Molecular epidemiology of clinical Enterococcus faecium

4 LIST OF PUBLICATIONS 6 LIST OF ABBREVIATIONS 9 INTRODUCTION 11 The Enterococcus genus 11 Taxonomy 11 Enterococcus faecium 12 Characteristics 12 Natural habitats 12 Virulence 12 Exchange of genetic material 14 Enterococcus faecium as a nosocomial pathogen 15 Epidemiology 15 Infection control 16 Subspecies typing methods 17 Advantages and disadvantages of different typing methods.. 17 Antibiotic resistance 17 Antibiotic susceptibility tests 18 Intrinsic resistance 18 Acquired resistance 18 Novel agents 21 AIMS OF THE THESIS 22 General aims 22 Specific aims 22 MATERIAL AND METHODS 23 Bacterial samples 23 Strain collection 23 Reference strains 23 Microbiological assays 24 The agar dilution method 24 In vitro conjugation assay using filter mating 24 PCR 25 Sequencing 27 Genotyping 28 Pulsed-field gel electrophoresis 28 Multiple-locus variable-number tandem repeat analysis ...... 30 Multilocus sequence typing 31 Statistical and data analyses 32 RESULTS 34 Bacterial isolates 34 Antibiotic susceptibility 34 Clinical E. faecium isolates 34 Normal microflora 35 Conjugation frequencies 36