Use of tissue-engineered skin to study in vitro biofilm development

A standardized wound infection model for antimicrobial testing of wound dressings in vitro

To investigate the effectiveness of antimicrobial agents against wound infections, experiments using either 2D cultures with planktonic microorganisms or animal infection models are frequently carried out. However, the transferability of the results to human skin is limited by the lack of complexity of the 2D models or by the poor translation of the results from animal models. Hence, there is a need for wound infection models capable of assessing antimicrobial agents. In this study, an easily standardized wound infection model was established. This model consists of a mechanically wounded human skin model on a collagen matrix infected with various clinically relevant bacteria. Infection of the model led to recognition of the pathogens and induction of an inflammatory response. The untreated infection spread over time, causing significant tissue damage. By applying an antimicrobial-releasing wound dressing, the bacterial load could be reduced and the success of the treatment could be further measured by a decrease in the inflammatory reaction. In conclusion, this wound infection model can be used to evaluate new antimicrobial therapeutics as well as to study host-pathogen interactions.

Novel methodologies for host-microbe interactions and microbiome-targeted therapeutics in 3D organotypic skin models

BACKGROUND

Following descriptive studies on skin microbiota in health and disease, mechanistic studies on the interplay between skin and microbes are on the rise, for which experimental models are in great demand. Here, we present a novel methodology for microbial colonization of organotypic skin and analysis thereof.

RESULTS

An inoculation device ensured a standardized application area on the stratum corneum and a homogenous distribution of bacteria, while preventing infection of the basolateral culture medium even during prolonged culture periods for up to 2 weeks at a specific culture temperature and humidity. Hereby, host-microbe interactions and antibiotic interventions could be studied, revealing diverse host responses to various skin-related bacteria and pathogens.

CONCLUSIONS

Our methodology is easily transferable to a wide variety of organotypic skin or mucosal models and different microbes at every cell culture facility at low costs. We envision that this study will kick-start skin microbiome studies using human organotypic skin cultures, providing a powerful alternative to experimental animal models in pre-clinical research. Video Abstract.

Organotypic 3D Co-Culture of Human Pleura as a Novel In Vitro Model of Staphylococcus aureus Infection and Biofilm Development

Bacterial pleural infections are associated with high mortality. Treatment is complicated due to biofilm formation. A common causative pathogen is Staphylococcus aureus (S. aureus). Since it is distinctly human-specific, rodent models do not provide adequate conditions for research. The purpose of this study was to examine the effects of S. aureus infection on human pleural mesothelial cells using a recently established 3D organotypic co-culture model of pleura derived from human specimens. After infection of our model with S. aureus, samples were harvested at defined time points. Histological analysis and immunostaining for tight junction proteins (c-Jun, VE-cadherin, and ZO-1) were performed, demonstrating changes comparable to in vivo empyema. The measurement of secreted cytokine levels (TNF-α, MCP-1, and IL-1β) proved host-pathogen interactions in our model. Similarly, mesothelial cells produced VEGF on in vivo levels. These findings were contrasted by vital, unimpaired cells in a sterile control model. We were able to establish a 3D organotypic in vitro co-culture model of human pleura infected with S. aureus resulting in the formation of biofilm, including host-pathogen interactions. This novel model could be a useful microenvironment tool for in vitro studies on biofilm in pleural empyema.

Novel 3D organotypic co-culture model of pleura

Pleural mesothelial cells are the predominant cell type in the pleural cavity, but their role in the pathogenesis of pleural diseases needs to be further elucidated. 3D organotypic models are an encouraging approach for an in vivo understanding of molecular disease development. The aim of the present study was to develop a 3D organotypic model of the pleural mesothelium. Specimens of human pleura parietalis were obtained from patients undergoing surgery at the University Hospital Leipzig, Germany. 3D co-culture model of pleura was established from human pleural mesothelial cells and fibroblasts. The model was compared to human pleura tissue by phase-contrast and light microscopy, immunochemistry and -fluorescence as well as solute permeation test. Histological assessment of the 3D co-culture model displayed the presence of both cell types mimicking the morphology of the human pleura. Vimentin and Cytokeratin, PHD1 showed a similar expression pattern in pleural biopsies and 3D model. Expression of Ki-67 indicates the presence of proliferating cells. Tight junctional marker ZO-1 was found localized at contact zones between mesothelial cells. Each of these markers were expressed in both the 3D co-culture model and human biopsies. Permeability of 3D organotypic co-culture model of pleura was found to be higher for 70 kDa-Dextran and no significant difference was seen in the permeability for small dextran (4 kDa). In summary, the presented 3D organoid of pleura functions as a robust assay for pleural research serving as a precise reproduction of the in vivo morphology and microenvironment.

