Rifampicin as monotherapy for infections caused by Staphylococcus aureus: considerations for not applying...

Area of Science:

• Clinical microbiology and infectious diseases.
• Antimicrobial resistance.
• Pharmacology and therapeutics.

Background:

• The European Committee on Antimicrobial Susceptibility Testing (EUCAST) uses 'breakpoints in brackets' to indicate agents not recommended for monotherapy.
• Rifampicin monotherapy is seldom used for Staphylococcus aureus infections, but its breakpoints are not currently bracketed by EUCAST.
• Emergent resistance to rifampicin is common in Staphylococcus aureus.

Purpose of the Study:

• To evaluate the appropriateness of unbracketed rifampicin breakpoints for Staphylococcus aureus infections.
• To determine if frequent emergent resistance meets EUCAST criteria for bracketing an antimicrobial agent.

Main Methods:

• Review of EUCAST guidance on breakpoint bracketing criteria.
• Analysis of the clinical implications of emergent rifampicin resistance in Staphylococcus aureus.
• Comparison of resistance patterns with EUCAST's definition of inherent monotherapy ineffectiveness.

Main Results:

• Frequent emergent resistance to rifampicin often limits its use as monotherapy for Staphylococcus aureus.
• Emergent resistance does not fulfill EUCAST's core criterion for bracketing, which requires an agent to be inherently ineffective as monotherapy.
• Rifampicin's clinical utility is impacted by resistance, but it is not inherently ineffective in monotherapy.

Conclusions:

• The current EUCAST breakpoint status for rifampicin regarding Staphylococcus aureus infections warrants consideration.
• While resistance is frequent, it does not meet the specific EUCAST criterion for bracketing breakpoints.
• Further evaluation may be needed to align breakpoint guidance with clinical resistance patterns.