Use of the 'ex vivo' test to study long-term bacterial survival on human skin and their sensitivity to antisepsis

Gel-Dispersed Nanostructured Lipid Carriers Loading Thymol Designed for Dermal Pathologies

Purpose

Acne vulgaris is one of the most prevalent dermal disorders affecting skin health and appearance. To date, there is no effective cure for this pathology, and the majority of marketed formulations eliminate both healthy and pathological microbiota. Therefore, hereby we propose the encapsulation of an antimicrobial natural compound (thymol) loaded into lipid nanostructured systems to be topically used against acne.

Methods

To address this issue, nanostructured lipid carriers (NLC) capable of encapsulating thymol, a natural compound used for the treatment of acne vulgaris, were developed either using ultrasonication probe or high-pressure homogenization and optimized using 22-star factorial design by analyzing the effect of NLC composition on their physicochemical parameters. These NLC were optimized using a design of experiments approach and were characterized using different physicochemical techniques. Moreover, short-term stability and cell viability using HaCat cells were assessed. Antimicrobial efficacy of the developed NLC was assessed in vitro and ex vivo.

Results

NLC encapsulating thymol were developed and optimized and demonstrated a prolonged thymol release. The formulation was dispersed in gels and a screening of several gels was carried out by studying their rheological properties and their skin retention abilities. From them, carbomer demonstrated the capacity to be highly retained in skin tissues, specifically in the epidermis and dermis layers. Moreover, antimicrobial assays against healthy and pathological skin pathogens demonstrated the therapeutic efficacy of thymol-loaded NLC gelling systems since NLC are more efficient in slowly reducing C. acnes viability, but they possess lower antimicrobial activity against S. epidermidis, compared to free thymol.

Conclusion

Thymol was successfully loaded into NLC and dispersed in gelling systems, demonstrating that it is a suitable candidate for topical administration against acne vulgaris by eradicating pathogenic bacteria while preserving the healthy skin microbiome.

Colloidal hydrogel systems of thymol-loaded PLGA nanoparticles designed for acne treatment

Thymol-loaded PLGA nanoparticles (TH-NPs) were incorporated into different semi-solid formulations using variable gelling agents (carbomer, polysaccharide and poloxamer). The formulations were physicochemically characterized in terms of size, polydispersity index and zeta potential. Moreover, stability studies were performed by analyzing the backscattering profile showing that the gels were able to increase the nanoparticles stability at 4 °C. Moreover, rheological properties showed that all gels were able to increase the viscosity of TH-NPs with the carbomer gels showing the highest values. Moreover, the observation of carbomer dispersed TH-NPs under electron microscopical techniques showed 3D nanometric cross-linked filaments with the NPs found embedded in the threads. In addition, cytotoxicity studies showed that keratinocyte cells in contact with the formulations obtained cell viability values higher than 70 %. Furthermore, antimicrobial efficacy was assessed against C. acnes and S. epidermidis showing that the formulations eliminated the pathogenic C. acnes but preserved the resident S. epidermidis which contributes towards a healthy skin microbiota. Finally, biomechanical properties of TH-NPs dispersed in carbomer gels in contact with healthy human skin were studied showing that they did not alter skin properties and were able to reduce sebum which is increased in acne vulgaris. As a conclusion, TH-NPs dispersed in semi-solid formulations and, especially in carbomer gels, may constitute a suitable solution for the treatment of acne vulgaris.

In Situ Real-Time Monitoring for Aseptic Drilling: Lessons Learned from the Atacama Rover Astrobiology Drilling Studies Contamination Control Strategy and Implementation and Application to the Icebreaker Mars Life Detection Mission

