Heydari Ali, Kim Nick D, Biggs Patrick J, Horswell Jacqui, Gielen Gerty J H P, Siggins Alma, Bromhead Collette, Meza-Alvarado Juan Carlos, Palmer Barry R
School of Health Sciences, Massey University, Wellington 6021, New Zealand.
School of Food Technology and Natural Sciences, Massey University, Palmerston North 4410, New Zealand.
Antibiotics (Basel). 2025 Feb 13;14(2):192. doi: 10.3390/antibiotics14020192.
BACKGROUND/OBJECTIVES: Agricultural soils accumulate inorganic contaminants from the application of phosphate fertilisers. An airstrip located at Belmont Regional Park (BRP), near Wellington, New Zealand, has been found to have a gradient of cadmium contamination due to spillage of superphosphate fertiliser.
Soil samples from the BRP airstrip with a gradient of cadmium contamination, were used as a novel source to explore bacterial communities' resistance to heavy metals (HMs) and any co-selected antibiotic (Ab) resistance.
Differences between BRP soil samples with higher levels of HMs compared to those with lower HM concentrations showed significantly more bacterial isolates resistant to both HMs (40.6% versus 63.1% resistant to 0.01 mM CdCl, < 0.05) and Abs (23.4% versus 37.8% resistant to 20 μg/mL tetracycline, < 0.05) in soils with higher initial levels of HMs (1.14 versus 7.20 mg kg Cd). Terminal restriction fragment length polymorphism (TRFLP) and 16S rDNA next-generation sequencing profiling investigated changes in HM-induced bacterial communities. Significant differences were observed among the bacterial community structures in the selected BRP soil samples. Conjugative transfer of cadmium resistance from 23-38% of cadmium-resistant isolates to a characterised recipient bacterial strain in vitro suggested many of these genes were carried by mobile genetic elements. Transconjugants were also resistant to zinc, mercury, and Abs. Higher levels of HMs in soil correlated with increased resistance to HMs, Abs, and elevated levels of HMs thus disturbed the bacterial community structure in BRP soil significantly.
These findings suggest that HM contamination of agricultural soil can select for Ab resistance in soil bacteria with potential risks to human and animal health.
背景/目的：农业土壤会因施用磷肥而积累无机污染物。位于新西兰惠灵顿附近的贝尔蒙特地区公园（BRP）的一条简易跑道，由于过磷酸钙肥料的泄漏，已被发现存在镉污染梯度。
采集BRP简易跑道具有镉污染梯度的土壤样本，作为一种新的来源，以探索细菌群落对重金属（HMs）的抗性以及任何共同选择的抗生素（Ab）抗性。
与低HM浓度的BRP土壤样本相比，高HM水平的样本中，对HMs（对0.01 mM CdCl有抗性的细菌分离株分别为40.6%和63.1%，<0.05）和Abs（对20 μg/mL四环素有抗性的分别为23.4%和37.8%，<0.05）具有抗性的细菌分离株明显更多，初始HM水平较高的土壤中镉含量为1.14对7.20 mg/kg。采用末端限制性片段长度多态性（TRFLP）和16S rDNA下一代测序分析研究了HM诱导的细菌群落变化。在所选择的BRP土壤样本中，细菌群落结构存在显著差异。体外实验中，23 - 38%的镉抗性分离株将镉抗性接合转移到一个特征明确的受体细菌菌株，这表明许多此类基因由可移动遗传元件携带。接合子对锌、汞和Abs也具有抗性。土壤中较高水平的HMs与对HMs、Abs抗性的增加相关，因此较高水平的HMs显著扰乱了BRP土壤中的细菌群落结构。
这些发现表明，农业土壤中的HM污染可导致土壤细菌产生Ab抗性，对人类和动物健康存在潜在风险。
