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The following is a summary of “Criticality of Benzoyl Peroxide and Antibiotic Fixed Combinations in Combating Rising Resistance in Cutibacterium acnes,” published in the March 2025 issue of Clinical, Cosmetic and Investigational Dermatology by Ghannoum et al. 

Antibiotic resistance in Cutibacterium acnes (C. acnes) had been increasing globally, with many countries reporting resistance in over 50% of strains, suggesting that combination therapies of antibiotics and benzoyl peroxide (BPO) might have been considered to mitigate this risk, particularly with long-term use.  

Researchers conducted a retrospective study to evaluate the susceptibility of 31 C. acnes clinical strains and assess resistance development to antibiotics alone or in combination with BPO.  

They assessed C. acnes susceptibility to single-drug antibiotics using minimum inhibitory concentration (MIC) values from epsilometer tests, where lower MIC indicated higher susceptibility. Fixed-dose antibiotic and BPO combination susceptibility was estimated by measuring the zone of inhibition via the agar diffusion method, with larger diameters indicating greater bacterial inhibition. Clindamycin and BPO interaction effects (synergistic, additive, antagonistic, or indifferent [no interaction]) were analyzed using a checkerboard assay with varying concentrations of both compounds. Resistance development was examined through serial bacterial passage in increasing clindamycin concentrations alone or with BPO.  

The results showed that clindamycin, doxycycline, erythromycin, and minocycline had identical activity, but C. acnes susceptibility varied, with some strains displaying high MIC values, indicating resistance. Among 6 clindamycin-resistant strains (inhibitory zone = 0 cm), BPO formulations enhanced activity (range: 0.8–2.2 cm). Of 7 acne-associated strains, clindamycin and BPO had an additive effect against 4 and no interaction against 3. Bacterial cultures repeatedly exposed to clindamycin and BPO did not develop antibiotic resistance, unlike those exposed to clindamycin alone.  

Investigators concluded that antibiotic susceptibility in C. acnes varied by strain, but antibiotic formulations containing BPO showed increased activity against less susceptible strains. 

Source: dovepress.com/criticality-of-benzoyl-peroxide-and-antibiotic-fixed-combinations-in-c-peer-reviewed-fulltext-article-CCID