Analysis of antibiotic resistance genes and their effects on marine environment

DAI Yuanyuan, GAO Yan*, DONG Yubo

1. Fisheries Research Institute of Tianjin, Tianjin 300221, China;

2. Ministry of Education Key Lab. of Pollution Processes and Environmental Criteria of Nankai University,Tianjin 300350, China

Abstract: The application of overgrowth antibiotic resistance genes in marine research was discussed.Using the China National Knowledge Infrastructure(CNKI)network database to retrieve papers on resistance genes(n = 3 0627) and antibiotic resistance genes(n=3 277), the published trends, subject headings and other aspects of bibliometrics were analyzed. Literature in this field has increased rapidly in the past 38 years. 55.3% of the papers were published in the last ten years, 31.2% of the papers were published in the last five years. The relevance of research topics has increased in recent years, the current research mainly focus on antibiotics, resistance gene, antibiotic resistance gene,and drug resistance. Literature analysis is helpful to understand the overall development trend of overgrowth antibiotic resistance genes in marine research.

Keywords: CNKI database, antibiotic resistance genes, bibliometrics

Antibiotics are used for the prevention and treatment of human and animal diseases.They also are widely used in the aquaculture industry, as a growth promoter to add animal feed to the treatment dose[1]. For most antibiotics, only 15% of them can be absorbed, and the rest will be excreted into the natural ecosystem through urine and faeces[2]. Studies have shown that in 2013, about 53,800 tons of antibiotics in China were released into rivers and waterways[3]. Besides direct pollution, antibiotics entering the environment can induce the generation of antibiotic resistance bacteria and antibiotic resistance genes(ARGs) in the environment[4]. The widespread production and abuse of antibiotics promote the enrichment and dissemination of ARGs in the environment[5]. There are many researchers at home and abroad studying on the content of groundwater, surface water,sewage treatment plant wastewater, antibiotics and ARGs in drinking water[6]. Antibiotics and ARGs are detected in the Pearl River, Huangpu River, Yellow River and Haihe River basin in China[7]. Lin et al.(2015) studied the ARGs of the estuaries and coastal sediments of the Yangtze River, and found that the sul, Tet, int gene were prevalent in this area, and the content from the estuary to the coast showed a downward trend[8].With the development of molecular biology technology, more and more researches have been made on the determination of resistant genes in macrogenomics[9-11]. However, the complexity of marine factors has brought some difficulties to the study of resistant genes in the marine environment. The aim of this study is to analyze the progress of resistance genes in marine environment, so as to provide assistance for further research.

1 The sources of data

Literature data comes from the retrieval results of China National Knowledge Infrastructure(CNKI) database. The retrieval time was set from 1981 to 2019, and the retrieval date was September 6, 2019. To comprehensively search the resistance genes in marine related research, retrieval type 1 "resistance genes”was set, and 30627 papers were retrieved to be consistent with theme. Then the statistical analysis from the published annual distribution, research level distribution and keywords “author, research institutions, fund sources, subject distribution, source distribution”were carried out. At the same time, to analyze resistance gene related research, retrieval type 2 "antibiotic resistance genes”was set, with 3 277 paper being retrieved. Thomson Data Analyzer software is used to visually analyze the correlation degree of subject words according to the frequency of occurrence.

2 Infusions and analysis

2.1 Document overview

When the retrieval strategy was set up as retrieval type 23 277 papers on antibiotic resistance genes were obtained. Published papers in the past 38 years are shown in Fig. 1. From 1983 to the beginning of 2000, 62 research papers were published. There’s an increasing trends of scientific papers from 2004 to 2014, with 325 research papers published, and the year of 2014 reached a peak of 70 papers. The papers from 2010 to 2019 accounted for 22.8% of the total publication, and the papers from 2014 to 2019 accounted for 18%, showing the enthusiasm of researchers in this field. In 2017, the number of communications reached 127. However, since 2016, the number of related literatures has dropped to 101, and more than 137 articles are expected in 2019. These are related to the development of new macrogenomic technology.

2.2 Keyword analysis

Fig. 1 Annual growth of papers included in CNKI database

The key words of the literature can reflect the content, methods and objects of the study, and the focus of the research can be seen from the distribution of high-frequency keywords. In this study, the key words of 3 277 research papers were analyzed, and the synonyms were cleaned manually according to the meaning of keywords. Antibiotics,resistance genes, and antibiotic resistance genes are the most frequently used keywords.According to the metabolites, types, functions, resistance identification, structure analysis and classification of resistant genes strains, 19 high frequency keywords related to antibiotic resistance genes were identified. Fig. 2 shows that antibiotic resistance genes research mainly concentrated on the drug resistance gene and resistance genes of antibiotics, in addition, the analysis of methods of molecular biology, transformation, gene knockout, homologous recombination and conjugation such as the theme of the study; the major strains including Escherichia coli, Lactic acid bacteria, Staphylococcus aureus, multidrug resistant bacteria. Based on the statistical sorting of keywords, the visualization graph of association between keywords is generated (Fig. 3).

