Persistence and prevalence of pathogenic and extended-spectrum beta-lactamase-producing Escherichia coli in municipal wastewater treatment plant receiving slaughterhouse wastewater

Population Ecology-Quantitative Microbial Risk Assessment (QMRA) Model for Antibiotic-Resistant and Susceptible E. coli in Recreational Water

Understanding and predicting the role of waterborne environments in transmitting antimicrobial-resistant (AMR) infections are critical for public health. A population ecology-quantitative microbial risk assessment (QMRA) model is proposed to evaluate urinary tract infection (UTI) development due to recreational waterborne exposures to Escherichia coli (E. coli) and antibiotic-resistant extended-spectrum β-lactamase-producing (ESBL) E. coli. The horizontal gene transfer (HGT) mechanism of conjugation and other evolutionary factors were modeled separately in the environment and the gut. Persistence/dilution dominated HGT in the environment; however, HGT highly impacted predicted ESBL populations in the body. Predicted disability life year (DALY) risks from exposure to ESBL E. coli at concentrations consistent with US recreational water criteria were less than the 10-6 pppy benchmark value but greater than the susceptible E. coli DALY risks associated with a UTI health outcome. However, the prevailing susceptible dose-response relationship may underestimate ESBL risk if HGT rates in vivo approach those reported in vitro. A sensitivity analysis demonstrated that DALY values, E. coli/ESBL concentrations, and exposure parameters were influential on predicted risks. The model is a preliminary tool to begin the expansion of the QMRA paradigm to explore the impacts of evolutionary changes in AMR risk assessment.

Can Wastewater Surveillance Enhance Genomic Tracking of Climate-Driven Pathogens?

Climate change heightens the threat of infectious diseases in Europe, necessitating innovative surveillance methods. Based on 390 scientific papers, for the first time, this review associates climate-related pathogens, data related to their presence in wastewater, and associated available genomic detection methods. This deep analysis reveals a wide range of pathogens that can be tracked through methods such as quantitative and digital PCR, as well as genomic pathogen enrichment in combination with sequencing and metagenomics. Nevertheless, significant gaps remain in the development of methods, particularly for vector-borne pathogens, and in their general harmonization relating to performance criteria. By offering an overview of recent advancements while identifying critical gaps, we advocate for collaborative research and validation to integrate detection techniques into surveillance frameworks. This will enhance public health resilience against emerging infectious diseases driven by climate change.

Symbiotic virus-bacteria interactions in biological treatment of coking wastewater manipulating bacterial physiological activities

Biological treatment is commonly used in coking wastewater (CWW) treatment. Prokaryotic microbial communities in CWW treatment have been comprehensively studied. However, viruses, as the critical microorganisms affecting microbial processes and thus engineering parameters, still remain poorly understood in CWW treatment context. Employing viromics sequencing, the composition and function of the viral community in CWW treatment were discovered, revealing novel viral communities and key auxiliary metabolic functions. Caudovirales appeared to be the predominant viral order in the oxic-hydrolytic-oxic (OHO) CWW treatment combination, showing relative abundances of 62.47 %, 56.64 % and 92.20 % in bioreactors O1, H and O2, respectively. At the family level, Myoviridae, Podoviridae and Siphoviridae mainly prevailed in bioreactors O1 and H while Phycodnaviridae dominated in O2. A total of 56.23-92.24% of novel viral contigs defied family-level characterization in this distinct CWW habitat. The virus-host prediction results revealed most viruses infecting the specific functional taxa Pseudomonas, Acidovorax and Thauera in the entire OHO combination, demonstrating the viruses affecting bacterial physiology and pollutants removal from CWW. Viral auxiliary metabolic genes (AMGs) were screened, revealing their involvement in the metabolism of contaminants and toxicity tolerance. In the bioreactor O1, AMGs were enriched in detoxification and phosphorus ingestion, where glutathione S-transferase (GSTs) and beta-ketoadipyl CoA thiolase (fadA) participated in biodegradation of polycyclic aromatic hydrocarbons and phenols, respectively. In the bioreactors H and O2, the AMGs focused on cell division and epicyte formation of the hosts, where GDPmannose 4,6-dehydratase (gmd) related to lipopolysaccharides biosynthesis was considered to play an important role in the growth of nitrifiers. The diversities of viruses and AMGs decreased along the CWW treatment process, pointing to a reinforced virus-host adaptive strategy in stressful operation environments. In this study, the symbiotic virus-bacteria interaction patterns were proposed with a theoretical basis for promoting CWW biological treatment efficiency. The findings filled the gaps in the virus-bacteria interactions at the full-scale CWW treatment and provided great value for understanding the mechanism of biological toxicity and sludge activity in industrial wastewater treatment.

Virulence-associated genes and antimicrobial resistance patterns in bacteria isolated from pregnant and nonpregnant women with urinary tract infections: the risk of neonatal sepsis

Uropathogenic Escherichia coli (UPEC) is classified as the major causative agent of urinary tract infections (UTIs). UPEC virulence and antibiotic resistance can lead to complications in pregnant women and (or) newborns. Therefore, the aim of this study was to determine the etiological agents of UTIs, as well as to identify genes related to virulence factors in bacteria isolated from pregnant and nonpregnant women. A total of 4506 urine samples were collected from pregnant and nonpregnant women. Urine cultures were performed, and PCR was used to identify phylogroups and virulence-related genes. Antibiotic resistance profiles were determined. The incidence of UTIs was 6.9% (pregnant women, n = 206 and nonpregnant women, n = 57), and UPEC belonging to phylogroup A was the most prevalent. The presence of genes related to capsular protection, adhesins, iron acquisition, and serum protection in UPEC was associated with not being pregnant, while the presence of genes related to adhesins was associated with pregnancy. Bacteria isolated from nonpregnant women were more resistant to antibiotics; 36.5% were multidrug resistant, and 34.9% were extensively drug resistant. Finally, UTIs were associated with neonatal sepsis risk, particularly in pregnant women who underwent cesarean section while having a UTI caused by E. coli. In conclusion, UPEC isolated from nonpregnant women carried more virulence factors than those isolated from pregnant women, and maternal UTIs were associated with neonatal sepsis risk.

