In vitro antimicrobial activity of benzoyl peroxide against Propionibacterium acnes assessed by a novel susceptibility testing method

"Rich arginine and strong positive charge" antimicrobial protein protamine: From its action on cell membranes to inhibition of bacterial vital functions

Protamine, an antimicrobial protein derived from salmon sperm with a molecular weight of approximately 5 kDa, is composed of 60-70 % arginine and is a highly charged protein. Here, we investigated the mechanism of antimicrobial action of protamine against Cutibacterium acnes (C. acnes) focusing on its rich arginine content and strong positive charge. Especially, we focused on the attribution of dual mechanisms of antimicrobial protein, including membrane disruption or interaction with intracellular components. We first determined the dose-dependent antibacterial activity of protamine against C. acnes. In order to explore the interaction between bacterial membrane and protamine, we analyzed cell morphology, zeta potential, membrane permeability, and the composition of membrane fatty acid. In addition, the localization of protamine in bacteria was observed using fluorescent-labeled protamine. For investigation of the intracellular targets of protamine, bacterial translation was examined using a cell-free translation system. Based on our results, the mechanism of the antimicrobial action of protamine against C. acnes is as follows: 1) electrostatic interactions with the bacterial cell membrane; 2) self-internalization into the bacterial cell by changing the composition of the bacterial membrane; and 3) inhibition of bacterial growth by blocking translation inside the bacteria. However, owing to its strong electric charge, protamine can also interact with DNA, RNA, and other proteins inside the bacteria, and may inhibit various bacterial life processes beyond the translation process.

A novel long-acting antimicrobial nanomicelle spray

Contaminated surfaces play a major role in disease transmission to humans. The vast majority of commercial disinfectants provide short-term protection of surfaces against microbial contamination. The Covid-19 pandemic has attracted attention to the importance of long-term disinfectants as they would reduce the need for staff and save time. In this study, nanoemulsions and nanomicelles containing a combination of benzalkonium chloride (BKC; a potent disinfectant and a surfactant) and benzoyl peroxide (BPO; a stable form of peroxide that is activated upon contact with lipid/membranous material) were formulated. The prepared nanoemulsion and nanomicelle formulas were of small sizes <80 nm and high positive charge >45 mV. They showed enhanced stability and prolonged antimicrobial efficacy. The antibacterial potency was evaluated in terms of long-term disinfection on surfaces as verified by repeated bacterial inoculums. Additionally, the efficacy of killing bacteria upon contact was also investigated. A nanomicelle formula (NM-3) consisting of 0.8% BPO in acetone and 2% BKC plus 1% TX-100 in distilled water (1 : 5 volume ratio) demonstrated overall surface protection over a period of 7 weeks upon a single spray application. Furthermore, its antiviral activity was tested by the embryo chick development assay. The prepared NM-3 nanoformula spray showed strong antibacterial activities against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus as well as antiviral activities against infectious bronchitis virus due to the dual effects of BKC and BPO. The prepared NM-3 spray shows great potential as an effective solution for prolonged surface protection against multiple pathogens.

Minimum Contact Time of 1.25%, 2.5%, 5%, and 10% Benzoyl Peroxide for a Bactericidal Effect Against Cutibacterium acnes

Purpose

Benzoyl peroxide (BPO) is an effective acne treatment and has been used as a cleanser and short contact therapy. However, data on the minimum contact time of BPO needed to kill Cutibacterium acnes are lacking. Thus, the aim of this study was to determine the minimum contact time of commonly used BPO concentrations for bactericidal effects on C. acnes.

Materials and Methods

An in vitro experimental study of clinically isolated C. acnes was performed to determine the minimal inhibitory concentration (MIC) of BPO using the broth microdilution method. Subsequently, the minimum contact times of various concentrations of BPO were evaluated, and their bactericidal effects were assessed by the plate count method.

Results

The median MIC of BPO was 9375 µg/mL, which did not significantly differ between antibiotic-resistant and nonresistant C. acnes. The minimum contact time of BPO with C. acnes was significantly different among the BPO concentrations. For bactericidal activity against all isolates, 1.25%, 2.5%, 5%, and 10% BPO required 60 min, 15 min, 30 sec, and 30 sec, respectively.

Conclusion

BPO demonstrated bactericidal activity against both antibiotic-resistant and antibiotic-susceptible C. acnes. The in vitro contact time needed to kill C. acnes was almost immediate with 5% or more BPO, but ≤ 2.5% BPO required longer contact times for bactericidal effects.