[Oral microbiome in children with dystrophic recessive epidermolysis bullosa]

THE AIM OF THE STUDY

Was to assess bacterial load in oral wounds in children with recessive dystrophic epidermolysis bullosa (RDEB).

MATERIALS AND METHODS

The study comprised 77 RDEB children aged 3-18 years (mean age 9.5±3.6 years) and 27 healthy children aged 4-18 years (mean age 9.8±4.1 years) who served as controls. Swabs for bacteriological study were taken from the oral wounds in RDEB patients and non-affected corresponding oral mucosa areas in controls. The microorganism growth was assessed after 24, 48 and 72 hours of incubation (37 °C and 30 °C) with subsequent identification in automatic bacteriological analyzer MicroScan Walk Away (Simens, USA). Results. The study revealed high prevalence and concentrations of Candida albicans (in 40.3% children), Staphilococcus aureus (23.4%), Enterobacter cloacae (9.1%), and Enterobacteria (10.4%) in RDEB children. From these species, only Candida albicans was present in controls (26%). The prevalence and concentration of commensal and pathogenic species correlated positively with age and significant difference was revealed between children at the age of 3-6 and 7-10 years (p=0.001). Thus, bacterial load in oral wounds correlates with the RDEB natural history and fibrosis progression. Delayed oral wound healing was associated with microbiome shift towards biofilm-producing bacteria Staphilococcus aureus and Enterobacter cloacae.

CONCLUSION

Oral wounds microbiome may be an indicator of RDEB severity and tendency to oral fibrosis. The decrease of bacterial load in the oral wounds may remove one of the healing obstacles and serve as fibrosis prevention measure.

Development and assessment of a high-throughput biofilm and biomass testing platform

OBJECTIVE

To develop and evaluate a simple platform technology for developing static biofilms in a 96-well microtitre plate for various downstream applications. The technology allows monitoring of growth rate, biofilm formation and quantifying biofilm biomass by using crystal violet (CV) and safranin O (SO) staining over seven-day time periods for pathogens including clinical isolates most commonly associated with hard-to-treat wound infections.

METHOD

A total of 157 bacteria including Acinetobacter, Enterobacter, Klebsiella, Pseudomonas and Staphylococcus spp. were used in the study. Bacterial growth was measured at 600nm optical density (OD). Biofilm formation was monitored and assessed quantitatively with CV at 570nm and SO staining at 492nm for one-, two-, three- and seven-day incubation periods.

RESULTS

Bacterial growth rate and static biofilm biomass in the 96-well plates varied for various strains tested. Both CV and SO staining showed similar results in the biomass, with SO assay displaying more reproducible data throughout the study. Most of the strains were metabolically active even at the seven-day incubation period. Microbial adherences of all bacterial strains on the plastic surface was assessed with CV staining: 28 Acinetobacter, 17 Staphylococcus, 12 Pseudomonas and four Enterobacter strains were strong biofilm producers. Moderate biofilm-producing strains included 27 Staphylococcus, 14 Acinetobacter, eight Pseudomonas and three Enterobacter. Weak biofilm-producing strains included: 33 Staphylococcus, six Enterobacter, two Pseudomonas and one Acinetobacter. Only one Pseudomonas aeruginosa strain did not develop biofilm.

CONCLUSION

Our results demonstrate the feasibility of using 96-well microtitre plates as a high-throughput platform for quantitative measurement and assessment of biofilm development over time. Studying microbial adherence or biofilm biomass generated on various surfaces using a high-throughput system could provide valuable information for in vitro testing and developing therapeutics for biofilm infections. Employing the biofilm testing platform described in this study makes it possible to simultaneously develop different biofilms formed by specific pathogens, and study potential association between the quantity of bacterial biomass and strength of a biofilm formed by specific wound pathogens. In addition, the described testing approach could provide an optimal model for standardised and high-throughput screening of candidate antibiofilm therapeutics.

