Reversible neutrophil defect in patients with bacterial endocarditis

Area of Science:

• Immunology
• Infectious Diseases
• Hematology

Background:

• Neutrophilic polymorphonuclear leukocytes (PMN) are crucial for combating bacterial infections.
• Bacterial endocarditis (BE) is a severe infection affecting heart valves.
• The function of PMN in BE patients requires further investigation.

Purpose of the Study:

• To compare the bactericidal capacity of PMN from patients with bacterial endocarditis (BE), other acute bacterial infections (ABI), and normal subjects (NS).
• To investigate the nature of neutrophil dysfunction in BE patients.

Main Methods:

• A novel technique was employed to assess PMN bactericidal activity against Staphylococcus aureus.
• Five increasing bacteria-to-neutrophil ratios were used, ranging from 1.25 to 100.
• Neutrophil function was assessed before and after antibiotic treatment in BE patients.

Main Results:

• PMN from NS and ABI patients exhibited similar, reproducible bactericidal abilities.
• PMN from untreated BE patients showed significantly depressed bactericidal activity, especially at high bacterial loads.
• The defect in BE neutrophils was related to intracellular killing, not bacterial uptake or glucose oxidation.

Conclusions:

• Neutrophil dysfunction in BE is an acquired defect, likely due to the infectious process.
• Antibiotic treatment rapidly restored normal PMN bactericidal function in BE patients.
• The findings highlight an intracellular killing defect in neutrophils during active bacterial endocarditis.