Integrating life cycle assessment with quantitative microbial risk assessment for a holistic evaluation of sewage treatment plant

An integrated approach was employed in the present study to combine life cycle assessment (LCA) with quantitative microbial risk assessment (QMRA) to assess an existing sewage treatment plant (STP) at Roorkee, India. The midpoint LCA modeling revealed that high electricity consumption (≈ 576 kWh.day^-1) contributed to the maximum environmental burdens. The LCA endpoint result of 0.01 disability-adjusted life years per person per year (DALYs pppy) was obtained in terms of the impacts on human health. Further, a QMRA model was developed based on representative sewage pathogens, including E. coli O157:H7, Giardia sp., adenovirus, norovirus, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The public health risk associated with intake of pathogen-laden aerosols during treated water reuse in sprinkler irrigation was determined. A cumulative health risk of 0.07 DALYs pppy was obtained, where QMRA risks contributed 86 % of the total health impacts. The annual probability of illness per person was highest for adenovirus and norovirus, followed by SARS-CoV-2, E. coli O157:H7 and Giardia sp. Overall, the study provides a methodological framework for an integrated LCA-QMRA assessment which can be applied across any treatment process to identify the hotspots contributing maximum environmental burdens and microbial health risks. Furthermore, the integrated LCA-QMRA approach could support stakeholders in the water industry to select the most suitable wastewater treatment system and establish regulations regarding the safe reuse of treated water.

Prevalence and distribution of antimicrobial resistance in effluent wastewater from animal slaughter facilities: A systematic review

The extensive use of antibiotics in food animal production and disposal of untreated wastewater from food animal slaughter facilities may create a shift in microbiomes of different ecosystems by generating reservoirs of antimicrobial resistance along the human-animal-environmental interface. This epidemiological problem has been studied, but its magnitude and impact on a global scale is poorly characterised. A systematic review was done to determine global prevalence and distribution patterns of antimicrobial resistance in effluent wastewater from animal slaughter facilities. Extracted data were stratified into rational groups for secondary analyses and presented as percentages. Culture and sensitivity testing was the predominant method; Escherichia spp., Enterococcus spp., and Staphylococcus aureus were the most targeted isolates. Variable incidences of resistance were detected against all major antimicrobial classes including reserved drugs such as ceftazidime, piperacillin, gentamicin, ciprofloxacin, and chloramphenicol; the median frequency and range in resistant Gram-negative isolates were: 11 (0-100), 62 (0-100), 8 (0-100), 14 (0-93) and 12 (0-62) respectively. Ciprofloxacin was the most tested drug with the highest incidences of resistance in livestock slaughterhouses in Iran (93%), Nigeria (50%) and China (20%), and poultry slaughterhouses in Germany (21-81%) and Spain (56%). Spatial global distribution patterns for antimicrobial resistance were associated with previously reported magnitude of antibiotic use in livestock or poultry farming and, the implicit existence of jurisdictional policies to regulate antibiotic use. These data indicate that anthropogenic activities in farming systems are a major contributor to the cause and dissemination of antimicrobial resistance into the environment via slaughterhouse effluents.

Naturalized Escherichia coli in Wastewater and the Co-evolution of Bacterial Resistance to Water Treatment and Antibiotics

Antibiotic resistance represents one of the most pressing concerns facing public health today. While the current antibiotic resistance crisis has been driven primarily by the anthropogenic overuse of antibiotics in human and animal health, recent efforts have revealed several important environmental dimensions underlying this public health issue. Antibiotic resistant (AR) microbes, AR genes, and antibiotics have all been found widespread in natural environments, reflecting the ancient origins of this phenomenon. In addition, modern societal advancements in sanitation engineering (i.e., sewage treatment) have also contributed to the dissemination of resistance, and concerningly, may also be promoting the evolution of resistance to water treatment. This is reflected in the recent characterization of naturalized wastewater strains of Escherichia coli-strains that appear to be adapted to live in wastewater (and meat packing plants). These strains carry a plethora of stress-resistance genes against common treatment processes, such as chlorination, heat, UV light, and advanced oxidation, mechanisms which potentially facilitate their survival during sewage treatment. These strains also carry an abundance of common antibiotic resistance genes, and evidence suggests that resistance to some antibiotics is linked to resistance to treatment (e.g., tetracycline resistance and chlorine resistance). As such, these naturalized E. coli populations may be co-evolving resistance against both antibiotics and water treatment. Recently, extraintestinal pathogenic strains of E. coli (ExPEC) have also been shown to exhibit phenotypic resistance to water treatment, seemingly associated with the presence of various shared genetic elements with naturalized wastewater E. coli. Consequently, some pathogenic microbes may also be evolving resistance to the two most important public health interventions for controlling infectious disease in modern society-antibiotic therapy and water treatment.

Prevalence of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in wastewater: a systematic review and meta-analysis

Wastewater is considered a hotspot niche of multi-drug and pathogenic bacteria such as Enterobacteriaceae-producing extended-spectrum beta-lactamases (ESBL-E). Thus, the aim of this meta-analysis was to evaluate the prevalence of ESBL-E in different wastewater sources. Different databases (Medline, EMBASE, and Cochrane Library) were searched from inception to March 2021. Data were analyzed using random-effects modeling, and subgroup and meta-regression analyses were used to ascertain heterogeneity among the subgroups. Fifty-seven observational studies were selected, and the pooled prevalence of ESBL-E in wastewater was 24.81% (95% CI, 19.28-30.77). Escherichia coli had the highest ESBL prevalence. The blaCTX-M genes were the most prevalent in the selected studies (66.56%). The pooled prevalence of ESBL was significantly higher in reports from America (39.91%, 95% CI, 21.82-59.51) and reports studying hospital and untreated wastewaters (33.98%, 95% CI, 23.82-44.91 and 27.36%, 95% CI, 19.12-36.42). Overall, this meta-analysis showed that the prevalence of ESBL-E in wastewater is increasing over time and that hospital wastewater is the most important repository of ESBL-E. Therefore, there is a need for developing new sewage treatment systems that decrease the introduction of resistant bacteria and antibiotic residues.

Evaluation of Antibiotic Resistance in Bacterial Strains Isolated from Sewage of Slaughterhouses Located in Sicily (Italy)

Antimicrobial resistance is presently one of the most public health critical concerns. The frequent and often incorrect use of antibiotics in animal husbandry has led to the spread of antimicrobial resistance in this setting. Wastewater from slaughterhouses can be contaminated with multidrug-resistant bacteria, representing a possible cross-contamination route. We evaluated the presence of antibiotic-resistant bacteria in wastewater samples from slaughterhouses located in an Italian region. Specifically, 18 slaughterhouses were included in the study. Of the tested samples, 40 bacterial strains were chosen, identified, and tested for antibiotic susceptibility. Pseudomonas spp., Proteus spp., Enterobacter spp., Aeromonas spp., and Citrobacter spp. were the most detected genera. The most resistant strains were on average those belonging to Enterobacter spp. The highest resistance rate was recorded for macrolides. Among β-lactams, penicillins and cephalosporins were by far the molecules towards which the highest resistance was detected. A very interesting finding is the difference found in strains detected in wastewater from poultry slaughterhouses, in which higher levels for almost all the considered drugs were detected compared to those from ungulates slaughterhouses. Our results indicate wastewater from slaughterhouses as a potential vehicle of resistant bacteria and highlight the importance of correct management of these kinds of waters.