The Co-Culture of Staphylococcal Biofilm and Fibroblast Cell Line: The Correlation of Biological Phenomena with Metabolic NMR1 Footprint

Staphylococcus aureus is one of the most prevalent pathogens associated with several types of biofilm-based infections, including infections of chronic wounds. Mature staphylococcal biofilm is extremely hard to eradicate from a wound and displays a high tendency to induce recurring infections. Therefore, in the present study, we aimed to investigate in vitro the interaction between S. aureus biofilm and fibroblast cells searching for metabolites that could be considered as potential biomarkers of critical colonization and infection. Utilizing advanced microscopy and microbiological methods to examine biofilm formation and the staphylococcal infection process, we were able to distinguish 4 phases of biofilm development. The analysis of staphylococcal biofilm influence on the viability of fibroblasts allowed us to pinpoint the moment of critical colonization-12 h post contamination. Based on the obtained model we performed a metabolomics analysis by ¹H NMR spectroscopy to provide new insights into the pathophysiology of infection. We identified a set of metabolites related to the switch to anaerobic metabolism that was characteristic for staphylococcal biofilm co-cultured with fibroblast cells. The data presented in this study may be thus considered a noteworthy but preliminary step in the direction of developing a new, NMR-based tool for rapid diagnosing of infection in a chronic wound.

Active neutrophil responses counteract Candida albicans burn wound infection of ex vivo human skin explants

Burn wounds are highly susceptible sites for colonization and infection by bacteria and fungi. Large wound surface, impaired local immunity, and broad-spectrum antibiotic therapy support growth of opportunistic fungi such as Candida albicans, which may lead to invasive candidiasis. Currently, it remains unknown whether depressed host defenses or fungal virulence drive the progression of burn wound candidiasis. Here we established an ex vivo burn wound model, where wounds were inflicted by applying preheated soldering iron to human skin explants, resulting in highly reproducible deep second-degree burn wounds. Eschar removal by debridement allowed for deeper C. albicans penetration into the burned tissue associated with prominent filamentation. Active migration of resident tissue neutrophils towards the damaged tissue and release of pro-inflammatory cytokine IL-1β accompanied the burn. The neutrophil recruitment was further increased upon supplementation of the model with fresh immune cells. Wound area and depth decreased over time, indicating healing of the damaged tissue. Importantly, prominent neutrophil presence at the infected site correlated to the limited penetration of C. albicans into the burned tissue. Altogether, we established a reproducible burn wound model of candidiasis using ex vivo human skin explants, where immune responses actively control the progression of infection and promote tissue healing.

Utilizing Organoid and Air-Liquid Interface Models as a Screening Method in the Development of New Host Defense Peptides

Host defense peptides (HDPs), also known as antimicrobial peptides, are naturally occurring polypeptides (~12–50 residues) composed of cationic and hydrophobic amino acids that adopt an amphipathic conformation upon folding usually after contact with membranes. HDPs have a variety of biological activities including immunomodulatory, anti-inflammatory, anti-bacterial, and anti-biofilm functions. Although HDPs have the potential to address the global threat of antibiotic resistance and to treat immune and inflammatory disorders, they have yet to achieve this promise. Indeed, there are several challenges associated with bringing peptide-based drug candidates from the lab bench to clinical practice, including identifying appropriate indications, stability, toxicity, and cost. These challenges can be addressed in part by the development of innate defense regulator (IDR) peptides and peptidomimetics, which are synthetic derivatives of HDPs with similar or better efficacy, increased stability, and reduced toxicity and cost of the original HDP. However, one of the largest gaps between basic research and clinical application is the validity and translatability of conventional model systems, such as cell lines and animal models, for screening HDPs and their derivatives as potential drug therapies. Indeed, such translation has often relied on animal models, which have only limited validity. Here we discuss the recent development of human organoids for disease modeling and drug screening, assisted by the use of omics analyses. Organoids, developed from primary cells, cell lines, or human pluripotent stem cells, are three-dimensional, self-organizing structures that closely resemble their corresponding in vivo organs with regards to immune responses, tissue organization, and physiological properties; thus, organoids represent a reliable method for studying efficacy, formulation, toxicity and to some extent drug stability and pharmacodynamics. The use of patient-derived organoids enables the study of patient-specific efficacy, toxicogenomics and drug response predictions. We outline how organoids and omics data analysis can be leveraged to aid in the clinical translation of IDR peptides.

Bioengineered Platforms for Chronic Wound Infection Studies: How Can We Make Them More Human-Relevant?

