Occurrence and new mutations involved in rifampicin-resistant Propionibacterium acnes strains isolated from biofilm or device-related infections

• rpoB gene mutations in clinical strains of Propionibacterium acnes lead to rifampicin resistance.
• Mutations were found in both clusters I and II.
• High-level rifampicin resistance occurred in clinical strains of P. acnes.
• Mutation at position 442 constitutes a hot spot.
• Susceptibility testing is clearly important in deep or biofilm-related infections.

We described for the first time the amino acid substitutions conferring rifampicin resistance in eight Propionibacterium acnes strains isolated from patients with biofilm or device-related infections. We identified different mutations in cluster I and one mutation, never reported, in cluster II of the rpoB gene (I480V) associated with the most frequent one in cluster I (S442L). Half of the patients previously received treatment with rifampicin.