Nosocomial pneumonia

This chapter explores nosocomial pneumonia (NP), which may be defined as pneumonia that occurs after 5 or more days in hospital. NP is synonymous with hospital-acquired pneumonia (HAP). The subset of NP/ HAP patients on ventilators are referred to as ventilator-associated pneumonias (VAP). NP occurring early, i.e., less than 5 days after admission, actually represents incubating community-acquired pneumonia (CAP) that has become clinically manifest early after hospital admission. For this reason, the respiratory pathogens causing “early NP” are the usual CAP pathogens, e.g., Streptococcus pneumoniae. With true NP, the respiratory pathogens acquired in hospital are aerobic gram-negative bacilli (GNB). The most important, but not the most common, NP pathogen is Pseudomonas aeruginosa; some other GNB are also important NP pathogens, e.g., Klebsiella pneumoniae.