Antibiotic Resistance in Community-Acquired Pneumonia Caused by Streptococcus pneumoniae, Methicillin-Resistant Staphylococcus aureus, and Acinetobacter baumannii

Antimicrobial therapy is the mainstay of management for community-acquired pneumonia (CAP). Accordingly, the choices of treatment are influenced by the likely etiologies, local resistance patterns of the pathogens, as well as patient factors. As the leading cause of acute CAP, the susceptibility patterns of Streptococcus pneumoniae have greatly influenced antimicrobial agents and dosage recommended for empirical treatment of this condition. The worldwide emergence of community-acquired methicillin-resistant Staphylococcus aureus has also led to discussion of this pathogen in recent revisions of the international CAP guidelines. This pathogen is important because of its resistance to antibiotics commonly recommended for the empirical treatment of CAP and the association with a rapidly fatal form of pneumonia characterized by tissue necrosis, pulmonary hemorrhage, and rapid progression to respiratory failure. In tropical regions of Australia and Asia, CAP due to Acinetobacter baumannii is also increasingly recognized. This review discusses their recent epidemiology, microbiology, clinical features, and treatment of CAP caused by these antimicrobial-resistant pathogens.