Antibacterials (ABX) Practice Exam

Atypical pneumonias are typically caused by organisms such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. These pathogens often lack a typical cell wall or live inside host cells, so antibiotics that target bacterial cell walls or require good oxygen-dependent uptake are less effective. Macrolides work by binding to the 50S ribosomal subunit and inhibiting protein synthesis, which gives them good activity against these atypical organisms. They also penetrate well into lung tissue and intracellularly, making them a reliable choice for treating atypical pneumonia, often as outpatient therapy. In contrast, penicillins and cephalosporins target cell wall synthesis and are less active against atypicals, and SAMPLEaminoglycosides rely on oxygen-dependent uptake and have limited activity and penetration in pneumonia.