBL genes belonged to the blaCTX-M group. Among the typeable isolates from the farm with the largest proportion of ESBL-EC isolates (N = 14), we observed nine unique pulsed-field gel electrophoresis (PFGE) patterns, with identical patterns present across pig and chicken isolates. PFGE patterns in the three farms with ESBL-EC isolates were different. Conclusions: These results lend support for future routine AR monitoring activities at the livestock-wildlife interface in Galápagos to characterize potential interspecies transmission of AR bacteria and AR genes in this unique protected ecosystem, and the related human, animal, and environmental health impacts, and to formulate interventions to reduce AR spread in this setting.

Characterization of microbial community and antibiotic resistome in intra urban water, Wenzhou China

The present study investigated the water quality index, microbial composition and antimicrobial resistance genes in urban water habitats. Combined chemicals testing, metagenomic analyses and qualitative PCR (qPCR) were conducted on 20 locations, including rivers from hospital surrounds (n = 7), community surrounds (n = 7), and natural wetlands (n = 6). Results showed that the indexes of total nitrogen, phosphorus, and ammonia nitrogen of hospital waters were 2-3 folds high than that of water from wetlands. Bioinformatics analysis revealed a total of 1,594 bacterial species from 479 genera from the three groups of water samples. The hospital-related samples had the greatest number of unique genera, followed by those from wetlands and communities. The hospital-related samples contained a large number of bacteria associated with the gut microbiome, including Alistipes, Prevotella, Klebsiella, Escherichia, Bacteroides, and Faecalibacterium, which were all significantly enriched compared to samples from the wetlands. Nevertheless, the wetland waters enriched bacteria from Nanopelagicus, Mycolicibacterium and Gemmatimonas, which are typically associated with aquatic environments. The presence of antimicrobial resistance genes (ARGs) that were associated with different species origins in each water sample was observed. The majority of ARGs from hospital-related samples were carried by bacteria from Acinetobacter, Aeromonas and various genera from Enterobacteriaceae, which each was associated with multiple ARGs. In contrast, the ARGs that were exclusively in samples from communities and wetlands were carried by species that encoded only 1 to 2 ARGs each and were not normally associated with human infections. The qPCR showed that water samples of hospital surrounds had higher concentrations of intI1 and antimicrobial resistance genes such as tetA, ermA, ermB, qnrB, sul1, sul2 and other beta-lactam genes. Further genes of functional metabolism reported that the enrichment of genes associated with the degradation/utilization of nitrate and organic phosphodiester were detected in water samples around hospitals and communities compared to those from wetlands. Finally, correlations between the water quality indicators and the number of ARGs were evaluated. The presence of total nitrogen, phosphorus, and ammonia nitrogen were significantly correlated with the presence of ermA and sul1. Furthermore, intI1 exhibited a significant correlation with ermB, sul1, and bla_SHV, indicating a prevalence of ARGs in urban water environments might be due to the integron intI1's diffusion-promoting effect. However, the high abundance of ARGs was limited to the waters around the hospital, and we did not observe the geographical transfer of ARGs along with the river flow. This may be related to water purifying capacity of natural riverine wetlands. Taken together, continued surveillance is required to assess the risk of bacterial horizontal transmission and its potential impact on public health in the current region.

[Health risks from crop irrigation with treated wastewater containing antibiotic residues, resistance genes, and resistant microorganisms]

This review describes the effects and potential health risks of resistant microorganisms, resistance genes, and residues of drugs and biocides that occur when re-using wastewater for crop irrigation. It focusses on specific aspects of these contaminants and their interactions, but does not provide a general risk assessment of the microbial load when using reclaimed water.Antimicrobial residues, antimicrobial resistant microorganisms, and resistance genes are frequently detected in treated wastewater. They have effects on the soil and plant-associated microbiota (total associated microorganisms) and can be taken up by plants. An interaction of residues with microorganisms is mainly expected before using the water for irrigation. However, it may also occur as a combined effect on the plant microbiome and all the abundant resistance genes (resistome). Special concerns are raised as plants are frequently consumed raw, that is, without processing that might reduce the bacterial load. Washing fruits and vegetables only has minor effects on the plant microbiome. On the other hand, cutting and other processes may support growth of microorganisms. Therefore, after such process steps, cooling of the foods is required.Further progress has to be made in the treatment of wastewater that will be used for crop irrigation with respect to removing micropollutants and microorganisms to minimize the risk of an increased exposure of consumers to transferable resistance genes and resistant bacteria.

