# Busulfan inhibits Pseudomonas aeruginosa growth and reduces biofilm biomass and pyocyanin production

## TL;DR

Busulfan, a cancer drug, inhibits the growth of Pseudomonas aeruginosa and reduces its harmful effects like biofilm and toxin production.

## Contribution

Busulfan's antibacterial activity and impact on P. aeruginosa virulence factors are newly demonstrated.

## Key findings

- Busulfan inhibited P. aeruginosa growth by 84% at 108 μg/mL.
- It reduced biofilm formation by 55% and pyocyanin production by 57%.
- Busulfan showed moderate synergy with gentamicin at higher concentrations.

## Abstract

Pseudomonas aeruginosa remains a serious threat in clinical settings, especially among patients who are immunocompromised, receiving chemotherapy, or in intensive care units. With the rise of antibiotic resistance, drug repurposing offers a promising alternative strategy. Busulfan, an anticancer alkylating agent that induces DNA cross-linking and cytotoxic effects in cancer cells, may exert similar effects on microorganisms, as reported for other alkylating agents.

This study evaluated the antibacterial potential of busulfan against P. aeruginosa. Initially, the antimicrobial activity of busulfan was assessed using the microdilution method, followed by investigations of key virulence factors of the PAO1 strain after treatment.

Busulfan inhibited bacterial growth in a dose-dependent manner, with 84% inhibition observed at 108 μg/mL, whereas bactericidal activity was only observed at much higher concentrations (MBC >512 and <1,024 μg/mL). Busulfan significantly reduced biofilm formation by 55%, decreased live-cell viability by 67% as observed using confocal laser scanning microscopy (CLSM), decreased pyocyanin production by 57%, and impaired iron chelation by 25%. Moreover, moderate synergy with gentamicin was observed at higher concentrations of busulfan. However, treatment with 108 μg/mL busulfan showed no effect on PAO1 hemolysis or motility.

Overall, busulfan demonstrates antimicrobial activity against P. aeruginosa, particularly through its effects on virulence factors. These preliminary results support the potential value of busulfan for repurposing, although further studies are needed to clarify its mechanism and therapeutic relevance.