Globally, wastewater represents an important hotspot for the rapid dissemination of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) in the environment [1]. Antimicrobial resistance (AMR) can spread between people, animals, and the environment through different pathways [2]. Significantly, the environment has been identified as a bridge for different transmission pathways, from animals to compost, soil to water, and sediments to sewage. As a reservoir, the environment may simultaneously mix mobile genetic elements (MGEs) before their eventual diffusion into human and animal hosts [3]. Notably, the ARGs are not biodegradable and can be distributed among microbial communities when they find their way into natural environments, which carries additional implications for promoting the emergence of multidrug-resistant organisms. Discharging improperly treated effluent into surface waters greatly impacts the quality of these surface waters. The presence of antibiotics, ARB, and ARGs causes changes to indigenous microbial communities in surface waters and contributes to the acquisition and spread of waterborne diseases in people who use them [1].

Escherichia coli (E. coli) was recently listed among the high-priority pathogens since their presence may threaten human health [4]. In addition, the transmission of uropathogenic E. coli strains via environmental water-related routes remains an emerging concern globally [4]. Notably, multidrug resistance in E. coli is becoming a growing concern for humans worldwide. Intrinsically, E. coli is vulnerable to virtually every important clinical antimicrobial. However, the microbe can store resistant genes, often via horizontal gene transfer [5]. The highest challenging E. coli mechanisms match with the ability to acquire extended-spectrum $\beta$-lactamase (ESBL) genes, which confer non-susceptibility on genes for plasmid-mediated quinolone resistance, carbapenemases, which confer carbapenems resistance, mcr genes, which codes for polymyxins resistance, and methylases 16S rRNA, which encodes aminoglycosides pan-resistance. Enterobacteriaceae AMR is a challenging concern for public health, especially for developing nations. The E. coli genome is very flexible, as the virulence factors can be moved between strains within extrachromosomal plasmids on large pathogenicity islands (PAIs) [6]. The presence of ESBL in Enterobacteriaceae has contributed to the emerging concern of antibiotic resistance globally. ESBLs hydrolyze and inactivate beta-lactam antibiotics and those of the third-generation cephalosporins [7]. ESBL-producing bacteria exhibit co-resistance to aminoglycosides, quinolones, and sulphonamides, which has led to the emergence of multidrug resistance [6]. The isolates’ resistance to penicillin G and some other beta-lactams is chromosomes conciliated with a broad diversity of genetic determinants, while resistance to many of the glycopeptides and carbapenems often results in stable mutations. This chromosome-mediated resistance has been reported mainly against third-generation cephalosporins [7]. Among the uropathogens associated with developing urinary tract infections (UTIs), uropathogenic Escherichia coli (UPEC) is most frequently involved. Most UPEC isolates were found to secrete soluble toxins, especially $\alpha$-hemolysin (hlyA), and a strong correlation was found between hlyA expression by UPEC and UTI severity [6].

The WHO has rated wastewater treatment plants (WTPs) as the leading cause of environmental contamination by antibiotics [4]. WTP refining has been shown to select antimicrobial-resistant isolates [8], and reports of multidrug resistance are common in hospital environments [9]. Effluents of WTPs, as well as wastewater directly dumped into the University of Nigeria, Nsukka (UNN), and Kogi State University (KSU)’s hostel drains are used to water vegetables as well as other food crops within the area, and this may add to causes of human infections after such vegetables are consumed. Reportedly, these disposal habits have been associated with antibiotic resistance spread via horizontal gene transfer [10]. In the study areas, little or no data regarding the occurrence and distribution of UPEC and associated genes in wastewater environments are available. Thus, it is important to appraise the quality of effluent and surface waters in the area and to determine if wastewater plays a role in the spread of virulence genes and antibiotic resistance. Therefore, the current study was designed to isolate UPEC from water samples obtained from UNN-WTP presumptively and hostel drains at UNN and KSU, determine the antimicrobial susceptibility patterns of the isolates, and further screen the isolates showing multiple drug resistance for resistance and virulence genes using the molecular technique.

