The susceptibility of prosthetic biomaterials to infection

Outcomes of synthetic and biologic mesh in abdominal wall reconstruction: A propensity-matched analysis in Centers for Disease Control and Prevention class 1 and 2 wounds

INTRODUCTION

The choice of biologic compared with synthetic mesh in abdominal wall reconstruction remains controversial, especially in Centers for Disease Control and Prevention class 1 and 2 wounds. This study evaluated wound complications and hernia recurrence with a 2:1 propensity-matched sample and extended follow-up.

METHODS AND PROCEDURES

A prospectively maintained abdominal wall reconstruction database was queried for patients undergoing open abdominal wall reconstruction using biologic or synthetic mesh in Centers for Disease Control and Prevention class 1 and 2 wounds. Patients receiving synthetic or biologic mesh were propensity score matched in a 2:1 fashion. Univariate, bivariate, and inferential analyses were conducted. Unless stated, data are reported as biologic compared with synthetic.

RESULTS

In total, 519 patients were compared, 173 with biologic and 346 with synthetic mesh. Defect size (215.2 ± 153.6 cm2 vs 251.5 ± 284.3 cm2), body mass index (33.6 ± 9 kg/m2 vs 34 ±17.7 kg/m2), and comorbidities were well matched (all P > .05). Although Centers for Disease Control and Prevention wound class was used in the match, it was significantly different between groups (Centers for Disease Control and Prevention 1:43.4% vs 81.2%, Centers for Disease Control and Prevention 2:56.6% vs 18.8%; P < .001). The rate of component separation (40.1% vs 44.2%; P = .397), fascial closure (97.7% vs 98.3%; P = .738), and panniculectomy (33.5% vs 29.2%; P = .315) were similar. Mesh size was also similar (816.4 ± 555.5 vs 892.2 ± 487.8 cm2; P = .112). Wound complications were equal, including wound breakdown (10.5% vs 7.5%; P = .315), wound cellulitis (5.2% vs 5.8%; P = .843), wound infection (7.5% vs 4.6%; P = .223), seroma requiring intervention (6.4% vs 7.8%; P = .597), and mesh infection (1.2% vs 0.9%; P > .999). The biologic group had an increased length of stay (6.8 ± 5.5 days vs 5.4 ± 2.3 days; P < .001) and greater hospital charges ($82,181 ± 50,356 vs $62,221 ± 26,817 USD; P < .001). Mean follow-up after biologic repair was longer (33.9 ± 36.6 months vs 23.3 ± 32.3 months; P < .001). Hernia recurrence between the biologic and synthetic groups was not significantly different (2.9% vs 1.4%; P = .313). On multivariable regression, wound complications were predictive of recurrence, and panniculectomy was predictive of wound complications.

CONCLUSION

In a 2:1 matched analysis of Centers for Disease Control and Prevention 1 and 2 wounds with nearly 3-years of follow-up, biologic and synthetic mesh had similar rates of wound complications and recurrence in abdominal wall reconstruction.

Meshing around: high-risk hernias and infected mesh

Open laparotomy carries a risk up to 20% for an incisional hernia, making repair one of the most common operations performed by general surgeons in the USA. Despite a multitude of mesh appliances and techniques, no size fits all, and there is continued debate on what is the best mesh type, especially in high-risk patients with contaminated hernias. Infected mesh carries a significant burden to the patient, the surgeon and overall healthcare costs with medical legal implications. A stepwise approach that involves optimization of patient comorbidities, patient selective choice of mesh and technique is imperative in mitigating outcomes and recurrence rates. This review will focus on the avoidance of mesh infection and the selection of mesh in patients with contaminated wounds.

Acellular cadaveric dermal matrix grafts for orbital wall reconstruction in patients with sinonasal malignancies

PURPOSE

To describe the utilization of acellular cadaveric dermal matrix (ACDM) in patients undergoing orbital wall reconstruction after orbital preservation surgery for sinonasal malignancy.

METHODS

Retrospective case series of seven patients with sinonasal malignancy who had orbital reconstruction with ACDM implants from January 2012 to August 2020. Orbital preservation was performed in all patients with tumor extension up to and including periorbital. The main outcome measures were implant exposure, orbital infection, diplopia in primary gaze, enophthalmos, and eyelid malposition.

RESULTS

Patients ranged 37-78 years old (median: 66 years) and included 4 females and 3 males. The median follow-up time was 9 months (range 6-43 months) from the date of surgery. Squamous cell carcinoma comprised the majority of tumors with all patients needing medial wall reconstruction. Three patients received postoperative radiation therapy. No patients had any implant exposure, orbital infection, enophthalmos, or eyelid malposition.

CONCLUSIONS

ACDM grafts can be used safely in orbital wall reconstruction in patients with sinonasal malignancies.

State-of-the-art abdominal wall reconstruction and closure

Open ventral hernia repair is one of the most common operations performed by general surgeons. Appropriate patient selection and preoperative optimization are important to ensure high-quality outcomes and prevent hernia recurrence. Preoperative adjuncts such as the injection of botulinum toxin and progressive preoperative pneumoperitoneum are proven to help achieve fascial closure in patients with hernia defects and/or loss of domain. Operatively, component separation techniques are performed on complex hernias in order to medialize the rectus fascia and achieve a tension-free closure. Other important principles of hernia repair include complete reduction of the hernia sac, wide mesh overlap, and techniques to control seroma and other wound complications. In the setting of contamination, a delayed primary closure of the skin and subcutaneous tissues should be considered to minimize the chance of postoperative wound complications. Ultimately, the aim for hernia surgeons is to mitigate complications and provide a durable repair while improving patient quality of life.