Antibiotic-resistant bacteria, antibiotic resistance genes, and antibiotic residues in wastewater from a poultry slaughterhouse after conventional and advanced treatments

Slaughterhouse wastewater is considered a reservoir for antibiotic-resistant bacteria and antibiotic residues, which are not sufficiently removed by conventional treatment processes. This study focuses on the occurrence of ESKAPE bacteria (Enterococcus spp., S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp.), ESBL (extended-spectrum β-lactamase)-producing E. coli, antibiotic resistance genes (ARGs) and antibiotic residues in wastewater from a poultry slaughterhouse. The efficacy of conventional and advanced treatments (i.e., ozonation) of the in-house wastewater treatment plant regarding their removal was also evaluated. Target culturable bacteria were detected only in the influent and effluent after conventional treatment. High abundances of genes (e.g., bla_TEM, bla_CTX-M-15, bla_CTX-M-32, bla_OXA-48, bla_CMY and mcr-1) of up to 1.48 × 10⁶ copies/100 mL were detected in raw influent. All of them were already significantly reduced by 1–4.2 log units after conventional treatment. Following ozonation, mcr-1 and bla_CTX-M-32 were further reduced below the limit of detection. Antibiotic residues were detected in 55.6% (n = 10/18) of the wastewater samples. Despite the significant reduction through conventional and advanced treatments, effluents still exhibited high concentrations of some ARGs (e.g., sul1, ermB and bla_OXA-48), ranging from 1.75 × 10² to 3.44 × 10³ copies/100 mL. Thus, a combination of oxidative, adsorptive and membrane-based technologies should be considered.

Extended Spectrum Beta-Lactamase Escherichia coli in River Waters Collected from Two Cities in Ghana, 2018-2020

Infections by Extended-Spectrum Beta-Lactamase producing Escherichia coli (ESBL-Ec) are on the increase in Ghana, but the level of environmental contamination with this organism, which may contribute to growing Antimicrobial Resistance (AMR), is unknown. Using the WHO OneHealth Tricycle Protocol, we investigated the contamination of E. coli (Ec) and ESBL-Ec in two rivers in Ghana (Odaw in Accra and Okurudu in Kasoa) that receive effluents from human and animal wastewater hotspots over a 12-month period. Concentrations of Ec, ESBL-Ec and percent ESBL-Ec/Ec were determined per 100 mL sample. Of 96 samples, 94 (98%) were positive for ESBL-Ec. concentrations per 100 mL (MCs100) of ESBL-Ec and %ESBL-Ec from both rivers were 4.2 × 10⁴ (IQR, 3.1 × 10³–2.3 × 10⁵) and 2.79 (IQR, 0.96–6.03), respectively. MCs100 were significantly lower in upstream waters: 1.8 × 10⁴ (IQR, 9.0 × 10³–3.9 × 10⁴) as compared to downstream waters: 1.9 × 10⁶ (IQR, 3.7 × 10⁵–5.4 × 10⁶). Both human and animal wastewater effluents contributed to the increased contamination downstream. This study revealed high levels of ESBL-Ec in rivers flowing through two cities in Ghana. There is a need to manage the sources of contamination as they may contribute to the acquisition and spread of ESBL-Ec in humans and animals, thereby contributing to AMR.

Evaluation of Metagenomic-Enabled Antibiotic Resistance Surveillance at a Conventional Wastewater Treatment Plant

Wastewater treatment plants (WWTPs) receive a confluence of sewage containing antimicrobials, antibiotic resistant bacteria, antibiotic resistance genes (ARGs), and pathogens and thus are a key point of interest for antibiotic resistance surveillance. WWTP monitoring has the potential to inform with respect to the antibiotic resistance status of the community served as well as the potential for ARGs to escape treatment. However, there is lack of agreement regarding suitable sampling frequencies and monitoring targets to facilitate comparison within and among individual WWTPs. The objective of this study was to comprehensively evaluate patterns in metagenomic-derived indicators of antibiotic resistance through various stages of treatment at a conventional WWTP for the purpose of informing local monitoring approaches that are also informative for global comparison. Relative abundance of total ARGs decreased by ∼50% from the influent to the effluent, with each sampling location defined by a unique resistome (i.e., total ARG) composition. However, 90% of the ARGs found in the effluent were also detected in the influent, while the effluent ARG-pathogen taxonomic linkage patterns identified in assembled metagenomes were more similar to patterns in regional clinical surveillance data than the patterns identified in the influent. Analysis of core and discriminatory resistomes and general ARG trends across the eight sampling events (i.e., tendency to be removed, increase, decrease, or be found in the effluent only), along with quantification of ARGs of clinical concern, aided in identifying candidate ARGs for surveillance. Relative resistome risk characterization further provided a comprehensive metric for predicting the relative mobility of ARGs and likelihood of being carried in pathogens and can help to prioritize where to focus future monitoring and mitigation. Most antibiotics that were subject to regional resistance testing were also found in the WWTP, with the total antibiotic load decreasing by ∼40–50%, but no strong correlations were found between antibiotics and corresponding ARGs. Overall, this study provides insight into how metagenomic data can be collected and analyzed for surveillance of antibiotic resistance at WWTPs, suggesting that effluent is a beneficial monitoring point with relevance both to the local clinical condition and for assessing efficacy of wastewater treatment in reducing risk of disseminating antibiotic resistance.

Detection of mcr-1-positive Escherichia coli in slaughterhouse wastewater collected from Dawen river

BACKGROUND

Low levels of mcr-1 were detected in Escherichia coli from wastewater samples across the world; hence, further monitoring and management of accumulation of mcr-1-positive bacteria in wastewater are urgently recommended.

OBJECTIVES

In this study, we have reported the detection of E. coli strains carrying the colistin resistance gene mcr-1 in slaughterhouse wastewater discharged into Dawen river.

METHODS

Twenty samples were collected aseptically and subjected to polymerase chain reaction (PCR) analysis, multilocus sequence typing and antibiotic resistance tests. Conjugation tests were also performed.

RESULTS

The screening results showed a positive rate of 20% (4/20), which suggested that the mcr-1 gene had polluted the environment of the river. The mcr-1 gene had successfully transferred from the donor to recipient cells, which showed the possibility of horizontal transfer of mcr-1 and subsequently, the formation of multidrug resistant bacteria in the river.

CONCLUSIONS

Our findings demonstrated a high occurrence of colistin-resistant E. coli carrying the mcr-1 gene on transferrable plasmids in slaughterhouses and indicated their dissemination into river. Large-scale cross-border cooperation would be required for the effective control of the spread of antibiotic-resistant bacteria.

Waterborne Urinary Tract Infections: Have We Overlooked an Important Source of Exposure?

