摘要
出身背景
预计到2050年，抗生素耐药性（AMR）将成为死亡的主要原因，抗生素耐药性是其中的一个重要组成部分。人为污染将抗生素抗性细菌（ARB）和抗生素抗性基因（ARGs）引入自然环境。目前，只有有限的经验证据表明人类是否暴露于环境AMR，以及这种暴露是否会导致可衡量的人类健康结果。近年来，人们对环境的作用越来越感兴趣，并产生了关于AMR向人类传播的不同证据，但还没有系统地尝试对此进行总结。我们的目标是创建两个系统地图，以整理（1）抗生素耐药性在全球范围内从自然环境向人类传播的证据，以及（2）英国环境中抗生素耐药性的状态。
方法
为每张地图制定了搜索策略。在13个书目数据库中进行了检索。对主要网站进行了搜索，并向专家咨询了灰色文献。使用EndNote X8管理搜索结果。筛选标题和摘要，然后是全文。文章在两个阶段都进行了双重筛选，最低筛选率为10%，并在出现分歧时进行一致性检查和讨论。数据提取在Excel中进行，并设计了定制表格。从每项选定研究中提取的数据包括：书目信息；研究地点；暴露源；暴露途径；人类健康成果（地图1）；ARB/抗生素耐药性元素的流行率/百分比/丰度（图2）和研究设计。EviAtlas用于可视化输出。
后果
对于Map 1，从搜索中发现的11016篇独特文章中包括了40篇文章，这些文章调查了AMR从环境向人类的传播。地图1的结果显示，食用/摄入是研究最多的传播途径。暴露（n = 17） ，感染（n = 16） 和殖民化（n = 11） 作为一种结果研究的次数相似，很少研究死亡率（n = 2). 此外，大肠杆菌是研究最多的细菌（n = 16). 对于Map 2，我们纳入了62项量化英国环境中ARB或耐药性元素的研究，其中6874篇独特的文章在搜索中被识别。研究最多的物种是混合群落（n = 32). 在这个研究问题中使用的最常见的方法是表型测试（n = 37). 最常见的报告结果是ARBs（n = 40），然后对ARGs（n = 35). 其他遗传因素，如intI1（n = 15） （其编码1类整合子，用作环境ARGs的代理）和点突变（n = 1） 报告频率较低。这两张地图都表明研究的重点是水生环境。
结论
政策制定者可以使用这两张地图来显示全球（地图1）和英国（地图2）的研究景观，并概述AMR在环境中的状态以及与环境相互作用对人类健康的影响。我们还确定了（1）可用于进行荟萃分析的研究集群，以及（2）未来初级研究应重点关注的证据库缺口。
Abstract
Background
Antimicrobial resistance (AMR) is predicted to become the leading cause of death by 2050 with antibiotic resistance being an important component. Anthropogenic pollution introduces antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) to the natural environment. Currently, there is limited empirical evidence demonstrating whether humans are exposed to environmental AMR and whether this exposure can result in measurable human health outcomes. In recent years there has been increasing interest in the role of the environment and disparate evidence on transmission of AMR to humans has been generated but there has been no systematic attempt to summarise this. We aim to create two systematic maps that will collate the evidence for (1) the transmission of antibiotic resistance from the natural environment to humans on a global scale and (2) the state of antibiotic resistance in the environment in the United Kingdom.

Methods
Search strategies were developed for each map. Searches were undertaken in 13 bibliographic databases. Key websites were searched and experts consulted for grey literature. Search results were managed using EndNote X8. Titles and abstracts were screened, followed by the full texts. Articles were double screened at a minimum of 10% at both stages with consistency checking and discussion when disagreements arose. Data extraction occurred in Excel with bespoke forms designed. Data extracted from each selected study included: bibliographic information; study site location; exposure source; exposure route; human health outcome (Map 1); prevalence/percentage/abundance of ARB/antibiotic resistance elements (Map 2) and study design. EviAtlas was used to visualise outputs.

Results
For Map 1, 40 articles were included, from 11,016 unique articles identified in searches, which investigated transmission of AMR from the environment to humans. Results from Map 1 showed that consumption/ingestion was the most studied transmission route. Exposure (n = 17), infection (n = 16) and colonisation (n = 11) being studied as an outcome a similar number of times, with mortality studied infrequently (n = 2). In addition, E. coli was the most highly studied bacterium (n = 16). For Map 2, we included 62 studies quantifying ARB or resistance elements in the environment in the UK, from 6874 unique articles were identified in the searches. The most highly researched species was mixed communities (n = 32). The most common methodology employed in this research question was phenotypic testing (n = 37). The most commonly reported outcome was the characterisation of ARBs (n = 40), followed by characterisation of ARGs (n = 35). Other genetic elements, such as screening for intI1 (n = 15) (which encodes a Class 1 integron which is used as a proxy for environmental ARGs) and point mutations (n = 1) were less frequently reported. Both maps showed that research was focused towards aquatic environments.

Conclusions
Both maps can be used by policy makers to show the global (Map 1) and UK (Map 2) research landscapes and provide an overview of the state of AMR in the environment and human health impacts of interacting with the environment. We have also identified (1) clusters of research which may be used to perform meta-analyses and (2) gaps in the evidence base where future primary research should focus.

https://environmentalevidencejournal.biomedcentral.com/articles/10.1186/s13750-022-00262-2