Skin Tissue Culture Research Articles

P-750. The Use of Doxycycline for MRSA SSTIs in the Setting of Tetracycline Resistance (The DOXY-MASTER Study)

Abstract Background Inducible doxycycline resistance has been reported in tetracycline (TET)-resistant methicillin-resistant Staphylococcus aureus (MRSA) isolates. The two major resistance mechanisms found in MRSA involve efflux pump expression and ribosomal protection proteins (RPP), both of which are mediated by the presence of tet genes. In isolates that are positive for tetK and negative for tetM, in vitro studies have demonstrated an increase in the mean minimum inhibitory concentration (MIC) of doxycycline above the Clinical and Laboratory Standards Institute (CLSI) breakpoint for susceptibility after incubation in broth containing doxycycline. This study aims to investigate the presence of inducible resistance as defined by treatment failure with the use of doxycycline for MRSA skin and soft tissue infections (SSTIs) in the setting of tetracycline resistance. Methods This retrospective study analyzed patients from a 5-hospital health system and ensuing outpatient clinics from January 1, 2022 to February 29, 2024. Eligible patients were adults that had received doxycycline for the treatment of SSTI with a positive skin and soft tissue culture for MRSA that was susceptible to doxycycline. Exclusion criteria included presence of other organisms or concomitant infections requiring antimicrobial therapy, receipt of > 24 hours of effective systemic antimicrobial therapy against MRSA, and suspected or confirmed osteomyelitis or septic arthritis. Results A total of 164 patients were screened, and 35 patients met the inclusion criteria for analysis: 11 in the TET-resistant arm and 24 in the TET-susceptible arm. Any readmission occurred in 6 (54.5%) patients in the TET-resistant arm and 7 (29.2%) patients in the TET-susceptible arm. However, readmission for SSTIs occurred in 1 patient (9.1%) in the TET-resistant arm and 2 patients (8.3%) in the TET-susceptible arm (p >0.999) with an average of 39.3 and 20.3 days to readmission (p = 0.179), respectively. Conclusion In this small study sample, the use of doxycycline for MRSA SSTIs in the setting of tetracycline-resistance had no difference in treatment failure when compared to its use in tetracycline-susceptible isolates. This data suggests that susceptibility to doxycycline may be preserved in tetracycline-resistant MRSA isolates. Disclosures All Authors: No reported disclosures

P-1477. In vitro efficacy of Minocycline on Skin, Soft Tissue and Musculoskeletal Gram Negative bacterial isolates

Abstract Background Minocycline is a second-generation tetracycline with a broad antimicrobial spectrum. It is often used in chronic suppression of musculoskeletal infections, given activity against gram positive organisms. Efficacy of Minocycline against gram negative skin and soft tissue infection has not previously been defined. In this study, we review in vitro minocycline efficacy against isolates from skin, muscle, and bone sources.Fig 1.Organisms isolated Methods We conducted a retrospective review of all minocycline susceptibility testing performed on musculoskeletal GNB isolates performed at the Mayo Clinic reference lab between 2013-2022. We describe the isolates broken down by site of culture and organism isolated. Then, we calculated the overall susceptibility of these isolates to Minocycline and susceptibility of the most common 6 organisms isolated.Fig 2.Sites of gram negative isolation Results During the study timeframe, we identified 13,567 gram negative isolates from musculoskeletal sites. Of 330 species identified, 19 were identified in at least 100 isolates (fig 1). Of 36 unique sites, 19 sites were each identified in at least 100 isolates (fig 2). 1920 isolates were tested for susceptibility to minocycline. Of these, 1584 (82.5%) were susceptible to minocycline. Of the most common organisms identified and tested for minocycline susceptibility, 99% of Stenotrophomonas maltophilia, 83% of Enterobacter cloacae, 80% of Escherichia coli, 68% of Acinetobacter baumanii, 1% of Proteus mirabilis, 53% of Klebsiella pneumoniae, 65% of Serratia marcescens isolates were susceptible to minocycline (fig 3). Pseudomonas aeruginosa isolates were not tested, due to innate resistance.Fig 3.Minocycline susceptibility compared to key organisms Conclusion A majority of skin and soft tissue cultures positive for Gram negative isolates were below the waist line. Of these, we reported organisms most commonly found. Minocycline showed in vitro activity against some commonly isolated gram negative organisms, especially E.coli, Acinetobacter, and Stenotrophomonas. Further research is needed into the efficacy of minocycline in gram negative skin and soft tissue infections, but it may represent a viable oral option, especially in the end of life. Disclosures All Authors: No reported disclosures