The presence of intestinal pathogenic Escherichia coli in drinking water is well recognized as a risk for diarrhea. The role of drinking water in extraintestinal infections caused by E. coli-such as urinary tract infections (UTIs)-remains poorly understood. Urinary tract infections are a leading cause of outpatient infections globally, with a lifetime incidence of 50-60% in adult women. We reviewed the scientific literature on the occurrence of uropathogenic E. coli (UPEC) in water supplies to determine whether the waterborne route may be an important, overlooked, source of UPEC. A limited number of studies have assessed whether UPEC isolates are present in drinking water supplies, but no studies have measured whether their presence in water may increase UPEC colonization or the risk of UTIs in humans. Given the prevalence of drinking water supplies contaminated with E. coli across the globe, efforts should be made to characterize UTI-related risks associated with drinking water, as well as other pathways of exposure.

Prevalence of ESBL-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae in treated wastewater: a comparison with nosocomial infection surveillance

The increasing prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae (CRE) is a worldwide health threat. Monitoring of these resistant bacteria in the environment can provide regional prevalence reflecting both healthy and infected populations, although the quantitative monitoring of those resistant bacteria, especially CRE, is difficult due to their low proportion in the total Enterobacteriaceae population and the possible interference by autochthonous species with intrinsic resistance. In this study, these resistant bacteria in treated wastewater were quantified at 12 different treatment plants. The proportions of cefotaxime-resistant and ESBL-producing E. coli in the total E. coli population in the chlorinated effluents in Tokyo were 5.7 and 5.3%, respectively. The estimated proportion of CRE was 0.007% with the constituting species of Klebsiella spp. and Enterobacter spp., although the conditions during the first incubation may have affected the estimation even after the correction by the proportion of resistant population in the isolates. The observed resistant proportions in this study were lower than those in the surveillance on nosocomial infection not only for inpatients but also for outpatients, and higher than those in the veterinary monitoring.

Antibiotic-resistant bacteria and antimicrobial residues in wastewater and process water from German pig slaughterhouses and their receiving municipal wastewater treatment plants

Slaughterhouse process- and wastewater are considered as a hotspot for antibiotic-resistant bacteria and antimicrobial residues and may thus play an important role for their dissemination into the environment. In this study, we investigated occurrence and characteristics of ESKAPE bacteria (E. faecium, S. aureus, K. pneumoniae, A. baumannii, P. aeruginosa, Enterobacter spp.) and ESBL (extended spectrum β-lactamase) -producing E. coli in water samples of different processing stages of two German pig slaughterhouses (S1/S2) as well as their municipal wastewater treatment plants (mWWTPs). Furthermore, residues of various antimicrobials were determined. A total of 103 water samples were taken in delivery and dirty areas of the slaughterhouses S1/S2 (n = 37), their in-house WWTPs (n = 30) and mWWTPs including their receiving water bodies (n = 36). The recovered isolates (n = 886) were characterized for their antimicrobial resistance pattern and its genetic basis. Targeted species were ubiquitous along the slaughtering and wastewater chains. Phenotypic and genotypic analyses revealed a broad variety of resistance phenotypes and β-lactamase genes. Carbapenemase-producing Enterobacteriaceae (CPE), vancomycin-resistant enterococci (VRE) and healthcare-associated (HA) MRSA were recovered only from mWWTPs and their preflooders. In contrast, the mcr-1 gene was exclusively detected in E. coli from S1/S2. Residues of five antimicrobials were detected in 14.9% (10/67) of S1/S2 samples in low range concentrations (≤1.30 μg/L), whereas 91.7% (33/36) of mWWTPs samples exhibited residues of 22 different antibiotics in concentrations of up to 4.20 μg/L. Target bacteria from S1/S2 and mWWTPs exhibited differences in their abundances, resistance phenotypes and genotypes as well as clonal lineages. S1/S2 samples exhibited bacteria with zoonotic potential (e.g. MRSA of CC398, E. coli of significant clones), whereas ESKAPE bacteria exhibiting resistances of clinical importance were mainly detected in mWWTPs. Municipal WWTPs seem to fail to eliminate these bacteria leading to a discharge into the preflooder and a subsequent dissemination into the surface water.

Antibiotic resistant and extended-spectrum β-lactamase producing faecal coliforms in wastewater treatment plant effluent

Wastewater treatment plants (WWTPs) provide optimal conditions for the maintenance and spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). In this work we describe the occurrence of antibiotic resistant faecal coliforms and their mechanisms of antibiotic resistance in the effluent of two urban WWTPs in Ireland. This information is critical to identifying the role of WWTPs in the dissemination of ARB and ARGs into the environment. Effluent samples were collected from two WWTPs in Spring and Autumn of 2015 and 2016. The bacterial susceptibility patterns to 13 antibiotics were determined. The phenotypic tests were carried out to identify AmpC or extended-spectrum β-lactamase (ESBL) producers. The presence of ESBL genes were detected by PCR. Plasmids carrying ESBL genes were transformed into Escherichia coli DH5α recipient and underwent plasmid replicon typing to identify incompatibility groups. More than 90% of isolated faecal coliforms were resistant to amoxicillin and ampicillin, followed by tetracycline (up to 39.82%), ciprofloxacin (up to 31.42%) and trimethoprim (up to 37.61%). Faecal coliforms resistant to colistin (up to 31.62%) and imipenem (up to 15.93%) were detected in all effluent samples. Up to 53.98% of isolated faecal coliforms expressed a multi-drug resistance (MRD) phenotype. AmpC production was confirmed in 5.22% of isolates. The ESBL genes were confirmed for 11.84% of isolates (9.2% of isolates carried bla_TEM, 1.4% bla_SHV-12, 0.2% bla_CTX-M-1 and 1% bla_CTX-M-15). Plasmids extracted from 52 ESBL isolates were successfully transformed into recipient E. coli. The detected plasmid incompatibility groups included the IncF group, IncI1, IncHI1/2 and IncA/C. These results provide evidence that treated wastewater is polluted with ARB and MDR faecal coliforms and are sources of ESBL-producing, carbapenem and colistin resistant Enterobacteriaceae.

