Study data published in Dermatology and Therapy suggest that biotype and phenotype distribution in Cutibacterium acnes (C acnes) may be associated with acne severity. Additionally, erythromycin and clindamycin resistances were commonly detected in C acnes isolates.

Investigators collected skin lesion samples from adult (>18 years) patients with facial acne who visited the dermatologic department at the Huashan Hospital in Shanghai, China. Acne severity was graded using the Pillsbury scale; grades I and IV described mild and severe acne, respectively, while grades II and III denoted moderate acne. C acnes samples were isolated and cultured from facial lesion samples. Agar dilution assays were used to measure the minimum inhibitory concentrations of clinical C acnes isolates for various antibiotics. C acnes biotypes and phylotypes were determined using fermentation tests and multiplex touchdown polymerase chain reaction, respectively. Fisher exact test with Bonferroni correction was performed to examine the relationship between disease severity and distribution of biotypes and phylotypes.

Samples were collected from 100 patients, and C acnes strains were identified in 63. Among these 63 patients (57.1% men), the mean (SD) age was 22.4 (4.5) years. Mean (SD) disease duration was 13.1 (1.1) months. According to the Pillsbury grading system, 5 patients had grade I acne; 16 patients had grade II; 23 had grade III; and 19 had grade IV. Among all isolated C acnes strains, 18 (28.6%), 31 (49.2%), and 4 (6.3%) were resistant to clindamycin, erythromycin, and moxifloxacin, respectively. All strains were resistant to metronidazole, while no strains were resistant to tetracycline, minocycline, fusidic acid, or β-lactam. Multidrug resistance was observed in 3 strains. The most commonly observed biotype was biotype III (50.8%), followed by biotypes I and V (both 15.9%), biotype II (12.7%), and biotype IV (4.8%). The predominant phylotype was IA1 (71.4%), followed by IA2 (19.0%), II (4.8%), IB (3.2%), and IC (1.6%). Phylotype III was not detected. All detected phylotypes were found to have antibiotic-susceptible subtypes. Biotype and phylotype distribution differed by acne grade. Specifically, the biotype distribution of mild acne was significantly different from that of moderate acne (P =.016). Between moderate and severe acne, phylotype distributions also differed significantly (P =.011). Biotype and phylotype distributions were not different between antibiotic-resistant and antibiotic-susceptible strains.

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These data indicate that different degrees of acne severity may reflect different biotypes and phylotypes in C acnes. However, further study in a prospective cohort is necessary to confirm these findings. Additionally, while resistance to erythromycin and clindamycin was common, susceptibility to cyclines remained high. “Our findings may provide evidence for clinical studies about drug resistance and help elucidate the biologic and phylogenetic characteristics of C acnes,” investigators wrote.  

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Reference

Zhang N, Yuan R, Xin KZ, Lu Z, Ma Y. Antimicrobial susceptibility, biotypes and phylotypes of clinical Cutibacterium (formerly Propionibacterium) acnes strains isolated from acne patients: an observational study [published online September 19, 2019]. Dermatol Ther (Heidelb). doi:10.1007/s13555-019-00320-7