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A better understanding of the association between systemic antibiotics and the populations of bacteria in the skin microbiota may help clinicians better address related comorbidities.
Treating acne with oral antibiotics changes not only the population of Cutibacterium acnes (formerly Propionibacterium acnes) but also the composition and diversity of other bacterial species within the skin microbiota, and these may not always recover rapidly once the antibiotic treatment ceases, shows a small study published in JAMA Dermatology.1
“Understanding the timing and significance of shifts in microbial flora associated with antibiotic treatment, both during and after therapy, may help clinicians decrease the likelihood of skin comorbidities related to dysbiosis,” says one of the researchers Luis Garza, M.D., Ph.D., associate professor, department of dermatology at Johns Hopkins School of Medicine, Baltimore, Md. “This may involve concurrent monitoring of the skin microbiota, a more targeted antibiotic approach, or additional therapies to sustain ‘good’ flora during treatment.”
The study included four women diagnosed with acne: two were 25 years old, one was 29, and one was 35 years; and two were white, one was African American, and one was Asian. All four women received a one-month course of oral minocycline, 100mg, twice daily for four weeks. Surface swabs of the bilateral forehead, cheek, and chin were taken before and immediately after treatment, and again at one and eight weeks after treatment concluded. Bacterial taxonomic assignment was performed by amplification and sequencing of V3/V4hypervariable region of the bacterial 16S ribosomal gene.
In general, antibiotic administration was associated with an initial decrease from baseline of bacterial diversity followed by recovery.
While changes occurred in the composition of an individual patient’s skin microbiome during the study period, their samples remained more similar to samples taken from them at different times than to samples taken from other patients at the same point, demonstrating that aspects of the skin microbiome are highly individualized, and that specific strains may persist on a given person for years.
However, within an individual participant, dynamic shifts in bacterial community composition were observed across the four time points, suggesting antibiotic-induced selection pressure. Pooled analysis of samples from all four women showed C. acnes levels fell 1.4-fold between baseline and the end of the one-month course of oral minocycline. Levels were still low one week later but then recovered. Two patients displayed clinical improvements in acne severity concurrent with the reduction in C. acnes.
Minocycline was also associated with sustained decreases in other bacterial genera, including Corynebacterium, Prevotella, and several Lactobacillus species, and temporary or sustained increases in others.
There was a transient 5.6-fold increase in the abundance of Pseudomonas species immediately following antibiotic treatment, a persistent 1.7-fold increase in the abundance of Streptococcus species and a 4.7-fold decrease in the abundance of Lactobacillus species eight weeks following antibiotic treatment withdrawal.
“Our study shows that this negative association between C. acnes and Pseudomonas species persists on disruption of skin microbiota with minocycline and suggests that C. acnes and Pseudomonas species may compete for the same microenvironments within skin microbiota,” Dr. Garza says. “The transient growth of bacterial populations, such as Pseudomonas species,
immediately following antibiotic treatment points toward the possibility of opportunistic skin infections, such as gram-negative folliculitis, with prolonged antibiotic therapy for acne.”
Other studies have suggested an association between antibiotic treatment of acne and upper respiratory tract infections, particularly pharyngitis.
“Although we did not sample the oropharynx in the present study, our observation of increased Streptococcus species on facial skin following systemic antibiotic treatment raises the question of whether a similar growth of Streptococcus species occurs in the oropharynx,” Dr. Garza adds.
Systemic antibiotic treatment of acne may also reduce bacterial populations beneficial to skin health. “Several members of the Lactobacillus genus, for instance, have been associated with protective effects against Staphylococcus aureus infections, atopic dermatitis, and acne,” he points out.
Tetracycline-class antibiotics, such as minocycline and doxycycline, are commonly used as first-line treatment of moderate-to-severe acne because of their antimicrobial and anti-inflammatory actions. Although guidelines recommend limiting their duration of use to three to four months, treatment often exceeds this. The mean treatment duration was 6.5 months among patients with acne who were treated by US dermatologists between 2004 and 2013.2
“It is important to understand their effects not only on C. acnes but also on the complete bacterial community of the skin,” Dr. Garza emphasises.
1 Chien AL, Tsai J, Leung S, et al. Association of systemic antibiotic treatment of acne with skin microbiota characteristics [published online February 13, 2019]. JAMA Dermatol.
2 Barbieri JS, JamesWD, Margolis DJ. Trends in prescribing behavior of systemic agents used in the treatment of acne among dermatologists and nondermatologists: a retrospective analysis, 2004-2013. J AmAcad Dermatol. 2017;77(3):456-463.