Cutibacterium acnes Phylotyping and Antibiotic Resistance to Six Antibiotics: A Bulgarian Study

Cutibacterium acnes subspecies/phylotypes can cause infections requiring antibiotic therapy. Phylotyping of 73 (55 acneic and 18 non-acneic) C. acnes strains was performed, and antibiotic susceptibility was tested by E tests, breakpoint susceptibility test, or disk diffusion method. The dominant phylotype in both acneic and non-acneic strains was IA1 (56.2%). Phylotype II was >3-fold more frequent in non-acneic than acneic isolates. Resistance in acneic strains was >41% for clindamycin, 36.4% for tetracycline and 15.9% for levofloxacin, and that in non-acneic strains was >38% for clindamycin, 22.2% for tetracycline and 5.6% for levofloxacin. No strain was piperacillin/tazobactam or vancomycin resistant. Amoxicillin resistance was found in both acneic (5.4%) and non-acneic strains (11.1%), and was rare (1.8%) in phylotype I but higher (23.5%) in other strains. Double resistance was found in 32.6% of acneic and 22.2% of the non-acneic strains, and 9.3% of acneic strains displayed multidrug resistance. In conclusion, IA1 phylotype was dominant in both acneic and non-acneic strains, and type II was more frequent in non-acneic isolates. The detection (at >6%) of amoxicillin resistance represents a rare yet important finding. The presence of double/multidrug resistance strongly implies the need of susceptibility-guided therapy of the associated infections.