A basic fact about pneumonia is that physicians recommend treatment without knowing the specific pathogen.This is because we have no reliable tests that will identify the culprit bug quickly and accurately.We have to decide on treatment based on what are believed to be the likely etiological agents in a given clinical situation. A scheme that has worked out fairly well is to consider where the infection began,namely in or out of the hospital because different sets of infectious agents are likely to be involved based on that simple dichotomy. So that we talk about community acquired pneumonia (CAP) and nosocomial or hospital acquired pneumonia(NP) and base empirical treatment accordingly.It is also useful to split out those patients who acquire pneumonia while receiving mechanical ventilation (VAP) or ventilator acquired pneumonia because certain bacteria are likely to be involved.
A large data base review by Kollef et al in the December 2005 issue of Chest argues for also splitting off from CAP those patients designated as having "health care associated pneumonia" (HCAP).This designation applies to patients who have been in contact with the health care environment or have been recently hospitalized. It includes therapy in a dialysis center,a nursing home or extended care facility, patients receiving home infusion therapy or home wound care. Kollef's data indicate that patients in these categories are likely to be infected with bacteria that would not be typically covered by the usual antibiotic regimens chosen for empirical treatment of CAP. The data indicate that HCAP is more like NP that it is CAP.
The recent guidelines from the American Thoracic Society and the Infectious disease Society of America for the treatment of NP include patients with HCAP in their nosocomial pneumonia recommendations. Basically this mean that HCAP patients be treated for potential multidrug resistant pathogens including MRSA (methicillin resistant staph. aureus) and resistant gram negative bacteria. It has been my experience that generally physicians are treating nursing home patients with pneumonia with coverage for those two possibilities already but the HCAP category will likely be useful to alert doctors to other non-hospitalized patients who need an antibiotic combo different from the usual garden variety CAP.