Staphylococcus aureus α-Toxin Effect on Acinetobacter baumannii Behavior

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Polymicrobial infections present significant treatment challenges, contributing to morbidity and mortality.
• Gram-negative bacteria can exploit Staphylococcus aureus alpha-toxin effects on host defenses for proliferation.
• Previous studies suggest S. aureus influences co-infecting pathogen behavior.

Purpose of the Study:

• To investigate the impact of Staphylococcus aureus secreted molecules on Acinetobacter baumannii behavior.
• To elucidate the mechanisms by which S. aureus influences A. baumannii motility, biofilm formation, and antibiotic resistance.

Main Methods:

• Phenotypic analysis of A. baumannii motility and biofilm formation upon exposure to S. aureus cell-free conditioned media (CFCM).
• Hemolytic activity assays.
• Transcriptomic analysis (RNA-seq) of A. baumannii exposed to S. aureus CFCM.

Main Results:

• S. aureus CFCM differentially affected A. baumannii motility; motility decreased with USA300 and LS1 CFCM but increased with USA300 Δhla and LS1 ΔagrA CFCM.
• A. baumannii exhibited increased biofilm formation and tetracycline resistance in the presence of S. aureus USA300 CFCM.
• Transcriptomic analysis revealed 463 differentially expressed genes in A. baumannii, related to biofilm, virulence, and antibiotic susceptibility.

Conclusions:

• Acinetobacter baumannii can sense and respond to molecules secreted by Staphylococcus aureus.
• These findings highlight inter-species communication in polymicrobial environments and its impact on bacterial virulence and resistance.