Multidrug resistance and high prevalence of class 1 integrons inEscherichia coliisolated from waters and vegetables in Nsukka and Enugu, Nigeria

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...