ESKAPE Bacteria and Extended-Spectrum-β-Lactamase-Producing Escherichia coli Isolated from Wastewater and Process Water from German Poultry Slaughterhouses

The wastewater of livestock slaughterhouses is considered a source of antimicrobial-resistant bacteria with clinical relevance and may thus be important for their dissemination into the environment. To get an overview of their occurrence and characteristics, we investigated process water (n = 50) from delivery and unclean areas as well as wastewater (n = 32) from the in-house wastewater treatment plants (WWTPs) of two German poultry slaughterhouses (slaughterhouses S1 and S2). The samples were screened for ESKAPE bacteria (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) and Escherichia coli Their antimicrobial resistance phenotypes and the presence of extended-spectrum-β-lactamase (ESBL), carbapenemase, and mobilizable colistin resistance genes were determined. Selected ESKAPE bacteria were epidemiologically classified using different molecular typing techniques. At least one of the target species was detected in 87.5% (n = 28/32) of the wastewater samples and 86.0% (n = 43/50) of the process water samples. The vast majority of the recovered isolates (94.9%, n = 448/472) was represented by E. coli (39.4%), the A. calcoaceticus-A. baumannii (ACB) complex (32.4%), S. aureus (12.3%), and K. pneumoniae (10.8%), which were widely distributed in the delivery and unclean areas of the individual slaughterhouses, including their wastewater effluents. Enterobacter spp., Enterococcus spp., and P. aeruginosa were less abundant and made up 5.1% of the isolates. Phenotypic and genotypic analyses revealed that the recovered isolates exhibited diverse resistance phenotypes and β-lactamase genes. In conclusion, wastewater effluents from the investigated poultry slaughterhouses exhibited clinically relevant bacteria (E. coli, methicillin-resistant S. aureus, K. pneumoniae, and species of the ACB and Enterobacter cloacae complexes) that contribute to the dissemination of clinically relevant resistances (i.e., blaCTX-M or blaSHV and mcr-1) in the environment.IMPORTANCE Bacteria from livestock may be opportunistic pathogens and carriers of clinically relevant resistance genes, as many antimicrobials are used in both veterinary and human medicine. They may be released into the environment from wastewater treatment plants (WWTPs), which are influenced by wastewater from slaughterhouses, thereby endangering public health. Moreover, process water that accumulates during the slaughtering of poultry is an important reservoir for livestock-associated multidrug-resistant bacteria and may serve as a vector of transmission to occupationally exposed slaughterhouse employees. Mitigation solutions aimed at the reduction of the bacterial discharge into the production water circuit as well as interventions against their further transmission and dissemination need to be elaborated. Furthermore, the efficacy of in-house WWTPs needs to be questioned. Reliable data on the occurrence and diversity of clinically relevant bacteria within the slaughtering production chain and in the WWTP effluents in Germany will help to assess their impact on public and environmental health.

Multidrug resistance and diversity of resistance profiles in carbapenem-resistant Gram-negative bacilli throughout a wastewater treatment plant in Colombia

OBJECTIVES

Carbapenem-resistant Gram-negative bacilli (CRGNB) have been reported in different wastewater treatment plants (WWTPs) throughout the world; however, few studies have described the antimicrobial resistance profile in different CRGNB throughout WWTPs, information that would identify points of selection of resistant bacteria. The objective of this work was to characterize the resistance profile of CRGNB harbouring blaKPC-2 from a Colombian WWTP.

METHODS

Six samples were taken from four points of a WWTP. CRGNB were selected in chromID® CARBA and identified by 16S rRNA. Carbapenemases were determined by polymerase chain reaction (PCR), and susceptibility was assessed using VITEK2.

RESULTS

One hundred and forty-two CRGNB harbouring blaKPC-2 were detected: 41% corresponded to Aeromonas spp. (n = 58) and 59% to Enterobacteriaceae. To establish the resistance profile, 50% of the isolates were selected proportionally by family and sampling point (26 Aeromonadaceae and 45 Enterobacteriaceae). All Enterobacteriaceae showed resistance to carbapenems and penicillins + inhibitors, high percentages of resistance to ceftriaxone (88.9%), and ciprofloxacin (44.4%), and low resistance to other antibiotics (>30%). In Aeromonadaceae, 76.9% were resistant to ceftriaxone, 58% to carbapenems, and 65.4% to ciprofloxacin. Twenty-one resistance profiles were observed, the most common of which were resistant to penicillins + inhibitor, cephalosporins (third to fourth generation), and carbapenems (19%). The percentage of multidrug resistance was 91% and was similar at all points of the WWTP.

CONCLUSIONS

The high frequency of multidrug resistance and great diversity of resistance profiles observed throughout the WWTP is of concern, and shows the role of WWTP as a reservoir and dissemination source of antimicrobial resistance to water sources.

The Role of Plasmids in the Multiple Antibiotic Resistance Transfer in ESBLs-Producing Escherichia coli Isolated From Wastewater Treatment Plants

We compared the diversity of extended-spectrum β-lactamases (ESBLs) producing Escherichia coli (E. coli) in wastewater of a municipal wastewater treatment plant. This was done by analyzing multiple antibiotic resistant phenotypes and genotypes. Also, we investigated the antibiotic resistance transfer mechanism of the plasmid by comparing the antibiotic resistance gene linked transfer using a conjugative test, and by analyzing the full-length DNA sequence of one plasmid. The results showed that 50 ESBLs-producing E. coli isolates were isolated from 80 wastewater samples at the rate of 62.5% (50/80), out of which 35 transconjugants were obtained with the multiple antibiotic resistant transfer rate as high as 70.0% (35/50). Multiple antibiotic resistance was shown in all transconjugants and donor bacteria, which were capable of resistance to 11 out of 15 kinds of antibiotics. Both transconjugants and donors were capable of resistance to the Ampicillin and Cefalotin at a rate of 100.00% (35/35), while the total antibiotic resistant spectrum of transconjugants narrowed at the rate of 94.29% (33/35) and broadened at the rate of 5.71% (2/35) after conjugate to the donor bacteria. PCR showed that the resistant genotypes decreased or remained unchanged when compared to donor bacteria with transconjugants while the blaTEM and blaCTX-M genes were transferred and linked at a rate of 100.00% (35/35) and the blaSHV gene was at the rate as high as 94.29% (33/35). However, the qnrS gene was transferred at a low rate of 4.17% (1/24). In addition, the major resistance gene subtypes were blaTEM- 1, blaSHV -11 , and blaCTX-M-15 according to sequencing and Blast comparison. Plasmid wwA8 is a closed-loop DNA molecule with 83157 bp, and contains 45 predicted genes, including three antibiotic resistant resistance genes, blaCTX-M-15 , blaTEM-1 and qnrS1, which can be transferred with E. coli in vitro. This study shows that E. coli isolated from wastewater was capable of transferring resistance genes and producing antibiotic resistant phenotypes. The plasmids containing different resistance genes in E. coli play an important role in the multiple antibiotic resistant transfer. Most importantly, antibiotic resistant resistance genes have different transfer efficiencies, the blaTEM and blaCTX-M genes transferred at a rate of 100.00% and linked transfer in all 35 transconjugants.

