Through a prospective randomized controlled trial, we systematically evaluate the effects of Yiqi Huoxue Jiedu Formula combined with bacteriophage therapy on the bacterial clearance rate, disease improvement rate and mortality rate in patients with severe pneumonia caused by drug-resistant bacteria, so as to clarify its clinical transformation value.

Inclusion Criteria:

• Patients who meet the diagnostic criteria for severe pneumonia caused by drug-resistant Gram-negative bacilli and conform to the TCM syndrome differentiation of Qi deficiency, toxin accumulation and blood stasis syndrome; patients confirmed by rapid on-site microbiological evaluation (M-ROSE), clinical microbial culture and drug susceptibility testing (based on the drug susceptibility test results of our hospital or other Grade A tertiary hospitals) to be infected with multidrug-resistant Klebsiella pneumoniae, Acinetobacter baumannii or Pseudomonas aeruginosa; aged 18 to 85 years old; patients or their family members agree to cooperate with the collection of upper and lower respiratory tract specimens, consent to bronchoscopy plus bronchoalveolar lavage, and agree to receive nebulized inhalation of bacteriophage therapy; patients or their family members have fully read, understood and signed the informed consent form.

Exclusion Criteria:

• Women who are pregnant or lactating; patients with immunodeficiency; patients receiving immunosuppressive therapy or suffering from immunodeficiency diseases; patients who have received mechanical ventilation for more than 60 days prior to enrollment; patients with active pulmonary tuberculosis, lung abscess, or Grade D chronic obstructive pulmonary disease (COPD); patients with incomplete sampling or clinical data; patients with known allergies to bacteriophage products or the components of Yiqi Huoxue Jiedu Formula; patients judged by the researchers as unsuitable for participation in this study.