The lung bacterial microbiome in community-acquired and nosocomial pneumonia

Pneumonia has long been regarded as a disease with a relatively simple pathogenesis: a pathogen enters the LRT and starts growing in an otherwise sterile environment. With new insights into the pulmonary microbiome, pneumonia could be defined in ecological terms as “the acute loss of biodiversity due to the overgrowth of a single or several pathogenic micro-organisms causing lung inflammation and damage”. Understanding the ecological perspective is important when dealing with pneumonia patients with pre-existing problems; underlying colonisation can frequently be detected by traditional microbiological methods, and more subtle aberrations in the microbiome may be important, especially in immunocompromised patients and in those with chronic pulmonary diseases. Intubation and mechanical ventilation result in a rapid change in the pulmonary microbiome, and these changes are associated with ventilator-associated pneumonia.