In 2019, the Atacama Rover Astrobiology Drilling Studies (ARADS) project field-tested an autonomous rover-mounted robotic drill prototype for a 6-Sol life detection mission to Mars (Icebreaker). ARADS drilled Mars-like materials in the Atacama Desert (Chile), one of the most life-diminished regions on Earth, where mitigating contamination transfer into life-detection instruments becomes critical. Our Contamination Control Strategy and Implementation (CCSI) for the Sample Handling and Transfer System (SHTS) hardware (drill, scoop and funnels) included out-of-simulation protocol testing (out-of-sim) for hardware decontamination and verification during the 6-Sol simulation (in-sim). The most effective five-step decontamination combined safer-to-use sterilants (3%_hydrogen-peroxide-activated 5%_sodium-hypochlorite), and in situ real-time verification by adenosine triphosphate (ATP) and Signs of Life Detector (SOLID) Fluorescence Immunoassay for characterization hardware bioburden and airborne contaminants. The 20- to 40-min protocol enabled a 4-log bioburden reduction down to <0.1 fmoles ATP detection limit (funnels and drill) to 0.2-0.7 fmoles (scoop) of total ATP. The (post-cleaning) hardware background was 0.3 to 1-2 attomoles ATP/cm2 (cleanliness benchmark background values) equivalent to ca. 1-10 colony forming unit (CFU)/cm2. Further, 60-100% of the in-sim hardware background was ≤3-4 bacterial cells/cm2, the threshold limit for Class <7 aseptic operations. Across the six Sols, the flux of airborne contaminants to the drill sites was ∼5 and ∼22 amoles ATP/(cm2·day), accounting for an unexpectedly high Fluorescence Intensity (FI) signal (FI: ∼6000) against aquatic cyanobacteria, but negligible anthropogenic contribution. The SOLID immunoassay also detected microorganisms from multiple habitats across the Atacama Desert (anoxic, alkaline/acidic microenvironments in halite fields, playas, and alluvial fans) in both airborne and post-cleaning hardware background. Finally, the hardware ATP background was 40-250 times lower than the ATP in cores. Similarly, the FI peaks (FImax) against the microbial taxa and molecular biomarkers detected in the post-cleaned hardware (FI: ∼1500-1600) were 5-10 times lower than biomarkers in drilled sediments, excluding significant interference with putative biomarker found in cores. Similar protocols enable the acquisition of contamination-free materials for ultra-sensitive instruments analysis and the integrity of scientific results. Their application can augment our scientific knowledge of the distribution of cryptic life on Mars-like grounds and support life-detection robotic and human-operated missions to Mars.

Evaluating the antimicrobial efficacy of long-lasting hand sanitizers on skin

BACKGROUND

The microbicidal efficacy of hand sanitizer formulations is usually measured through standardized quantitative suspension tests and fingerpad tests; these cannot evaluate long-lasting formulations or are impractical due to biological risks, high cost, or time required for testing. With increased numbers of long-lasting microbicidal activity claims of commercially available hand sanitizers, alternative testing strategies are required.

AIM

To explore the use of a standardized ex-vivo pig skin model to reproducibly measure long-lasting efficacy of an alcohol-free hand sanitizer formulation.

METHODS

The microbicidal efficacy of an alcohol-free hand sanitizer was tested against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, and the enveloped virus SARS-CoV-2 with quantitative suspension tests (EN13727 and EN14476) with a contact time of 5 min. The product was then tested over a 6 h period using an ex-vivo pig skin model with a modified version of PAS 2424 to simulate the impact of skin abrasion.

FINDINGS

Quantitative suspension tests yielded a >5 log10 reduction for all organisms tested within a 5 min contact time. Pig skin tests showed reduced but consistent efficacy at all time points and indicated no significant impact of abrasion on efficacy.

CONCLUSION

The use of the ex-vivo pig skin model provides a potentially viable and convenient model system to test long-lasting hand sanitizer formulations, providing a path for sustainable hand sanitizer formulation claims of activity on skin.

