Forging New Antibiotic Combinations under Iron-Limiting Conditions

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Pseudomonas aeruginosa and Acinetobacter baumannii are significant multidrug-resistant nosocomial pathogens.
• Previous work demonstrated thiostrepton (TS) synergy with deferasirox (DSX) against these bacteria.
• Resistance to TS-DSX combinations necessitates exploring alternative synergistic agents.

Purpose of the Study:

• To identify novel compounds that synergize with thiostrepton (TS) against resistant strains of P. aeruginosa and A. baumannii.
• To investigate the mechanism of synergy, specifically the role of iron sequestration.
• To evaluate the efficacy of triple drug combinations for enhanced antimicrobial activity.

Main Methods:

• Literature review to select 14 iron-chelating compounds and one iron analogue.
• Synergy testing of selected compounds with TS against P. aeruginosa and A. baumannii clinical isolates.
• Spectrophotometric analysis and Chrome Azurol S agar assay to confirm iron sequestration mechanism.

Main Results:

• Doxycycline (DOXY), ciclopirox olamine (CO), tropolone (TRO), clioquinol (CLI), and gallium nitrate (GN) showed synergy with TS.
• Combinations of TS with these chelators exhibited bactericidal activity, unlike the bacteriostatic individual compounds.
• A triple combination of TS, DSX, and DOXY demonstrated the most potent activity; tailored triple combinations addressed resistant isolates.

Conclusions:

• A diverse range of iron chelators can potentiate TS activity by sequestering iron.
• These synergistic combinations, especially triple therapies, offer a promising strategy to overcome multidrug resistance in P. aeruginosa and A. baumannii.
• The findings enable the development of tailored antimicrobial regimens for challenging clinical isolates.