In vitro antimicrobial susceptibility of Propionibacterium acnes isolated from acne patients in northern Mexico

Background Antimicrobials are essential in acne therapy. In the last decades, Propionibacterium acnes has become resistant to different antibiotics. Objective To determine antimicrobial susceptibility patterns of P. acnes to frequently used drugs. Materials and methods Cutaneous lesion samples were obtained from 50 patients with acne vulgaris, which were cultured in anaerobic media to demonstrate the presence of P. acnes. After that, antimicrobial susceptibility tests to tetracycline, minocycline, doxycycline, erythromycin, azithromycin, clindamycin, trimethoprim/sulfamethoxazole (SXT) and levofloxacin were performed. Results In the general study group, resistance to azithromycin was 82%, the most prevalent one (P < 0.05), followed by trimethoprim/sulfamethoxazole (68%) and erythromycin (46%). On the other hand, all strains isolated were susceptible to minocycline. Resistance bias were similar when subgroups with and without the previous antimicrobial therapy were performed, finding a low prevalence of resistance to tetracyclines and levofloxacin in both groups. Conclusions In our region, P. acnes is highly resistant to azithromycin, SXT, erythromycin and clindamycin; and being very susceptible to minocycline, levofloxacin and tetracycline, in vitro in both groups: with and without the previous antibiotic use. To our knowledge, high resistance prevalence to azithromycin and SXT has never been reported.