Antimicrobial Resistance and Microbial Ecology Group, School of Medicine, University of Galway, Ireland; Food Safety Department, Teagasc Food Research Centre Ashtown, Dublin, Ireland.
Food Safety Department, Teagasc Food Research Centre Ashtown, Dublin, Ireland; School of Veterinary Medicine, University College Dublin, Dublin, Ireland.
Environ Pollut. 2024 Nov 15;361:124774. doi: 10.1016/j.envpol.2024.124774. Epub 2024 Aug 22.
Antimicrobial resistant bacteria can occur in the primary food production environment. The emergence and dissemination of antimicrobial resistance (AMR) in the environment can be influenced by several factors, including the presence of heavy metals. The aim of this study was to examine the presence and characteristics of antimicrobial resistant Enterobacterales in soils and spinach grown in soils with and without zinc amendment. A total of 160 samples (92 soil and 68 spinach) were collected from two locations, in which some plots had been amended with zinc. Samples were cultured on selective agars for detection of extended-spectrum beta-lactamase-producing Enterobacterales (ESBL), carbapenem-resistant Enterobacterales and ciprofloxacin-resistant Enterobacterales. Samples were also cultured for enumeration of total Enterobacterales. Isolates were identified by MALDI-TOF. Antimicrobial susceptibility testing was carried out in accordance with EUCAST and CLSI criteria. The whole genome sequence (WGS) of selected isolates was determined. Inductively coupled plasma atomic emission spectrometry was also performed on soil samples in order to measure the concentration of zinc. In total 20 antimicrobial resistant Enterobacterales were isolated from the soil (n = 8) and spinach samples (n = 12). In both sample types, Serratia fonticola (n = 16) was the dominant species, followed by Escherichia coli (n = 1), Citrobacter freundii (n = 1) and Morganella morganii (n = 1) detected in spinach samples, and Enterobacter cloacae (n = 1) detected in a soil sample. The WGS identified genes conferring resistance to different antimicrobials in agreement with the phenotypic results; 14 S. fonticola isolates were confirmed as ESBL producers and harboured the bla gene. Genes that encoded for zinc resistance and multidrug efflux pumps, transporters that can target both antimicrobials and heavy metals, were also identified. Overall, the findings of this study suggest the presence of zinc did not influence the AMR Enterobacterales in soil or spinach samples.
抗微生物耐药细菌可出现在初级食品生产环境中。抗微生物耐药性（AMR）在环境中的出现和传播可能受到多种因素的影响，包括重金属的存在。本研究的目的是检查土壤中存在的和在添加锌的和未添加锌的土壤中生长的菠菜中具有抗微生物活性的肠杆菌科的特征和情况。从两个地点共采集了 160 个样本（92 个土壤样本和 68 个菠菜样本），其中一些样本进行了锌添加。将样本接种在选择性琼脂上，以检测产超广谱β-内酰胺酶的肠杆菌科（ESBL）、耐碳青霉烯肠杆菌科和耐环丙沙星的肠杆菌科。还对土壤样本进行了总肠杆菌科的计数培养。使用 MALDI-TOF 进行了鉴定。根据欧盟药敏试验委员会（EUCAST）和美国临床和实验室标准协会（CLSI）的标准进行了抗微生物药敏试验。对选定的分离株进行了全基因组序列（WGS）测定。还对土壤样本进行了电感耦合等离子体原子发射光谱法（ICP-AES），以测量锌的浓度。总共从土壤（n=8）和菠菜样本（n=12）中分离出 20 株抗微生物的肠杆菌科。在这两种样本类型中，丰原沙雷氏菌（Serratia fonticola）（n=16）是主要的物种，其次是大肠埃希菌（Escherichia coli）（n=1）、弗氏柠檬酸杆菌（Citrobacter freundii）（n=1）和摩氏摩根菌（Morganella morganii）（n=1），在菠菜样本中检测到，而在土壤样本中检测到阴沟肠杆菌（Enterobacter cloacae）（n=1）。WGS 鉴定出与表型结果一致的不同抗微生物药物耐药基因；14 株 S. fonticola 分离株被确认为 ESBL 生产者，并携带 bla 基因。还鉴定出编码锌耐药性和多药外排泵的基因，这些基因可以靶向抗微生物药物和重金属。总的来说，本研究的结果表明，锌的存在并没有影响土壤或菠菜样本中的 AMR 肠杆菌科。