Screening of tropical estuarine water in south-west coast of India reveals emergence of ARGs-harboring hypervirulent Escherichia coli of global significance

The goal of this study was to investigate the involvement of a tropical Indian estuary in the emergence of antibiotic resistance genes (ARGs)-harboring hypervirulent E. coli of global significance. A total of 300 E. coli isolates was tested for antibiotic susceptibility to β-lactams, aminoglycosides, chloramphenicol, quinolones, sulphonamides, tetracyclines, and trimethoprim. The E. coli isolates were screened for the presence of antibiotic resistance genes (bla_TEM, bla_CTX-M, tetA, tetB, sul1, sul2, strA, aphA2, catI, dhfr1, and dhfr7), integrase (int1, int2, and int3), Shiga toxin genes (stx1 and stx2) and extraintestinal virulence genes (papAH, papC, sfa/focDE, kpsMT II, and iutA). The highest prevalence of antibiotic resistance was observed for ampicillin, followed by tetracycline, and nalidixic acid. Among E. coli isolates, 64% were resistant to at least one of the 15 antibiotics tested, and approximately 40% were multiple antibiotic-resistant (MAR). More than 40% (n = 122) of E. coli isolates had ARGs. Integrase 1 (int1) was found in 7.6% of E. coli isolates. Among E. coli isolates, 16.3% (n = 49) were extraintestinal pathogenic E. coli (ExPEC), and approximately 34.6% (n = 17) of ExPEC had ARGs. A hypervirulent ARGs-harboring STEC was isolated. The prevalence of Shiga toxin-producing E. coli (STEC) was low (n = 1). The prevalence of ARGs-harboring pathogenic E. coli isolates was higher in stations close to the City (urban area), than that of other stations. ERIC-PCR (enterobacterial repetitive intergenic consensus sequence polymerase chain reaction) analysis revealed a high degree of genetic diversity among the ARGs-harboring E. coli isolates. The results demonstrate a high prevalence of ARGs-harboring E. coli in estuarine water and confirm the need for a better wastewater treatment facility and proper control measures to reduce the discharge of sewage and wastewater into the aquatic environments.

Reviewing Interventions against Enterobacteriaceae in Broiler Processing: Using Old Techniques for Meeting the New Challenges of ESBL E. coli?

Extended-spectrum beta-lactamase- (ESBL-) producing Enterobacteriaceae are frequently detected in poultry and fresh chicken meat. Due to the high prevalence, an impact on human colonization and the spread of antibiotic resistance into the environment is assumed. ESBL-producing Enterobacteriaceae can be transmitted along the broiler production chain but also their persistence is reported because of insufficient cleaning and disinfection. Processing of broiler chickens leads to a reduction of microbiological counts on the carcasses. However, processing steps like scalding, defeathering, and evisceration are critical concerning fecal contamination and, therefore, cross-contamination with bacterial strains. Respective intervention measures along the slaughter processing line aim at reducing the microbiological load on broiler carcasses as well as preventing cross-contamination. Published data on the impact of possible intervention measures against ESBL-producing Enterobacteriaceae are missing and, therefore, we focused on processing measures concerning Enterobacteriaceae, in particular E. coli or coliform counts, during processing of broiler chickens to identify possible hints for effective strategies to reduce these resistant bacteria. In total, 73 publications were analyzed and data on the quantitative reductions were extracted. Most investigations concentrated on scalding, postdefeathering washes, and improvements in the chilling process and were already published in and before 2008 (n=42, 58%). Therefore, certain measures may be already installed in slaughterhouse facilities today. The effect on eliminating ESBL-producing Enterobacteriaceae is questionable as there are still positive chicken meat samples found. A huge number of studies dealt with different applications of chlorine substances which are not approved in the European Union and the reduction level did not exceed 3 log10 values. None of the measures was able to totally eradicate Enterobacteriaceae from the broiler carcasses indicating the need to develop intervention measures to prevent contamination with ESBL-producing Enterobacteriaceae and, therefore, the exposure of humans and the further release of antibiotic resistances into the environment.

Mixing of Shiga toxin-producing and enteropathogenic Escherichia coli in a wastewater treatment plant receiving city and slaughterhouse wastewater

Wastewater of human and animal may contain Shiga toxin-producing (STEC) and enteropathogenic (EPEC) Escherichia coli. We evaluated the prevalence of such strains in a wastewater treatment plant (WWTP) receiving both city and slaughterhouse wastewater. PCR screenings were performed on 12,248 E. coli isolates. The prevalence of STEC in city wastewater, slaughterhouse wastewater and treated effluent was 0.22%, 0.07% and 0.22%, respectively. The prevalence of EPEC at the same sampling sites was 0.63%, 0.90% and 0.55%. No significant difference was observed between the sampling points. Treatment had no impact on these prevalences. Enterohemorrhagic E. coli (EHEC) O157:H7 and O111:H8 were isolated from the treated effluent rejected into the river. The characteristics of STEC and EPEC differed according to their origin. City wastewater contained STEC with various stx subtypes associated with serious human disease, whereas slaughterhouse wastewater contained exclusively STEC with stx_2e subtype. All the EPEC strains were classified as atypical and were screened for the ε, γ1 and β1 subtypes, known to be associated with the EHEC mainly involved in human infections in France. In city wastewater, eae subtypes remained largely unidentified; whereas eae-β1 was the most frequent subtype in slaughterhouse wastewater. Moreover, the EPEC isolated from slaughterhouse wastewater were positive for other EHEC-associated virulence markers, including top five serotypes, the ehxA gene, putative adherence genes and OI-122 associated genes. The possibility that city wastewater could contain a pool of stx genes associated with human disease and that slaughterhouse wastewater could contain a pool of EPEC sharing similar virulence genes with EHEC, was highlighted. Mixing of such strains in WWTP could lead to the emergence of EHEC by horizontal gene transfer.

Characterization of extended spectrum β-lactamase (ESBL)-producing Escherichia coli in Asi (Orontes) River in Turkey

In this study, the presence of extended spectrum β-lactamase (ESBL)-producing Escherichia coli in aquatic environments (the Orontes River and an urban wastewater) was investigated. Fifty-four E. coli strains resistant to cefotaxime were isolated from the river waters and nearby waste water treatment plant and screened for ESBL gene variants, different classes of integrons and sulfonamide resistance genes. The ESBL-producing E. coli strains were further characterized by PhP-typing system, phylogenetic grouping and antimicrobial susceptibility testing. Of the 54 ESBL-producing strains, 14 (25.9%) belonged to four common PhP types and the remaining were of single types. CTX-M type ESBL genes were identified in 68% of the isolates. The most predominant specific CTX-M subtype identified was bla_CTX-M-15 (n = 36), followed by bla_CTX-M-1 (n = 1). None of the isolates were SHV and OXA positive. Most of the ESBL positive isolates (n = 37; 68.5%) were harboring sul gene. This study indicates a widespread distribution of CTX-M-15 producing E. coli strains in the surface waters in part of Turkey, suggesting an aquatic reservoir for ESBL genes.

