摘要
      沙门氏菌是一种人畜共患的食源性细菌病原体，可严重危害健康。在洪水和自然条件下，沙门氏菌和抗生素抗性基因（ARGs）在不同类型的土壤中的持久性很少被探索。本研究在实验室规模上研究了三种施用猪粪的土壤中沙门氏菌、ARGs和细菌群落的动态变化。鼠伤寒沙门氏菌在土壤中的丰度降低到检测极限，从40天到180天不等，大多数沙门氏菌不能在土壤中存活超过90天。洪水和土壤质地（沙子含量）促进了沙门氏菌的下降速度。90天后，没有发现沙门氏菌从土壤或粪便中获得抗性基因。64个ARGs和11个MGE被定量，这些基因和危险ARGs的丰度都随着时间的延长而逐渐下降。大多数外源性ARGs不能在土壤中定植，细胞保护和抗生素失活是它们的主要耐药机制。多药耐药性和外排泵是土壤内源性ARGs的主要种类和机制。洪水可以通过减少侵入土壤的外源性ARGs的类型来影响ARGs谱，并抑制内源性基因的增殖。土壤含砂量、土壤水分和营养浓度对ARGs的丰度或分布有显著的直接影响。土壤细菌群落结构也随着时间的延长而变化，并受到洪水的影响。ARGs和细菌分类群之间的网络分析表明，放线菌和粘球菌是内源性ARGs的主要宿主，一些分类群可能在抑制外源性ARGs在土壤中的定殖方面发挥作用。这些发现揭示了用水饱和土壤可能在降低农田环境中沙门氏菌和ARGs的潜在风险方面发挥积极作用。
Abstract
Salmonella is a zoonotic foodborne bacterial pathogen that can seriously harm health. Persistence of Salmonella and antibiotic resistance genes (ARGs) in different types of soil under flooding and natural conditions are rare explored. This study investigated the dynamic changes of the Salmonella, ARGs and bacterial communities in three types of soils applied with pig manure in lab scale. Abundance of the Salmonella Typhimurium in soils reduced to the detection limit varied from 40 to 180 days, most of the Salmonella did not survive in soil for more than 90 days. Flooding and soil texture (content of sand) promote the decline rate of Salmonella. No Salmonella was found have acquired resistance gene from the soil or manure after 90 days. 64 ARGs and 11 MGEs were quantified, abundance of these genes and risky ARGs both gradually decline along with the extension of time. Most of the extrinsic ARGs cannot colonize in soil, cellular protection and antibiotic deactivation were their main resistance mechanism. Multidrug resistance and efflux pump were the dominant class and mechanism of soil intrinsic ARGs. Flooding can affect the ARGs profiles by reducing the types of extrinsic ARGs invaded into soil and inhibit the proliferation of intrinsic genes. Soil sand content, soil moisture and nutrition concentrations had significant direct effect on the abundance or profile of ARGs. Soil bacterial community structures also changed along with the extension of time and affected by flooding. Network analyses between ARGs and bacteria taxa revealed that Actinobacteria and Myxococcia were the main hosts of intrinsic ARGs, some taxa may play a role in inhibiting extrinsic ARGs colonization in the soils. These findings unveil that saturate soil with water may play a positive role in reducing potential risk of Salmonella and ARGs in the farmland environment.

https://www.sciencedirect.com/science/article/pii/S0147651322011708