Lung abscess is seen in all except:
a. Lung abscess is defined as pulmonary parenchymal necrosis and cavitation resulting from infection.
b. The development of a lung abscess implies a high microorganism burden as well as inadequate microbial clearance from the airways.
c. Aspiration is the most common cause; factors that portend an increased risk of aspiration include esophageal dysmotility, seizure disorders, and neurologic conditions causing bulbar dysfunction. Other predisposing conditions for lung abscess include periodontal disease and alcoholism.
d. Anaerobic bacteria are the most common causative organisms for lung abscess.
e. Aerobic or facultative bacteria such as S. aureus, Klebsiella pneumoniae, Nocardia sp., and gram-negative organisms, as well as nonbacterial pathogens like fungi and parasites, may also cause abscess formation. In the immunocompromised host, aerobic bacteria and opportunistic pathogens may predominate.