Antimicrobial Meshes for Hernia Repair: Current Progress and Perspectives

Recent advances in the development of biomaterials have given rise to new options for surgery. New-generation medical devices can control chemical breakdown and resorption, prevent post-operative adhesion, and stimulate tissue regeneration. For the fabrication of medical devices, numerous biomaterials can be employed, including non-degradable biomaterials (silicone, polypropylene, expanded polytetrafluoroethylene) or biodegradable polymers, including implants and three-dimensional scaffolds for tissue engineering, which require particular physicochemical and biological properties. Based on the combination of new generation technologies and cell-based therapies, the biocompatible and bioactive properties of some of these medical products can lead to progress in the repair of injured or harmed tissue and in tissue regeneration. An important aspect in the use of these prosthetic devices is the associated infection risk, due to the medical complications and socio-economic impact. This paper provides the latest achievements in the field of antimicrobial surgical meshes for hernia repair and discusses the perspectives in the development of these innovative biomaterials.

Mandibular osteomyelitis after hyaluronic acid injection

BACKGROUND

Mandibular osteomyelitis after filler injection is extremely rare.

AIMS

We reported a case of mandibular osteomyelitis after hyaluronic acid injection.

PATIENTS

A 33-year-old woman received 1 mL hyaluronic acid injection on her chin 1 year ago, after which her chin kept swelling and painful, and gradually ulcerated with pus flowing out. She received antibiotics, debridement procedures, negative pressure wound therapy, and hyperbaric oxygen therapy without symptoms improved. Cone-beam computed tomography scan showed local bone destruction, sequestrum formation, and tissue calcification on the right mandible body. The patient was diagnosed with mandibular osteomyelitis and received local curettage for the removal of necrotized bone.

RESULTS

Literature search found no case reports on mandibular osteomyelitis after filler injection so far.

CONCLUSION

Minimizing the risk of contamination and infection is strictly required during the filler injection process. Once the patient shows signs of incurable mandibular infection postoperation, clinicians should consider the possibility of osteomyelitis.

Biological Mesh in Contaminated Fields—Overuse without Data: A Systematic Review of Their Use in Abdominal Wall Reconstruction

Ventral hernia repair in contaminated fields is a significant problem for surgeons. We performed a systematic review regarding the use of biological mesh in contaminated fields for abdominal wall reconstruction. The primary end points were recurrence and infection of the hernia repair. An independent search of scientific papers in the English language was performed by three reviewers. Articles were chosen based on reference to ventral hernias, their use in infected fields, and in human subjects. Papers were scored using the Methodological Index for Non-Randomized Studies and those with a score of 8 or more were combined to evaluate the end points. A total of 16 studies from six different mesh products met our criteria. These papers comprised 554 patients with an overall infection rate of 24 per cent and a recurrence rate of 20 per cent. The largest study used 116 patients. All papers were case series. Overall the data for use of biological mesh products in contaminated fields are limited. Further controlled studies are needed to address this important and clinically relevant question. Caution should be used when using biological mesh products in infected fields because there is a paucity of controlled data and none have U.S. Food and Drug Administration approval for use in infected fields.

A critical review of the in vitro and in vivo models for the evaluation of anti-infective meshes

BACKGROUND

Infectious complications following mesh implantation for abdominal wall repair appear in 0.7 up to 26.6% of hernia repairs and can have a detrimental impact for the patient. To prevent or to treat mesh-related infection, the scientific community is currently developing a veritable arsenal of antibacterial meshes. The numerous and increasing reports published every year describing new technologies indicate a clear clinical need, and an academic interest in solving this problem. Nevertheless, to really appreciate, to challenge, to compare and to optimize the antibacterial properties of next generation meshes, it is important to know which models are available and to understand them.

PURPOSE

We proposed for the first time, a complete overview focusing only on the in vitro and in vivo models which have been employed specifically in the field of antibacterial meshes for hernia repair.

RESULTS AND CONCLUSION

From this investigation, it is clear that there has been vast progress and breadth in new technologies and models to test them. However, it also shows that standardization or adoption of a more restricted number of models would improve comparability and be a benefit to the field of study.

Infections associated with mesh repairs of abdominal wall hernias: Are antimicrobial biomaterials the longed-for solution?

The incidence of mesh-related infection after abdominal wall hernia repair is low, generally between 1 and 4%; however, worldwide, this corresponds to tens of thousands of difficult cases to treat annually. Adopting best practices in prevention is one of the keys to reduce the incidence of mesh-related infection. Once the infection is established, however, only a limited number of options are available that provides an efficient and successful treatment outcome. Over the past few years, there has been a tremendous amount of research dedicated to the functionalization of prosthetic meshes with antimicrobial properties, with some receiving regulatory approval and are currently available for clinical use. In this context, it is important to review the clinical importance of mesh infection, its risk factors, prophylaxis and pathogenicity. In addition, we give an overview of the main functionalization approaches that have been applied on meshes to confer anti-bacterial protection, the respective benefits and limitations, and finally some relevant future directions.

