Department of Plant and Soil Sciences, University of Pretoria, Hatfield, Pretoria 0002, South Africa.
Department of Science and Innovation-National Research Foundation Centre of Excellence in Food Security, South Africa.
J Food Prot. 2022 Jan 1;85(1):122-132. doi: 10.4315/JFP-21-125.
Leafy green vegetables have increasingly been reported as a reservoir of multidrug-resistant pathogenic Enterobacteriaceae, with Shiga toxin-producing Escherichia coli frequently implicated in disease outbreaks worldwide. This study examined the presence and characteristics of antibiotic resistance, diarrheagenic virulence genes, and phylogenetic groupings of E. coli isolates (n = 51) from commercially produced lettuce and spinach from farms, through processing, and at the point of sale. Multidrug resistance was observed in 33 (64.7%) of the 51 E. coli isolates, with 35.7% (10 of 28) being generic and 100% (23 of 23) being extended-spectrum β-lactamase/AmpC producing. Resistance of E. coli isolates was observed against neomycin (51 of 51, 100%), ampicillin (36 of 51, 70.6%), amoxicillin (35 of 51, 68.6%), tetracycline (23 of 51, 45%), trimethoprim-sulfamethoxazole (22 of 51, 43%), chloramphenicol (13 of 51, 25.5%), Augmentin (6 of 51, 11.8%), and gentamicin (4 of 51, 7.8%), with 100% (51 of 51) susceptibility to imipenem. Virulence gene eae was detected in two E. coli isolates from irrigation water sources only, whereas none of the other virulence genes for which we tested were detected. Most of the E. coli strains belonged to phylogenetic group B2 (25.5%; n = 13), B1 (19.6%; n = 10), and A (17.6%; n = 9), with D (5.9%; n = 3) less distributed. Although diarrheagenic E. coli was not detected, antibiotic resistance in E. coli prevalent in the supply chain was evident. In addition, a clear link between E. coli isolates from irrigation water sources and leafy green vegetables through DNA fingerprinting was established, indicating the potential transfer of E. coli from irrigation water to minimally processed leafy green vegetables.
多药耐药性致病性肠杆菌科越来越多地被报道为绿叶蔬菜的储库，在全球范围内，产志贺毒素的大肠杆菌经常与疾病爆发有关。本研究从农场、加工过程中和销售点检查了商业生产的生菜和菠菜中的大肠杆菌（n = 51）分离株的抗生素耐药性、腹泻性毒力基因和系统发育分组。51 株大肠杆菌分离株中观察到多药耐药性，其中 35.7%（28 株中的 10 株）为通用型，100%（23 株中的 23 株）为产超广谱β-内酰胺酶/ AmpC。大肠杆菌分离株对新霉素（51 株中的 51 株，100%）、氨苄西林（36 株中的 36 株，70.6%）、阿莫西林（35 株中的 35 株，68.6%）、四环素（23 株中的 23 株，45%）、复方磺胺甲噁唑（22 株中的 22 株，43%）、氯霉素（13 株中的 13 株，25.5%）、奥格门汀（6 株中的 6 株，11.8%）和庆大霉素（4 株中的 4 株，7.8%）有耐药性，而对亚胺培南（51 株中的 51 株，100%）敏感。我们检测的其他毒力基因均未检测到，只有 2 株来自灌溉水源的大肠杆菌分离株检测到 eae 毒力基因。大多数大肠杆菌菌株属于 B2 群（25.5%；n = 13）、B1 群（19.6%；n = 10）和 A 群（17.6%；n = 9），而 D 群（5.9%；n = 3）分布较少。尽管未检测到腹泻性大肠杆菌，但在供应链中流行的大肠杆菌的抗生素耐药性是显而易见的。此外，通过 DNA 指纹图谱建立了来自灌溉水源的大肠杆菌与绿叶蔬菜之间的明确联系，表明大肠杆菌有可能从灌溉水转移到经过最低限度加工的绿叶蔬菜。
