Isothiazolinone derivatives and allergic contact dermatitis: a review and update

Epidemics of Dermatitis

Allergic contact dermatitis (ACD) remains a globally prevalent disease for both children and adults. The silent ACD epidemic continues to be fueled by the introduction of novel allergens in industrial and household products and the continued presence of known allergens. In 1997, Allan Dillarstone noted a sinusoidal pattern to epidemics when allergenic preservatives were replaced by alternative chemicals within the market, which then similarly increased in allergenicity. A call for public health vigilance and prevention initiatives is needed to intervene in the ACD epidemic.

Development of Hinoline® as a natural preservative for cosmetic product using bioinspiration and Greenpharma Database

AIMS

The cosmetic industry needs new preservatives that are effective, natural, safe, cost effective, sustainable and compliant with regulatory standards. This necessity has posed challenges requiring obligations, bioinformatics and bioinspiration as driving forces.

METHODS AND RESULTS

Twenty natural extracts were selected from the Greenpharma Database with parameter filters corresponding to development constraints and antimicrobial properties. We confirmed using minimum inhibition concentration (MIC) assays that eight of the extracts have good bactericidal properties and that one has a high antifungal activity. The latter was purified hinokitiol, a bioproduct from Aomori Hiba wood. This substance provides high resistance against putrefaction; for instance, old Japanese temples were made of Aomori Hiba wood. The combination of hinokitiol with levulinic acid, another bioproduct, demonstrated complementary antimicrobial activities and synergistic effects in MIC studies and measurements according to Kull synergy index. Further, the mixture Hinoline® was tested at 2% in challenge tests and fulfilled criteria A of different standards. It also exerted complementary preservative effects with potassium sorbate and beneficial effects in unbalanced skin microbiota.

CONCLUSION

Hinoline, a new effective preservative from renewable bioresources, was developed.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study accelerates the development of a preservative solution for cosmetics selected from Greenpharma Database, through bioinspiration and the identification of cost-effective investments and resources.

Prevalence and trend of allergen sensitization in patients referred for patch testing with a final diagnosis of psoriasis: North American Contact Dermatitis Group data, 2001-2016

BACKGROUND

Little is known about the relationship between psoriasis and allergic contact dermatitis (ACD).

OBJECTIVE

To examine the associations with ACD, related clinical characteristics, and common positive and clinically relevant allergens of patients with a final diagnosis of psoriasis who were referred for patch testing.

METHODS

Retrospective analysis of 38 723 patients from the North American Contact Dermatitis Group.

RESULTS

Patients with a final diagnosis of psoriasis had lower proportions of ACD than those without psoriasis (32.7% vs 57.8%). In multivariable logistic regression models, psoriasis was inversely associated with female sex, Black or Asian race, and history of atopic dermatitis and hay fever. Patients with a final diagnosis of psoriasis were less likely to have one or more positive allergic patch-test reactions or to have a current clinically relevant patch-test reaction to the majority of the most commonly positive and/or relevant allergens. The most clinically relevant allergens included nickel sulfate, methylisothiazolinone, and fragrance mix I.

CONCLUSION

Approximately one-third of patients who were referred for patch testing with a final diagnosis of psoriasis were also diagnosed with ACD. In select patients with suspected psoriasis who also have a clinical presentation suggestive of ACD, patch testing may be helpful.

What Is New in Occupational Allergic Contact Dermatitis in the Year of the COVID Pandemic?

PURPOSE OF REVIEW

This article aims to summarize some recent trends in occupational allergic contact dermatitis (ACD), including dermatitis related to pandemic-level personal protective equipment in healthcare workers, hazards patients may experience when working from home, and occupational perspectives on the recent American Contact Dermatitis Society (ACDS) allergens of the year and ACDS Core Allergen Series updates.

RECENT FINDINGS

Recent ACDS Allergens of the Year may be particularly relevant to healthcare workers, including isobornyl acrylate, which is present in glucose sensors and propylene glycol present in hand cleansers and disinfectants. Lavender, limonene, and linalool, all of which are new additions to the ACDS Core Allergen Series, have been reported as causes for occupational ACD in massage therapists and aromatherapists. Isothiazolinone allergy continues to rise in both consumer and occupational settings. Finally, the COVID-19 pandemic has resulted in a wave of occupational ACD in healthcare workers to personal protective equipment, and revealed new potential allergens for individuals working from home. Occupational allergic contact dermatitis continues to exert a significant occupational disease burden. Remaining aware of the current trends in allergens may allow for earlier recognition, diagnosis, and treatment, subsequently helping our patients to work in healthier and safer environments.

