Araújo Susana, A T Silva Isabel, Tacão Marta, Patinha Carla, Alves Artur, Henriques Isabel
Department of Biology, CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
Geosciences Department, Geobiotec, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Int J Food Microbiol. 2017 Sep 18;257:192-200. doi: 10.1016/j.ijfoodmicro.2017.06.020. Epub 2017 Jun 22.
This study aimed to characterize Escherichia coli present in irrigation water and vegetables from 16 household farms. Isolates were obtained from 50% of water (n=210 isolates) and 38% of vegetable samples (n=239). Phylogroups B1 (56% of isolates) and A (22%) were the most prevalent both in water and vegetables. Diarrheagenic strains were detected in vegetables. Irrespective of the source (i.e. water or vegetables), the most common antibiotic resistance was against streptomycin (89% resistant isolates) and tetracycline (24%). Common acquired genes (e.g. bla, tetA, tetB) were found in isolates from both sources. Class I integrons were detected in water (arrays dfrA1-aadA1 and dfr16-blaP1b-aadA2-ereA) and vegetables (unknown arrays). intI2 was detected in water (dfrA1-sat2-aadA1). Plasmids were detected in 14 isolates (IncFIC, IncFIB, IncFrep, IncI1 in both samples; IncY in vegetables). Plasmids from seven isolates were transferrable by conjugation, conferring resistance to antibiotics to the recipient strain. Multidrug-resistant (MDR) strains were isolated from water (12% of the unique isolates) and vegetables (21%). Predominant sequence types (STs) among MDR isolates were ST10, ST297 and ST2522. In some cases, the same STs and identical clones (as showed by rep-PCR typing) were detected in water and vegetables, suggesting cross-contamination. This study identified several risk factors in E. coli isolates from vegetables and irrigation water, raising health concerns. Also, results suggest that irrigation groundwater constitutes a source of E. coli that may enter the food chain through vegetables ingestion.
本研究旨在对16个家庭农场灌溉用水和蔬菜中存在的大肠杆菌进行特征描述。从50%的水样（n = 210株分离株）和38%的蔬菜样本（n = 239）中获得了分离株。B1菌系（占分离株的56%）和A菌系（22%）在水和蔬菜中最为常见。在蔬菜中检测到了致泻菌株。无论来源（即水或蔬菜）如何，最常见的抗生素耐药性是对链霉素（89%的耐药分离株）和四环素（24%）。在来自两种来源的分离株中都发现了常见的获得性基因（如bla、tetA、tetB）。在水中（阵列dfrA1-aadA1和dfr16-blaP1b-aadA2-ereA）和蔬菜中（未知阵列）检测到了I类整合子。在水中（dfrA1-sat2-aadA1）检测到了intI2。在14株分离株中检测到了质粒（两个样本中均有IncFIC、IncFIB、IncFrep、IncI1；蔬菜中有IncY）。来自7株分离株的质粒可通过接合转移，赋予受体菌株抗生素耐药性。从水中（占独特分离株的12%）和蔬菜中（21%）分离出了多重耐药（MDR）菌株。MDR分离株中主要的序列类型（STs）是ST10、ST297和ST2522。在某些情况下，在水和蔬菜中检测到了相同的STs和相同的克隆（如rep-PCR分型所示），这表明存在交叉污染。本研究确定了蔬菜和灌溉用水中大肠杆菌分离株的几个风险因素，引发了对健康的担忧。此外，结果表明灌溉地下水构成了大肠杆菌的一个来源，可能通过摄入蔬菜进入食物链。