Chronic wound infections are an important cause of delayed wound healing, posing a significant healthcare burden with consequences that include hospitalization, amputation, and death. These infections most often take the form of three-dimensional biofilm communities, which are notoriously recalcitrant to antibiotics and immune clearance, contributing to the chronic wound state. In the chronic wound microenvironment, microbial biofilms interact closely with other key components, including host cellular and matrix elements, immune cells, inflammatory factors, signaling components, and mechanical cues. Intricate relationships between these contributing factors not only orchestrate the development and progression of wound infections but also influence the therapeutic outcome. Current medical treatment for chronic wound infections relies heavily on long-term usage of antibiotics; however, their efficacy and reasons for failure remain uncertain. To develop effective therapeutic approaches, it is essential to better understand the complex pathophysiology of the chronic wound infection microenvironment, including dynamic interactions between various key factors. For this, it is critical to develop bioengineered platforms or model systems that not only include key components of the chronic wound infection microenvironment but also recapitulate interactions between these factors, thereby simulating the infection state. In doing so, these platforms will enable the testing of novel therapeutics, alone and in combinations, providing insights toward composite treatment strategies. In the first section of this review, we discuss the key components and interactions in the chronic wound infection microenvironment, which would be critical to recapitulate in a bioengineered platform. In the next section, we summarize the key features and relevance of current bioengineered chronic wound infection platforms. These are categorized and discussed based on the microenvironmental components included and their ability to recapitulate the architecture, interactions, and outcomes of the infection microenvironment. While these platforms have advanced our understanding of the underlying pathophysiology of chronic wound infections and provided insights into therapeutics, they possess certain insufficiencies that limit their clinical relevance. In the final section, we propose approaches that can be incorporated into these existing model systems or developed into future platforms developed, thus enhancing their biomimetic and translational capabilities, and thereby their human-relevance.

Does Suture Type Influence Bacterial Retention and Biofilm Formation After Irrigation in a Mouse Model?

BACKGROUND

Irrigation and débridement are frequently utilized in the management of surgical infections, but even with aggressive débridement, it is difficult to remove all the suture material from the tissues and retained suture material may harbor bacteria and/or biofilm. The degree to which barbed or braided sutures may differentially influence the risk of infection has not been defined in a well-controlled animal model.

QUESTIONS/PURPOSES

We compared braided and barbed monofilament sutures after irrigation of an infected mouse air pouch model to determine whether the suture type influenced the effectiveness of the irrigation. After irrigation of infected pouches, sutures were compared for (1) bacterial adherence and bacterial retention; (2) qualitative and quantitative pouch thickness and cellular density; and (3) quantitative biofilm formation.

METHODS

Soft tissue air pouches were created on the backs of 60 female, mature 10-week-old BALB/cJ mice by sequentially introducing air into the subcutaneous tissue and allowing the pouch to mature. The pouches were inoculated with Staphylococcus aureus and braided or barbed monofilament sutures were implanted. Pouch irrigation was performed Day 7 after suture implantation. Suture segments were collected before and after irrigation. After euthanasia on Day 14, pouch tissues with residual suture segments were collected for analysis: microbiologic analysis done using optical density as a measure of the concentration of bacteria in the culture (the larger concentration indicates higher number of bacteria) and histologic evaluation of the pouch tissues were semiquantitative, whereas environmental scanning electron microscopy (ESEM) and confocal analyses of the biofilm and bacteria on the sutures were qualitative.

RESULTS

Histologic evaluation of pouch tissue showed all groups had inflammatory responses. Quantitatively microbiology showed no difference in bacterial number calculated from the optical density (OD) values between the two suture materials at any time point in the irrigation group. In the no-irrigation group, for the Day 7 time point, mean (± SD) OD was greater in the barbed than the OD in the braided sutures (0.52 ± 0.12 versus 0.37 ± 0.16, mean difference 0.43 [95% confidence interval, 0.08-0.13]; p = 0.007). Qualitatively, ESEM showed more bacterial retention by braided sutures before and after irrigation. Confocal imaging of the sutures demonstrated penetration of biofilm into the interstices of braided sutures and less adhesion in barbed monofilament sutures. The quantification of the biomass showed no differences between groups at all time points (before-irrigation biomass was 11.2 ± 9.3 for braided versus 5.2 ± 4.7 for barbed sutures, p = 0.196; and after-irrigation biomass was 7.2 ± 7.5 for braided versus 3.3 ± 4.3 for barbed suture, p = 0.259).

