The pathogens of lung abscess are often colonizing bacteria of the upper respiratory tract and oral cavity, including aerobic, anaerobic and parthenogenic anaerobes. 90% of patients have anaerobic infections in combination, and the more virulent anaerobes can cause disease alone in some patients. What causes can lead to lung abscess? According to the route of infection, lung abscess can be divided into the following types: 1. Inhaled lung abscess: when there is impaired consciousness, such as in anesthesia, intoxication, drug overdose, cerebrovascular accident, or due to cold, extreme fatigue and other triggers, the systemic immunity and airway defense clearance function is reduced, and the inhaled pathogenic bacteria can cause disease. The pathogens are mostly anaerobic bacteria. The right lung is more likely to be involved. In supine position, it is more likely to occur in the posterior segment of the upper lobe or the dorsal segment of the lower lobe, and in sitting position, it is more likely to occur in the posterior basal segment of the lower lobe. 2.Secondary lung abscess: secondary infections such as certain bacterial pneumonia (Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae), bronchiectasis, bronchial cysts, bronchopulmonary carcinoma, tuberculosis cavity, etc. can lead to secondary lung abscess. 3.Hematogenous lung abscess: Infection poisoning caused by skin trauma infection, boil, carbuncle, etc., the bacteriophage spreads to the lung through bloodstream, causing small vessel embolism, inflammation and necrosis and forming lung abscess. Staphylococcus aureus is the common causative organism.