Broad spectrum in vitro microbicidal activity of benzoyl peroxide against microorganisms related to cutaneous diseases

The in vitro microbicidal activity of benzoyl peroxide against Cutibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, Malassezia furfur, Malassezia restricta, and Malassezia globosa was investigated. These strains were incubated for 1 h in the presence of 0.25, 0.5, 1, or 2 mmol/L benzoyl peroxide in phosphate buffered saline supplemented with 0.1% glycerol and 2% Tween 80. After exposure to benzoyl peroxide, counts of viable Gram-positive bacteria and fungi were markedly decreased, whereas counts of Gram-negative bacteria were unchanged. Transmission electron microscopy images showed a decrease in electron density and the destruction of C. acnes and M. restricta cell walls after exposure to 2 mmol/L benzoyl peroxide. In conclusion, this study showed that benzoyl peroxide has a potent and rapid microbicidal activity against Gram-positive bacteria and fungi that are associated with various cutaneous diseases. This suggests that the direct destruction of bacterial cell walls by benzoyl peroxide is an essential mechanism of its rapid and potent microbicidal activity against microorganisms.

Safety and efficacy of a novel three-step anti-acne regimen formulated specifically for women

Background

Due to ambient environmental- and lifestyle-associated stressors, the prevalence of acne in adult women has been increasing. Classical anti-acne treatments using benzoyl peroxide technology are associated with dehydration of the skin, which may accelerate aging and further reduce treatment compliance. The addition of bio-functional actives intended to replenish hydration and improve barrier function may hasten the onset of anti-acne benefits while restoring a healthy appearance and counteracting skin aging effects.

Objective

The objective of this study was to test the safety and efficacy of a new three-step topical anti-acne regimen designed specifically to improve the overall condition and appearance of the skin in women with acne.

Methods

Safety and efficacy were tested in an 8-week study of women ages 22 to 44 years with mild to moderate acne. Skin endpoints were monitored at baseline and weeks 1, 4, and 8 by clinical grading, measurement of sebum secretion using a sebumeter, standardized pictures, and self-validation questionnaires.

Results

A total of 31 women completed the study. Acne severity and lesion counts, including comedones and papules, improved gradually starting from week 1 and continued to improve throughout the study period, reaching statistical and clinical relevance at weeks 4 and 8. Moreover, significant improvements in skin roughness, radiance, overall healthy appearance, and oiliness (further confirmed with decreased sebum production) were observed. Compared with baseline responses, participants reported noticeable improvements in acne lesions and overall healthier-looking skin. Participants also noticed overall younger-looking skin at the end of the study period.

Conclusion

This three-step regimen provided efficacious anti-acne benefits to the skin that were also gentle, safe, and well tolerated.

Exploring the Anti-Acne Potential of Impepho [Helichrysum odoratissimum (L.) Sweet] to Combat Cutibacterium acnes Virulence

The Gram-positive bacterium Cutibacterium acnes (previously Propionibacterium acnes), plays an important role in the pathogenesis and progression of the dermatological skin disorder acne vulgaris. The methanolic extract of Helichrysum odoratissimum (L.) Sweet (HO-MeOH) was investigated for its ability to target bacterial growth and pathogenic virulence factors associated with acne progression. The gas chromatography-mass spectrometry (GC-MS) analysis of HO-MeOH identified α-humulene (3.94%), α-curcumene (3.74%), and caryophyllene (8.12%) as major constituents, which correlated with previous reports of other Helichrysum species. The HO-MeOH extract exhibited potent antimicrobial activity against C. acnes (ATCC 6919) with a minimum inhibitory concentration (MIC) of 7.81 µg/ml. It enhanced the antimicrobial activity of benzoyl peroxide (BPO). The extract showed high specificity against C. acnes cell aggregation at sub-inhibitory concentrations, preventing biofilm formation. Mature C. acnes biofilms were disrupted at a sub-inhibitory concentration of 3.91 µg/ml. At 100 µg/ml, HO-MeOH reduced interleukin-1α (IL-1α) cytokine levels in C. acnes-induced human keratinocytes (HaCaT) by 11.08%, highlighting its potential as a comedolytic agent for the treatment of comedonal acne. The extract exhibited a 50% inhibitory concentration (IC50) of 157.50 µg/ml against lipase enzyme activity, an enzyme responsible for sebum degradation, ultimately causing inflammation. The extract's anti-inflammatory activity was tested against various targets associated with inflammatory activation by the bacterium. The extract inhibited pro-inflammatory cytokine levels of IL-8 by 48.31% when compared to C. acnes-induced HaCaT cells at 7.81 µg/ml. It exhibited cyclooxygenase-II (COX-II) enzyme inhibition with an IC50 of 22.87 µg/ml. Intracellular nitric oxide (NO) was inhibited by 40.39% at 7.81 µg/ml when compared with NO production in lipopolysaccharide (LPS)-induced RAW264.7 cells. The intracellular NO inhibition was potentially due to the 2.14 fold reduction of inducible nitric oxide synthase (iNOS) gene expression. The HO-MeOH extract exhibited an IC50 of 145.45 µg/ml against virulent hyaluronidase enzyme activity, which is responsible for hyaluronan degradation and scar formation. This study provides scientific validation for the traditional use of H. odoratissimum as an ointment for pimples, not only due to its ability to control C. acnes proliferation but also due to its inhibitory activity on various targets associated with bacterial virulence leading to acne progression.

