Evaluating the Value of Defensins for Diagnosing Secondary Bacterial Infections in Influenza-Infected Patients

Area of Science:

• Infectious Diseases
• Immunology
• Genomics

Background:

• Severe pneumonia can result from influenza virus infections, often complicated by secondary bacterial infections.
• Defensins, host-expressed antimicrobial peptides, are potential biomarkers for differentiating these infections.
• Accurate diagnosis is crucial for effective treatment of complex respiratory infections.

Purpose of the Study:

• To investigate the correlation between defensin gene expression and viral/bacterial loads in severe pneumonia.
• To evaluate the diagnostic potential of defensins in distinguishing viral from bacterial pneumonia.

Main Methods:

• A longitudinal, precision-medical study of a patient with influenza A H7N9 virus-induced severe pneumonia.
• Correlation analysis (Spearman) between defensin gene expression and influenza A H7N9 viral load in blood.
• Analysis of defensin expression correlations with bacterial load.
• Validation of diagnostic potential on an independent dataset of bacterial and viral pneumonia patients.

Main Results:

• DEFA5 gene expression positively correlated with influenza A H7N9 viral load (r = 0.735, p < 0.05).
• DEFB116 and DEFB127 showed positive correlation with bacterial load; DEFB108B and DEFB114 showed negative correlation.
• Defensin expression levels achieved 93% accuracy in discriminating between bacterial and viral pneumonia in an independent cohort.

Conclusions:

• Blood defensin expression levels serve as valuable diagnostic indicators for viral and bacterial infections in pneumonia.
• Defensins offer a promising biomarker strategy for improving the diagnosis and management of severe pneumonia.