Introduction
Pneumonia is one of the most common conditions among hospitalized patients, represented as either community-acquired pneumonia (CAP) or hospital-acquired pneumonia (HAP). Certain forms of pneumonia may fall into a gray area between CAP and HAP, such as in nursing home patients who are hospitalized with pneumonia. These patients often have different organisms than those responsible for true CAP, and thus perhaps a better term for this condition is healthcare-associated pneumonia. Given that this population is not very well defined and that the organisms may well be similar to hospital-acquired pneumonia, for the purposes of this discussion, we will consider all non-CAPs as falling under the rubric of HAP. An important subset of HAP is the group of patients who are mechanically ventilated at the time that they developed pneumonia, representing the subset of patients with ventilator-associated pneumonia (VAP). The subset is important because of an attributable increase in length of stay, hospital costs, and mortality.