A hypervirulent Acinetobacter baumannii strain has robust anti-phagocytosis ability

• Published in: BMC microbiology 2024-04, Vol.24 (1), p.106-106, Article 106
• Main Authors: Li, Yan, Jv, Mohan, Zhuang, Yuan, Zhao, Xu, Hu, Xiaoxiong
• Format: Article
• Language: English
• Subjects: Acinetobacter baumannii; Analysis; Animal tissues; Animals; Anti-phagocytosis; Antimicrobial agents; Bacteria; Blood; Body temperature; Care and treatment; Chemokines; Community-Acquired Infections - microbiology; Community-acquired pneumonia; Computed tomography; Cough; Cross infection; Cytokines; Diagnosis; DNA sequencing; Edema; Gene sequencing; Genes; Genetic aspects; Genomes; Hospitals; Humans; Hypervirulent; Immunogenicity; Inflammation; Inoculation; Liver; Lung - microbiology; Lungs; Macrophages; Male; Males; Medical imaging; Mice; Microbiological strains; Middle Aged; Mortality; Neutrophils; Nosocomial infection; Nosocomial infections; Nucleotide sequencing; Pathogenesis; Pathogenicity; Pathogens; Pathology; Phagocytes; Phagocytosis; Pneumonia; Pneumonia, Bacterial - microbiology; Prevention; Risk factors; Robustness; Sequencing; Spleen; Sputum; Tumor necrosis factor-α; Type VI secretion system; Virulence; Virulence (Microbiology); Whole genome sequencing
• ISSN: 1471-2180; 1471-2180
• DOI: 10.1186/s12866-024-03264-x

Acinetobacter baumannii (A. baumannii) is associated with both hospital-acquired infections (HAP) and community-acquired pneumonia (CAP). In this study, we present a novel CAP-associated A. baumannii (CAP-AB) strain causing severe pneumonia in an afore healthy male patient without underlying conditions. Subsequently, we investigated the pathogenicity and immunogenicity of this CAP-AB strain using a mice pneumonia model. A 58-year-old male patient with no underlying conditions experienced worsening symptoms of a productive cough, sputum, and fever that developed acutely, in just 24 h. The diagnosis was severe community-acquired pneumonia (CAP) and type-1 respiratory failure. An A. baumannii strain was isolated from his sputum and blood cultures. To gain a deeper understanding of the rapid progression of its pathology, we utilized the CAP-associated A. baumannii strain YC128, a previously obtained hospital-acquired pneumonia A. baumannii (HAP-AB) strain YC156, and a highly virulent A. baumannii control strain LAC-4 to construct a mouse pneumonia model, and subsequently compared the mortality rate of the three groups. Following inoculation with 10  CFU of A. baumannii, the mortality rate for the YC128, LAC-4, and YC156 groups was 60% (6/10), 30% (3/10), and 0%, respectively. The bacterial burden within the pulmonary, liver, and spleen tissues of mice in the YC128 group was significantly higher than that of the YC156 group, and slightly higher than that of the LAC-4 group. Pathological analysis of lung tissue using HE-staining revealed that the inflammatory pathological changes in mice from the YC128 group were significantly more severe than those in the YC156 group. Additionally, CT scan images displayed more pronounced inflammation in the lungs of mice from the YC128 group compared to the YC156 group. Local levels of cytokines/chemokines such as IL-1β, IL-6, TNF-α, and CXCL1 were assessed via RT-qPCR in lung tissues. In comparison with the YC156 strain, the highly virulent YC128 strain induced the expression of proinflammatory cytokines more rapidly and severely. Furthermore, we examined the in vitro anti-phagocytosis ability of YC128 and YC156 strains against mice peritoneal macrophages, revealing that the highly virulent YC128 isolate displayed greater resistance to macrophage uptake in contrast to YC156. Results from Whole Genome Sequencing (WGS) indicated that YC128 harbored a complete type VI secretion system (T6SS) gene cluster, while YC156 lacked the