JAAD Game Changers: Diagnosis of deep cutaneous fungal infections: Correlation between skin tissue culture and histopathology

JAAD Game Changers: Diagnosis of deep cutaneous fungal infections: Correlation between skin tissue culture and histopathology

The effect of histopathologic analysis and tissue cultures on inpatient management of cellulitis: a randomized control trial

Background: In the absence of a gold-standard diagnostic modality for cellulitis, sterile inflammatory disorders may be misdiagnosed as cellulitis. Objective: To determine the utility of skin biopsy and tissue culture for the diagnosis and management of patients admitted with a diagnosis of presumed cellulitis. Design: Pilot single-blind parallel group randomized controlled clinical trial in 56 patients with a primary diagnosis of presumed cellulitis. In the intervention group only, skin biopsy and tissue culture results were made available to the primary care team to guide diagnosis and management. Length of hospital stay and antibiotic use were evaluated as outcome measures. Results: Length of stay showed the greatest opportunity for further study as a primary outcome (intervention: 4, IQR (2–6) vs. control: 5 IQR (3–8) days; p = 0.124). Limitations: The COVID-19 pandemic placed limitations on participant enrollment and study duration; in addition, data was collected from a single medical center. Conclusion: This study demonstrates that length of stay and anti-pseudomonal antibiotic de-escalation are endpoints that may be influenced by biopsy and tissue culture results in presumed cellulitis patients; these outcomes warrant further study.

Genital ulcers in hospitalized patients: How often is genital herpes the culprit?

AbstractBackgroundGenital herpes (GH) is the main infectious cause of genital ulcers worldwide. Clinical diagnosis alone may be misleading, especially in immunocompromised patients in whom atypical presentations are common.ObjectivesTo assess the herpetic etiology of genital ulcers in immunocompromised and immunocompetent hospitalized adults, and to identify the most frequent differential diagnoses within each patient group.MethodsWe conducted a retrospective transverse study at a third‐level center in Mexico City using PCR testing (HSV‐1, HSV‐2, VZV) in hospitalized patients with genital ulcers to diagnose GH. When negative, biopsy and tissue cultures were taken to establish the final diagnosis. Data from a 2‐year period (March 2021 to April 2023), including demographic characteristics, comorbidities, initial clinical suspicion, PCR test results, skin tissue biopsy results, cultures results, and final diagnosis, were collected from May 2023 to June 2023.ResultsA total of 59 hospital patients with genital ulcers underwent PCR testing due to clinical suspicion of GH, of which 39 (66%) were immunocompromised. The diagnosis was confirmed in 32/59 cases (54%), of which 22/32 (69%) were immunocompromised and 10/32 (31%) immunocompetent. In the 17 immunocompromised adults in whom GH was excluded, other viral (34%) or bacterial (23%) infections were the next most frequent etiologies. Meanwhile, among the 10 immunocompetent patients without GH, noninfectious causes, such as incontinence‐associated dermatitis (15%) and trauma or pressure ulcers (15%), were the most prevalent.ConclusionsGenital ulcers in hospitalized adults should raise the suspicion of infectious etiologies, particularly of GH. Diagnostic confirmation with tests such as PCR is crucial given the uncertainty of its clinical diagnosis. Once GH diagnosis is excluded, immunocompromised patients should be evaluated for other infectious etiologies, while noninfectious causes should be considered first in immunocompetent patients.