Prevalence and Trend of Allergen Sensitization in Adults and Children with Atopic Dermatitis Referred for Patch Testing, North American Contact Dermatitis Group Data, 2001-2016

BACKGROUND

The association between atopic dermatitis (AD) and allergic contact dermatitis (ACD) is controversial.

OBJECTIVE

To analyze the prevalence, reaction strength, and trends of the most commonly positive and relevant allergens in patients with AD referred for patch testing.

METHODS

This was a retrospective analysis of 38,482 patients from the North American Contact Dermatitis Group, 2001 to 2016.

RESULTS

Most adults (56.0%) and children (52.8%) with a history of AD had a final diagnosis of ACD. Adults (66.5% vs 65.6%; χ², P = .1459) and children (61.4% vs 62.3%, P = .7074) with or without a history of AD had similar proportions of one or more allergic patch test reactions. Adults with a history of AD had a greater number of allergic patch test positive reactions than those without it (2.0 ± 2.4 vs 1.9 ± 2.3; t test, P < .0001), whereas children did not (1.5 ± 1.8 vs 1.4 ± 1.6; P = .3839). Nickel sulfate, methylisothiazolinone, formaldehyde, fragrance mix I, sodium gold thiosulfate, and thimerosal were the most common allergens in adults and children with a history of AD. In multivariable logistic regression models, adults with versus without a history of AD had increased odds of reacting to 10 of the top 25 North American Contact Dermatitis Group screening allergens. Most allergens had similar strengths of reaction in adults or children with and without a history of AD or a current AD diagnosis; cobalt, fragrance mix I, and propylene glycol had weaker reactions. In multivariable logistic regression, adults with versus without an AD history had increased odds of relevance for 10 of the 25 most currently relevant allergens, whereas children with an AD history did not have increased relevance for any specific allergens.

CONCLUSIONS

Most patients referred for patch testing with AD history had a final diagnosis of ACD. Patients with AD history had a similar likelihood of having a positive patch test reaction as those without an AD history. Adults with an AD history had a higher number of positive patch test reactions.

A Commonly Used Biocide 2-N-octyl-4-isothiazolin-3-oneInduces Blood-Brain Barrier Dysfunction via Cellular Thiol Modification and Mitochondrial Damage

Isothiazolinone (IT) biocides are potent antibacterial substances commonly used as preservatives or disinfectants, and 2-n-Octyl-4-isothiazolin-3-one (OIT; octhilinone) is a common IT biocide that is present in leather products, glue, paints, and cleaning products. Although humans are exposed to OIT through personal and industrial use, the potentially deleterious effects of OIT on human health are still unknown. To investigate the effects of OIT on the vascular system, which is continuously exposed to xenobiotics through systemic circulation, we treated brain endothelial cells with OIT. OIT treatment significantly activated caspase-3-mediated apoptosis and reduced the bioenergetic function of mitochondria in a bEnd.3 cell-based in vitro blood–brain barrier (BBB) model. Interestingly, OIT significantly altered the thiol redox status, as evidenced by reduced glutathione levels and protein S-nitrosylation. The endothelial barrier function of bEnd.3 cells was significantly impaired by OIT treatment. OIT affected mitochondrial dynamics through mitophagy and altered mitochondrial morphology in bEnd.3 cells. N-acetyl cysteine significantly reversed the effects of OIT on the metabolic capacity and endothelial function of bEnd.3 cells. Taken together, we demonstrated that the alteration of the thiol redox status and mitochondrial damage contributed to OIT-induced BBB dysfunction, and we hope that our findings will improve our understanding of the potential hazardous health effects of IT biocides.

Isothiazolinones Common in Children's Toy Slime

BACKGROUND

Contact dermatitis to homemade slime has been frequently reported, with isothiazolinones as a likely sensitizer. Little is known on the presence of these preservatives in commercial, store-bought slime products.

OBJECTIVES

The aims of the study were to review the literature on "slime dermatitis" and to assess for the presence of isothiazolinones in commercially available slime products and homemade slime components.

METHODS

An experimental, colorimetric spot test was used to verify the presence of isothiazolinones in 38 slime products of the 16 best-selling commercial slime kits, 1 finished homemade slime, and 4 common components of homemade slime. High-performance liquid chromatography with UV detection was performed on 8 commercial slime products.

