The Genetic Tree of Seven Cutibacterium acnes Strains and their Susceptibility to Common Antibiotics

This study was conducted to investigate one of the most prominent bacteria that causes acne (Cutibacterium acnes), studying the spread of the phenomenon of resistance to the various antibiotics used to treat acne and studying the evolutionary relationship between isolates of Cutibacterium acnes. 125 samples were collected from patients with acne vulgaris cases in Mosul city, from dermatology consultations at Al-Salam Teaching Hospital and Mosul General Hospital, the diagnosis was made for samples through routine examinations (macroscopic and microscopic) and through molecular diagnosis based on universal 16s rRNA gene, the results of the isolation and diagnosis were obtaining seven isolates of Cutibacterium acnes and one isolate of Cutibacterium avidum with (5.6%) and (0.8%) respectively from all samples.Eight antibiotics were chosen to perform the susceptibility tests by disc diffusion assay, the study showed that seven of C. acnes isolates were resistant to fusidic acid and azithromycin with 85.7%, tetracycline with 71.4%, clindamycin, and gentamycin with 57.1% respectively and vancomycin 42.8% the isolates were sensitive 100% to imipenem and levofloxacin. In this study, an evolutionary tree was created depending on the degree of neighbor- joining among these molecularly diagnosed isolates based on the MEGA11 program strains 103, 107, and 111 each showed a genetic similarity with 93%, and their cluster formed a 91% similarity with strain 112, which in turn clustered with 89% with strain 118 and their similarity with strain 117 decreased to 74%. In turn, it clustered with strain 110 at a rate of 99%. C. avidum strain was distant fromC. acnes strain. Naturally, the Staphylococcus aureus strain was at the end of the tree, which was used to create a root for the genetic tree of the strains .