CONCLUSIONS

All sutures can retain bacteria and biofilm, but it is rarely possible to remove all suture material at the time of irrigation to treat infection. After an irrigation procedure, qualitatively braided sutures appeared to harbor more bacteria and to retain more biofilm than barbed monofilaments.

CLINICAL RELEVANCE

When saline irrigation was used to simulate infection treatment in an infected mouse air pouch model, bacteria/biofilm was not completely eliminated from either braided or barbed monofilament sutures. The irrigation appeared to clear more bacteria and biofilm from the monofilament despite having barbs. Unfortunately, current technologies do not allow direct quantitative comparisons of biofilm retention. Clinicians should be aware that in the face of infection, any retained sutures may harbor bacteria despite irrigation.

Skin microbiota and human 3D skin models

Although the role of the microbiota in skin homeostasis is still emerging, there is growing evidence that an intact microbiota supports the skin barrier. The increasing number of research efforts that are trying to shed more light on the human skin-microbiota interaction requires the use of suitable experimental models. Three-dimensional (3D) skin equivalents have been established as a valuable tool in dermatological research because they contain a fully differentiated epidermal barrier that reflects the morphological and molecular characteristics of normal human epidermis. In this review, we provide an overview of current 3D skin models and illustrate the potential of 3D skin models to study the human skin-microbiota interplay.

In vitro studies evaluating the effects of biofilms on wound-healing cells: a review

Chronic wounds are characterized as wounds that have failed to proceed through the well-orchestrated healing process and have remained open for months to years. Open wounds are at risk for colonization by opportunistic pathogens. Bacteria that colonize the open wound bed form surface-attached, multicellular communities called biofilms, and chronic wound biofilms can contain a diverse microbiota. Investigators are just beginning to elucidate the role of biofilms in chronic wound pathogenesis, and have simplified the complex wound environment using in vitro models to obtain a fundamental understanding of the impact of biofilms on wound-healing cell types. The intent of this review is to describe current in vitro methodologies and their results. Investigations started with one host cell-type and single species biofilms and demonstrated that biofilms, or their secretions, had deleterious effects on wound-healing cells. More complex systems involved the use of multiple host cell/tissue types and single species biofilms. Using human skin-equivalent tissues, investigators demonstrated that a number of different species can grow on the tissue and elicit an inflammatory response from the tissue. A full understanding of how biofilms impact wound-healing cells and host tissues will have a profound effect on how chronic wounds are treated.

Decreased Bacterial Adherence, Biofilm Formation, and Tissue Reactivity of Barbed Monofilament Suture in an In Vivo Contaminated Wound Model

BACKGROUND

Monofilament and barbed monofilament sutures have been shown in in vitro models to have less bacterial adherence than braided suture. This study evaluates bacterial adherence to suture materials and tissue reactivity with an in vivo contaminated wound mouse model.

METHODS

Staphylococcus aureus was used to create an in vivo contaminated wound model at 2 amounts (10⁶ colony-forming units [CFU] and 10⁸ CFU) using a mouse air pouch. Three types of commonly used absorbable suture were evaluated: braided, monofilament, and barbed monofilament. Bacterial suture adherence was evaluated with suture culture, a photon-capturing camera system, and scanning electron microscopy. Tissue reactivity was assessed through histology and protein expression.

RESULTS

The braided suture group with the high amount of S aureus exhibited frank purulence and air pouch hypertrophy in all 8 mice. A significant difference was found between suture groups inoculated with 10⁸ CFU (P < .05) as measured by bacterial culture concentration using the optical density method. The braided suture hosted more bacteria than either monofilament (P < .005) or barbed monofilament suture (P < .005). No difference was appreciated between the monofilament and barbed monofilament groups. Kruskal-Wallis test demonstrated a significant difference between groups in regard to levels of tumor necrosis factor-α (P < .05) and interleukin-1 (P < .05).

CONCLUSION

Our in vivo contaminated wound model demonstrated that barbed monofilament suture performed similarly to monofilament suture and better than braided suture in terms of bacterial adherence, biofilm formation, and tissue reactivity.