RESULTS

According to the spot test, 27 (71%) of the 38 commercial slime products contained isothiazolinones. High-performance liquid chromatography with UV detection analyses indicated, however, that false-positives and false-negatives readily occur: isothiazolinone content was correctly identified in only 4 (50%) of the 8 samples.

CONCLUSIONS

This study is the first to demonstrate the presence of isothiazolinones in commercial slime toys. Although the colorimetric spot test may have some utility as a screening assay, it is far from specific and likely not sensitive enough to reliably identify methylisothiazolinone.

Isothiazolinone Detection in Dish Soap and Personal Care Products: Comparison of Lovibond Isothiazolinone Test Kit and Ultrahigh-Performance Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

Isothiazolinones are commonly used preservatives, which may cause allergic contact dermatitis. The Lovibond Isothiazolinone Test Kit (LITK) has been reported to successfully identify clinically relevant, occult isothiazolinones in patient personal care products.

OBJECTIVE

The aim of the study was to analyze dish soaps and personal care products that do not declare isothiazolinones ("no-ISO") for the presence of isothiazolinones via 2 methods: LITK and ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

METHODS

No-ISO dish soaps (n = 9), a convenience sample of patient products (n = 6), and controls (positive [isothiazolinone declared], n = 5; negative, n = 2) were tested with LITK (X3) and UHPLC-MS/MS.

RESULTS

Several no-ISO dish soaps and personal products were positive for isothiazolinones (LITK, n = 12; UHPLC-MS/MS, n = 3). Ultrahigh-performance liquid chromatography-tandem mass spectrometry specifically identified methylisothiazolinone alone in 1 no-ISO dish soap, methylchloroisothiazolinone in another, and both in a third. Using UHPLC-MS/MS as the criterion standard, we observed the accuracy of LITK for 9 dish soaps was poor (sensitivity, 66.7%; specificity, 20%) and very poor for 6 personal care products (sensitivity, 0%; specificity, 0%).

CONCLUSIONS

Personal products may contain undeclared isothiazolinones. The current study found that LITK had poor accuracy for testing dish soap and personal care products. Clinicians should be aware of these factors when managing patients with contact allergy to isothiazolinones.

Allergic contact dermatitis: From pathophysiology to development of new preventive strategies

As the body's first line of defense, the skin is the organ most frequently exposed to chemicals present in personal hygiene products, household products, or materials used in the work environment. In this context, skin disorders account for more than 40 % of all occupational and work-related diseases, constituting a significant public health burden. Among skin disorders, allergic contact dermatitis (ACD) is the most prevalent occupational disease and the most common form of immunotoxicity in humans. ACD is a T-cell-mediated skin inflammation resulting from the priming and expansion of allergen-specific CD4⁺ and CD8⁺ T cells. The clinical condition is characterized by local skin rash, itchiness, redness, swelling, and lesions, being mainly diagnosed by the patch test. Upon ACD diagnosis, avoiding the exposure to the triggering allergen is the mainstay of treatment to prevent future flares. In cases where avoidance is not possible, the use of a standard of care interim treatments such as steroid creams or ointments, barrier creams, and moisturizers are strongly recommended to alleviate symptoms. In this review, we sought to provide the reader with an overview of the pathophysiology of ACD as well as the currently available pharmacological treatment options. Furthermore, a comprehensive outline of several preventive strategies is also provided.

Allergic contact dermatitis to cosmetics: retrospective analysis of a population subjected to patch tests between 2004 and 2017

Background

Cosmetics are part of the daily life of the population, and their use can lead to allergic contact dermatitis.

Objectives

To assess the profile of patients diagnosed with allergic contact dermatitis to cosmetics treated at a referral center for 13 years, as well as the characteristics of the clinical picture and allergens involved.

Methods

This was a retrospective study, with analysis of medical records of patients attended at this service. The individuals included had a diagnostic hypothesis of allergic contact dermatitis to cosmetics and had previously been submitted to epicutaneous tests.

Results

A total of 1405 medical records were analyzed, 403 (28.7%) with suspected allergic contact dermatitis to cosmetics and 232 (16.5%) with confirmed diagnosis. Of these, 208 (89.7%) were women, and the age group most affected was 31 − 60 years. The most common locations were face in 195 cases (25.8%), cervical region in 116 (15.3%), and trunk in 96 (12.6%). The main allergens in the contact tests were toluene-sulfonamide-formaldehyde resin in 69 cases (29.7%), paraphenylenediamine in 54 (26.3%), Kathon CG® in 41 (20.7%), and fragrance-mix 1 in 29 (16.4%). In 154 (66.4%) of the 232 patients with a confirmed diagnosis of allergic contact dermatitis to cosmetics it was possible to specify the cosmetic product responsible for the lesions.