Fig. 2 The distribution of keywords

Fig. 3 The Association visualization graph of keywords

The colorful dots in Fig. 3 represent the topic of study. The connection between dots and their distances represents the degree of association among them. The closer the line is, the shorter the distance is, the higher the correlation between them. It can be seen that there is a strong association between antibiotics and resistance gene, antibiotics and antibiotics resistance gene between RT-PCR and drug, indicating that there is a large correlation between these research hotspots.

2.3 Research field and periodical distribution

Field and periodical distribution of the core Chinese statistical retrieval, and statistical analysis were made according to the majorsubjectareas(Fig.4).The distribution of important source journals were collected and analyzed(Fig.5). Data show that biological and environmental science and resource utilization research papers involved in many subjects,among which biology is the hottest subject with 401 papers, accounting for 30.56%of the total number of publications. The subject area of environmental science and resource utilization is secondary, where 250 papers were published, accounting for 19.05% of the total number of publications. Among the top five subjects, a total of 920 papers were published, accounting for 70.12% of the total number of publications. Biology,environmental science and resource utilization, and fisheries were paid more attention to in the field of marine microbiology.

Fig. 4 The distribution of subjects

The distribution of the top 10 important journals in the paper is shown in Fig. 5,demonstrating the most papers are published by Huazhong Agricultural University of China. A total of 27 papers were published, accounting for 8.26% of the total publications.Zhejiang University, Environmental Science, Nanjing Agricultural University are the core Chinese journals in the field of environmental science and resource utilization. The number of publications in these journals is basically the same, and the impact factors are also less significant. Data show that in the antibiotics resistance gene research, Huazhong Agricultural University of China and the Zhejiang University made the main contribution,where Zhejiang University research mainly focuses on the epiphytic marine resistance gene, and Huazhong Agricultural University of China, mainly engaged in multi-drug resistant bacteria analysis. This is probably related to the difference of marine resources between the south and the north China.

Fig. 5 The distribution of literature sources

2.4 The analysis of research level

It can be seen from Fig. 6 that the antibiotics resistance gene are mainly divided into five research levels. The basic and applied basic research is the most important source of publications, which has 805 papers, accounting for 79.08% of the total number of publications.

Fig. 6 The study of hierarchical distribution

2.5 The Analysis of project fund sources

According to Fig. 7 the source of fund is mainly the support of National Science Foundation. There are 253 papers supported by the National Natural Science Foundation,accounting for 25.3% of the total number; the second is supported by the National High Technology Research and Development Program of China, accounting for 4.9%. The National Basic Research and Development Plan, the National Science and Technology Support Plan, the Knowledge Innovation Project of Chinese Academy of Sciences contribution rate were 2.0%, 1.2% and 1.2%, respectively.

Fig. 7 The distribution of project fund sources

3 Expectation

Bibliometric studies for a subject may be influenced by the type of database, the key words, the time of retrieval, and the tools of statistical analysis.

This article uses the literature metrology method for the analysis of antibiotics resistance gene related literature, to help marine ecological environment researchers,marine fishery producers, marine environmental monitoring departments and marine drug research and development institutions, production enterprises to understand and grasp the domestic antibiotic resistance gene research progress, especially to understand its focus and problems to be solved, thus to strengthen academic exchanges, effective research cooperation, innovative ideas, and carry out new fields.

All the data are from the CNKI database, but because of the different retrieval conditions, may be different from the other two research results. Due to the author's knowledge level in the field of research, the analysis of the literature inevitably has omissions, and the analysis of the details is not perfect, which needs further study.

The present analysis have uncertainty because of the following reasons: (1) retrieval style setting cannot fully include the target literature, different articles have multiple expressions of the same meaning, and words are diversified. (2) Domestic scientific research continuously updated literature database retrieval every day. With new literature increasing, the study can only be locked in a specific time range. (3) The existence of error analysis, such as the different authors with the same name confusion or the same author mistakenly believed to be a different one and other circumstances.

Acknowledgements

This work was supported by the Opening Foundation of Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria (2019-04).Youth Science and Technology Innovation Project of Tianjin Agricultural Development Service Center(19KY11).