Disseminated Fusarium spp. Infection in an Immunocompromised Patient

Fusarium infections are rare opportunistic mycosis caused by Fusarium spp. Its clinical presentation depends on the immunological status of the host; those immunosuppressed hemato-oncological diseases can present invasive fungal. Diagnosis is through Skin or blood culture and it is treated with antifungal medication such as amphotericin B and voriconazole alone or in combination. We present the case of a neutropenic 55-year-old woman undergoing chemotherapy treatment for B-cell acute lymphoblastic leukemia who presented disseminated skin lesions which included macules, papules and violaceous nodules, with a central necrotic crust. A skin biopsy, KOH exam, tissue and blood cultures were carried out where Fusarium spp. were identified. Treatment with amphotericin b combined with voriconazole was initiated, with good results and complete disappearance of the lesions.

Impact of Pharmacist Involvement in Post-Discharge Emergency Department Culture Review.

Background: Many infectious diseases are diagnosed in emergency departments (ED) and patients are prescribed antimicrobial therapy. Results from cultures typically take a few days to become finalized. Following up on these results is necessary when medication changes are indicated due to results that show bacteria are resistant to the prescribed antibiotics. Involving pharmacists in assessing the culture and sensitivity results, and making interventions when needed, is an innovative way to ensure that patients receive appropriate antimicrobial therapy based on the culture and sensitivity data. This study analyzed the impact of pharmacist involvement in the ED's post-discharge positive culture review process on ED re-visits and hospitalizations. Methods: This single-center, pre- and post-implementation study examined the impact of pharmacist involvement in the post-ED visit culture review process on ED re-visits and hospitalizations. Positive microbiological results included documented growth from urine, skin and soft tissue, throat, blood, or stool cultures. Patients included in the study were of 18 years of age or older and had a positive culture result post ED-discharge. Patients were excluded from the study if they were admitted to the hospital or transferred to another facility. The primary outcomes included ED re-visits within 7 days and hospital readmissions within 30 days for the same condition. The secondary outcomes were percentage of pharmacist interventions accepted and types of pharmacist interventions implemented. Results: A total of 141 patients were included in the study, with 65 in the pre-implementation group and 76 in the post-implementation group. The primary outcome of ED re-visits within 7 days for the same condition occurred in 11 (17%) patients in the pre-implementation group and 5 (7%) patients in the post-implementation group (P = .0454). The primary outcome of hospitalizations within 30 days for the same condition occurred in 5 (8%) patients in the pre-implementation group and 1 (1%) patient in the post-implementation group (P = .0137). Seventeen (94%) out of the 18 pharmacist interventions were accepted and implemented. The intervention types implemented were to recommend to: change antibiotic (35%), not initiate antibiotic (24%), initiate antibiotic (24%), and continue antibiotic (18%). Conclusion: Pharmacist involvement in the ED post-discharge positive culture review process showed a decrease in ED re-visits and hospitalizations for the same condition.

Feasibility of engineered Bacillus subtilis for use as a microbiome-based topical drug delivery platform.

Non-adherence to medication is a major challenge in healthcare that results in worsened treatment outcomes for patients. Reducing the frequency of required administrations could improve adherence but is challenging for topical drug delivery due to the generally short residence time of topical formulations on the skin. In this study, we sought to determine the feasibility of developing a microbiome-based, long-acting, topical delivery platform using Bacillus subtilis for drug production and delivery on the skin, which was assessed using green fluorescent protein as a model heterologous protein for delivery. We developed a computational model of bacteria population dynamics on the skin and used its qualitative predictions to guide experimental design choices. Using an ex vivo pig skin model and a human skin tissue culture model, we saw persistence of delivered bacteria for multiple days and observed little evidence of cytotoxicity to human keratinocyte cells in vitro. Finally, using an in vivo mouse model, we found that the delivered bacteria persisted on the skin for at least 1 day during every-other-day application and did not appear to present safety concerns. Taken together, our results support the feasibility of using engineered B. subtilis for topical drug delivery.

