Etiology of pulmonary fungal infection

Pulmonary fungal infection is allergic, purulent inflammatory reaction or chronic granuloma caused by different pathogens. Pathogens causing fungal infection in lower respiratory tract can be divided into pathogenic fungi and conditional pathogenic fungi: ① Pathogenic fungi are primary pathogens, which often lead to primary fungal infection and can invade hosts with normal immune function, and patients with immunodeficiency are prone to systemic transmission. Pathogenic fungi mainly include histoplasma, coccidiosis, parasporidium, blastomyces dermatitidis, tinea pedis and sporotrichosis. ② Conditional pathogenic fungi or conditional pathogenic fungi, such as Candida, Aspergillus, Cryptococcus, Mucor and Penicillium, Rhizopus, Plough, Fusarium and Pneumocystis. Most of these fungi are saprophytic bacteria, and their pathogenicity to human body is weak. However, when the host has susceptible factors, it will lead to deep fungal infection, but cases without clear host factors can also be seen in clinic. Clinical common fungal pathogens include Candida, Aspergillus, Mucor, Cryptococcus, Histoplasma and so on. In recent years, with the aging population, organ transplantation, tumor radiotherapy and chemotherapy, hematopoietic stem cell transplantation, the application of extended-spectrum antibiotics, the application of corticosteroids and various catheter interventional treatments, the incidence of pulmonary fungal infection has increased year by year.