Growth of MRSA and Pseudomonas aeruginosa in a fine-celled foam model containing sessile commensal skin bacteria

Sessile cultures of the skin bacteria Staphylococcus saprophyticus and Corynebacterium xerosis were grown using novel fine-celled foam substrata to test the outcome of challenge by methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa under three growth medium regimens (simulated sweat, simulated serum or simulated sweat substituted with simulated serum during the microbial challenge). S. saprophyticus and C. xerosis significantly limited MRSA and P. aeruginosa immigration respectively, under the simulated sweat and serum medium regimes. Under the substitution medium regime however, MRSA and P. aeruginosa integrated into pre-established biofilms to a significantly greater extent, attaining cell densities similar to the axenic controls. The outcome of challenge was influenced by the medium composition and test organism but could not be predicted based on planktonic competition assays or growth dynamics. Interactions between skin and wound isolates could be modelled using the fine-celled foam-based system. This model could be used to further investigate interactions and also in preclinical studies of antimicrobial wound care regimens.

Chronic Wound Biofilm Model

Significance: Multispecies microbial biofilms may contribute to wound chronicity by derailing the inherent reparative process of the host tissue. In the biofilm form, bacteria are encased within an extracellular polymeric substance and become recalcitrant to antimicrobials and host defenses. For biofilms of relevance to human health, there are two primary contributing factors: the microbial species involved and host response which, in turn, shapes microbial processes over time. This progressive interaction between microbial species and the host is an iterative process that helps evolve an acute-phase infection to a pathogenic chronic biofilm. Thus, long-term wound infection studies are needed to understand the longitudinal cascade of events that culminate into a pathogenic wound biofilm. Recent Advances: Our laboratory has recently published the first long-term (2 month) study of polymicrobial wound biofilm infection in a translationally valuable porcine wound model. Critical Issues: It is widely recognized that the porcine system represents the most translationally valuable approach to experimentally model human skin wounds. A meaningful experimental biofilm model must be in vivo, include mixed species of clinically relevant microbes, and be studied longitudinally long term. Cross-validation of such experimental findings with findings from biofilm-infected patient wounds is critically important. Future Directions: Additional value may be added to the experimental system described above by studying pigs with underlying health complications (e.g., metabolic syndrome), as is typically seen in patient populations.

Biofilms in wounds: a review of present knowledge

Following confirmation of the presence of biofilms in chronic wounds, the term biofilm became a buzzword within the wound healing community. For more than a century pathogens have been successfully isolated and identified from wound specimens using techniques that were devised in the nineteenth century by Louis Pasteur and Robert Koch. Although this approach still provides valuable information with which to help diagnose acute infections and to select appropriate antibiotic therapies, it is evident that those organisms isolated from clinical specimens with the conditions normally used in diagnostic laboratories are mainly in a planktonic form that is unrepresentative of the way in which most microbial species exist naturally. Usually microbial species adhere to each other, as well as to living and non-living surfaces, where they form complex communities surrounded by collectively secreted extracellular polymeric substances (EPS). Cells within such aggregations (or biofilms) display varying physiological and metabolic properties that are distinct from those of planktonic cells, and which contribute to their persistence. There are many factors that influence healing in wounds and the discovery of biofilms in chronic wounds has provided new insight into the reasons why. Increased tolerance of biofilms to antimicrobial agents explains the limited efficacy of antimicrobial agents in chronic wounds and illustrates the need to develop new management strategies. This review aims to explain the nature of biofilms, with a view to explaining their impact on wounds.

Wound biofilms: lessons learned from oral biofilms

Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

Differential effects of planktonic and biofilm MRSA on human fibroblasts

Bacteria colonizing chronic wounds often exist as biofilms, yet their role in chronic wound pathogenesis remains unclear. Staphylococcus aureus biofilms induce apoptosis in dermal keratinocytes, and given that chronic wound biofilms also colonize dermal tissue, it is important to investigate the effects of bacterial biofilms on dermal fibroblasts. The effects of a predominant wound pathogen, methicillin-resistant S. aureus, on normal, human, dermal fibroblasts were examined in vitro. Cell-culture medium was conditioned with equivalent numbers of either planktonic or biofilm methicillin-resistant S. aureus and then fed to fibroblast cultures. Fibroblast response was evaluated using scratch, viability, and apoptosis assays. The results suggested that fibroblasts experience the same fate when exposed to the soluble products of either planktonic or biofilm methicillin-resistant S. aureus, namely limited migration followed by death. Enzyme-linked immunosorbent assays demonstrated that fibroblast production of cytokines, growth factors, and proteases were differentially affected by planktonic and biofilm-conditioned medium. Planktonic-conditioned medium induced more interleukin-6, interleukin-8, vascular endothelial growth factor, transforming growth factor-β1, heparin-bound epidermal growth factor, matrix metalloproteinase-1, and metalloproteinase-3 production in fibroblasts than the biofilm-conditioned medium. Biofilm-conditioned medium induced more tumor necrosis factor-α production in fibroblasts compared with planktonic-conditioned medium, and suppressed metalloproteinase-3 production compared with controls.

