Pathogenic Mechanisms and Resistance Strategies of Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic pathogen responsible for high morbidity and mortality in healthcare settings worldwide. Its success stems from a diverse array of virulence determinants and formidable resistance strategies that are often co-expressed. Surface structures such as chaperone–usher pathway pili and outer membrane proteins mediate adhesion to host tissues and medical devices, enabling the establishment of biofilms. Within these biofilms, cells are protected from host defences and antibiotics. Iron scavenging via multiple siderophores, notably acinetobactin, is essential for survival in iron-restricted host environments and underpins systemic invasion. A. baumannii also deploys type VI secretion systems to compete with rival microbes and secure ecological niches. Genetic plasticity is a hallmark of this species: horizontal gene transfer, facilitated by natural competence and modulated by epigenetic methylation patterns, promotes acquisition of resistance genes. Enzymatic mechanisms such as carbapenemases, combined with efflux pumps and alterations in membrane permeability, confer resistance to virtually all classes of antibiotics. The convergence of virulence and resistance traits has rendered many A. baumannii strains extensively drug-resistant, posing a critical challenge to global public health. Recent advances have elucidated how interspecies interactions and environmental reservoirs contribute to its persistence and dissemination, informing strategies for novel therapeutics and infection control.

Research from Nature Portfolio

Recent studies have revealed syntrophic interactions between A. baumannii and co-isolated species in polymicrobial infections. Metabolite cross-feeding allows A. baumannii to utilise fermentation by-products from Klebsiella pneumoniae, while reciprocal protection enhances tolerance to cephalosporins. These findings underscore the complexity of microbial communities in clinical infections, where metabolic cooperation can potentiate both virulence and antibiotic resistance, informing the design of targeted therapies that disrupt such interactions.

Pathogenic Mechanisms and Resistance Strategies of Acinetobacter baumannii publication trend

The graph below shows the total number of articles in pathogenic mechanisms and resistance strategies of acinetobacter baumannii across all publications each year (not limited to Nature Index journals).

Technical terms

Horizontal gene transfer (HGT): the non-vertical exchange of genetic material between organisms, aiding the spread of resistance genes.

Siderophore: a high-affinity iron chelator secreted by bacteria to scavenge iron from the host environment.

Chaperone–usher pathway (CUP) pili: filamentous surface appendages assembled via the chaperone–usher system that mediate adhesion and biofilm formation.

Type VI secretion system (T6SS): a contractile nanomachine used by bacteria to inject effector proteins into neighbouring cells, facilitating competition.

Restriction–modification (RM) system: a bacterial defence mechanism comprising restriction enzymes that degrade foreign DNA and methyltransferases that protect host DNA.

Minimum inhibitory concentration (MIC): the lowest concentration of an antimicrobial that prevents visible growth of a microorganism in vitro.

Methylome: the complete set of DNA methylation marks in a cell, influencing gene regulation and genome stability.

References

1. Cross-protection and cross-feeding between Klebsiella pneumoniae and Acinetobacter baumannii promotes their co-existence. Nature Communications (2023).
2. Acinetobacter baumannii can use multiple siderophores for iron acquisition, but only acinetobactin is required for virulence. PLOS Pathogens (2020).
3. Acinetobacter baumannii Utilizes a Type VI Secretion System for Bacterial Competition. PLOS ONE (2013).
4. DNA modifications impact natural transformation of Acinetobacter baumannii. Nucleic Acids Research (2023).
5. Carbapenemases: Transforming Acinetobacter baumannii into a Yet More Dangerous Menace. Biomolecules (2020).
6. Tracing clinically-relevant antimicrobial resistances in Acinetobacter baumannii-calcoaceticus complex across diverse environments: A study spanning clinical, livestock, and wastewater treatment settings. Environment International (2024).
7. Structure–function correlates of fibrinogen binding by Acinetobacter adhesins critical in catheter-associated urinary tract infections. Proceedings of the National Academy of Sciences of the United States of America (2023).