These authors point out that, while tetracylines are often used to treat Propionibacterium infections, many tetracycline-resistant P. acnes strains have been isolated in part due to the frequent use of oral tetracycline is frequently used as an acne treatment.
They report a novel tetracycline resistance mechanism in P. acnes. They isolated three doxycycline-resistant strains and six strains that had reduced susceptibility compared to susceptible strains.
All doxycycline-resistant strains had a G1058C mutation in the 16S rRNA gene in addition to an amino acid substitution in the ribosomal S10 protein encoded by rpsJ. Their results show that the S10 protein amino acid substitution contributes to reduced doxycycline susceptibility in P. acnes and suggests that tetracyclines resistance is acquired through a 16S rRNA mutation after the S10 protein amino acid substitution.
Comment: There is no question that Propionibacterium are acquire resistance to Clindamycin and to tetracyclines. Currently, it is not common practice to obtain sensitivities on Propi cultures, but it may be time for this practice to change.
Of note is another recent article:
Antimicrobial activity of topical agents against Propionibacterium acnes: an in vitro study of clinical isolates from a hospital in Shanghai, China
These authors determined the susceptibilities of Propionibacterium to clindamycin and erythromycin The resistance rates to neomycin sulfate, erythromycin, and clindamycin were 11.7%, 49.3%, and 33.4%, respectively.
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