In-vitro Antimicrobial Study of Non/irradiated Ylang-ylang Essential Oil Against Multi Drug Resistant Pathogens with Reference to Microscopic Morphological Alterations

Essential oils have proven to possess great potential in the field of biomedicine due to their ability to effectively eradicate a diverse range of pathogenic microbes. In this study, the antimicrobial activity of ylang-ylang essential oil (YY-EO) was screened against twelve multidrug-resistant pathogens. The YY-EO was effective up to 536 μg/ml, with the highest inhibition zone in case of S. aureus MMCC21 and Escherichia coli MMCC24. The least effect on both Bacillus cereus MMCC11 and Klebsiella pneumonia MMCC16. The major components of the essential oil were identified using GC–MS analysis. Different gamma irradiation doses against the YY-EO were evaluated as a tool of natural decontamination. Moreover, the antimicrobial assay after irradiation proved no significant changes regarding the antimicrobial activity before and after irradiation of EO at the applied dose. The minimum inhibitory concentration (MIC) for the EO against the tested pathogens was detected. The possible morphological changes in some of the bacterial and yeast cells at the recognized MIC and 2MIC were detected using the scanning electron microscope (SEM). Results revealed a notable change in terms of both the microbial cell population and the morphology of the tested bacterial and yeast cells. The cytotoxicity of ylang-ylang EO was evaluated against normal skin tissue culture and showed a potential cytotoxic effect at concentrated doses. These results refer to the importance of YY-EO as a natural antimicrobial agent and the possible application of YY-EO as a surface decontaminant, but they also draw attention to the importance of the EO concentration used in different applications to avoid possible toxic effects.

Functional outcomes and complications of patients contaminated with Cutibacterium acnes during primary reverse shoulder arthroplasty: study at two- and five-years of follow-up.

The objective of the study was to compare the functional outcomes and the complication rate of the patients with C. acnes contamination at the end of the primary reverse shoulder arthroplasty (RSA) surgery to those patients without C. acnes contamination. A total of 162 patients were included. In all cases, skin and deep tissue cultures were obtained. A molecular typing characterization of the C. acnes strains was performed. Functional outcomes were assessed with the Constant score at the two and fiveyear follow-up and all complications were also recorded. A total of 1380 cultures were obtained from the 162 primary RSA surgeries. Of those, 96 turned out to be positive for C. acnes. There were 25 patients with positive cultures for C. acnes. The overall postoperative Constant score was not significantly different between those patients having C. acnes-positive cultures and those with negative cultures at the two and fiveyear follow-up (59.2 vs. 59.6 at two years, p 0.870, and 59.5 vs. 62.4 at five years, p 0.360). Patients with positive cultures presented a higher complication rate (p 0.001) with two infections, one revision surgery, and one dislocation. Patients ending up with C. acnes-positive cultures after primary shoulder arthroplasty surgery do not have worse clinical outcomes when compared to patients having negative cultures, but a greater number of complications were found in those patients with C. acnes-positive cultures.

DNA microarray chip assay in new use: early diagnostic value in cutaneous mycobacterial infection.

The clinical practicability of DNA microarray chip in detecting the presence of mycobacterial species/isolates directly in the skin tissues has not been evaluated, nor the efficacy of DNA microarray chip as a novel diagnostic tool for the early diagnosis of cutaneous mycobacterial infections is known. The present study analyzed the incidence of cutaneous mycobacterial infections in Shanghai and explored the efficacy of a novel DNA microarray chip assay for the clinical diagnosis of the disease from skin tissue specimens compared to traditional detection methods. A total of 60 participants fulfilling the defined diagnostic criteria and confirmed positive for cutaneous mycobacterial infections from 2019 to 2021 were enrolled in the study. Subsequent to recording the participants' medical history and clinical characteristics, the skin tissue specimens were collected for analyses. The specimens underwent histopathological analyses, skin tissue culture, and DNA microarray chip assay. Increased incidence of cutaneous mycobacterial infection was detected from 2019 to 2021. The most common infecting pathogen was M. marinum followed by M. abscessus. The sensitivity, specificity and accuracy of the skin tissue culture method were 70%, 100% and 76.62%, respectively, while that of the DNA microarray chip assay were 91.67%, 100% and 93.51%, respectively. The sensitivity and accuracy of the DNA microarray chip assay were significantly higher than those of the skin tissue culture method. The positive likelihood and diagnostic odds ratio were >10 and >1, respectively for both the methods. The negative likelihood ratio was significantly higher (30% vs 8.33%) and the Youden's index was significantly lower (70.00% vs 91.67%) in the skin culture method compared to that of the DNA microarray chip assay. There was a significant association of false negative results with a history of antibiotic use in the skin tissue culture method. Given the increasing incidence of cutaneous mycobacterial infections, early diagnosis remains a prime clinical focus. The DNA microarray chip assay provides a simple, rapid, high-throughput, and reliable method for the diagnosis of cutaneous mycobacterial infections with potential for clinical application.