* The New Zealand White Rabbit as a Model for Preclinical Studies Addressing Tissue Repair at the Level of the Abdominal Wall

In this report, we review the use of the New Zealand White rabbit as the experimental animal for several models of abdominal wall repair. For the repair of an abdominal wall defect, such as a hernia in clinical practice, multiple types of prosthetic material exist. Before their marketing, each of these biomaterials needs to be tested in a preclinical setting to confirm its biocompatibility and appropriate behavior at the different tissue interfaces. For preclinical trials, we have always used the New Zealand White rabbit as the model owing to its ease of handling and suitable size. This size allows for laparoscopic studies designed to follow the behavior in real time of a biomaterial implanted at the peritoneal interface, a delicate interface that often gives rise to complications in human practice. The size of the rabbit also offers a sufficiently large number of implant samples to be harvested for a complete battery of tests at several time points postimplant. In this review, we first describe the models established and then provide the results obtained so far using these models to test the different types of biomaterial. We end our review with a discussion of the clinical implications of these results.

Laparoscopic ventral hernia repair using a composite mesh with polypropylene and expanded polytetrafluoroethylene: a prospective, multicentre registry

BACKGROUND

Abdominal wall hernias are a common problem. Composite meshes placed intraperitoneally for abdominal wall hernia repair are widely used. This registry evaluated the safety and efficacy of one specific composite mesh with polypropylene and expanded polytetrafluoroethylene (Intramesh^® T1) in laparoscopic ventral hernia repair.

METHODS

A prospective multicentre registry with data from seven centres was collected between January 2013 and September 2014. Primary endpoint was recurrence rate at 12 months determined by clinical examination. Secondary outcome measures included intraoperative complications, complications during hospitalisation and at 1-month and 12-months follow-up.

RESULTS

The registry included 90 patients (30 female and 60 male). Fifty-five patients (61.1%) presented with primary ventral hernias and 35 patients (38.9%) with incisional ventral hernias. Median hernia size was 4 cm². Intraoperative complications were reported in two patients (2.2%). Complications during hospitalisation were reported in four (4.4%) patients. At 1-month follow-up, 17 (18.9%) patients had postoperative complications, of which 5 complications were major and 19 were minor. Late complications at 12-months were observed in 10 patients (11.1%), of which 2 were major and 8 minor complications.

CONCLUSION

Intramesh^® T1 is a safe and effective composite mesh with favourable short and midterm outcome and morbidity. (NCT01816867).

Anti-inflammatory coatings of hernia repair meshes: A pilot study

The current prevalence of postoperative chronic pain from hernioplasty procedures employing polymer mesh is close to 30%. Most of the researchers agree that oxidative stress, resulting from the release of oxidants and enzymes during acute inflammatory response, is a key factor in the development of posthernioplasty complications. This results in both the decrease of the biomechanical properties and stiffening of the polymer fibers of the mesh, leading to chronic pain. Moreover, enhanced activity of inflammatory cells can lead to an excessive deposition of connective tissue around the implant. In this study polypropylene hernia repair meshes coated with vitamin E (α-tocopherol), a known antioxidant, were prepared and characterized. The absorption isotherm of vitamin E on the mesh was characterized and a release profile study yielded a promising results, showing sustained release of the drug over a 10-day period. An animal study was conducted, and histological analysis five weeks after implantation exhibited a reduced host tissue response for a modified mesh as compared to a plain mesh, as evidenced by a higher mature collagen to immature collagen ratio, as well as lower level of fatty infiltrates, neovascularization and fibrosis in the case of modified mesh. These results support the use of α-tocopherol as a potential coating in attempt to reduce the extent of postoperative inflammation, and thereby improve long-term outcomes of hernioplasty. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 589-597, 2018.

An immobilized liquid interface prevents device associated bacterial infection in vivo

Virtually all biomaterials are susceptible to biofilm formation and, as a consequence, device-associated infection. The concept of an immobilized liquid surface, termed slippery liquid-infused porous surfaces (SLIPS), represents a new framework for creating a stable, dynamic, omniphobic surface that displays ultralow adhesion and limits bacterial biofilm formation. A widely used biomaterial in clinical care, expanded polytetrafluoroethylene (ePTFE), infused with various perfluorocarbon liquids generated SLIPS surfaces that exhibited a 99% reduction in S. aureus adhesion with preservation of macrophage viability, phagocytosis, and bactericidal function. Notably, SLIPS modification of ePTFE prevents device infection after S. aureus challenge in vivo, while eliciting a significantly attenuated innate immune response. SLIPS-modified implants also decrease macrophage inflammatory cytokine expression in vitro, which likely contributed to the presence of a thinner fibrous capsule in the absence of bacterial challenge. SLIPS is an easily implementable technology that provides a promising approach to substantially reduce the risk of device infection and associated patient morbidity, as well as health care costs.

Design Strategies and Applications of Biomaterials and Devices for Hernia Repair

Hernia repair is one of the most commonly performed surgical procedures worldwide, with a multi-billion dollar global market. Implant design remains a critical challenge for the successful repair and prevention of recurrent hernias, and despite significant progress, there is no ideal mesh for every surgery. This review summarizes the evolution of prostheses design toward successful hernia repair beginning with a description of the anatomy of the disease and the classifications of hernias. Next, the major milestones in implant design are discussed. Commonly encountered complications and strategies to minimize these adverse effects are described, followed by a thorough description of the implant characteristics necessary for successful repair. Finally, available implants are categorized and their advantages and limitations elucidated, including non-absorbable and absorbable (synthetic and biologically derived) prostheses, composite prostheses, and coated prostheses. This review not only summarizes the state of the art in hernia repair, but also suggests future research directions toward improved hernia repair utilizing novel materials and fabrication methods.

