Commonest cause of lung abscess is
Lung abscess Lung abscess refers to a microbial infection of the lung that results in necrosis of the pulmonary parenchyma MC cause of primary lung abscess : Anaerobic bacteria Etiology of anaerobic lung abscess : Aspiration Routes of infection Aspiration of organisms that colonize oropharynx (MC) Inhalation of infection or aerosols Hematogenous dissemination from extrapulmonary site Direct inoculation (as in tracheal intubation or stab wounds) Contiguous spread from an adjacent site of infection Ref: schwaz's principle of surgery 10th edition Pgno : 650
Aspiration
Hematogenous spread from distant date
Direct contact
Lymphatic spread
Cardio thoracic surgery  