High rate of invasive fungal infections during early cycles of azacitidine for patients with acute myeloid leukemia.

Acute myeloid leukemia (AML) is a form of cancer that is characterized by infiltration of the bone marrow, blood, and other tissues by proliferative, clonal, abnormally differentiated, and occasionally poorly differentiated cells of the hematopoietic system. Patients with acute myeloid leukemia (AML) receiving azacitidine (AZA) alone or in combination with venetoclax (VEN-AZA) are at increased risk for invasive fungal infections (IFIs). We compared the incidence and risk of IFI during these treatment regimens in a single Taiwan hospital. A total of 61 patients with AML received at least one course of AZA in the hematology ward of China Medical University Hospital (Taichung, Taiwan) between September 2012 and June 2020. Thirty-eight patients (62.3%) received AZA monotherapy; 23 (37.7%) received VEN-AZA. Incidence rates of probable and proven IFI were 18% and 1.6%, respectively, during AZA treatment. One proven case of Fusarium spp. infection was isolated by skin and soft tissue culture. Most (75%) IFI cases occurred during the first cycle of AZA therapy. Half of all IFI cases occurred in patients with prolonged neutropenia. The risk of IFI was significantly higher for the European LeukemiaNet (ELN) nonfavorable-risk group (intermediate- and adverse-risk group) versus the ELN favorable-risk group and for patients with prolonged neutropenia versus those without (P<0.05 for both comparisons). In this study, median OS did not differ significantly between patients with and without IFIs during AZA-containing regimens (14.6 months vs 13.7 months; P=0.59). The incidence of IFI was high in this AML cohort treated with AZA-containing regiments in Taiwan. The majority of IFI cases occurred during the early cycles of AZA (cycles 1-2). Prospective studies are needed to determine the optimal choice of antifungal prophylaxis agent during VEN-AZA therapy for AML.

Mitigation strategies among cutaneous T-cell lymphoma patients with positive Staphylococcus aureus skin and soft tissue cultures have unclear impacts on the risk of subsequent bacteremia

Infections originating in the skin/soft tissue are a major cause of mortality in cutaneous T-cell lymphoma (CTCL). We performed a retrospective analysis to characterize cutaneous cultures and assess risk factors for bacteremia among 69 patients with CTCL. Cutaneous infections and antimicrobial resistance were common. Black race and lymph node involvement were associated with bacteremia. Mitigating strategies for invasive infections in CTCL remain unclear. Highlights Skin/soft tissue infections are common in cutaneous T-cell lymphoma (CTCL). Black race, lymph node involvement, and positive cultures for S. aureus, Gram-negative bacteria, or multiple organisms were associated with an increased rate of bacteremia. The role of antimicrobial prophylaxis and staphylococcus decolonization is unclear.

Bedside Diagnosis for Disseminated Deep Dermatophytosis: a Case Series Study.

Deep cutaneous fungal infections including deep dermatophytosis are responsible for significant morbidity and mortality, especially in immunocompromised patients. Variable and longer turnaround time on tissue culture results delay diagnosis. We sought to seek the fast bedside diagnosis for disseminated deep dermatophytosis by direct microscopy using a blunt scalpel or needle aspiration before biopsy. This is a 6-year retrospective review of patients with a diagnosis of disseminated deep dermatophytosis seen at a single tertiary care institution. Trichophyton rubrum was isolated in four patients, and T. mentagrophyte complex in one patient. All the dermatophyte isolates can grow at 37°C. Microscopy of purulence sampling from intact nodules demonstrated abundant septate hyphae, and also isolation from purulence was concordance with skin tissue culture. Ultrasound-guided sampling from non-eroded can yield purulence, and direct microscopy of purulence may facilitate rapid diagnosis of deep dermatophytosis and serve to prevent disease progression and dissemination.