Evaluation of a fully absorbable poly-4-hydroxybutyrate/absorbable barrier composite mesh in a porcine model of ventral hernia repair

Background

The objective of this study was to evaluate the mechanical and histological properties of a fully absorbable poly-4-hydroxybutyrate/absorbable barrier composite mesh (Phasix™ ST) compared to partially absorbable (Ventralight™ ST), fully absorbable (Phasix™), and biologically derived (Strattice™) meshes in a porcine model of ventral hernia repair.

Methods

Bilateral abdominal surgical defects were created in twenty-four Yucatan pigs, repaired with intraperitoneal (Phasix™ ST, Ventralight™ ST) or retromuscular (Phasix™, Strattice™) mesh, and evaluated at 12 and 24 weeks (n = 6 mesh/group/time point).

Results

Prior to implantation, Strattice™ demonstrated significantly higher (p < 0.001) strength (636.6 ± 192.1 N) compared to Ventralight™ ST (324.3 ± 37.1 N), Phasix™ ST (206.9 ± 11.3 N), and Phasix™ (200.6 ± 25.2 N). At 12 and 24 weeks, mesh/repair strength was significantly greater than NAW (p < 0.01 in all cases), and no significant changes in strength were observed for any meshes between 12 and 24 weeks (p > 0.05). Phasix™ mesh/repair strength was significantly greater than Strattice™ (p < 0.001) at 12 and 24 weeks, and Ventralight™ ST mesh/repair strength was significantly greater than Phasix™ ST mesh (p < 0.05) at 24 weeks. At 12 and 24 weeks, Phasix™ ST and Ventralight™ ST were associated with mild inflammation and minimal–mild fibrosis/neovascularization, with no significant differences between groups. At both time points, Phasix™ was associated with minimal–mild inflammation/fibrosis and mild neovascularization. Strattice™ was associated with minimal inflammation/fibrosis, with minimal neovascularization at 12 weeks, which increased to mild by 24 weeks. Strattice™ exhibited significantly less neovascularization than Phasix™ at 12 weeks and significantly greater inflammation at 24 weeks due to remodeling.

Conclusions

Phasix™ ST demonstrated mechanical and histological properties comparable to partially absorbable (Ventralight™ ST) and fully resorbable (Phasix™) meshes at 12 and 24 weeks in this model. Data also suggest that fully absorbable meshes with longer-term resorption profiles may provide improved mechanical and histological properties compared to biologically derived scaffolds.

Evaluation of the Antimicrobial Efficacy of a Novel Rifampin/Minocycline-Coated, Noncrosslinked Porcine Acellular Dermal Matrix Compared With Uncoated Scaffolds for Soft Tissue Repair

Background Despite meticulous aseptic technique and systemic antibiotics, bacterial colonization of mesh remains a critical issue in hernia repair. A novel minocycline/rifampin tyrosine-coated, noncrosslinked porcine acellular dermal matrix (XenMatrix AB) was developed to protect the device from microbial colonization for up to 7 days. The objective of this study was to evaluate the in vitro and in vivo antimicrobial efficacy of this device against clinically isolated methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. Methods XenMatrix AB was compared with 5 existing uncoated soft tissue repair devices using in vitro methods of zone of inhibition (ZOI) and scanning electron microscopy (SEM) at 24 hours following inoculation with MRSA or E coli These devices were also evaluated at 7 days following dorsal implantation and inoculation with MRSA or E coli (60 male New Zealand white rabbits, n = 10 per group) for viable colony-forming units (CFU), abscess formation and histopathologic response, respectively. Results In vitro studies demonstrated a median ZOI of 36 mm for MRSA and 16 mm for E coli for XenMatrix AB, while all uncoated devices showed no inhibition of bacterial growth (0 mm). SEM also demonstrated no visual evidence of MRSA or E coli colonization on the surface of XenMatrix AB compared with colonization of all other uncoated devices. In vivo XenMatrix AB demonstrated complete inhibition of bacterial colonization, no abscess formation, and a reduced inflammatory response compared with uncoated devices. Conclusion We demonstrated that XenMatrix AB possesses potent in vitro and in vivo antimicrobial efficacy against clinically isolated MRSA and E coli compared with uncoated devices.

Development of a novel murine model for treatment of infected mesh scenarios

BACKGROUND

Indications regarding hernia repair after removal of previously infected prostheses remain unclear. Patients may receive staged primary repair or single-stage reconstructions, neither of which may be ideal. Although animal models have simulated contamination by direct inoculation of implants with bacteria, there remains a paucity of literature, which simulates a field following mesh infection and removal. We aimed to develop a murine model to mimic this complex scenario to allow for further testing of various implants.

METHODS

Thirty-six female CL57BL/6J mice underwent implantation of a 0.7 × 0.7 cm polyester mesh in the dorsal subcutaneous position. Wounds were closed and inoculated with 100 µL containing 1 × 10⁴ CFU of GFP-labeled MSSA. After 2 weeks, the infected mesh was removed and the cavity was copiously irrigated with saline. Mice were split into four groups: with three groups receiving new polyester, polypropylene, and porcine mesh and remaining as non-mesh controls. Mice were survived for another 2 weeks and underwent necropsy. Gross infection was evaluated at 2 and 4 weeks. Tissue homogenization and direct plating to recover GFP MSSA was completed at 4 weeks.