The presence of pathogens in the environment is a great challenge because of their negative impact on human health. The presence of E. coli in the environment is frequently used to predict pathogen presence in the environment, most importantly, surface water. Evidently, WTP has been identified as a common source of E. coli contamination for most surface water worldwide [18]. Nevertheless, there is currently no documented information regarding the presence of this pathogen and the occurrence of its antimicrobial resistance genes in the study area.

In the present study, various degrees of resistance to antibiotics (100%: AMC, VA, and P; 95.2% against E; 88.9% against S; 69.8% against AMP; 66.7% against TE; 65.1% against CN) were observed, which suggest that the circulation of this environmental strains may be contributing to antimicrobial resistance spreads in the area. The high resistance levels to AMC, VA, and P observed with UPEC strains in the current study have been previously documented [7]. Previously, 100% resistance to tetracycline, amoxicillin/clavulanic acid, vancomycin, ciprofloxacin, penicillin, erythromycin, and gentamycin have been reported [19], corroborating the observations in our current study except for ciprofloxacin, which indicated a complete sensitivity. Various levels of resistance to some classes of antibiotics have been observed elsewhere. For instance, a study by Pokharel et al. [18] showed that tetracycline was the least potent, followed by ampicillin. A similar antibiotic resistance pattern was reported in more recent studies by Karam et al. [19] and Whelan et al. [20].

MDR has been regularly recorded among UPEC strains in Nigeria [17, 21, 22]. In the current study, the UPEC isolates from the KSU hostel drains had a higher multiple antimicrobial resistance range (0.33–0.73) than those from UNN (0.33–0.67). The maximum level (66.7%–73%) of multidrug resistance demonstrated by the isolates in our study is comparable with the 77% MAR level in E. coli strains previously isolated from a wastewater treatment facility [23]. According to Osundiya et al. [23], the level of non-susceptibility to amoxicillin/clavulanic acid demonstrated by the isolates in this study remains a regular occurrence in E. coli. Previously, Tang et al. [24] determined antibiotic resistance profiles of E. coli strains from a river watershed in France, and the study demonstrated antimicrobial resistance in 42% of the E. coli isolates, of which 35% exhibited MAR—the MAR index range among UPEC isolates in this study is considerably higher than those published by Tang et al. [24].

The level of potential UPEC strains observed in association with UNN-WTP influents and effluents is above the acceptable threshold. This observation may relate to the influx rates differential of domestic and industrial effluent into the plant, inefficient wastewater treatment processes, and non-adherence to standard treatment protocol. In our study, the findings of a significantly higher MAR in connection with UPEC strain from UNN effluent discharges support the assertion of Fouz et al. [2], who posited that high levels of ARB, MDR strains, and diverse ARGs are common in wastewater worldwide. Unsurprisingly, many studies have shown that effluent samples collected from urban, environmental, hospital, and pharmaceutical-treated wastewater still contain elevated levels of diverse ARGs, ARB, and antimicrobial drugs. For instance, a recent study demonstrated that the abundance of ARGs was significantly higher in effluent wastewater samples than in influents collected from low-income countries compared to high-income countries [25]. The spotting of potentially pathogenic E. coli in effluent from WTP could be associated with the inefficient removal of this bacteria during the treatment process. In another study, potentially pathogenic E. coli bacteria were reported in samples from a wastewater treatment facility at Hawassa University Referral Hospital [26]. According to the authors, the treatment could only remove larger dirt, leaving more organic matter for the remaining pathogens to use as substrates, further increasing the virulence and pathogenicity of pathogens [26].

