Comparative Respiratory Tract Microbiome Between Carbapenem-Resistant Acinetobacter baumannii Colonization and...

Area of Science:

• Microbiology
• Genomics
• Infectious Diseases

Background:

• Carbapenem-resistant Acinetobacter baumannii (CRAB) is a significant cause of ventilator-associated pneumonia (VAP) in intensive care units (ICUs).
• Distinguishing between CRAB infection and colonization is challenging, potentially leading to antibiotic overuse and resistance.
• Understanding the lower respiratory tract (LRT) microbiota offers new insights into CRAB VAP diagnosis, pathogenesis, and treatment.

Purpose of the Study:

• To investigate the role of lower respiratory tract microbiota in differentiating CRAB VAP from colonization.
• To identify microbial signatures associated with CRAB VAP.
• To provide data for improved diagnostic and therapeutic strategies for CRAB VAP.

Main Methods:

• A prospective study involving 52 ICU patients with mechanical ventilation was conducted.
• Multi-genomic analyses, including 16S rRNA amplicon sequencing, metagenomics, and whole-genome sequencing (WGS), were performed on endotracheal deep aspirates (ETA).
• Patients were categorized into CRAB VAP (CRAB-I), CRAB colonization (CRAB-C), and CRAB-negative (CRAB-N) groups.

Main Results:

• Pulmonary microbiota diversity was significantly lower in CRAB-I patients compared to CRAB-C and CRAB-N patients (Shannon index).
• Abundances of key genera differed, with Acinetobacter being most prevalent in CRAB-I.
• Metagenomics and WGS revealed higher virulence gene abundance in CRAB-I, and MLST identified ST208 and ST938 as dominant CRAB types.

Conclusions:

• Lower respiratory tract microbiota dysbiosis, characterized by increased Acinetobacter abundance and reduced bacterial interactions, is associated with CRAB VAP.
• Enrichment of virulence factors in CRAB isolates may contribute to VAP development.
• These findings suggest microbiota analysis can aid in CRAB VAP diagnosis and management.