Characterization of the Diversity in Host Range of an Extensively Drug-Resistant (XDR) Type IV Secretion...

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• Antimicrobial resistance is a major global health threat, with multidrug-resistant Acinetobacter baumannii identified as a priority pathogen.
• The spread of antibiotic resistance, virulence, and biofilm formation genes in bacteria is often mediated by plasmid conjugation.
• Understanding the mechanisms of Acinetobacter baumannii pathogenesis and gene transfer is crucial for combating infections.

Purpose of the Study:

• To investigate the host range diversity for a representative Type IV Secretion System (T4SS)-encoding plasmid from an extensively drug-resistant (XDR) A. baumannii strain.
• To determine if this XDR plasmid can be transferred to a broader array of Acinetobacter strains, including non-baumannii species.
• To provide insights into the role of this plasmid family in the adaptation and evolution of Acinetobacter species.

Main Methods:

• Conjugative transfer experiments were performed using A. baumannii AB5075-UW (harboring the XDR plasmid p1AB5075) as the donor strain.
• Recipient strains included genetically divergent A. baumannii strains and various non-baumannii Acinetobacter species from both clinical and environmental sources.
• The study utilized previously characterized Acinetobacter strains, including those within and outside the Acinetobacter calcoaceticus-baumannii (ACB) complex.

Main Results:

• The XDR plasmid p1AB5075 successfully transferred from A. baumannii AB5075-UW to genetically diverse A. baumannii strains.
• Conjugation was also demonstrated to non-baumannii Acinetobacter species, both within and outside the ACB complex.
• Successful plasmid recipients were identified across a range of clinical and environmental Acinetobacter isolates, indicating a broad host range.

Conclusions:

• The studied XDR plasmid exhibits a wide host range, capable of conjugating into diverse Acinetobacter species beyond its original host.
• This broad transmissibility suggests that T4SS-encoding plasmids play a significant role in the genetic exchange and adaptation of Acinetobacter populations.
• Findings emphasize the importance of these plasmids as mobile genetic elements in the evolution of multidrug resistance and pathogen adaptation, informing future surveillance efforts.