Table of Contents 1. The Power of Bacteria 2. Skin and Mucosa: the First Lines of Defense against Bacterial Infections 3. The Innate Immune System: Always on Guard 4. The Second Line of Defense: Antibodies and Cytotoxic T Cells 5. The Normal Human Microbiota 6. Microbes and Disease: Establishing a Connection 7. Mechanisms of Genetic Modification and Exchange: Role in Pathogen Evolution 8. Identification of Virulence Factors: Measuring Infectivity and Virulence 9. Identification of Virulence Factors: Molecular Approaches for Bacterial Factors 10. Identification of Virulence Factors: Molecular Approaches for Host Factors 11. Bacterial Strategies for Evading or Surviving Host Defense Systems 12. Toxins and Other Toxic Virulence Factors 13. Delivery of Virulence Factors 14. Virulence Regulation 15. Antibiotics and Their Targets 16. How Bacteria Become Resistant to Antibiotics 17. Vaccination—an Underappreciated Component of the Modern Medical Armamentarium 18. The Gram-Positive Opportunistic Pathogens 19. The Gram-Negative Opportunistic Pathogens 20. Biosecurity: the Changing Roles of Microbiologists in an Age of Bioterrorism and Emerging Diseases