Background: Occurrences of pathogens in environmental and irrigation waters, as well as the use of inadequately treated sewage for fresh produce constitute potential public health threats worldwide. Objective: To investigate the treated wastewater used in fresh produce irrigation in Nsuskka, Southeastern Nigeria, as a reservoir enterotoxigenic and multidrug-resistant Escherichia coli. Methods: Treated wastewater (from the sewage treatment facility at Nsukka, Southeast Nigeria), soil and irrigated vegetable samples were collected and analyzed using standard procedures. Escherichia coli isolated from the samples were screened for the presence of enterotoxigenic E. coli strain encoding lt gene and profiled for antibiotic resistance using the conventional PCR and standardized agar disk diffusion assays respectively. Results: Of the total presumptive 103 isolates, PCR detected uidA gene in 87 (84 %), of which 23 (26 %) harboured the lt encoding ETEC gene. Generally, imipenem, cefuroxime and norfloxacin proved to be most effective of all the antibiotics employed. Wastewater isolates were variously susceptible to ciprofloxacin (95 %), norfloxacin (95 %), cefuroxime (93 %), chloramphenicol (93 %), trimethoprim and tetracycline (88 %), soil isolates to streptomycin (75 %) and vegetable isolates to cefuroxime (90 %), norfloxacin (86 %), ciprofloxacin (81 %) and chloramphenicol. Contrariwise, high resistances observed to other antibiotics were in the order; ampicillin (95 %), penicillin (93 %), erythromycin (90 %) and clarithromycin (83 %) among wastewater isolates, ciprofloxacin and norfloxacin (75 %) in soil isolates; penicillin, vancomycin and erythromycin (98 %), rifampicin and clarithromycin (93 %), sulphamethoxazole (83 %), ampicillin (81 %), tetracycline and imipenem (76 %), trimethoprim (72 %) and amoxicillin (71 %) among vegetable isolates, with multidrug resistance patterns ranging from three to seventeen. Conclusions: Our results reveal the treated wastewater as a reservoir of enterotoxigenic E. coli as well as multidrug resistance that may pose a health hazard for humans and animals when released to the natural environment. Hence, there is need to develop management strategies and ensure compliance in order to prevent water-borne diarrhoea caused by ETEC and reduce the menace of antibiotic resistance in the environment.

Hawliau Cyffredinol / General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

No abstract

41In spite of treated wastewater presenting itself as an attractive alternative to scarce quality water 42 in the developing countries, the associated contamination of fresh produce by irrigation waters 43 leading to outbreak of foodborne illnesses is on the rise. Horizontal transfer of integrons play 44 important role in the spread and maintenance of antimicrobial resistance among strains of 45 Escherichia coli. This study assessed the effluents from the University of Nigeria, Nsukka 46 Wastewater Treatment Plant (UNN-WWTP) as well as vegetables irrigated with the effluent, and 47 vegetables sold in selected markets from Nsukka and Enugu cities for the presence of E. coli and 48 determined the prevalence integrons in multidrug-resistant isolates. Isolation of E. coli was done 49 using eosin methylene blue agar and isolates subjected to Gram staining for identification of 50 presumptive colonies. Confirmation of E. coli was achieved by polymerase chain reaction (PCR) 51 technique, targeting beta-glucuronidase (uidA). Resistance to antibiotics was determined using the 52 Bauer-Kirby disk diffusion assay and the Clinical and Laboratory Standard Institute criteria.53Integrons were detected by multiplex PCR using primers specific for class 1 and 2 integrons. A 54 total of 178 E. coli isolates were obtained from WWTP effluent (41), and vegetables from 55 greenhouse (46), farms (55) and market (36). Multi-drug resistance was detected in all the isolates, 56 ranging from five-drug resistance in a single isolate to 16-drug resistance patterns in two different 57 isolates. Of the total isolates, class 1 integrons were abundantly detected in 175 (98.3%) and class 58 2 in 5 (2.8%). All the class 2 integrons were found in isolates that were positive for class 1. The 59 high detection of E. coli in the studied effluent and vegetables pose potential public health hazards 60 heightened by observed multidrug resistance in all the isolates and the high prevalence of class 1 61 integron. It is concluded that the vegetable samples are significant reservoirs for potentially 62 pathogenic E. coli. Therefore, vegetable irrigation farming with unsafe water should be 63 discontinued, while appropriate improvement strategies to ensure compliance should be facilitated 64 without further delay. 65 66 Pathogenic Escherichia coli causes significant morbidity and mortality worldwide [1-3]. Reported 68 risk factors in the developing countries and sub-Saharan African regions include poor hygiene, 69 unsafe water, improper disposal of waste and faeces, and contaminated food, local beverages and 70 vegetables [2, 4, 5]. Vegetables can become contaminated with pathogenic and commensal 71 bacteria from animals and humans, during growth, harvesting, distribution, storage and processing 72 [6]. Although the contamination of fresh produce by irrigation waters has led to outbreak of 73 foodborne illnesses, yet treated wastewater presents itself as an attractive alternative to scarce 74 quality water in the developing countries. 75 E. coli has bee...