RESULTS

At 2 weeks, all mice were noted to have gross mesh infection. One animal died due to overwhelming infection and wound breakdown. At 4 weeks, 5/6 (83 %) control mice who did not have a second mesh implantation had full clearance of their wounds. In contrast, 9/10 (90 %) mice with re-implantation of polypropylene were noted to have pus and recovery of GFP MSSA on plating. This was also observed in 100 % of mice with polyester and porcine mesh.

CONCLUSION

Our novel murine model demonstrates that mesh re-implantation after infected mesh removal results in infection of the newly placed prosthesis, regardless of the material characteristic or type. This model lays foundation for development and investigation of implants for treatment strategies following infected mesh removal.

Mesh Infection and Hernia Repair: A Review

BACKGROUND

The use of a prosthetic mesh to repair a tissue defect may produce a series of post-operative complications, among which infection is the most feared and one of the most devastating. When occurring, bacterial adherence and biofilm formation on the mesh surface affect the implant's tissue integration and host tissue regeneration, making preventive measures to control prosthetic infection a major goal of prosthetic mesh improvement.

METHODS

This article reviews the literature on the infection of prosthetic meshes used in hernia repair to describe the in vitro and in vivo models used to examine bacterial adherence and biofilm formation on the surface of different biomaterials. Also discussed are the prophylactic measures used to control implant infection ranging from meshes soaked in antibiotics to mesh coatings that release antimicrobial agents in a controlled manner.

RESULTS

Prosthetic architecture has a direct effect on bacterial adherence and biofilm formation. Absorbable synthetic materials are more prone to bacterial colonization than non-absorbable materials. The reported behavior of collagen biomeshes, also called xenografts, in a contaminated environment has been contradictory, and their use in this setting needs further clinical investigation. New prophylactic mesh designs include surface modifications with an anti-adhesive substance or pre-treatment with antibacterial agents or metal coatings.

CONCLUSIONS

The use of polymer coatings that slowly release non-antibiotic drugs seems to be a good strategy to prevent implant contamination and reduce the onset of resistant bacterial strains. Even though the prophylactic designs described in this review are mainly focused on hernia repair meshes, these strategies can be extrapolated to other implantable devices, regardless of their design, shape or dimension.

Preclinical Bioassay of a Polypropylene Mesh for Hernia Repair Pretreated with Antibacterial Solutions of Chlorhexidine and Allicin: An In Vivo Study

INTRODUCTION

Prosthetic mesh infection constitutes one of the major complications following hernia repair. Antimicrobial, non-antibiotic biomaterials have the potential to reduce bacterial adhesion to the mesh surface and adjacent tissues while avoiding the development of novel antibiotic resistance. This study assesses the efficacy of presoaking reticular polypropylene meshes in chlorhexidine or a chlorhexidine and allicin combination (a natural antibacterial agent) for preventing bacterial infection in a short-time hernia-repair rabbit model.

METHODS

Partial hernia defects (5 x 2 cm) were created on the lateral right side of the abdominal wall of New Zealand White rabbits (n = 21). The defects were inoculated with 0.5 mL of a 106 CFU/mL Staphylococcus aureus ATCC25923 strain and repaired with a DualMesh Plus antimicrobial mesh or a Surgipro mesh presoaked in either chlorhexidine (0.05%) or allicin-chlorhexidine (900 μg/mL-0.05%). Fourteen days post-implant, mesh contraction was measured and tissue specimens were harvested to evaluate bacterial adhesion to the implant surface (via sonication, S. aureus immunolabeling), host-tissue incorporation (via staining, scanning electron microscopy) and macrophage response (via RAM-11 immunolabeling).

RESULTS

The polypropylene mesh showed improved tissue integration relative to the DualMesh Plus. Both the DualMesh Plus and the chlorhexidine-soaked polypropylene meshes exhibited high bacterial clearance, with the latter material showing lower bacterial yields. The implants from the allicin-chlorhexidine group displayed a neoformed tissue containing differently sized abscesses and living bacteria, as well as a diminished macrophage response. The allicin-chlorhexidine coated implants exhibited the highest contraction.

CONCLUSIONS

The presoaking of reticular polypropylene materials with a low concentration of chlorhexidine provides the mesh with antibacterial activity without disrupting tissue integration. Due to the similarities found with the antimicrobial DualMesh Plus material, the chlorhexidine concentration tested could be utilized as a prophylactic treatment to resist infection by prosthetic mesh during hernia repair.

An in vivo analysis of Miromesh--a novel porcine liver prosthetic created by perfusion decellularization

BACKGROUND

Bioprosthetics derived from human or porcine dermis and intestinal submucosa have dense, homogenous, aporous collagen structures that potentially limit cellular penetration, undermining the theoretical benefit of a "natural" collagen scaffold. We hypothesized that Miromesh-a novel prosthetic derived from porcine liver by perfusion decellularization-provides a more optimal matrix for tissue ingrowth.

METHODS

Thirty rats underwent survival surgery that constituted the creation of a 4 × 1 cm abdominal defect and simultaneous bridged repair. Twenty rats were bridged with Miromesh, and 10 rats were bridged with non-cross-linked porcine dermis (Strattice). Ten Miromesh and all 10 Strattice were rinsed in vancomycin solution and inoculated with 10(4) colony-forming units of green fluorescent protein-labeled Staphylococcus aureus (GFP-SA) after implantation. Ten Miromesh controls were neither soaked nor inoculated. No animals received systemic antibiotics. All animals were euthanized at 90 d and underwent an examination of their gross appearance before being sectioned for quantitative bacterial culture and histologic grading. A pathologist scored specimens (0-4) for cellular infiltration, acute inflammation, chronic inflammation, granulation tissue, foreign body reaction, and fibrous capsule formation.

