May be acquired from diverse environmental sources (e.g. tap water).
Patients with bronchiectasis may be colonized (e.g. CF patients).
Must distinguish colonization from clinically significant infection.
Most common reason for positive culture is colonization of the respiratory tract.
Most common true infections:
Blood stream infection (usually from vascular catheter)
Pneumonia
Other rare manifestations:
Endocarditis
Sinusitis
Cellulitis
May require contact precautions.
True pneumonia more likely in ICU and oncology patients, and in those of advanced age and after/during treatment with broad spectrum antimicrobial use.