Study limitations

The absence of some allergens considered important in the world as causes of allergic contact dermatitis, which are not readily accessible among us.

Conclusions

The data of the analyzed population (predominance of young women), as well as the location of the lesions (face and cervical area) and the main allergens involved were consistent with those from the world literature.

Methylchloroisothiazolinone/methylisothiazolinone and methylisothiazolinone contact allergy: A 24-year, single-center, retrospective cohort study from Turkey

BACKGROUND

Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) and MI allergy caused a global epidemic during the period 2010 to 2015, reaching its peak in 2013/14.

OBJECTIVE

To investigate the characteristics of MCI/MI and MI allergy in Turkey over 24 years.

METHODS

A total of 2310 patients patch tested between 1996 and 2019 with MCI/MI 0.01% aq. or MCI/MI 0.02% aq., with or without MI 0.2% aq., were analyzed.

RESULTS

The overall prevalence of contact sensitization was 3.3% (n = 77) with a peak level of 16.4% in 2015. The prevalence gradually decreased thereafter, but was still high (6.5%) in 2019. Seventy-three patients had clinically relevant sensitizations. MI could detect clinically relevant sensitizations in all seven patients with a negative patch test reaction to MCI/MI 0.02%. Non-occupational allergic contact dermatitis (ACD) was most frequently seen, mainly in women, with hand/face eczema from rinse-off or leave-on cosmetics, such as wet wipes. Occupational ACD was mainly seen among men with airborne eczema from wall paints in house painters, or with hand eczema from hair gel/wax in men's barbers.

CONCLUSIONS

The prevalence of MCI/MI and MI sensitization in Turkey following the peak in 2015 is still high. This is probably due to the currently allowed level of 100 ppm for MI in rinse-off cosmetics. This needs to be urgently reduced.

Pediatric contact dermatitis: what's new

PURPOSE OF REVIEW

Allergic contact dermatitis (ACD) was once thought to be rare in children but recent studies have demonstrated that the prevalence of ACD is common and appears to be increasing in children. Current trends including toys, hobbies, and personal care products may play a role in potentially new allergen exposure or resurgence of certain allergens, making ACD a moving target in children.

RECENT FINDINGS

ACD and atopic dermatitis can coexist and certain clinical features can help differentiate ACD from endogenous atopic dermatitis in children. It is important to consider ACD in children with recalcitrant atopic dermatitis or dermatitis with atypical distribution. Patch testing has become a more common practice in children. In 2018, the first expert consensus-derived pediatric baseline series consisting of 38 allergens was proposed to aid in the diagnosis of ACD in children. Comparing recent patch testing data in the pediatric population, the top allergens ubiquitously identified were nickel, cobalt, neomycin, Myroxylon pereirae (balsam of Peru), fragrance mix I, fragrance mix II, methylisothiazolinone, methylchloroisothiazolinone/ methylisothiazolinone, formaldehyde, and lanolin.

SUMMARY

ACD is a common problem in children. Detection through patch testing, avoidance of offending allergens, and prevention of common allergens are the main focus of management of ACD in children.

In vivo demonstration of immunologic cross-reactivity to octylisothiazolinone in patients primarily and strongly sensitized to methylisothiazolinone

BACKGROUND

Notwithstanding that concomitant exposure to different isothiazolinone derivatives may result in concomitant sensitization, clinical and animal studies have suggested cross-reactivity between these derivatives, notably between methylisothiazolinone (MI) and octylisothiazolinone (OIT).

OBJECTIVE

To investigate if patients sensitized to MI show cross-reactions to OIT and/or to benzisothiazolinone (BIT) by applying the concept of the re-test method.

PATIENTS AND METHODS

From March to October 2019 consecutive patients were patch tested with MI 0.2% aqueous in duplicate at the two lower corners of both shoulder blades. Patients sensitized to MI, but not to OIT 0.1% petrolatum (pet.) nor to BIT 0.1% pet., were re-tested, 2 months later, with the latter two derivatives at the skin sites where the MI reactions had fully disappeared.