RESULTS

All but one rat repaired with Strattice survived until the 90-d euthanization. All quantitative bacterial cultures for inoculated specimens were negative for GFP-SA. Of nine Strattice explants, none received a cellular infiltration score >0, consistent with a poor tissue-mesh interface observed grossly. Of 10 Miromesh explants also inoculated with GFP-SA, seven of 10 demonstrated cellular infiltration with an average score of +2.7 ± 0.8, whereas sterile Miromesh implants received an average score of 0.8 ± 1.0. Two inoculated Miromesh implants demonstrated acute inflammation and infection on histology.

CONCLUSIONS

A prosthetic generated from porcine liver by perfusion decellularization provides a matrix for superior cellular infiltration compared with non-cross-linked porcine dermis.

A case report on management of synergistic gangrene following an incisional abdominal hernia repair in an immunocompromised obese patient

•

Synergistic gangrene is generated from bacterial colonies present in necrotic tissues. Within our case, continual removal of the necrotic burden was essential in wound bed preparation, reducing contamination and tissue destruction.

•

In surgery, wide necrotic wound debridement, early and repetitive wound drainages with the use of a large pore polypropylene mesh with a detailed surgical follow up is recommended.

•

This case has demonstrated how a planned multidisciplinary action can produce prosperous results in a severely obese immunocompromised patient with an SSI, following an incisional hernia repair.

•

Our selective case is unique within current literature, being the first to illustrate mesh salvage in a morbid obese patient with chronic lymphoblastic leukaemia.

Introduction

We present a case on conservative management of salvaging the mesh in an immunocompromised morbidly obese patient, who developed a synergistic gangrene infection following a primary open mesh repair of an incisional hernia.

Presentation of case

Our patient presented with a surgical wound infection, comorbidities were Chronic Lymphoblastic Leukemia (CLL), Body Mass Index (BMI) of 50, hypertension and diet controlled type-2 diabetes. In surgery, wide necrotic wound debridement, early and repetitive wound drainages with the use of a large pore polypropylene mesh and a detailed surgical follow up was required. High dose intravenous broad-spectrum antibiotic treatment and Negative Pressure Wound Therapy (NPWT) was administrated in combination with adopting a multidisciplinary approach was key to our success.

Discussion

Stoppa Re et al. complied a series of 360 ventral hernia mesh repairs reporting an infection rate of 12% that were managed conservatively. However, our selective case is unique within current literature, being the first to illustrate mesh salvage in a morbid obese patient with CLL. Recent modifications in mesh morphology, such as lower density, wide pores, and lighter weight has led to considerable improvements regarding infection avoidance.

Conclusion

This case has demonstrated how a planned multidisciplinary action can produce prosperous results in a severely obese immunocompromised patient with an SSI, following an incisional hernia repair.

Postoperative Mesh Infection-Still a Concern in Laparoscopic Era

Introduction of synthetic mesh was a landmark breakthrough in the management of hernia repair and has significantly reduced recurrence rates. But in addition to the benefits, some more problems have come in picture major being 'mesh infection'. Prolene mesh has shown promise when used in abdominal and inguinal hernia repair, especially when used in planned surgeries. This material, derived from monofilament polypropelene, is found to be biologically inert in almost every person. Being a foreign material, a slightest breach in asepsis can lead to favourable environment for bacterial proliferation and form a 'biofilm'. This phenomenon especially after laparoscopic surgeries gives rise to chronic discharging sinus at the port site, abscess formation around mesh and even sepsis. It appears that laparoscopic hernia repair is a promising method but having chances of mesh infection owing to difficult approach and lack of uniformity in sterilization of laparoscopic instruments. Slightest breach in sterility or protocols might lead to such a large ventral wall sinus, increasing morbidity and cost of treatment. Treatment of infected mesh is possible by local debridement, irrigation, mesh removal and systemic antibiotics culminating in increased morbidity over duration of disease, but still it would be worth emphasizing-'Prevention is better than cure'.

Chitosan finishing nonwoven textiles loaded with silver and iodide for antibacterial wound dressing applications

Polyethylene terephtalate (PET) and Polypropylene (PP) textiles are widely used in biomedical application such as wound dressings and implants. The aim of this work was to develop an antibacterial chitosan (CHT) coating activated by silver or by iodine. Chitosan was immobilized onto PET and PP supports using citric acid (CTR) as a crosslinking agent through a pad-dry-cure textile finishing process. Interestingly, depending on the CHT/CTR molar ratio, two different systems were obtained: rich in cationic ammonium groups when the CTR concentration was 1%w/v, and rich in anionic carboxylate groups when the CTR concentration was 10%w/v. As a consequence, such samples could be selectively loaded with iodine and silver nitrate, respectively.Both types of coatings were analyzed using SEM and FTIR, their sorption capacities were evaluated toward iodide/iodate anions (I(-)/IO3(-)) and the silver cations (Ag(+)) were evaluated using elemental analysis. Finally, in vitro evaluations were carried out to evaluate the cytocompatibility on the epithelial cell line. The silver loaded textile reported a stronger antibacterial effect against E.coli (5 log10 reduction) than toward S. aureus (3 log10) while the antibacterial effect of the iodide loaded textiles was limited to 1 log10 to 2 log10 on both strains.