The impact of bioactive textiles on human skin microbiota

In order to support the elevated market demand for the development of textiles with specific benefits for a healthy and safe lifestyle, several bioactive textiles with defined properties, including antimicrobial, antioxidant, anti-inflammatory, anti-odor, and anti-repellent, anti-ultraviolet (UV) radiation, have been proposed. Antimicrobial textiles, particularly, have received special interest considering the search for smart, protective textiles that also impact health and well-being. Although the incorporation of antimicrobials into textile material has been well succeeded, the addition of such components in textile clothing can influence the balance of the skin microbiota of the wearer. While most antimicrobial textiles have demonstrated good biocompatibility and antimicrobial performance against bacteria, fungi, and viruses, some problems such as textile biodegradation, odor, and dissemination of unwanted microorganisms might arise. However, little is known about the impact of such antimicrobial textile-products on human skin microbiota. To address this issue, the present review, for the first time, gives an overview about the main effects of antimicrobial textiles, i.e., antibacterial, antifungal, and antiviral, on skin microbiota while driving future investigation to elucidate their putative clinical relevance and possible applications according to their impact on skin microbiota. This knowledge may open doors for the development of more microbiota friendly textiles or antimicrobial textile-products able to target specific populations of the skin microbiota aiming to alleviate skin disorders, malodor, and allergies by avoiding the growth and spread of pathogenic microorganisms.

Thymol-loaded PLGA nanoparticles: an efficient approach for acne treatment

Background

Acne is a common skin disorder that involves an infection inside the hair follicle, which is usually treated with antibiotics, resulting in unbalanced skin microbiota and microbial resistance. For this reason, we developed polymeric nanoparticles encapsulating thymol, a natural active compound with antimicrobial and antioxidant properties. In this work, optimization physicochemical characterization, biopharmaceutical behavior and therapeutic efficacy of this novel nanostructured system were assessed.

Results

Thymol NPs (TH-NP) resulted on suitable average particle size below 200 nm with a surface charge around − 28 mV and high encapsulation efficiency (80%). TH-NP released TH in a sustained manner and provide a slow-rate penetration into the hair follicle, being highly retained inside the skin. TH-NP possess a potent antimicrobial activity against Cutibacterium acnes and minor effect towards Staphylococcus epidermis, the major resident of the healthy skin microbiota. Additionally, the stability and sterility of developed NPs were maintained along storage.

Conclusion

TH-NP showed a promising and efficient alternative for the treatment of skin acne infection, avoiding antibiotic administration, reducing side effects, and preventing microbial drug resistance, without altering the healthy skin microbiota. Additionally, TH-NP enhanced TH antioxidant activity, constituting a natural, preservative-free, approach for acne treatment.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01092-z.

Iktishaf+: A Big Data Tool with Automatic Labeling for Road Traffic Social Sensing and Event Detection Using Distributed Machine Learning

Digital societies could be characterized by their increasing desire to express themselves and interact with others. This is being realized through digital platforms such as social media that have increasingly become convenient and inexpensive sensors compared to physical sensors in many sectors of smart societies. One such major sector is road transportation, which is the backbone of modern economies and costs globally 1.25 million deaths and 50 million human injuries annually. The cutting-edge on big data-enabled social media analytics for transportation-related studies is limited. This paper brings a range of technologies together to detect road traffic-related events using big data and distributed machine learning. The most specific contribution of this research is an automatic labelling method for machine learning-based traffic-related event detection from Twitter data in the Arabic language. The proposed method has been implemented in a software tool called Iktishaf+ (an Arabic word meaning discovery) that is able to detect traffic events automatically from tweets in the Arabic language using distributed machine learning over Apache Spark. The tool is built using nine components and a range of technologies including Apache Spark, Parquet, and MongoDB. Iktishaf+ uses a light stemmer for the Arabic language developed by us. We also use in this work a location extractor developed by us that allows us to extract and visualize spatio-temporal information about the detected events. The specific data used in this work comprises 33.5 million tweets collected from Saudi Arabia using the Twitter API. Using support vector machines, naïve Bayes, and logistic regression-based classifiers, we are able to detect and validate several real events in Saudi Arabia without prior knowledge, including a fire in Jeddah, rains in Makkah, and an accident in Riyadh. The findings show the effectiveness of Twitter media in detecting important events with no prior knowledge about them.

Transfer of Enteric Viruses Adenovirus and Coxsackievirus and Bacteriophage MS2 from Liquid to Human Skin

Enteric viruses (viruses that infect the gastrointestinal tract) are responsible for most water-transmitted diseases. They are shed in high concentrations in the feces of infected individuals, persist for an extended period of time in water, and are highly infective. Exposure to contaminated water directly (through ingestion) or indirectly (for example, through hand-water contacts followed by hand-to-mouth contacts) increases the risk of virus transmission. The work described herein provides a quantitative model for estimating human-pathogenic virus retention on skin following contact with contaminated water. The work will be important in refining the contribution of indirect transmission of virus to risks associated with water-related activities.

