# In vitro efficacy of disinfectants against Cutibacterium acnes

## TL;DR

This study tested how well different disinfectants kill Cutibacterium acnes, a bacteria linked to acne, and found that olanexidine works well even under acne-like conditions.

## Contribution

The study provides new in vitro evidence on the efficacy of disinfectants against C. acnes, highlighting olanexidine's performance under acne-like conditions.

## Key findings

- Benzethonium, chlorhexidine, isopropyl methylphenol, and olanexidine showed high bactericidal activity against C. acnes.
- Olanexidine retained effectiveness at low concentrations even when artificial sebum was added.
- Disinfectant efficacy was significantly reduced under in vitro acne conditions with artificial sebum.

## Abstract

Introduction. The abnormal proliferation of Cutibacterium acnes, a human skin commensal bacterium, aggravates acne. Prompt and aggressive treatment of acne in its initial stages is essential because of the increased psychological distress experienced by patients. Over-the-counter medications containing disinfectants are sometimes used to treat acne because they are widely available, exhibit broad-spectrum activity and have a likelihood of causing resistance.

Gap statement. Limited information is available regarding the bactericidal effects of disinfectants against C. acnes.

Aim. In the present study, we comprehensively evaluated the efficacy of various disinfectants.

Methodology.
C. acnes ATCC6919 and eight clinical isolates with different genotypes obtained from patients with acne were used. Benzethonium, chlorhexidine, resorcinol, homosulfamine, isopropyl methylphenol and olanexidine were used as disinfectants. The bactericidal activity of these disinfectants against C. acnes was assessed using a time–kill kinetic assay. Three independent experiments were conducted to ensure reproducibility of the results.

Results. Benzethonium, chlorhexidine, isopropyl methylphenol and olanexidine exhibited high efficacy. However, under in vitro acne conditions, with the addition of artificial sebum, the bactericidal efficacy of the disinfectants was significantly reduced. However, olanexidine retained bactericidal activity at concentrations as low as 0.2%, comparable with that at 1.5%.

Conclusion. This study showed that the disinfectants benzethonium, isopropyl methylphenol, chlorhexidine and olanexidine have high bactericidal activity against C. acnes. In particular, olanexidine demonstrated a strong bactericidal effect even under in vitro acne conditions. Further in vivo validation is required to determine whether olanexidine could be a new treatment option for managing acne.