This document provides a summary of microbiology, infections, and antibiotic therapy. It discusses bacterial cell structure and growth, normal flora, host defenses, clinical microbiology including common bacteria and diseases. It also covers mechanisms and classes of antibiotics including beta-lactams, protein synthesis inhibitors, and others. Antimicrobial therapy for specific bacteria such as mycobacteria, spirochetes, and anaerobes is described. Surgical antibiotic prophylaxis and indications are also summarized.