Indirect exposure to waterborne viruses increases the risk of infection, especially among children with frequent hand-to-mouth contacts. Here, we quantified the transfer of one bacteriophage (MS2) and two enteric viruses (adenovirus and coxsackievirus) from liquid to skin. MS2, a commonly used enteric virus surrogate, was used to compare virus transfer rates in a volunteer trial to those obtained using human cadaver skin and synthetic skin. MS2 transfer to volunteer skin was similar to transfer to cadaver skin but significantly different from transfer to synthetic skin. The transfer of MS2, adenovirus, and coxsackievirus to cadaver skin was modeled using measurements for viruses attaching to the skin (adsorbed) and viruses in liquid residual on skin (unadsorbed). We find virus transfer per surface area is a function of the concentration of virus in the liquid and the film thickness of liquid retained on the skin and is estimable using a linear model. Notably, the amount of MS2 adsorbed on the skin was on average 5 times higher than the amount of adenovirus and 4 times higher than the amount of coxsackievirus. Quantification of pathogenic virus retention to skin would thus be overestimated using MS2 adsorption data. This study provides models of virus transfer useful for risk assessments of water-related activities, demonstrates significant differences in the transfer of pathogenic virus and MS2, and suggests cadaver skin as an alternative testing system for studying interactions between viruses and skin.

IMPORTANCE Enteric viruses (viruses that infect the gastrointestinal tract) are responsible for most water-transmitted diseases. They are shed in high concentrations in the feces of infected individuals, persist for an extended period of time in water, and are highly infective. Exposure to contaminated water directly (through ingestion) or indirectly (for example, through hand-water contacts followed by hand-to-mouth contacts) increases the risk of virus transmission. The work described herein provides a quantitative model for estimating human-pathogenic virus retention on skin following contact with contaminated water. The work will be important in refining the contribution of indirect transmission of virus to risks associated with water-related activities.

Bacteriological Aspects of Hand Washing: A Key for Health Promotion and Infections Control

The aim of this review is to show the historical aspects of hands washing for healthy life and explains how can reduce the transmission of community-acquired infectious agents by healthcare workers and patients. This review article is prepared based on available database. The key words used were hands washing, risk assessment, hands hygiene, bacterial flora, contamination, infection, nosocomial, tap water, sanitizer, bacterial resistance, hands bacterial flora, washing methods, antiseptics, healthcare workers, healthcare personnel, from PubMed, ScienceDirect, Embase, Scopus, Web of Sciences, and Google Scholar. Data were descriptively analyzed. The insistence on hand washing has a history of 1400 years. The research results indicate that the bacteria released from the female washed hands in wet and dry condition was lower than from the male's hands with a significance level (3 CFU vs. 8 CFU; confidence interval 95%, P ≤ 0.001). The valuable results of the study indicated that released amount of bacterial flora from wet hands is more than 10 times in compared to dry hands. In addition, established monitoring systems for washing hands before and after patient's manipulation as well as after toilet were dominant indices to prevent the transfer of infectious agents to the patients. Increasing awareness and belief of the healthcare workers have shown an important role by about 30% reduction in the transfection. Hand washing could reduce the episodes of transmission of infectious agents in both community and healthcare settings. However, hand washing is an important key factor to prevent transmission of infectious agents to patients. There is no standard method for measuring compliance. Thus, permanent monitoring of hand washing to reduce the transmission of infections is crucial. Finally, the personnel must believe that hand washing is an inevitable approach to infection control.

Rapid Antibacterial Activity of 2 Novel Hand Soaps: Evaluation of the Risk of Development of Bacterial Resistance to the Antibacterial Agents

Objective.

To evaluate the antimicrobial efficacy of and risk of organisms developing resistance to 2 novel hand soaps: (1) a soap containing triclosan, polyhexamethylene biguanide, and benzethonium chloride added to a soap base (TPB soap); and (2) a soap containing farnesol, polyhexamethylene biguanide, and benzethonium chloride added to a soap base (FPB soap). Tests also included soaps containing only triclosan.

