1. Pathogenesis and epidemiology Actinomyces is a genus of parthenogenic anaerobic bacteria, Gram stain positive, belonging to the order Actinomyces. Often parasitic in human or animal oral caries, tonsil crypt, upper respiratory tract, gastrointestinal tract and urogenital tract (female external genitalia). The causative organism is mostly Actinomyces yedoensis (Israel), other rare species include Actinomyces nei, Actinomyces caries, etc. The incidence of pulmonary actinomycosis is extremely low, with an annual incidence of about 1/300,000, but it accounts for 15% of fatal pulmonary disease. It can occur in all age groups, with the highest incidence in young adults and a male to female ratio of about 3:1. The incidence of combined pulmonary actinomycosis increases significantly when patients have respiratory disorders such as emphysema, chronic bronchitis and bronchiectasis (even in the early and mild stages). Alcohol abuse, poor oral hygiene, and pre-existing oral diseases are risk factors for pulmonary actinomycosis. With the improvement of people’s quality of life, hygiene conditions and treatment methods, the rate of actinomycosis infection has been significantly reduced. 2, pathogenesis Pulmonary actinomycosis is mostly accompanied by aspiration of oropharyngeal secretions caused by small bronchial aspiration of pulmonary atelectasis, pneumonia, direct source of infection can come from the cranial, cervical or abdominal cavity infection foci. In the absence of antibiotics, the main pathogenic route was the spread of abdominal infection through the diaphragm to the thoracic cavity causing pulmonary actinomycosis; with the widespread use of antibiotics, these routes of infection have been greatly reduced. Histopathology showed that acute inflammation was seen in the focal tissue surrounded by fibroblastic granulation tissue, and characteristic “sulfur granules” were seen. The “sulfur granules” consisted of actinomycetes, macrophages, epithelial-like cells, multinucleated giant cells, eosinophils and plasma cells and the outer layer of fibrin wrapped, yellow, the core part is the entanglement of mycelium, mycelium radially arranged in all directions, forming a daisy-like, mycelium ends with gelatinous material, forming a sheath surrounded, inflated rod-shaped, refractive Strong. 3, clinical features and diagnosis Most of the disease manifests as chronic progressive disease, with low or irregular fever, cough, coughing blood, coughing thick mucus sputum, chest pain, weight loss and other symptoms, similar to malignant tumor or tuberculosis. Almost half of the patients with pulmonary actinomycosis have 2 or more pulmonary cavities visible on chest X-ray, but there is no sulfur particle formation in the tissues of visceral injury caused by tumor or tuberculosis, so they can be differentiated by pathological histological examination. When the lesion involves the lung and adjacent pleura causing pleural effusion, abscess pleura, pleural hypertrophy and adjacent rib damage, high alert should be given to pulmonary actinomycete infection. There are no specific symptoms and signs in the early stage, and the early diagnosis rate is only less than 7%. Actinomyces is an anaerobic bacterium, which is difficult to detect by general sputum culture, and it is a putrefactive bacterium that can live in the necrotic tissue of the body, which is occasionally detected in the sputum of cancer patients, making it more likely to be misdiagnosed or missed. Clinically, lesions can be obtained by fiberoptic bronchoscopy under X-ray tomography and ultrasound guidance for diagnosis. Specimens should be cultured in an anaerobic environment for 2-4 weeks until division and proliferation, and semi-selective media can accelerate the rate of division and proliferation. Immunofluorescence can distinguish sulfur particles contained in formalin-fixed tissue specimens, so the diagnosis should be confirmed by a combination of clinical and pathological examination: positive bacterial culture, pathological examination to determine the discovery of sulfur particles combined with clinical symptoms, signs and the effectiveness of antibiotic treatment. Tuberculosis, mycobacterial infection, cryptococcal infection, anaerobic bacterial infection, bronchial lung cancer, lymphoma, mesothelioma, pulmonary infarction and other diseases are the differential diagnosis of pulmonary actinomycosis. 4, treatment Pulmonary actinomycosis is a lethal infectious disease, early treatment cure rate up to 90%. Through a large number of randomized controlled trials and clinical observations confirmed that penicillin is the antibiotic of choice for the treatment of actinomycosis, but the treatment plan should be individualized, and the recommended dose is generally: 18-24 million units of penicillin given intravenously every day for 2-6 weeks, and then continue to give penicillin or amoxicillin maintenance treatment for 6-12 months. Penicillin allergy can be replaced with tetracycline replacement therapy, pregnant women can switch to erythromycin, and chloramphenicol and clindamycin are also options. Surgical treatment is still controversial. In case of existing complications such as abscess chest, sinus tract, lung abscess, etc., antibiotic anti-infective treatment alone is not effective, and surgical drainage of abscess and abscess chest along with removal of sinus tract is required, and antibiotics are given immediately after surgery to prevent the spread of infection in the operated area. At present, percutaneous puncture and drainage combined with medical medication is a treatment modality endorsed by most clinicians. Kinnear and Macfarlare reported 19 patients with chest actinomycosis cured with antibiotics for a mean of 6 weeks (minimum of 1 week and maximum of 6 months), 7 of whom were treated with surgery at the same time. The intravenous administration was successful in 16 patients, but short-term therapy cannot be used in cases with large chest or abdominal infections (unless the infection is removed). Adequate antibiotics must be administered postoperatively, otherwise serious complications such as bronchopleural fistula or pustule can occur. There is no evidence that pulmonary actinomycete infections are directly related to organismal immunocompromise, but statistically disseminated cases of each are seen in immunocompromised or deficient patients with HIV infection, during chemotherapy for acute leukemia, after lung or (and) kidney transplantation and during hormonal therapy.