大腸埃希氏菌（Escherichia coli,E.coli）是一種常見的食源性、條件性致病菌,一般人畜呈無癥狀感染,但在一定的條件下能夠產(chǎn)生威脅人畜生命安全的并發(fā)癥。反芻動(dòng)物是致病性E.coli最重要的宿主之一。牦牛（Bos grunniens或Yak）是生活在青藏高原上特有的反芻動(dòng)物,也是當(dāng)?shù)啬撩裰饕馐称穪碓�。目�?由于藥物的濫用,導(dǎo)致大腸桿菌耐藥性不斷產(chǎn)生,耐藥基因不斷被發(fā)現(xiàn)。因此,越來越多的專家指出研究和評(píng)估食用性動(dòng)物（如牦牛）的抗菌耐藥性（Antimicrobial resistance,AMR）和致病因子（Virulence factors）對于公共衛(wèi)生安全非常重要�，F(xiàn)在臨床上關(guān)于細(xì)菌耐藥性的監(jiān)測還不夠全面,對動(dòng)物耐藥研究還沒形成完整的理論系統(tǒng),并且關(guān)于青藏高原地區(qū)牦牛大腸桿菌耐藥性報(bào)道也較少。因此,本研究開展對青藏高原地區(qū)牦牛大腸桿菌中致病基因、遺傳譜系、血清型和抗生素抗性模式的研究,以期為青藏高原地區(qū)牦牛肉食品安全性評(píng)估提供理論依據(jù)。研究內(nèi)容如下:1.青藏高原地區(qū)散養(yǎng)牦牛大腸埃希氏菌耐藥性研究在我國散養(yǎng)牦牛中關(guān)于抗生素耐藥性、血清型、遺傳譜系和相關(guān)毒力特征的研究還未見... 

