In this article, we will discuss about Etiology and Pathogenesis of Lung abscess. So, let’s get started.
Lung abscesses usually characterized as primary or secondary. Primary Lung abscesses are principally caused by anaerobic bacteria and usually arise from aspiration without any underlying pulmonary or systemic disease or condition. Secondary lung abscesses arise in the presence of any underlying pulmonary or systemic disease or condition such as HIV, cancer, etc.
Lung abscesses can also be characterized as acute (less than 4-6 weeks) or chronic.
The development of primary lung abscesses occurs when anaerobic bacteria present in the gingival crevices are aspirated into the lung parenchyma. Patients are unable to clear out the bacterial load. Patients initially develops pneumonitis and then over a period of 7-14 days, the anaerobic bacteria produce parenchymal necrosis. Anaerobic bacteria produce more extensive tissue necrosis in polymicrobial infections (multiple bacterias with high virulence factors produce significant destruction of the tissues).
The development of secondary lung abscesses depends upon the predisposing factor such as in case of malignancy the obstructing lesion prevents clearance of oropharyngeal secretion which eventually leads to abscess development. In the case of a systemic condition such as immunosuppression post bone marrow transplantation or organ transplantation, the host defense mechanism becomes impaired leading to increased susceptibility to pathogens (opportunistic infection) and abscess development.
Lung abscesses also arise from septic emboli, either in tricuspid valve endocarditis or in Lemierre’s syndrome in which an infection arises in the pharynx and then it spreads to the neck and carotid sheath causing septic thrombophlebitis
Reference Source: Harrison Principle of Internal Medicine