Antimicrobial Resistance Linked to Septic System Contamination in the Indiana Lake Michigan Watershed

Extended-spectrum β-lactamases confer resistance to a variety of β-lactam antimicrobials, and the genes for these enzymes are often found on plasmids that include additional antimicrobial resistance genes (ARG). We surveyed aquatic environments in the Indiana Lake Michigan watershed in proximity to areas with high densities of residential septic systems to determine if human fecal contamination from septic effluent correlated with the presence of antimicrobial resistance genes and phenotypically resistant bacteria. Of the 269 E. coli isolated from environmental samples and one septic source, 97 isolates were resistant to cefotaxime, a third-generation cephalosporin. A subset of those isolates showed phenotypic resistance to other β-lactams, fluoroquinolones, sulfonamides, and tetracyclines. Quantitative PCR was used to quantify human-associated Bacteroides dorei gene copies (Human Bacteroides) from water samples and to identify the presence of ARG harbored on plasmids from E. coli isolates or in environmental DNA. We found a strong correlation between the presence of ARG and human fecal concentrations, which supports our hypothesis that septic effluent is a source of ARG and resistant organisms. The observed plasmid-based resistance adds an additional level of risk, as human-associated bacteria from septic systems may expand the environmental resistome by acting as a reservoir of transmissible resistance genes.

Characterization of Third Generation Cephalosporin- and Carbapenem-Resistant Aeromonas Isolates from Municipal and Hospital Wastewater

Antibiotic resistance (AR) remains one of the greatest threats to global health, and Aeromonas species have the potential to spread AR in the aquatic environment. The spread of resistance to antibiotics important to human health, such as third-generation cephalosporins (3GCs) and carbapenems, is of great concern. We isolated and identified 15 cefotaxime (3GC)- and 51 carbapenem-resistant Aeromonas spp. from untreated hospital and treated municipal wastewater in January 2020. The most common species were Aeromonas caviae (58%), A. hydrophila (17%), A. media (11%), and A. veronii (11%). Almost all isolates exhibited a multidrug-resistant phenotype and harboured a diverse plasmidome, with the plasmid replicons ColE, IncU, and IncR being the most frequently detected. The most prevalent carbapenemase gene was the plasmid-associated blaKPC-2 and, for the first time, the blaVIM-2, blaOXA-48, and blaIMP-13 genes were identified in Aeromonas spp. Among the 3GC-resistant isolates, the blaGES-5 and blaMOX genes were the most prevalent. Of the 10 isolates examined, three were capable of transferring carbapenem resistance to susceptible recipient E. coli. Our results suggest that conventionally treated municipal and untreated hospital wastewater is a reservoir for 3GC- and carbapenem-resistant, potentially harmful Aeromonas spp. that can be introduced into aquatic systems and pose a threat to both the environment and public health.

Characterization of Two Novel AmpC Beta-Lactamases from the Emerging Opportunistic Pathogen, Cedecea neteri

The genus Cedecea (family Enterobacteriaceae) causes a wide spectrum of acute infections in immunocompromised hosts, from pneumonia and bacteremia to oral ulcers and dialysis-related peritonitis. While Cedecea infections are reported infrequently in the literature, documented clinical cases of this emerging opportunistic human pathogen have occurred worldwide. Cedecea neteri has clinical significance and exhibits antimicrobial drug resistance. However, little is known about the molecular basis underlying the resistance phenotypes in C. neteri. We previously hypothesized that the open-reading frame cnt10470 in the C. neteri SSMD04 genome encodes a chromosomal Ambler class C (AmpC) β-lactamase based on sequence homology. In this study, recombinant polyhistidine-tagged proteins were created by cloning the putative ampC genes from SSMD04 and C. neteri ATCC 33855 (a clinical isolate) into the pET-6xHN expression vector, overexpressing the proteins, and then purifying the recombinant AmpCs (rAmpCs) using immobilized metal affinity chromatography (Ni-NTA). The in vitro enzymatic analysis of the purified rAmpCs was performed to determine the K_m and k_cat for various β-lactam substrates. The rAmpCs are functional class C β-lactamases when assayed using the chromogenic β-lactamase substrate, nitrocefin. The presence of functional AmpCs in both C. neteri strains underscores the necessity of performing antibiotic susceptibility testing in the management of C. neteri infections.