Design.

The risk of emergence of resistant bacterial mutants was investigated by determining the susceptibility changes after repeated exposure of bacteria to the drugs and soaps in vitro. The effectiveness of the soaps was evaluated using an in vitro tube dilution method, a volunteer method (the ASTM standard), and 2 pig skin methods.

Results.

The minimum inhibitory concentration and minimum bactericidal concentration of triclosan against Staphylococcus, aureus increased 8- to 62.5-fold, whereas those of TPB and FPB (both alone and in soap) were unchanged. In vitro, TPB and FPB soaps produced higher log10 reductions in colony-forming units of all tested organisms (4.95-8.58) than did soaps containing triclosan alone (0.29-4.86). In the test using the pig skin and volunteer methods, TPB soap produced a higher log10 reduction in colony-forming units (3.1-3.3) than did the soap containing triclosan alone (2.6-2.8).

Conclusion.

The results indicate that TPB and FPB soaps may provide superior rapid and broad-spectrum efficacy with a lower risk of organisms developing resistance than do soaps containing triclosan alone. Pig skin methods may be used to predict the efficacy of antibacterial soaps in the rapid disinfection of contaminated hands. Hand washing with TPB and FPB soaps by healthcare workers and the general population may reduce the transmission of pathogens, with a lower risk of promoting the emergence of resistant organisms.

Catheter-related infection and septicemia: impact of seasonality and modifiable practices from the DOPPS

Hemodialysis (HD) catheter-related infection (CRI) and septicemia contribute to adverse outcomes. The impact of seasonality and prophylactic dialysis practices during high-risk periods remain unexplored. This multicenter study analyzed DOPPS data from 12,122 HD patients (from 442 facilities) to determine the association between seasonally related climatic variables and CRI and septicemia. Climatic variables were determined by linkage to National Climatic Data Center of National Oceanic and Atmospheric Administration data. Catheter care protocols were examined to determine if they could mitigate infection risk during high-risk seasons. Survival models were used to estimate the adjusted hazard ratio (AHR) of septicemia by season and by facility catheter dressing protocol. The overall catheter-related septicemia rate was 0.47 per 1000 catheter days. It varied by season, with an AHR for summer of 1.46 (95% CI: 1.19-1.80) compared with winter. Septicemia was associated with temperature (AHR = 1.07; 95% CI: 1.02-1.13; p < 0.001). Dressing protocols using chlorhexidine (AHR of septicemia = 0.55; 95% CI: 0.39-0.78) were associated with fewest episodes of CRI or septicemia. Higher catheter-related septicemia in summer may be due to seasonal conditions (e.g., heat, perspiration) that facilitate bacterial growth and compromise protective measures. Extra vigilance and use of chlorhexidine-based dressing protocols may provide prophylaxis against CRI and septicemia.

Antimicrobial activity of a chlorhexidine intravascular catheter site gel dressing

OBJECTIVES

The antimicrobial efficacy of a chlorhexidine gluconate (CHG) intravascular catheter gel dressing was evaluated against methicillin-resistant Staphylococcus aureus (MRSA) and an extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. Chlorhexidine deposition on the skin surface and release from the gel were determined.

METHODS

The antimicrobial efficacy was evaluated in in vitro studies following microbial inoculation of the dressing and application of the dressing on the inoculated surface of a silicone membrane and donor skin [with and without a catheter segment and/or 10% (v/v) serum] on diffusion cells. Antimicrobial activity was evaluated for up to 7 days. Chlorhexidine skin surface deposition and release were also determined.

RESULTS

MRSA and E. coli were not detectable within 5 min following direct inoculation onto the CHG gel dressing. On the silicone membrane, 3 log and 6 log inocula of MRSA were eradicated within 5 min and 1 h, respectively. Time to kill was prolonged in the presence of serum and a catheter segment. Following inoculation of donor skin with 6 log cfu of MRSA, none was detected after 24 h. Chlorhexidine was released from the gel after a lag time of 30 min and increasing amounts were detected on the donor skin surface over the 48 h test period. The CHG gel dressing retained its antimicrobial activity on the artificial skin for 7 days.

