This research is to evaluate the effect of different antibiotics (Moxifloxacin Hydrochloride and Sodium Chloride Injection vs. β-lactam antibiotics for injection +/- Azithromycin for Injection) on the early deterioration or progression (<72 h of treatment) of community acquired pneumonia and to study the effect of the early deterioration or progression on the prognosis of community acquired pneumonia.

Inclusion Criteria:

1. Age>=18y.
2. Diagnosed with CAP.
3. Need hospitalization.
4. Receive Moxifloxacin Hydrochloride and Sodium Chloride Injection or β-lactam antibiotics for injection +/- Azithromycin for Injection as initial treatment.
5. Signed informed consent form.

Exclusion Criteria:

Patients who meet any of the following criteria will not be included in the study:

1. Pneumonia is aquired more than 48h after admission or the patient was admitted to hospital within 30 days prior to admission.
2. Start antibiotic treatment before admission.
3. Gestational period or suckling period.
4. Admitted to ICU.
5. Immunocompromised patients.
6. Pneumonia is the terminal event of a serious disease.
7. Tuberculosis, lung cancer, non-infectious interstitial lung disease, pulmonary edema, atelectasis, pulmonary embolism, pulmanory eosinophilia, pulmonary vasculitis.
8. Allergic to the antibiotics of the study.

All patients in the 17 centers of the study who meet the inclusion and exclusion criteria will be included.