Antimicrobial Resistance and Microbial Ecology Group, School of Medicine, University of Galway, Ireland; Food Safety Department, Teagasc Food Research Centre Ashtown, Dublin, Ireland.
School of Food Science and Environmental Health, Technological University Dublin, Dublin, Ireland.
Sci Total Environ. 2024 Nov 25;953:175905. doi: 10.1016/j.scitotenv.2024.175905. Epub 2024 Aug 30.
Heavy metals occur naturally in the environment, and their concentration varies in soil across different regions. However, the presence of heavy metals may influence the antimicrobial resistance (AMR) in bacterial populations. Therefore, the objective of this study was to investigate and characterise the antimicrobial resistance profiles of Enterobacterales in soil and bovine milk filters from high and low zinc-containing regions in Ireland. In total, 50 soil samples and 29 milk filters were collected from two geographic locations with varying soil zinc concentrations. Samples were cultured for the enumeration and detection of Enterobacterales. Specifically, extended-spectrum beta-lactamase-producing Enterobacterales, carbapenem-resistant Enterobacterales and ciprofloxacin-resistant Enterobacterales were isolated using selective media. Species identification was performed using MALDI-TOF. The phenotypic resistance profiles of selected Enterobacterales were determined by disk diffusion testing, following EUCAST and CLSI criteria; while, the genotypic resistance profiles of the same isolates were determined by whole genome sequencing (WGS). Heavy metal concentrations were also measured for all soil samples. A total of 40 antimicrobial resistant Enterobacterales were identified in soil (n = 31) and milk filters (n = 9). The predominant species detected in the high zinc-containing region was Escherichia coli in both sample types (soil n = 10, milk filters n = 2), while in the low zinc-containing region Serratia fonticola was predominant in soil samples (n = 8) and E. coli in milk filters (n = 4). Ten E. coli isolates identified from soil samples in the high zinc-containing region were multidrug resistant, showing resistance to all the antimicrobials tested, except for carbapenems. The WGS findings confirmed the phenotypic resistance results. Moreover, zinc resistance-associated genes and genes encoding for efflux pumps were identified. The current study revealed distinct phenotypic resistance profiles of Enterobacterales in low and high zinc-containing regions, and highlighted the benefit of utilising milk filters for AMR surveillance in dairy production.
重金属在环境中自然存在，其浓度在不同地区的土壤中有所不同。然而，重金属的存在可能会影响细菌种群中的抗菌药物耐药性（AMR）。因此，本研究的目的是调查和描述爱尔兰高锌和低锌地区土壤和牛奶奶滤器中肠杆菌科的抗菌药物耐药谱。总共从两个土壤锌浓度不同的地理位置采集了 50 个土壤样本和 29 个奶滤器。样本经过培养以计数和检测肠杆菌科。具体而言，使用选择性培养基分离产超广谱β-内酰胺酶的肠杆菌科、耐碳青霉烯肠杆菌科和耐环丙沙星的肠杆菌科。使用 MALDI-TOF 进行种属鉴定。使用 EUCAST 和 CLSI 标准通过纸片扩散试验确定所选肠杆菌科的表型耐药谱；同时，通过全基因组测序（WGS）确定相同分离株的基因型耐药谱。还测量了所有土壤样本中的重金属浓度。在土壤（n=31）和奶滤器（n=9）中总共鉴定出 40 株抗菌药物耐药肠杆菌科。在高锌含量地区，两种样本类型中均检测到优势种为大肠杆菌（土壤 n=10，奶滤器 n=2），而在低锌含量地区，土壤样本中优势种为粘质沙雷氏菌（n=8），奶滤器中为大肠杆菌（n=4）。从高锌含量地区土壤样本中鉴定出的 10 株大肠杆菌分离株为多药耐药株，对除碳青霉烯类外所有测试的抗菌药物均有耐药性。WGS 结果证实了表型耐药结果。此外，还鉴定了锌耐药相关基因和编码外排泵的基因。本研究揭示了低锌和高锌含量地区肠杆菌科的不同表型耐药谱，并强调了利用奶滤器进行乳制品生产中 AMR 监测的益处。