Bacterial adherence to high--tensile strength sutures

PURPOSE

The purpose of this study was to evaluate the bacterial adherence to high--tensile strength suture materials using a bioluminescent in vitro model.

METHODS

Eleven strands each of No. 2 MaxBraid (Arthrotek [Biomet], Warsaw, IN), FiberWire (Arthrex, Naples, FL), Ethibond (Ethicon, Somerville, NJ), Orthocord (DePuy Mitek, Raynham, MA), and silk (Ethicon) sutures were immersed in a broth of bioluminescent Staphylococcus aureus, which is genetically engineered to emit photons. After 12 hours in the broth, the suture strands were individually irrigated with 10 mL of low-pressure normal saline solution and imaged with a photon-capturing camera system that yields a total photon count that correlates directly with residual bacterial counts.

RESULTS

MaxBraid had the greatest adherence, followed by FiberWire, Ethibond, Orthocord, and silk. Orthocord had only 25% of the bacterial adherence of MaxBraid (P < .001). Ethibond and FiberWire had 53% (P < .001) and 75% (P = .003) of the adherence of MaxBraid, respectively. Differences between each suture were also statistically significant, with Ethibond and Orthocord having 71% (P = .007) and 33% (P < .001) of the adherence of FiberWire, respectively, and Orthocord having 47% (P < .001) of the adherence of Ethibond. The adherence to silk was statistically lower than all of the high-tensile strength sutures.

CONCLUSIONS

Among high--tensile strength sutures, Orthocord has significantly less bacterial adherence than MaxBraid and FiberWire. Although infections in arthroscopic shoulder surgery are rare, the physical properties of surgical implants should be known by surgeons. In addition, bacterial adherence may contribute to suture selection in a patient prone to infection or to the use of suture in other body areas at greater risk for contamination.

CLINICAL RELEVANCE

Bacterial adherence to high--tensile strength sutures may be a useful factor in implant selection in a patient with predisposition for contamination or infection.

Synergistic effect of 14-alpha-lipoyl andrographolide and various antibiotics on the formation of biofilms and production of exopolysaccharide and pyocyanin by Pseudomonas aeruginosa

Pseudomonas aeruginosa produces a biofilm that provides the bacteria with an effective barrier against antibiotics. Here, we investigated the synergy of various antibiotics with 14-alpha-lipoyl andrographolide (AL-1), focusing upon synthesis of the biofilm. AL-1 also inhibited the production of the exopolysaccharide and pyocyanin components. We propose that AL-1 may potentially serve as a cotherapy to combat P. aeruginosa.

Bacterial adherence to suture materials

BACKGROUND

Wound infections may be problematic for physicians. Whether a practitioner is managing complex penetrating trauma or a skin biopsy, there may be a need for suture closure. Suture material is an operator dependent variable and while little objective data exist to guide the choice of suture, it may play a role in wound infection. This study evaluates bacterial adherence to commonly used suture materials with a bioluminescent in vitro model.

METHODS

In all, 11 strands of size 2-0 poliglecaprone suture (Monocryl; Ethicon, Inc, Somerville, New Jersey), polypropylene suture (Prolene; Ethicon, Inc), silk suture (Ethicon, Inc), polyglycolic acid suture (Vicryl; Ethicon, Inc), and antimicrobial polyglycolic acid suture treated with triclosan (VicrylPlus; Ethicon, Inc) were immersed in a broth of Staphylococcus aureus engineered to emit photons. After biofilm formation, the suture strands were irrigated and imaged with a photon-capturing camera system yielding a total photon count that correlates with residual bacteria.

RESULTS

The Vicryl suture had the highest counts and was statistically significant in bacterial adherence versus all other sutures. No other suture material was significantly different from any other.

CONCLUSIONS

This study gives data to guide the selection of suture materials. Absorbable braided suture should not be used in closure of contaminated wounds or wounds at risk for developing infection. The antibiotic impregnated absorbable braided suture was similar to the other suture types; however, it is at risk for reverting to the properties of its untreated counterpart over time. The bacterial adherence of suture materials should be taken into account by all practitioners when closing wounds or debriding infected wounds.