Jongman Mosimanegape, Korsten Lise
Department of Plant Science, Faculty of Natural and Agricultural Sciences, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0082, South Africa.
J Food Prot. 2016 Nov;79(11):1846-1853. doi: 10.4315/0362-028X.JFP-16-117.
Foodborne disease outbreaks linked to contaminated irrigation water and fresh produce are a public health concern. The presence of Escherichia coli isolates from irrigation water and leafy green vegetables in different food production systems (large commercial farms, small-scale farms, and homestead gardens) was investigated. The prevalence of antibiotic resistance and virulence in these isolates was further assessed, and links between water source and irrigated crops were identified using antimicrobial and genotypic analyses. Presumptive E. coli isolates were identified by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy, and identities were confirmed by PCR using the uidA gene. Antimicrobial susceptibility was evaluated with the Kirby Bauer disk diffusion test; the presence of virulence genes was determined with enterobacterial repetitive intergenic consensus PCR assays. Of the 130 E. coli isolates from water (n =60) and leafy green vegetables (n =70), 19 (14.6%) were resistant to one antibiotic (tetracycline) and 92 (70.7%) were resistant to various antibiotics (including ampicillin, cefoxitin, and nalidixic acid). All E. coli isolates were susceptible to ceftriaxone and gentamicin. The virulence gene stx was detected in E. coli isolates from irrigation water (8 [13.3%] of 60 isolates) and cabbages (3 [7.5%] of 40), but the virulence genes eae and stx were not detected in any tested isolates from irrigation water and fresh produce samples. The prevalence of multidrug-resistant E. coli was lower in isolates from GLOBALG.A.P.-certified farms than in isolates from noncertified commercial and small-scale farms and homestead gardens. A link between the E. coli isolates from irrigation water sources and leafy green vegetables was established with phenotypic (antimicrobial) and genotypic (DNA fingerprinting) analyses. However, a link between virulence genes and the prevalence of antimicrobial resistance could not be established.
与受污染的灌溉水和新鲜农产品相关的食源性疾病暴发是一个公共卫生问题。本研究调查了不同食品生产系统（大型商业农场、小规模农场和家庭菜园）中灌溉水和绿叶蔬菜中大肠杆菌分离株的存在情况。进一步评估了这些分离株的抗生素耐药性和毒力，并通过抗菌和基因分析确定了水源与灌溉作物之间的联系。通过基质辅助激光解吸电离飞行时间质谱法鉴定推定的大肠杆菌分离株，并使用uidA基因通过PCR确认其身份。采用 Kirby Bauer 纸片扩散法评估抗菌药物敏感性；通过肠杆菌重复基因间共有序列PCR分析确定毒力基因的存在。在从水（n = 60）和绿叶蔬菜（n = 70）中分离出的130株大肠杆菌中，19株（14.6%）对一种抗生素（四环素）耐药，92株（70.7%）对多种抗生素（包括氨苄青霉素、头孢西丁和萘啶酸）耐药。所有大肠杆菌分离株对头孢曲松和庆大霉素敏感。在灌溉水分离株（60株中的8株 [13.3%]）和卷心菜（40株中的3株 [7.5%]）中检测到毒力基因stx，但在灌溉水和新鲜农产品样本的任何测试分离株中均未检测到毒力基因eae和stx。全球良好农业规范（GLOBALG.A.P.）认证农场分离株中多重耐药大肠杆菌的患病率低于未认证的商业农场、小规模农场和家庭菜园分离株。通过表型（抗菌）和基因型（DNA指纹图谱）分析建立了灌溉水源大肠杆菌分离株与绿叶蔬菜之间的联系。然而，毒力基因与抗生素耐药性患病率之间的联系尚未建立。
