Aetiology and pathogenesis

Infection and necrotic tissue are critical to the development of a lung abscess.

The organisms most commonly involved are aerobic and anaerobic streptococci, Staphylococcus aureus and a variety of different gram-negative organisms. (1) Anaerobes normally found in the oral cavity occur exclusively in 60% of cases - including Bacteroides, Fusobacterium, and Peptococcus.

Organisms may be introduced through: (2)

• aspiration
• antecedent primary bacterial infection
• septic emboli
• neoplasia
• other factors

Primary cryptogenic lung abscesses describe those for which no cause can be ascertained.

Reference

1. Takayanagi N, Kagiyama N, Ishiguro T, et al. Etiology and outcome of community-acquired lung abscess. Respiration. 2010;80(2):98-105.
2. Mwandumba HC, Beeching NJ. Pyogenic lung infections: factors for predicting clinical outcome of lung abscess and thoracic empyema. Curr Opin Pulm Med. 2000 May;6(3):234-9.