A relatively high prevalence (96%) of E. coli that produces ESBL in wastewater of a rural and urban hospital in central India has been reported [10, 26]. In our study, the presumptive UPEC isolates showing multidrug resistance were all found to contain beta-beta-D-glucuronidase (uidA) and hemolysin A (hlyA). The presence of the uidA marker genetically confirmed that the isolates were of the genus E. coli [19], which, in this study, were phenotypically typed as UPEC strains. The hlyA detected in the study is commonly found in most uropathogenic E. coli (UPEC) strains reported worldwide [27]; thus, it raises serious concerns about the E. coli strains circulating in the study environment. In several case-based surveillance studies, a significant percentage of UPEC isolates have been reported to secrete hemolysin, which is directly associated with the onset of urinary tract infections (UTIs) [27]. This strain has been reported to cause acute renal failure in renal transplant patients and healthy individuals [28]. The UPEC-bearing hlyA gene was documented to increase cellular toxicity and urothelial damage [27, 28]. The gene (uidA) detected in the isolates codes for beta-D-glucuronidase, an enzyme that catalyzes the cleavage of numerous varieties of 3-glucuronides [29]. This enzyme is why the uidA gene is often employed as a marker for E. coli in water quality determination. Hence, the uidA PCR method is recommended for use because of its sensitivity for specific detection in substrate tests of E. coli by the US Environmental Protection for water quality monitoring [29].

The findings of ARGs comprising the blaOXA-1, blaCTX-M3, and ant(2)-la genes in the isolates suggest that their circulation in the environment may contribute to drug resistance in the area. Unlike the equal circulation of blaOXA genes in the study, Öztürk and Murt [28] and Bush and Jacoby [29] have reported the occurrence of blaOXA-and blaCTX-M3, respectively, as predominant genes in the environmental reservoirs. However, This result differs from the report of Chandran et al. [30], who reported blaCTX-M more frequently compared to blaTEM and ant(2)-la in isolates of E. coli from hospital-associated wastewater in India. In Enterobacteriaceae that produce ESBL, genes blaTEM, blaCTXM group1, bla SHV, and blaCTXM9 have been detected in effluents of hospitals [31]. The ESBLs detected in the study, especially CTX-M enzymes, represent a significant health concern in clinical practice [32]. As previously reported [33], the ESBL-producing UPEC strains currently account for most community and healthcare-associated infections. However, our study has a limitation, as the lack of a separate set of virulence genes in UPEC makes it difficult to ascertain the true pathogenic potential of the presumptive UPEC strains from environmental reservoirs [33]. Consequently, uncertainty may exist regarding determining the actual public health risks associated with the presence of presumptive UPEC isolates in wastewater environments.

The current study confirms the circulation of potential uropathogenic E. coli in the various wastewater environments of two Nigerian tertiary institutions. Generally, more UPEC was isolated from KSU than the UNN campus. The UPEC strains were completely susceptible to meropenem and 100% non-susceptible to amoxicillin/clavulanic acid, vancomycin, and penicillin G. The high rate of multidrug resistance observed in the UPEC isolates coupled with the detection of virulence genes in the current study suggest a public health risk in association with wastewater reuse in the area. Thus, there is a need for continuous wastewater-based surveillance programs to monitor the spread and any potential effects associated with the distribution of antimicrobial resistance and virulence genes through wastewater treatment plants and sewage-receiving hostel gutters in the area.

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

OME and CA designed the research study. OME performed the research. CA supervised the work. OME, CAO, RFA, JOA, GKN, SOS and STG analyzed the data. OME, CA, CAO, JOA, RFA, GKN, SOS, and STG wrote the manuscript. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work to take public responsibility for appropriate portions of the content and agreed to be accountable for all aspects of the work in ensuring that questions related to its accuracy or integrity.

This study did not involve human participants or animal subjects and was conducted in compliance with regional regulations, which do not require ethical approval for environmentally based research.

Not applicable.

This research received no external funding.

The authors declare no conflict of interest.

Supplementary material associated with this article can be found, in the online version, at https://doi.org/10.31083/j.fbe1604038.