Laboratory of Food Microbiology and Food Preservation, Department of Food Safety and Food Quality, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
Appl Environ Microbiol. 2013 Nov;79(21):6677-83. doi: 10.1128/AEM.01995-13. Epub 2013 Aug 23.
Fresh produce is known to carry nonpathogenic epiphytic microorganisms. During agricultural production and harvesting, leafy greens can become contaminated with antibiotic-resistant pathogens or commensals from animal and human sources. As lettuce does not undergo any inactivation or preservation treatment during processing, consumers may be exposed directly to all of the (resistant) bacteria present. In this study, we investigated whether lettuce or its production environment (irrigation water, soil) is able to act as a vector or reservoir of antimicrobial-resistant Escherichia coli. Over a 1-year period, eight lettuce farms were visited multiple times and 738 samples, including lettuce seedlings (leaves and soil), soil, irrigation water, and lettuce leaves were collected. From these samples, 473 isolates of Escherichia coli were obtained and tested for resistance to 14 antimicrobials. Fifty-four isolates (11.4%) were resistant to one or more antimicrobials. The highest resistance rate was observed for ampicillin (7%), followed by cephalothin, amoxicillin-clavulanic acid, tetracycline, trimethoprim, and streptomycin, with resistance rates between 4.4 and 3.6%. No resistance to amikacin, ciprofloxacin, gentamicin, or kanamycin was observed. One isolate was resistant to cefotaxime. Among the multiresistant isolates (n = 37), ampicillin and cephalothin showed the highest resistance rates, at 76 and 52%, respectively. E. coli isolates from lettuce showed higher resistance rates than E. coli isolates obtained from soil or irrigation water samples. When the presence of resistance in E. coli isolates from lettuce production sites and their resistance patterns were compared with the profiles of animal-derived E. coli strains, they were found to be the most comparable with what is found in the cattle reservoir. This may suggest that cattle are a potential reservoir of antimicrobial-resistant E. coli strains in plant primary production.
新鲜农产品通常带有非病原性的附生微生物。在农业生产和收获过程中，叶类蔬菜可能会受到来自动物和人类源的抗生素耐药病原体或共生菌的污染。由于生菜在加工过程中不进行任何灭活或保存处理，消费者可能会直接接触到所有存在的（耐药）细菌。在这项研究中，我们调查了生菜或其生产环境（灌溉水、土壤）是否能够作为抗生素耐药大肠杆菌的载体或储库。在一年的时间里，我们多次访问了八家生菜农场，采集了 738 个样本，包括生菜幼苗（叶片和土壤）、土壤、灌溉水和生菜叶片。从这些样本中，获得了 473 株大肠杆菌分离株，并对其 14 种抗生素的耐药性进行了测试。有 54 株（11.4%）分离株对一种或多种抗生素具有耐药性。最高的耐药率出现在氨苄西林（7%），其次是头孢噻吩、阿莫西林-克拉维酸、四环素、甲氧苄啶和链霉素，耐药率在 4.4%至 3.6%之间。未观察到对阿米卡星、环丙沙星、庆大霉素或卡那霉素的耐药性。有一株分离株对头孢噻肟耐药。在多耐药分离株（n=37）中，氨苄西林和头孢噻吩的耐药率最高，分别为 76%和 52%。与土壤或灌溉水样本中的大肠杆菌分离株相比，生菜中大肠杆菌分离株的耐药率更高。当比较生菜生产地大肠杆菌分离株的耐药性及其耐药模式与动物源性大肠杆菌菌株的特征时，发现它们与牛储库中的耐药性最为相似。这可能表明牛是植物初级生产中抗生素耐药大肠杆菌菌株的潜在储库。