Can a biologic mesh survive a Candida krusei infection? A case report of infection of a biologic mesh following repair of abdominal wall hernia

The use of biologic mesh, which is considered resistant to infection, has become common. It is preferred over synthetic mesh for use in contaminated fields. Fungal infection with infiltration of biologic mesh is rare and has not been reported. In this paper, we report a case of a patient who underwent multiple laparotomies and received multiple antibiotics and an azole antifungal. Biologic mesh was used, but it ultimately required removal because of chronic infection with Candida krusei. On biopsy, the yeast was found to have infiltrated the mesh.

Characterization of the Mechanical Strength, Resorption Properties, and Histologic Characteristics of a Fully Absorbable Material (Poly-4-hydroxybutyrate-PHASIX Mesh) in a Porcine Model of Hernia Repair

Purpose. Poly-4-hydroxybutyrate (P4HB) is a naturally derived, absorbable polymer. P4HB has been manufactured into PHASIX Mesh and P4HB Plug designs for soft tissue repair. The objective of this study was to evaluate mechanical strength, resorption properties, and histologic characteristics in a porcine model. Methods. Bilateral defects were created in the abdominal wall of n = 20 Yucatan minipigs and repaired in a bridged fashion with PHASIX Mesh or P4HB Plug fixated with SorbaFix or permanent suture, respectively. Mechanical strength, resorption properties, and histologic characteristics were evaluated at 6, 12, 26, and 52 weeks (n = 5 each). Results. PHASIX Mesh and P4HB Plug repairs exhibited similar burst strength, stiffness, and molecular weight at all time points, with no significant differences detected between the two devices (P > 0.05). PHASIX Mesh and P4HB Plug repairs also demonstrated significantly greater burst strength and stiffness than native abdominal wall at all time points (P < 0.05), and material resorption increased significantly over time (P < 0.001). Inflammatory infiltrates were mononuclear, and both devices exhibited mild to moderate granulation tissue/vascularization. Conclusions. PHASIX Mesh and P4HB Plug demonstrated significant mechanical strength compared to native abdominal wall, despite significant material resorption over time. Histological assessment revealed a comparable mild inflammatory response and mild to moderate granulation tissue/vascularization.

Does presoaking synthetic mesh in antibiotic solution reduce mesh infections? An experimental study

BACKGROUND

Prosthetic mesh infection is one of the most challenging complications after hernia repair. We evaluate the efficacy of soaking mesh in antibiotics to prevent prosthetic infection in an animal model of clean-contaminated ventral hernia repair (VHR).

MATERIAL AND METHODS

Rats underwent an acute VHR with one of four synthetic meshes (composite multifilament polyester (Parietex PCO), multifilament polyester (Parietex TET), composite monofilament polypropylene (Ventralight), or monofilament polypropylene (SoftMesh)). Prior to implantation, mesh was soaked in saline or 10 mg/ml of vancomycin for 15 min. Following implantation, meshes were contaminated with 10(4) CFU of methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Thirty days after implantation, mesh samples were cultured and evaluated under scanning electron microscope for biofilm formation.

RESULTS

Presoaking meshes significantly improves bacterial clearance in composite meshes and multifilament polyester mesh. MRSA clearance was as follows for all meshes (saline-soaked vs. vanco-soaked): Parietex PCO (0 vs. 56 %, p = 0.006), Parietex TET (0 vs. 50 %, p = 0.01), Ventralight (20 vs. 78 %, p = 0.012), and SoftMesh (70 vs. 80 %, p = 0.6). MRSA biofilm formation was consistent with bacterial growth.

CONCLUSION

Presoaking multifilament and composite mesh in vancomycin solution reduces MRSA bacterial growth. Its implementation may reduce the risk of mesh infection in clean-contaminated cases, although further investigation with human trials should be performed.

Omentum patch substitute for facilitating endoscopic repair of GI perforations: an early laparoscopic pilot study with a foam matrix plug (with video)

BACKGROUND

Endoscopic perforations are surgically repaired by using an omentum patch. Omentum substitutes may have broader applications particularly in certain sites (eg, esophagus).

OBJECTIVE

Evaluate a self-expandable foam matrix plug as a synthetic omentum substitute for repairing iatrogenic gastric perforations in a 4-week survival pig model.

DESIGN

Experimental pilot study.

SETTING

Laboratory.

INTERVENTION

A laparoscopic plug repair of a 1-cm, full-thickness, gastric perforation was carried out by using either a polyurethane foam matrix plug (FMP, 8 animals) or an omentum plug (OP, 6 animals, control group).

MAIN OUTCOME MEASUREMENTS

Follow-up endoscopy was carried out at 1 and 4 weeks. At necropsy, the perforation site was evaluated for adhesions and histology by using hematoxylin and eosin analysis. A portion of the implant was sent for bacterial and fungal culture.

RESULTS

All procedures were technically simple and successful. Thirteen animals thrived well for 4 weeks. One animal from the FMP group died 3 days postoperatively from diffuse peritonitis because of a misplaced plug. All remaining FMPs were intact at 4 weeks and colonized with mixed bacteria, except one animal presenting with FMP migration after 1 week. Histologically, the FMP group had more prominent inflammation and suppuration as compared with the OP group, all limited to its adjacent tissue.

LIMITATIONS

Animal study.

CONCLUSION

The FMP offered a technically simple and feasible option for repairing iatrogenic gastric perforations. With effective sealing, the clinical outcome is similar to that of an omentum patch repair. Migration and inadequate sealing is a concern, which can lead to peritonitis and sepsis. Further development is needed to improve FMP performance.

