5-Fluorouracil sensitivity varies among oral micro-organisms

Area of Science:

• Microbiology
• Pharmacology
• Oral Medicine

Background:

• 5-Fluorouracil (5-FU) is a chemotherapy drug that can cause oral mucositis.
• Oral microorganisms are implicated in mucositis severity, but mechanisms are unclear.
• The antibacterial effects of 5-FU at oral cavity concentrations are unknown.

Purpose of the Study:

• To investigate the impact of physiological 5-FU concentrations on oral bacteria.
• To assess the role of dihydropyrimidine dehydrogenase (DPD) in 5-FU resistance.

Main Methods:

• Testing 5-FU concentrations (0.1-50 µM) on oral bacterial monocultures.
• Evaluating bacterial growth and viability.
• Assessing DPD activity in relation to 5-FU resistance.

Main Results:

• Oral bacteria show differential sensitivity to 5-FU.
• Some species (e.g., Klebsiella oxytoca, Streptococcus salivarius) are highly resistant.
• Other species (e.g., Lactobacillus oris, Fusobacterium nucleatum) are sensitive to low 5-FU concentrations.
• DPD was not found to be involved in 5-FU resistance.

Conclusions:

• Varied bacterial responses to 5-FU may explain oral dysbiosis and resistant organism overgrowth post-chemotherapy.
• Findings contribute to understanding 5-FU-induced oral mucositis mechanisms.