The contamination of fresh produce by irrigation waters has led to outbreaks of foodborne illness, yet treated wastewater presents itself as an attractive alternative to scarce quality water in the developing countries. Horizontal transfer of integrons play important role in the spread and maintenance of antimicrobial resistance among the Enterobacteriaceae.Study objectiveThis study assessed the effluent from the University of Nigeria, Nsukka Wastewater Treatment Plant (UNN‐WWTP) as well as vegetables irrigated with the effluent and vegetables sold in selected markets for the presence of Escherichia coli and determined the prevalence integrons in multidrug‐resistant isolates.MethodsIsolation and identification of presumptive E. coli was done using Eosin Methylene Blue (EMB) agar plates and the Gram‐staining procedure. The confirmation of E. coli and enterotoxigenic E. coli (ETEC) strain were achieved by polymerase chain reaction (PCR) detection of the target beta‐glucuronidase (uidA) and heat‐labile toxin (lt) genes respectively. Resistance to antibiotics was determined using the Bauer‐Kirby disk diffusion method and the Clinical and Laboratory Standard Institute criteria. Integrons were detected by multiplex PCR using primers specific for class 1 and 2 integrons.ResultsA total of the 178 E. coli isolates were obtained from WWTP effluent (41), Greenhouse vegetables (46), Farm vegetables (55) and Market vegetables (36). Twenty‐three of these 178 isolates (12.9%) were confirmed to be enterotoxigenic E. coli (ETEC) strains. The isolation rates of ETEC for the different sample types were: WWTP effluent, 20% (n=60), Greenhouse vegetables 8.3% (n=60), Farm vegetables 4.8% (n=84), and Market vegetables 2.4% (n=84). All the isolates were multi‐drug resistant. The most frequent resistance types in the 178 E. coli isolates were: Cloxacillin (100%), Metronidazole (100%), Vancomycin (98.8%), Erythromycin (94.3%), and Clarithromycin (89.6%). Multi‐drug resistance (MDR) was detected in isolates from all sources, ranging from a five‐drug resistance observed in a single isolate to 16‐drug resistance patterns found in two different isolates. Of the 178 E. coli isolates, class 1 integrons were detected in 175 (98.3%), and class 2 integrons were detected on 5 (2.8%). All the class 2 integrons were found in isolates that were positive for class 1.ConclusionsThe high detection rates for E. coli in the studied effluent and vegetable samples represent potential public health hazards heightened by observed multidrug resistance in all the isolates and the high prevalence of class 1 integrons. It is concluded that UNN‐WWTP is a significant reservoir for diarrheagenic E. coli. Vegetable farming at the site should therefore be discontinued as it presents significant threat to the health of consumers of such vegetables.Support or Funding InformationThe British Council Researcher Links Travel Grant (2014)