Phenotypic Characterization and Antibiograms of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli Isolated at the Human-Animal-Environment Interface Using a One Health Approach Among Households in Wakiso District, Uganda

Background

The occurrence of extended spectrum beta-lactamase (ESBL) producing bacteria such as Escherichia coli has increasingly become recognized beyond hospital settings. Resistance to other types of antibiotics limits treatment options while the existence of such bacteria among humans, animals, and the environment is suggestive of potential zoonotic and reverse-zoonotic transmission. This study aimed to establish the antibiotic susceptibility profiles of the ESBL-producing Escherichia coli (ESBL-EC) from human, animal, and environmental isolates obtained among farming households within Wakiso district using a One Health approach.

Methods

A total of 100 ESBL-EC isolates from humans 35/100 (35%), animals 56/100 (56%), and the environment 9/100 (9%) were tested for susceptibility to 11 antibiotics. This was done using the Kirby-Bauer disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Data were analyzed in STATA ver. 16 and graphs were drawn in Microsoft excel ver. 10.

Results

Most of the ESBL-EC isolates (98%) were resistant to more than two antibiotics. ESBL-EC isolates were most susceptible to meropenem (MEM) (88.0%), and imipenem (82.0%) followed by gentamicin (72%). ESBL-EC isolates from humans were most susceptible to meropenem (MEM) followed by imipenem (IPM)> gentamicin (CN)> ciprofloxacin (CIP). Animal samples were more susceptible to MEM, IPM, and CN but were highly resistant to cefotaxime (CTX)> cefepime (FEP)>other antibiotics. Multidrug resistance (MDR) was mostly reported among households keeping goats under intensive husbandry practices. Seven percent of the isolates exhibited carbapenem resistance while 22% showed aminoglycoside resistance. Similar resistance patterns among humans, animals, and environmental samples were also reported.

Conclusion

Our study provides baseline information on non-hospital-based MDR caused by ESBL-EC using a One Health approach. ESBL-EC isolates were prevalent among apparently healthy community members, animals, and their environment. It is important to conduct more One Health approach studies to generate evidence on the drivers, resistance patterns, and transmission of ESBL-producing organisms at the human-animal-environmental interface.

High Resistance to Antibiotics Recommended in Standard Treatment Guidelines in Ghana: A Cross-Sectional Study of Antimicrobial Resistance Patterns in Patients with Urinary Tract Infections between 2017-2021

Management of urinary tract infections is challenged by increasing antimicrobial resistance (AMR) worldwide. In this study, we describe the trends in antimicrobial resistance of uropathogens isolated from the largest private sector laboratory in Ghana over a five-year period. We reviewed positive urine cultures at the MDS Lancet Laboratories from 2017 to 2021. The proportions of uropathogens with antimicrobial resistance to oral and parenteral antimicrobials recommended by the Ghana standard treatment guidelines were determined. The proportion of multi-drug resistant isolates, ESBL and carbapenemase-producing phenotypes were determined. Of 94,134 urine specimens submitted for culture, 20,010 (22.1%) were culture positive. Enterobacterales was the most common group of organisms, E. coli (70.6%) being the most common isolate and Enterococcus spp. the most common gram-positive (1.3%) organisms. Among oral antimicrobials, the highest resistance was observed to ciprofloxacin (62.3%) and cefuroxime (60.2%) and the least resistance to fosfomycin (1.9%). The least resistance among parenteral antimicrobials was to meropenem (0.3%). The highest multi-drug resistance levels were observed among Klebsiella spp. (68.6%) and E. coli (64.0%). Extended-spectrum beta-lactamase (ESBL) positivity was highest in Klebsiella spp. (58.6%) and E. coli (50.0%). There may be a need to review the Ghana standard treatment guidelines to reflect increased resistance among uropathogens to recommended antimicrobials.

Identifying the Sources of Intestinal Colonization With Extended-Spectrum β-Lactamase-Producing Escherichia coli in Healthy Infants in the Community

The prevalence of fecal colonization with extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) among children in low- and middle-income countries is alarmingly high. This study aimed to identify the sources of ESBL-Ec colonization in children &lt; 1 year old through comparative analysis of E. coli isolates from child stool, child’s mother stool, and point-of-use drinking water from 46 rural households in Bangladesh. The pairwise similarity in antibiotic susceptibility of E. coli from all three sources was evaluated, followed by phylogenetic clustering using enterobacterial repetitive intergenic consensus polymerase chain reaction and whole-genome sequence analysis of the isolates. Matching antibiotic susceptibility and enterobacterial repetitive intergenic consensus polymerase chain reaction patterns were found among ESBL-Ec isolates from child–mother dyads of 24 and 11 households, respectively, from child–water dyads of 5 and 4 households, respectively, and from child–mother–water triads of 3 and 4 households, respectively. Whole-genome sequence analysis of 30 isolates from 10 households revealed that ESBL-Ec from children in five households (50%) was clonally related to ESBL-Ec either from their mothers (2 households), drinking water sources (2 households), or both mother and drinking-water sources (1 household) based on serotype, phylogroup, sequence type, antibiotic resistance genes, mobile genetic elements, core single-nucleotide polymorphisms, and whole-genome multilocus sequence typing. Overall, this study provides empirical evidence that ESBL-Ec colonization in children is linked to the colonization status of mothers and exposure to the household environments contaminated with ESBL-Ec. Interventions such as improved hygiene practices and a safe drinking water supply may help reduce the transmission of ESBL-Ec at the household level.