Change in the Structure of Escherichia coli Population and the Pattern of Virulence Genes along a Rural Aquatic Continuum

The aim of this study was to investigate the diversity of the Escherichia coli population, focusing on the occurrence of pathogenic E. coli, in surface water draining a rural catchment. Two sampling campaigns were carried out in similar hydrological conditions (wet period, low flow) along a river continuum, characterized by two opposite density gradients of animals (cattle and wild animals) and human populations. While the abundance of E. coli slightly increased along the river continuum, the abundance of both human and ruminant-associated Bacteroidales markers, as well as the number of E. coli multi-resistant to antibiotics, evidenced a fecal contamination originating from animals at upstream rural sites, and from humans at downstream urban sites. A strong spatial modification of the structure of the E. coli population was observed. At the upstream site close to a forest, a higher abundance of the B2 phylogroup and Escherichia clade strains were observed. At the pasture upstream site, a greater proportion of both E and B1 phylogroups was detected, therefore suggesting a fecal contamination of mainly bovine origin. Conversely, in downstream urban sites, A, D, and F phylogroups were more abundant. To assess the occurrence of intestinal pathogenic strains, virulence factors [afaD, stx1, stx2, eltB (LT), estA (ST), ipaH, bfpA, eae, aaiC and aatA] were screened among 651 E. coli isolates. Intestinal pathogenic strains STEC O174:H21 (stx2) and EHEC O26:H11 (eae, stx1) were isolated in water and sediments close to the pasture site. In contrast, in the downstream urban site aEPEC/EAEC and DAEC of human origin, as well as extra-intestinal pathogenic E. coli belonging to clonal group A of D phylogroup, were sampled. Even if the estimated input of STEC (Shiga toxin-producing E. coli) - released in water at the upstream pasture site - at the downstream site was low, we show that STEC could persist in sediment. These results show that, the run-off of small cattle farms contributed, as much as the wastewater effluent, in the dissemination of pathogenic E. coli in both water and sediments, even if the microbiological quality of the water was good or to average quality according to the French water index.

A nitrocefin-based amperometric assay for the rapid quantification of extended-spectrum β-lactamase-producing Escherichia coli in wastewaters

A sensitive and inexpensive amperometric assay based on the electrochemical detection of the β-lactamase activity using the nitrocefin as substrate was developed for the rapid and quantitative detection of extended spectrum beta-lactamase-producing Escherichia coli (ESBL-EC) in urban wastewaters. The specific detection of ESBL-EC was achieved by culturing the filtered sample in a medium containing the cefotaxime supplemented or not with the potassium clavulanate inhibitor. This step was followed by the incubation of each subculture filtrate with the nitrocefin substrate which hydrolysis was monitored by amperometry using disposable carbon screen-printed sensors. Current intensities i_Cef and i_Clav correspond to the intensity of the anodic current measured (∼+ 0.2 V vs. Ag/AgCl) for the sample incubated with the cefotaxime without and with potassium clavulanate, respectively. The intensity value i = i_Cef - i_Clav was chosen as the analytical response. ESBL-EC calibration plots were established with artificially contaminated wastewater samples. This assay allowed the detection of ESBL-EC amounts as low as 10 cfu in treated effluents and 100 cfu in raw wastewaters with short time analysis of 5.5 h and 4.5 h, respectively. The amperometric method was applied to the analysis of 38 wastewater samples and the results were in good agreement with CFU counts on a selective chromogenic medium for 24 h. Owing to its rapidity, convenience, low-cost and portability, this assay is a promising tool to obtain quantitative data on antimicrobial-resistant E. coli in wastewater effluents. Furthermore, this assay might be used to improve wastewater treatment plant processes in order to minimize the release of antibiotic resistant bacteria into the aquatic environment.

Free water surface constructed wetlands limit the dissemination of extended-spectrum beta-lactamase producing Escherichia coli in the natural environment

The fates of Escherichia coli and extended-spectrum beta-lactamase-producing E. coli (ESBL E. coli) were studied over a period of one year in a free water surface constructed wetland (FWS CW) with a succession of open water zones and vegetation ponds (Typha or Phragmites), that received the effluent from a wastewater treatment plant. ESBL E. coli were detected and isolated from all sampling areas of the FWS CW throughout the study period. They represented 1‰ of the total E. coli population regardless of the origin of samples. Two main factors affected the log removal of E. coli and of ESBL E. coli: the season and the presence of vegetation. Between the inlet and the outlet of the FWS CW, the log removal of E. coli ranged from 1.5 in the warmer season (summer and fall) to 3.0 in the colder season (winter and spring). The concentrations of E. coli decreased significantly in the vegetated areas during the colder season, but increased in the warmer season, suggesting an effect of the plant growth stage on the survival of E. coli. Among the 369 ESBL E. coli isolates collected during our study, 84% harbored the CTX-M-ESBL type and 55.3% carried bla genes on plasmid DNA. Furthermore, 93% of the ESBL E. coli isolates were multidrug resistant but the proportion of resistant strains did not change significantly along the FWS CW. ESBL E. coli were characterized by MLST analysis using the 7 genes based Achtman Scheme. ESBL E. coli isolated from water, sediments, roots and feces of myocastors collected in the FWS CW and in the recipient river were genotypically related, suggesting persistence and circulation of the ESBL producing E. coli throughout the FWS CW and in the receiving river. Overall, these observations show that FWS CW could be an efficient treatment for ESBL E. coli disinfection of wastewater and could limit their dissemination in the aquatic environment.

Dominant plasmids carrying extended-spectrum β-lactamases blaCTX-M genes in genetically diverse Escherichia coli from slaughterhouse and urban wastewaters

Wastewater treatment plants (WWTP) receiving effluents from food-producing animals and humans may contribute to the spread of extended-spectrum β-lactamases (ESBL)-carrying plasmids. This study was designed to investigate extended-spectrum cephalosporin resistant Escherichia coli strains, CTX-M distributions and the genetic lineage of bla_CTX-M -carrying plasmids from urban and slaughterhouse wastewaters. The level of extended-spectrum cephalosporin-resistant E. coli in slaughterhouse wastewater entering the WWTP was negligible compared with that of urban wastewater. The bla_CTX-M-1 gene was predominant in slaughterhouse wastewater whereas diverse bla_CTX-M genes were encountered in urban wastewater and WWTP outlet. Characterization of the main CTX-M-producing E. coli isolates by antibiotic resistance phenotyping, genotyping and typing of plasmids carrying bla_CTX-M genes revealed that bla_CTX-M-1 and bla_CTX-M-15 genes were harboured by the predominant bla_CTX-M-1 IncI1/ST3 and bla_CTX-M-15 F31:A4:B1 plasmids, which were recovered from unrelated E. coli genotypes in both slaughterhouse and urban wastewaters. This study highlighted the spread of predominant bla_CTX-M-1 and bla_CTX-M-15 plasmid lineages in diverse E. coli genotypes from humans and food-producing animals, their mixing in WWTP and final release into the aquatic environment. This could have a serious negative impact on public health and requires further evaluation.