CONCLUSIONS

The CHG intravascular catheter site gel dressing had detectable antimicrobial activity for up to 7 days, which should suppress bacterial growth on the skin at the catheter insertion site, thereby reducing the risk of infection.

Methods to evaluate the microbicidal activities of hand-rub and hand-wash agents

In vitro carrier tests, suspension tests, time-kill curves, and determinations of minimum inhibitory concentrations to evaluate the microbicidal activities of hand antiseptics provide only a preliminary indication of the antimicrobial spectrum and speed of action of a given formulation. Ex vivo testing with human or animal skin at human skin temperature and at contact times reflecting field conditions may give a better indication of a formulation's ability to tackle hand-transmitted pathogens. Field testing of hands for levels of skin microbiota before and after antisepsis may be easier to perform, but it is subject to many uncontrollable factors. Whereas randomised clinical trials may be the ultimate approach to assess the effectiveness of hand hygiene protocols and products in preventing microbial cross-transmission and, ultimately, infections, they can be prohibitively expensive, time-consuming, difficult to design, and therefore impractical. Hence, the primary emphasis should be on in vivo testing on human hands, using a well-designed protocol that closely simulates the recommended field use of the formulation, and possibly followed by clinical studies. The use of these method is the most likely to yield useful data on the potential of a formulation to interrupt the spread of pathogens transmitted by hands in healthcare settings. This review provides a critical assessment of the methods currently used to meet regulatory requirements for hand antiseptics in Europe and North America.

Determination of the antibacterial efficacy of a new porphyrin-based photosensitizer against MRSA ex vivo

Following extensive in vitro screening of new photosensitizers the purpose of the present study was to examine penetration as well as antibacterial efficacy of a lead photosensitizer against MRSA using an ex vivo porcine skin model. Two different applications were performed: (i) preincubation of bacteria in solution with a porphyrin-based photosensitizer XF73 and subsequent application on the ex vivo porcine skin; (ii) application of pure bacteria on the explants followed by an incubation with XF73 in a water-ethanol formulation for up to 60 min under occlusion. The localisation of XF73 was restricted to the stratum corneum. Different concentrations (0-10 microM) of XF73 and different incubation times (5-60 min) were used to determine phototoxicity against methicillin-resistant and methicillin-sensitive S. aureus, which was applied on the explants. Preincubation of S. aureus with 0.1 microM XF73 in solution prior to the application of these XF73-incubated bacteria on the skin demonstrates a higher efficacy (>3 log10) after irradiation. Antibacterial photodynamic inactivation resulted in a approximately 1 log10 (0.1 microM)-3.64+/-0.035 (10 microM) log10 growth reduction independently of the antibiotic resistance pattern of used S. aureus strains. Irradiation of applied bacteria without photosensitizer incubation did not show any marked decrease (<1 log10) of bacteria cell number, indicating a significant phototoxicity of the XF73. Histological evaluations of untreated and treated skin areas upon irradiation within 24 h showed no significant degree of necrosis or apoptosis determined by TUNEL-assay indicating that the porcine skin is still vital. This study demonstrates that this XF73 porphyrin-based photosensitizer had concentration-dependent differences in killing efficacy of MRSA in comparison to skin cells using an ex vivo porcine skin model. The results described here imply that topical delivery of XF73 may be considered as a possible treatment in patients with superficial infections of the skin.

Evidence-Based Practice in the Management of Vascular Access Devices for Home Parenteral Nutrition Therapy

Catheter-related bloodstream infection and catheter occlusion are potential significant complications of parenteral nutrition therapy. The increased incidence and associated morbidity, mortality, increased costs, and quality-of-life issues experienced with these adverse events necessitate specialized management of vascular access devices. The host coagulation response to biomaterials and the associated development of biofilm on vascular devices are complex phenomena. Multiple interventions are required to prevent access of bacteria to both intraluminal and extraluminal catheter surfaces, and the occurrence of catheter occlusion. The discovery of the biofilm form of microbial life and the associated recalcitrance of biofilm bacteria to antimicrobials has provided insight into the failure of current prevention, diagnostic, and treatment protocols. Critical interventions are presented correlating current evidence with new discoveries in pathogenesis.