RESULTS

Of 116 patients, 15 (13%) were sensitized to MI, eight of these not sensitized to BIT nor to OIT. Of these, seven patients, all (very) strongly sensitized to MI, were re-tested: five patients showed positive patch test reactions to OIT 0.1% pet.; one patient to OIT 0.1% pet. and BIT 0.1% pet.; and one other patient showed no reactions.

CONCLUSION

This study suggests that patients primarily and strongly sensitized to MI may show immunologic cross-reactions to OIT, and to a far lesser extent to BIT.

Methylisothiazolinone response on disposable electrochemical platforms modified with carbon, nickel or gold-based nanomaterials

Screen-printed carbon electrodes (SPCE) were modified with nanocomposite membranes based on polystyrene sulfonate (PSS) or poly(diallyldimethylammonium) (PDDA) matrices and different nanomaterials. Carbon nano-powders (CnP), carbon nano-fibers (CnF) and multi-walled carbon nano-tubes (MWCNTs) were incorporated on PSS matrix. Nickel was incorporated by ion exchange in PSS-CnP composite membranes. Gold nanoparticles (AuNp) were photochemically and electrochemically synthesised and introduced into PDDA membranes. The electrochemical behaviour of methylisothiazolinone (MIT) using these modified electrodes was studied by cyclic voltammetry in 0.1 mol L^-1 NaOH. No electrochemical response is obtained on PSS-nanocarbon transducers at the assayed conditions. The nickel-based transducers allow the MIT identification but not quantification. Using AuNp-based electrochemical transducers, it is observed that in presence of MIT, the electron transfer for AuNp reduction is inhibited, and an oxidation peak appears at + 0.45 V, indicating an interaction between MIT and AuNp on the electrode surface. These facts support the usefulness of the AuNp-based electrodes for the determination of MIT. The intensity of the anodic peak observed at + 0.45 V vs. Ag/AgCl was used as analytical signal for MIT determination. A linear relationship between anodic peak current and MIT concentration is observed in the range 8.7 to 36 mg L^-1 using the transducer prepared by incorporating gold into the PDDA membrane by ion exchange and synthesising AuNp electrochemically. For this electrode, the limit of detection is 2.6 mg L^-1 and the reproducibility, expressed as relative standard deviation (RSD), is lower than 7%. Graphical abstractSchematic representation of the preparation of gold nanoparticles (AuNp) and poly(diallyldimethylammonium) (PDDA)-based platforms and methylisothiazolinone (MIT) electrochemical response on these nanostructured platforms.

Isothiazolinone Biocides: Chemistry, Biological, and Toxicity Profiles

The importance of isothiazole and of compounds containing the isothiazole nucleus has been growing over the last few years. Isothiazolinones are used in cosmetic and as chemical additives for occupational and industrial usage due to their bacteriostatic and fungiostatic activity. Despite their effectiveness as biocides, isothiazolinones are strong sensitizers, producing skin irritations and allergies and may pose ecotoxicological hazards. Therefore, their use is restricted by EU legislation. Considering the relevance and importance of isothiazolinone biocides, the present review describes the state-of-the-art knowledge regarding their synthesis, antibacterial components, toxicity (including structure–activity–toxicity relationships) outlines, and (photo)chemical stability. Due to the increasing prevalence and impact of isothiazolinones in consumer’s health, analytical methods for the identification and determination of this type of biocides were also discussed.

Simultaneous Quantitative Analysis of Six Isothiazolinones in Water-Based Adhesive Used for Food Contact Materials by High-Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS)

In this study, a target analytical approach using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was developed to simultaneously determine six isothiazolinones containing 2-Methylisothiazol-3(2H)-one (MI), 5-Chloro-2-methyl-4-isothiazolin-3-one (CMI), 1,2-benzisothiazolin-3-one (BIT), 2-Octyl-3(2H)-isothiazolinone (OIT), Dichlorooctylisothiazolinone (DCOIT), and 2-methyl-1,2-benzisothiazolin-3-one (MBIT) in water-based adhesive used for food contact materials. The main factors affecting extraction efficiency such as extraction method, extraction time, extraction solvent, and solid–liquid ratio have been evaluated by using real adhesive samples. Multiple-reaction monitoring (MRM) was used for the qualitative and quantitative analyses of targeted isothiazolinones. This method was demonstrated as an effective and reliable technique for detecting multiple isothiazolinones with satisfactory recoveries (81.5~107.3%), and the limits of detection (LOD) and quantification (LOQ) were obtained at a low level. This method was validated and applied to the determination of six isothiazolinones in commercial water-based adhesives. The present results revealed that these adhesives contained a combination of isothiazolinones (BIT, MI, CMI, and MBIT) with the concentration ranging from 2.27 to 123.5 mg/kg. To our knowledge, it is the first time it has been reported that MBIT was detected in water-based adhesives used for food contact materials, which requires a further investigation for its migration to food and the risk to human health.

