Microbiology of Hospital-Acquired Pneumonia

The microbiology of hospital-acquired pneumonia reflects the pathogenesis and risk factors associated with both the disease itself and the various pathogens. The etiologic agents include aerobic gram-negative bacilli such as the Enterobacteriaceae, Haemophilus influenzae, Pseudomonas aeruginosa, and Acinetobacter spp., as well as grampositive cocci such as Staphylococcus aureus and Streptococcus pneumoniae. Other bacterial pathogens that may occur depending on the risk factors include anaerobes and Legionella spp.