Microbiology of Hospital-Acquired Pneumonia

Abstract

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.

This article reviews these pathogens from the point of view of their relevant microbiologic features and the risk factors that predispose patients to infection with these organisms. A discussion of the relevant antimicrobial resistance issues is also included. The latter provides an overview of resistance development and means of spread among pathogens as well as a more detailed examination of the specific resistance mechanisms to antibiotics as they relate to the pathogens that cause hospital-acquired pneumonia.

Key Words:

microbiology - nosocomial - pneumonia