Pan-genome and resistome analysis of extended-spectrum ß-lactamase-producing Escherichia coli: A multi-setting epidemiological surveillance study from Malaysia

Objectives

This study profiled the prevalence of extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-EC) in the community and compared their resistome and genomic profiles with isolates from clinical patients through whole-genome sequencing.

Methods

Fecal samples from 233 community dwellers from Segamat, a town in southern Malaysia, were obtained between May through August 2018. Putative ESBL strains were screened and tested using antibiotic susceptibility tests. Additionally, eight clinical ESBL-EC were obtained from a hospital in the same district between June through October 2020. Whole-genome sequencing was then conducted on selected ESBL-EC from both settings (n = 40) for pan-genome comparison, cluster analysis, and resistome profiling.

Results

A mean ESBL-EC carriage rate of 17.82% (95% CI: 10.48%– 24.11%) was observed in the community and was consistent across demographic factors. Whole-genome sequences of the ESBL-EC (n = 40) enabled the detection of multiple plasmid replicon groups (n = 28), resistance genes (n = 34) and virulence factors (n = 335), with no significant difference in the number of genes carried between the community and clinical isolates (plasmid replicon groups, p = 0.13; resistance genes, p = 0.47; virulence factors, p = 0.94). Virulence gene marker analysis detected the presence of extraintestinal pathogenic E. coli (ExPEC), uropathogenic E. coli (UPEC), and enteroaggregative E. coli (EAEC) in both the community and clinical isolates. Multiple blaCTX-M variants were observed, dominated by blaCTX-M-27 (n = 12), blaCTX-M-65 (n = 10), and blaCTX-M-15 (n = 9). The clinical and community isolates did not cluster together based on the pan-genome comparison, suggesting isolates from the two settings were clonally unrelated. However, cluster analysis based on carried plasmids, resistance genes and phenotypic susceptibility profiles identified four distinct clusters, with similar patterns between the community and clinical isolates.

Conclusion

ESBL-EC from the clinical and community settings shared similar resistome profiles, suggesting the frequent exchange of genetic materials through horizontal gene transfer.

Genetic characterization of extended-spectrum β-lactamase-producing Enterobacteriaceae from a biological industrial wastewater treatment plant in Tunisia with detection of the colistin-resistance mcr-1 gene

This study evaluated the occurrence of extended-spectrum β-lactamases (ESBL) and associated resistance genes, integrons, and plasmid types, as well as the genetic relatedness of enterobacterial isolates in the wastewater treatment plant (WWTP) of La Charguia, Tunis City (Tunisia). A total of 100 water samples were collected at different points of the sewage treatment process during 2017-2019. Antimicrobial susceptibility was conducted by the disc-diffusion method. blaCTX-M, blaTEM and blaSHV genes as well as those encoding non-β-lactam resistance, the plasmid types, occurrence of class1 integrons and phylogenetic groups of Escherichia coli isolates were determined by PCR/sequencing. Genomic relatedness was determined by multi-locus sequence typing (MLST) for selected isolates. In total, 57 ESBL-producer isolates were recovered (47 E. coli, eight Klebsiella pneumoniae, 1 of the Citrobacter freundii complex and 1 of the Enterobacter cloacae complex). The CTX-M-15 enzyme was the most frequently detected ESBL, followed by CTX-M-27, CTX-M-55 and SHV-12. One E. coli isolate harboured the mcr-1 gene. The following phylogroups/sequence types (STs) were identified among ESBL-producing E. coli isolates: B2/ST131 (subclade-C1), A/ST3221, A/ST8900, D/ST69, D/ST2142, D/ST38, B1/ST2460 and B1/ST6448. High numbers of isolates harboured the class 1 integrons with various gene cassette arrays as well as IncP-1 and IncFIB plasmids. Our findings confirm the importance of WWTPs as hotspot collectors of ESBL-producing Enterobacteriaceae with a high likelihood of spread to human and natural environments.