Highly Sensitive Detection of Benzoyl Peroxide Based on Organoboron Fluorescent Conjugated Polymers

The method capable of rapid and sensitive detection of benzoyl peroxide (BPO) is necessary and receiving increasing attention. In consideration of the vast signal amplification of fluorescent conjugated polymers (FCPs) for high sensitivity detection and the potential applications of boron-containing materials in the emerging sensing fields, the organoboron FCPs, poly (3-aminophenyl boronic acid) (PABA) is directly synthesized via free-radical polymerization reaction by using the commercially available 3-aminophenyl boronic acid (ABA) as the functional monomer and ammonium persulfate as the initiator. PABA is employed as a fluorescence sensor for sensing of trace BPO based on the formation of charge-transfer complexes between PABA and BPO. The fluorescence emission intensity of PABA demonstrates a negative correlation with the concentration of BPO. And a linear range of 8.26 × 10⁻⁹ M–8.26 × 10^–4 M and a limit of detection of 1.06 × 10^–9 M as well as a good recovery (86.25%–111.38%) of BPO in spiked real samples (wheat flour and antimicrobial agent) are obtained. The proposed sensor provides a promising prospective candidate for the rapid detection and surveillance of BPO.

In vitro Antimicrobial Activity of Acne Drugs Against Skin-Associated Bacteria

Acne is a common skin affliction that involves excess sebum production and modified lipid composition, duct blockage, colonization by bacteria, and inflammation. Acne drugs target one or more of these steps, with antibiotics commonly used to treat the microbial infection for moderate to severe cases. Whilst a number of other acne therapies are purported to possess antimicrobial activity, this has been poorly documented in many cases. We conducted a comparative analysis of the activity of common topical acne drugs against the principal etiological agent associated with acne: the aerotolerant anaerobic Gram-positive organism Propionibacterium acnes (recently renamed as Cutibacterium acnes). We also assessed their impact on other bacteria that could also be affected by topical treatments, including both antibiotic-sensitive and antibiotic-resistant strains, using broth microdilution assay conditions. Drugs designated specifically as antibiotics had the greatest potency, but lost activity against resistant strains. The non-antibiotic acne agents did possess widespread antimicrobial activity, including against resistant strains, but at substantially higher concentrations. Hence, the antimicrobial activity of non-antibiotic acne agents may provide protection against a background of increased drug-resistant bacteria.

New developments in acne treatment: role of combination adapalene-benzoylperoxide

The fixed-dose combination adapalene 0.1%/benzoylperoxide 2.5% (A/BPO) was introduced as an acne vulgaris therapeutic in 2007. It combines anti-inflammatory, keratolytic, comedolytic, and antibacterial properties. Thus, it addresses several pathophysiological factors involved in the pathophysiology of acne. This review highlights the rationale for the use of this fixed-dose combination product, its therapeutic efficacy including effects on adherence and quality of life, its use for different forms of acne, and the side-effect profile. In summary, the fixed-dose combination of A/BPO gel can be regarded as a highly effective and safe formulation. It is not associated with antibiotic resistance. It reduces factors that cause nonadherence and has positive effects on the quality of life of affected patients. The tolerance is good. The initial mild irritation potential can be addressed by adequate counseling. A/BPO can be used for all forms of inflammatory acne, including severe forms, as part of a combination with systemic antibiotics. Finally, it can also be used for the long-term treatment of chronic acne. Thus, it is a very valuable therapeutic option in daily practice, which is reflected by its strong recommendation in the “European S3-guidelines”.