【文章來源】：華中農(nóng)業(yè)大學(xué)湖北省 211工程院校 教育部直屬院校

【文章頁數(shù)】：153 頁

【學(xué)位級(jí)別】：博士

【文章目錄】：
摘要
ABSTRACT
LIST OF ABBREVIATIONS
CHAPTER 1 Introduction
    1.1 Antimicrobial resistance (AMR)
    1.2 Susceptibility testing
        1.2.1 Phenotype susceptibility testing methods
        1.2.2 Molecular characteristics of antimicrobial resistance
    1.3 How bacteria acquire resistance
        1.3.1 Mutation
        1.3.2 Horizontal and vertical transfer of resistance
        1.3.3 Mobile genetic elements
    1.4 How antimicrobials exert their effect
    1.5 How bacteria fight back against antimicrobials
    1.6 Main mechanisms of antibiotic resistance development to commonly used antibiotics in livestock (yak) herds
        1.6.1 Beta-lactams
        1.6.2 Tetracyclines
        1.6.3 Fluorquinolones and Quinolones
        1.6.4 Aminoglycosides and Aminocyclitols
        1.6.5 Chloramphenicol and Florfenicol
        1.6.6 Trimethoprim and Sulphonamides
        1.6.7 Co-resistance and cross-resistance
    1.7 Escherichia coli (E. coli) as an indicator organism
    1.8 Pathogenicity of E. coli and AMR
    1.9 Antibiotics usage: General considerations
        1.9.1 Reason for antimicrobial use in livestock
        1.9.2 Antimicrobial use and antimicrobial resistance
        1.9.3 Major multi-drug efflux pump and traditional Chinese medicine
        1.9.4 Challenges of antibiotic usage data collection
    1.10 Antimicrobial resistance in domestic yaks
        1.10.1 How this thesis will fill in the gaps demonstrated in this review
    1.11 Concluding statements
    1.12 Aims &Objectives
        1.12.1 Problem statement
        1.12.2 Aims
        1.12.3 Achieved goals
        1.12.4 Benefits from the project
CHAPTER 2 Antibiotic resistance of Escherichia coli in free-ranging healthy and diarrheic yaks (Bos grunniens) of Qinghai-Tibetan Plateau,China
    2.1 Objective of this study
    2.2 Materials and methods
        2.2.1 Sample collection, isolation, and identification
        2.2.2 Antibiotic sensitivity testing and screening of ESBL-producing strains
        2.2.3 DNA extraction
        2.2.4 Screening for resistance genes and virulence-associated genes
        2.2.5 Phylo groups of E. coli strains
        2.2.6 Sero-grouping
        2.2.7 Codon-based positive selection analysis
        2.2.8 Positive selection on amino acid positions
        2.2.9 Evolutionary analysis of diversifying selection
        2.2.10 Evolutionary finger printing of bla CTX-M gene
        2.2.11 Statistical analysis
    2.3 Results
        2.3.1 Isolation rate of E. coli
        2.3.2 Antibiotic resistance patterns of E. coli isolates
        2.3.3 Detection of resistance and virulence genes
        2.3.4 Occurrence of E. coli pathotypes
        2.3.5 Occurrence of phylogroups
        2.3.6 Association between antimicrobial resistance and virulence genes
        2.3.7 Occurrence of Serogroups
        2.3.8 Detection of ESBL genes
        2.3.9 Codon-based positive selection analysis in ESBL producing CTX-M gene
        2.3.10 Positive selection on amino acid positions
        2.3.11 Evolutionary analysis of diversifying selection
        2.3.12 Evolutionary finger printing of bla CTX-M gene
    2.4 Discussion
CHAPTER 3 Characteristics of integrons and associated gene cassettes in antibiotic resistant Escherichia coli isolated from free-ranging food animals in China
    3.1 Objective of this study
    3.2 Materials and Methods
        3.2.1 Ethics statement
        3.2.2 Study population and bacterial strains
        3.2.3 Characterization of the integrons
        3.2.4 Characterization of class 1 and 2 integron cassette arrays
        3.2.5 Restriction analysis of PCR products and DNA sequencing
        3.2.6 Sequence analysis and nucleotide accession number
        3.2.7 Conjugation studies and plasmid analysis
        3.2.8 Multilocus sequence typing of integrons positive E. coli
    3.3 Results
        3.3.1 Occurrence of class 1 and 2 integrons
        3.3.2 Characterization of integrons and transfer of class 1 integrons
        3.3.3 Multi-locus sequence analysis (MLSA)
        3.3.4 Conjugal transfer and plasmid profiling
    3.4 Discussion
CHAPTER 4 Experimental mouse lethality of Escherichia coli strains isolated from free ranging Tibetan Yaks
    4.1 Objective of this study
    4.2 Materials and Methods
        4.2.1 Ethics Statement
        4.2.2 Strains
        4.2.3 Serogrouping
        4.2.4 Mouse lethality assay
        4.2.5 Statistical analysis
    4.3 Results
        4.3.1 Lethality rate of E. coli strains
        4.3.2 Occurrence of Serogroups
        4.3.3 Mouse lethality assay
    4.4 Discussion
CHAPTER 5 Antibacterial effect and resistant regulation of Houttuynia cordata water extract against multi-drug resistant Escherichia coli
    5.1 Objective of this study
    5.2 Materials and Methods
        5.2.1 Materials and Reagents
        5.2.2 Water Extraction
        5.2.3 Bacterial Strains
        5.2.4 Antibacterial assay of H. cordata water extract
        5.2.5 Determination of minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)
        5.2.6 Reverse Transcription Quantitative-Real Time Polymerase Chain Reaction (RT-qPCR)
        5.2.7 Statistical analyses of the results
    5.3 Results
        5.3.1 Antibacterial effects of Houttuynia cordata water extract
        5.3.2 Transcriptional level of AcrA gene by RT-qPCR
    5.4 Discussion
CHAPTER 6 Conclusions and Future directions
    6.1 Study Ⅰ
    6.2 Study Ⅱ
    6.3 Study Ⅲ
    6.4 Study Ⅳ
    6.5 Future directions
References
Acknowledgements
List of Publications
Appendices
    Appendix 1
    Appendix 2
    Appendix 3


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