The rash that presents as a red swollen face

A red swollen face can be a skin sign of a potentially life-threatening condition. We present in detail the main clinical presentations, diagnostic tests, and management of some of the most severe conditions that can frequently present as a red and swollen face: acute or recurrent angioedema, mast cell-driven or bradykinin-mediated angioedema, nonhereditary and hereditary angioedema, allergic or photoallergic facial contact dermatitis, contact urticaria, severe adverse drug reactions (particularly drug reaction with eosinophilia and systemic symptoms [DRESS]), skin infections (erysipelas, cellulitis, necrotizing fasciitis), and autoimmune diseases (dermatomyositis). There are many other conditions that also have to be considered in the differential diagnosis of a red swollen face.

The epidemic of methylisothiazolinone contact allergy in Europe: follow-up on changing exposures

BACKGROUND

Methylisothiazolinone (MI) has caused an unprecedented epidemic of contact allergy in Europe and elsewhere. Subsequently, regulatory action has been taken, at least in Europe, aiming at reducing risk of MI sensitization.

OBJECTIVE

To follow-up on the prevalence of contact allergy to MI in consecutively patch tested patients and assess the spectrum of products containing MI or methylchloroisothiazolinone (MCI)/MI in patients positive to MI which elicited current allergic contact dermatitis.

METHODS

A cross-sectional survey was performed in 2016 and 2017, including all adult patients patch tested with the baseline series (including MI 0.2% aq.) between 1 May and 31 October at 14 centres in 11 European countries. Patients with positive reactions (+ to +++) to MI were further examined regarding history, clinical characteristics and eliciting products, which were categorized into 34 types and 4 classes (leave-on, rinse-off, household, occupational). The results were compared with the reference year 2015.

RESULTS

A total of 317 patients, n = 202 of 4278 tested in 2016 (4.72%) and n = 115 of 3879 tested in 2017 (2.96%), had positive reactions to MI; the previous result from 2015 was 5.97% (P < 0.0001). The share of currently relevant contact allergy among all positive reactions declined significantly as well (P = 0.0032). Concerning product classes, a relative decline of leave-on and a relative increase of rinse-off and household products was noted.

CONCLUSION

The prevalence of MI contact allergy decreased by 50% from 2015 to 2017. As a consequence of regulation, the share of cosmetics products (leave-on in particular) eliciting allergic contact dermatitis is decreasing. The chosen method of analysing causative products in sensitized patients has proven useful to monitor effects of intervention.

Novel photodynamic coating reduces the bioburden on near-patient surfaces thereby reducing the risk for onward pathogen transmission: a field study in two hospitals

BACKGROUND

Near-patient surfaces are recognized as a source for hospital-acquired infections. Such surfaces act as reservoirs for microbial contamination by which pathogens can be transmitted from colonized or infected patients to susceptible patients. Routine disinfection of surfaces only results in a temporal elimination of pathogens, and recontamination inevitably occurs shortly between disinfections.

AIM

A novel antimicrobial coating based on photodynamics was tested under laboratory conditions and subsequently in a field study in two hospitals under real-life conditions.

METHODS

Identical surfaces received a photodynamic or control coating. Bacterial counts [colony-forming units (cfu)/cm²) were assessed regularly for up to 6 months.

FINDINGS

The laboratory study revealed a mean reduction of several human pathogens of up to 4.0 ± 0.3 log₁₀. The field study in near-patient environments demonstrated mean bacterial values of 6.1 ± 24.7 cfu/cm² on all control coatings. Photodynamic coatings showed a significantly lower mean value of 1.9 ± 2.8 cfu/cm² (P<0.001). When considering benchmarks of 2.5 cfu/cm² or 5 cfu/cm², the relative risk for high bacterial counts on surfaces was reduced by 48% (odds ratio 0.38, P<0.001) or 67% (odds ratio 0.27, P<0.001), respectively.

CONCLUSION

Photodynamic coatings provide a significant and lasting reduction of bacterial counts on near-patient surfaces, particularly for high bacterial loads, in addition to routine hygiene. The promising results of this proof-of-concept study highlight the need for further studies to determine how this novel technology is correlated with the frequency of hospital-acquired infections.