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CsrA Supports both Environmental Persistence and Host-Associated Growth of Acinetobacter baumannii
John M Farrow1, Greg Wells1, Samantha Palethorpe1
1Department of Microbiology and Immunology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, USA.
Abstract:
Acinetobacter baumannii is an opportunistic and frequently multidrug-resistant Gram-negative bacterial pathogen that primarily infects critically ill individuals. Indirect transmission from patient to patient in hospitals can drive infections, supported by this organism's abilities to persist on dry surfaces and rapidly colonize susceptible individuals. To investigate how A. baumannii survives on surfaces, we cultured A. baumannii in liquid media for several days and then analyzed isolates that lost the ability to survive drying. One of these isolates carried a mutation that affected the gene encoding the carbon storage regulator CsrA. As we began to examine the role of CsrA in A. baumannii, we observed that the growth of ΔcsrA mutant strains was inhibited in the presence of amino acids. The ΔcsrA mutant strains had a reduced ability to survive drying and to form biofilms but an improved ability to tolerate increased osmolarity compared with the wild type. We also examined the importance of CsrA for A. baumannii virulence. The ΔcsrA mutant strains had a greatly reduced ability to kill Galleria mellonella larvae, could not replicate in G. mellonella hemolymph, and also had a growth defect in human serum. Together, these results show that CsrA is essential for the growth of A. baumannii on host-derived substrates and is involved in desiccation tolerance, implying that CsrA controls key functions involved in the transmission of A. baumannii in hospitals.
Insights
The carbon storage regulator CsrA is essential for Acinetobacter baumannii survival on surfaces and during infection. This finding offers insights into controlling the spread of this multidrug-resistant pathogen in hospitals.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Acinetobacter baumannii is a multidrug-resistant pathogen causing hospital-acquired infections.
- Its ability to persist on surfaces facilitates patient-to-patient transmission.
- Understanding survival mechanisms is crucial for infection control.
Purpose of the Study:
- To investigate the role of the carbon storage regulator CsrA in Acinetobacter baumannii survival and virulence.
- To identify factors contributing to Acinetobacter baumannii's ability to persist on surfaces.
Main Methods:
- Culturing Acinetobacter baumannii and analyzing isolates with impaired desiccation tolerance.
- Genetic analysis of a mutation affecting the CsrA gene.
- Phenotypic characterization of CsrA deletion mutants (ΔcsrA) regarding desiccation survival, biofilm formation, osmolarity tolerance, and virulence in Galleria mellonella and human serum.
Main Results:
- A ΔcsrA mutant exhibited reduced survival upon drying and impaired biofilm formation.
- The ΔcsrA mutant showed increased tolerance to high osmolarity.
- Virulence assays revealed significantly reduced killing of Galleria mellonella larvae and impaired growth in hemolymph and human serum for the ΔcsrA mutant.
Conclusions:
- CsrA is critical for Acinetobacter baumannii desiccation tolerance and virulence.
- CsrA regulates essential functions for pathogen survival on host-derived substrates.
- Targeting CsrA may represent a strategy to control Acinetobacter baumannii transmission in healthcare settings.
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