Diagnostic work-up and treatment in patients with pyoderma gangrenosum: retrospective analysis of US insurance claims-based data.

Pyoderma gangrenosum (PG) is a rare, and often challenging to diagnose, inflammatory disorder with relatively high rates of morbidity and mortality. Central to the diagnosis of PG is histologic evaluation and exclusion of other entities. Large-scale studies investigating the proportion of patients receiving a thorough diagnostic work-up, as well as prevalence studies regarding comorbidities and systemic treatment in PG using claims-based data, are sparse. Our objective was to identify patients diagnosed with PG and describe the diagnostic work-up and prevalence of common comorbidities and therapies in this population using claims-based data in a retrospective cohort study. In order to better understand practices of diagnostic work-up, we captured rates of skin biopsy, tissue culture, and/or surgical debridement prior to initial diagnosis. We also identified the prevalence of PG-associated comorbidities and initial immunosuppressive therapy given for PG. Of the 565 patients diagnosed with PG, 9.4% underwent skin biopsy, 8% tissue culture, and 1.4% both skin biopsy AND tissue culture prior to diagnosis. Inflammatory bowel disease was the most prevalent comorbidity (16.3%). The most common treatment administered was systemic corticosteroids (17%). Although practice guidelines explicitly delineate histology and exclusion of infection as important diagnostic criteria, only a minority of patients in this study underwent skin biopsy and/or tissue culture prior to receiving a diagnosis of PG, suggesting that patients may receive a diagnosis of PG without having tissue evaluation. Such discordance between practice guidelines and "real-world" practice inevitably increases the risk for misdiagnosis of PG and misdirected treatment with immunosuppressants for presumptive PG in cases of PG mimickers. Moreover, comorbidities associated with PG may occur, or be identified in, a lower proportion of patients as compared with what is reported in the existing literature. Study limitations include a population restricted to < 65 years with commercial insurance and the reliance upon ICD diagnostic coding to capture the population.

Characteristics of a kHz helium atmospheric pressure plasma jet interacting with two kinds of targets

This study investigates the influence of two types of target, skin tissue and cell culture medium, with different permittivities on a kHz helium atmospheric pressure plasma jet (APPJ) during its application for wound healing. The basic optical–electrical characteristics, the initiation and propagation and the emission spectra of the He APPJ under different working conditions are explored. The experimental results show that, compared with a jet freely expanding in air, the diameter and intensity of the plasma plume outside the nozzle increase when it interacts with the pigskin and cell culture medium targets, and the mean velocity of the plasma bullet from the tube nozzle to a distance of 15 mm is also significantly increased. There are also multiple increases in the relative intensity of OH (A2Σ → X2Π) and O (3p5S–3s5S) at a position 15 mm away from nozzle when the He APPJ interacts with cell culture medium compared with the air and pigskin targets. Taking the surface charging of the low permittivity material capacitance and the strengthened electric field intensity into account, they make the various characteristics of He APPJ interacting with two different targets together.

JAAD Game Changers∗: Diagnosis of deep cutaneous fungal infections: Correlation between skin tissue culture and histopathology

JAAD Game Changers∗: Diagnosis of deep cutaneous fungal infections: Correlation between skin tissue culture and histopathology

Complicated cutaneous leishmaniasis caused by an imported case of Leishmania tropica in Japan: a case report

