Propionibacterium acnes is developing gradual increase in resistance to oral tetracyclines

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Propionibacterium acnes (P. acnes) causes infections and acne vulgaris.
• Frequent use of tetracyclines for acne has led to resistant P. acnes strains.
• A novel tetracycline resistance mechanism in P. acnes requires investigation.

Purpose of the Study:

• To identify and characterize a novel tetracycline resistance mechanism in P. acnes.
• To investigate the genetic basis of doxycycline resistance in P. acnes strains.
• To elucidate the relationship between ribosomal protein mutations and tetracycline resistance.

Main Methods:

• Isolation and susceptibility testing of P. acnes strains from acne patients.
• Genetic analysis including sequencing of 16S rRNA and rpsJ genes.
• In vitro generation of mutants to assess the role of specific mutations.

Main Results:

• Three doxycycline-resistant P. acnes strains (MIC: 16 µg/mL) and six insusceptible strains (MIC: 1-2 µg/mL) were identified.
• Doxycycline-resistant strains possessed both a G1036C mutation in 16S rRNA and an amino acid substitution in the S10 protein.
• Insusceptible strains had only the S10 protein substitution; in vitro mutants showed S10 substitution conferred reduced susceptibility (MIC: 4 µg/mL).

Conclusions:

• Amino acid substitution in the ribosomal S10 protein is a key factor in reduced doxycycline susceptibility in P. acnes.
• A subsequent mutation in the 16S rRNA gene, following the S10 protein alteration, likely leads to acquired tetracycline resistance.
• Understanding this mechanism is crucial for developing effective acne treatments and combating antibiotic resistance.