Hospital-acquired pneumonia:: etiologic considerations

The development of pneumonia requires the pathogen to reach the alveoli and the host defenses to be overwhelmed, either by microorganism virulence or by inoculum size. Different microorganisms can be found depending on the onset time of pneumonia and on the local pattern variation encountered between different institutions and countries. A very important, unresolved issue is the definition of early and late-onset pneumonia. It still remains uncertain from the literature whether the given threshold refers to the number of days in hospital or to the number of days following intubation. Noninvasive ventilation is demonstrating that the term "ventilator-associated pneumonia" is perhaps inaccurate and should be referred to as "intubation-associated pneumonia."