Prevalence and Fate of Carbapenemase Genes in a Wastewater Treatment Plant in Northern China

Carbapenemase-producing strains of bacteria, which were primarily found in the medical field, have increasingly been found in the environment, thus posing potential risks to public health. One possible way for carbapenemase genes to enter the environment is via wastewater. Therefore, the goal of this study was to determine the occurrence and fate of five high-risk carbapenemase genes in a wastewater treatment plant (WWTP) in northern China using real-time qPCR. Results showed that the bla_KPC-2, bla_GES-1, and bla_IMP-1 genes prevailed throughout all processing stages (even in the chlorination disinfection unit) in the WWTP, whereas the bla_VIM-2 and bla_OXA-48 genes were not detected in all samples. Worryingly, considerable amounts of carbapenemase genes ((1.54 ± 0.61) × 10³ copies/mL to (2.14± 0.41) × 10⁵ copies/mL) were detected in WWTP effluent samples, while the majority of the carbapenemase genes were transported to the dewatered sludge with concentrations from (6.51 ± 0.14) × 10⁹ copies/g to (6.18 ± 0.63) × 10¹⁰ copies/g dry weight. Furthermore, a total of 97 KPC-2-producing strains, belonging to 8 bacterial genera, were isolated from the WWTP. Sequencing of 16S rRNA revealed that most of KPC-2 producing isolates were opportunistic pathogens, including Klebsiella spp. (10.3%), Enterococcus spp. (11.3%), Acinetobacter spp. (19.6%), Escherichia spp. (12.4%), Shigella spp. (17.5%), Stenotrophomonas spp. (10.3%) and Wautersiella spp. (9.3%). Moreover, bla_KPC-2 genes were identified for the first time in Paenibacillus spp. isolates (an indigenous bacteria), indicating an increased risk of horizontal transfer between clinical pathogens and environmental bacteria. Indeed, a conjugation experiment demonstrated transfer of the bla_KPC-2 gene to an E.coli J53 strain from a Klebsiella strain isolated from the WWTP. To our knowledge, this is the first study to obtain Paenibacillus spp. isolates carrying the carbapenemase gene and to quantify the abundance of carbapenemase genes in the environment.

Characteristics of extended-spectrum β-lactamase (ESBL)- and pAmpC beta-lactamase-producing Enterobacteriaceae of water samples in Tunisia

The presence of extended-spectrum beta-lactamase and plasmid-mediated AmpC beta-lactamase producing Enterobacteriaceae (ESBL-Eb and pAmpC-Eb, respectively) was analyzed in 57 wastewater and 57 surface-water samples in Tunisia. Twenty-four of the 57 wastewater samples (42.1%) and one of the 57 surface-water samples (1.7%, a river that received effluents of a wastewater-treatment-plant) contained ESBL-Eb or pAmpC-Eb; one ESBL/pAmpC-Eb per positive sample was further characterized. Beta-lactamase genes detected were as follows: blaCTX-M-1 (10 Escherichia coli),blaCTX-M-15 (eight E. coli, one Klebsiella pneumoniae, one Citrobacter freundii), blaCTX-M-14 (one E. coli) and blaCMY-2 (four E. coli). The blaTEM-1, blaOXA-1 or blaSHV-1 genes were also found in 72% of these isolates. The ISEcp1, orf477 or IS903 sequences were found upstream or downstream of blaCTX-M genes. Class 1 integrons were present in 16 of the 25 ESBL-Eb/pAmpC-Eb strains (64%), and contained five different gene-cassette arrays. Most of the strains (76%) showed a multiresistant phenotype and qnr genes were identified in four strains. Molecular typing of ESBL/CMY-2-producing E. coli isolates showed 23 different PFGE-patterns and 15 different sequence-types (ST10, ST46, ST48, ST58, ST69, ST101, ST117, ST131, ST141, ST288, ST359, ST399, ST405, ST617, and the new ST4530); these strains were ascribed to phylogroups A (11 isolates), B1 (3 isolates), D (6 isolates) and B2 (3 isolates). From one to five plasmids were detected in each strain (size from 30kb to >240kb) and ESBL or pAmpC genes were transferred by conjugation in 69.5% of the E. coli strains. In conclusion, ESBL-Eb and pAmpC-Eb strains are frequently detected in wastewater samples and they might be a source for dissemination in other environments with repercussion in public health.

Antibiotic resistance in wastewater: occurrence and fate of Enterobacteriaceae producers of class A and class C β-lactamases

Antibiotics have been intensively used over the last decades in human and animal therapy and livestock, resulting in serious environmental and public health problems, namely due to the antibiotic residues concentration in wastewaters and to the development of antibiotic-resistant bacteria. This study aimed to access the contribution of some anthropological activities, namely urban household, hospital and a wastewater treatment plant, to the spread of antibiotic resistances in the treated wastewater released into the Mondego River, Coimbra, Portugal. Six sampling sites were selected in the wastewater network and in the river. The ampicillin-resistant Enterobacteriaceae of the water samples were enumerated, isolated and phenotypically characterized in relation to their resistance profile to 13 antibiotics. Some isolates were identified into species level and investigated for the presence of class A and class C -lactamases. Results revealed high frequency of resistance to the -lactam group, cefoxitin (53.5%), amoxicillin/clavulanic acid combination (43.5%), cefotaxime (22.7%), aztreonam (21.3) cefpirome (19.2%), ceftazidime (16.2%) and to the non--lactam group, trimethoprim/sulfamethoxazol (21.1%), tetracycline (18.2%), followed by ciprofloxacin (14.1%). The hospital effluent showed the higher rates of resistance to all antibiotic, except two (chloramphenicol and gentamicin). Similarly, higher resistance rates were detected in the wastewater treatment plant (WWTP) effluent compared with the untreated affluent. Regarding the multidrug resistance, the highest incidence was recorded in the hospital sewage and the lowest in the urban waste. The majority of the isolates altogether are potentially extended-spectrum -lactamases positive (ESBL(+)) (51.9%), followed by AmpC(+) (44.4%) and ESBL(+)/AmpC(+) (35.2%). The most prevalent genes among the potential ESBL producers were blaOXA (33.3%), blaTEM (24.1%) and blaCTX-M (5.6%) and among the AmpC producers were blaEBC (38.9%), blaFOX (1.9%) and blaCIT (1.9%). In conclusion, the hospital and the WWTP activities revealed to have the highest contribution to the spread of multidrug resistant bacteria in the study area. Such data is important for future management of the environmental and public health risk of these contaminants. This is the first embracing study in the water network of Coimbra region on the dissemination of antibiotic resistance determinants. Moreover, it is also the first report with the simultaneous detection of multiresistant bacteria producers of AmpC and ESBLs -lactamases in aquatic systems in Portugal.