BackgroundLeishmaniasis is not endemic in Japan, and imported cases are rare. However, there are increasing concerns regarding imported cases of cutaneous leishmaniasis from endemic countries to Japan. This report describes a case of imported cutaneous leishmaniasis that was diagnosed and treated in Japan.Case presentationA 53-year-old Pakistani man presented with skin lesions on both malleoli of his right ankle and the dorsum of the left foot. The skin lesions manifested as erythematous nodules surrounding an ulcer in the center of the lesion. The lesions of the malleoli of his right ankle each measured 3 × 3 cm, and the lesion on the top of his left foot measured 5 × 4 cm. He had been living and working in Japan but had a history of a visit to Pakistan for about 2 months in 2018. The skin lesions were biopsied. Giemsa and hematoxylin and eosin staining of biopsy samples showed amastigotes of Leishmania in macrophages, and the presence of Leishmania was confirmed by skin tissue culture. Polymerase chain reaction using biopsy specimens identified Leishmania parasites, and DNA sequence analysis revealed that the species was Leishmania tropica. The patient was treated with intravenous liposomal amphotericin B for 6 days. The erythema disappeared, and the erythematous nodules resolved within 3 weeks.ConclusionThis is the first report of imported cutaneous leishmaniasis caused by L. tropica from Pakistan, and it is interesting that all three testing modalities showed positive results in this case.

Discovery of a Highly Selective MC1R Agonists Pentapeptide to Be Used as a Skin Pigmentation Enhancer and with Potential Anti-Aging Properties.

One of the first lines of cutaneous defense against photoaging is (a) the synthesis of melanin and (b) the initiation of an oxidative stress response to protect skin against the harmful effects of solar radiation. Safe and selective means to stimulate epidermal pigmentation associated with oxidative stress defense are; however, scarce. Activation of the melanocortin-1 receptor (MC1R) on epidermal melanocytes represents a key step in cutaneous pigmentation initiation and, additionally, it regulates cellular defense mechanisms like oxidative stress and DNA-repair. Thus, making the activation of MC1R an attractive strategy for modulating skin pigmentation and oxidative stress. In this context, we designed and synthesized pentapeptides that act as MC1R agonists. These peptides bound, with high potency, to MC1R and activated cAMP synthesis in CHO cells expressing human MC1R. Using one lead pentapeptide, we could show that this activation of MC1R was specific as testing the activation of other G-protein coupled receptors, including the MC-receptor family, was negative. In vitro efficacy on mouse melanoma cells showed similar potency as for the synthetic MC1R agonist alpha-melanocyte stimulating hormone (NDP-alpha-MSH). Moreover, we could reproduce this activity in human skin tissue culture. The lead pentapeptide was able to induce ex-vivo protein expression of key melanogenesis markers melanocyte inducing transcription factor (MITF), tyrosinase (TYR), and tyrosinase-related protein 1 (TYRP-1). Concerning oxidative stress response, we found that the pentapeptide enhanced the activation of Nrf2 after UVA-irradiation. Our results make this pentapeptide an ideal candidate as a skin pigmentation enhancer that mimics alpha-MSH and may also have anti-photoaging effects on the skin.

629 The ATP-dependent chromatin remodeler BRG1 controls epidermal keratinocytes migration during human cutaneous wound healing

SWI/SNF ATP-dependent chromatin remodelling complexes alter nucleosome structure, positioning and chromatin compaction state resulting in target gene activation or repression. The SWI/SNF complexes contain either BRG1 or BRM as the core ATPase together with other common and variable subunits. BRG1 is required for epidermal terminal differentiation in both mice and human; and for hair follicle stem cell activation during mouse hair regeneration and cutaneous wound healing. However, the role of SWI/SNF complexes in human skin wound healing remains unknown. Here, we demonstrate that genes encoding SWI/SNF complex subunits are expressed in human epidermis, and BRG1 is substantially upregulated in hyper-proliferating and migrating keratinocytes in healing cutaneous wounds. siRNA mediated BRG1 gene suppression leads to the substantial retardation of the wound closure in the full thickness human excision wounded skin tissue culture model and in scratched human primary keratinocyte monolayers. Furthermore, we showed that the retardation in the keratinocyte migration with no changes in cellular proliferation or apoptosis. Micro-array based transcriptome analysis revealed that BRG1 is required for full induction of genes encoding several signaling molecules, transcription factors and structural proteins involved in changes in cellular adhesion and cytoskeletal organization, driving keratinocyte migration during skin wound healing, including the stress cytokeratins 16 and 17. In summary, our data uncovered an essential role of the BRG1 chromatin remodeler in induction of the transcription programme driving keratinocyte migration during skin wound closure and re-epithelisation.