Effects of small intestinal submucosa (SIS) on the murine innate immune microenvironment induced by heat-killed Staphylococcus aureus

The use of biological scaffold materials for wound healing and tissue remodeling has profoundly impacted regenerative medicine and tissue engineering. The porcine-derived small intestinal submucosa (SIS) is a licensed bioscaffold material regularly used in wound and tissue repair, often in contaminated surgical fields. Complications and failures due to infection of this biomaterial have therefore been a major concern and challenge. SIS can be colonized and infected by wound-associated bacteria, particularly Staphylococcus aureus. In order to address this concern and develop novel intervention strategies, the immune microenvironment orchestrated by the combined action of S. aureus and SIS should be critically evaluated. Since the outcome of tissue remodeling is largely controlled by the local immune microenvironment, we assessed the innate immune profile in terms of cytokine/chemokine microenvironment and inflammasome-responsive genes. BALB/c mice were injected intra-peritoneally with heat-killed S. aureus in the presence or absence of SIS. Analyses of cytokines, chemokines and microarray profiling of inflammasome-related genes were done using peritoneal lavages collected 24 hours after injection. Results showed that unlike SIS, the S. aureus-SIS interactome was characterized by a Th1-biased immune profile with increased expressions of IFN-γ, IL-12 and decreased expressions of IL-4, IL-13, IL-33 and IL-6. Such modulation of the Th1/Th2 axis can greatly facilitate graft rejections. The S. aureus-SIS exposure also augmented the expressions of pro-inflammatory cytokines like IL-1β, Tnf-α, CD30L, Eotaxin and Fractalkine. This heightened inflammatory response caused by S. aureus contamination could enormously affect the biocompatibility of SIS. However, the mRNA expressions of many inflammasome-related genes like Nlrp3, Aim2, Card6 and Pycard were down-regulated by heat-killed S. aureus with or without SIS. In summary, our study explored the innate immune microenvironment induced by the combined exposure of SIS and S. aureus. These results have practical implications in developing strategies to contain infection and promote successful tissue repair.

Risk factors for mesh-related infections after hernia repair surgery: a meta-analysis of cohort studies

Mesh infection, although infrequent, is a devastating complication of mesh hernioplasties. The aim of this study was to systematically review and synthesize the available evidence on risk factors for synthetic mesh infection after hernioplasty. A systematic search was performed in PubMed and Scopus databases. The extracted data were synthesized with the methodology of meta-analysis. We identified six eligible studies that reported on 2,418 mesh hernioplasties. The crude mesh infection rate was 5%. Statistically significant risk factors were smoking (risk ratio [RR] = 1.36 [95% confidence interval (CI): 1.07, 1.73]; 1,171 hernioplasties), American Society of Anesthesiologists (ASA) score ≥3 (RR = 1.40 [1.15, 1.70]; 1,682 hernioplasties), and emergency operation (RR = 2.46 [1.56, 3.91]; 1,561 hernioplasties). Also, mesh infections were significantly correlated with patient age (weighted mean difference [WMD] = 2.63 [0.22, 5.04]; 2,364 hernioplasties), ASA score (WMD = 0.23 [0.08, 0.38]; 1,682 hernioplasties), and the duration of the hernioplasty (WMD = 44.92 [25.66, 64.18]; 833 hernioplasties). A trend toward higher mesh infection rates was observed in obese patients (RR = 1.41 [0.94, 2.11]; 2,243 hernioplasties) and in patients operated on by a resident (in contrast to a consultant; RR = 1.18 [0.99, 1.40]; 982 hernioplasties). Mesh infections usually resulted in mesh removal, and common pathogens included Staphylococcus spp., Enterococcus spp., and gram-negative bacteria. Patient age, ASA score, smoking, and the duration and emergency setting of the operation were found to be associated with the development of synthetic mesh infection. The heterogeneity of the available evidence should be taken under consideration. Prospective studies with a meticulous follow-up are warranted to further investigate mesh-related infections.

High-throughput assay for bacterial adhesion on acellular dermal matrices and synthetic surgical materials

BACKGROUND

There has been increasing use of synthetic and acellular dermal matrix materials in surgery, ranging from breast reconstruction to hernia repairs. There is a paucity of data on how acellular dermal matrix compares with other surgical materials as a substrate for bacterial adhesion, the first step in formation biofilm, which occurs in prosthetic wound infections. The authors have designed a high-throughput assay to evaluate Staphylococcus aureus adherence on various synthetic and biologically derived materials.

METHODS

Clinical isolates of S. aureus (strains SC-1 and UAMS-1) were cultured with different materials, and bacterial adherence was measured using a resazurin cell vitality assay. Four materials that are commonly used in surgery were evaluated: Prolene mesh, Vicryl mesh, and two different acellular dermal matrix preparations (AlloDerm and FlexHD). The authors were able to develop a high-throughput and reliable assay for quantifying bacterial adhesion on synthetic and biologically derived materials.

RESULTS

The resazurin vitality assay can be reliably used to quantify bacterial adherence to acellular dermal matrix material and synthetic material. S. aureus strains SC-1 and UAMS-1 both adhered better to acellular dermal matrix materials (AlloDerm versus FlexHD) than to the synthetic material Prolene. S. aureus also adhered better to Vicryl than to Prolene. Strain UAMS-1 adhered better to Vicryl and acellular dermal matrix materials than did strain SC-1.

CONCLUSIONS

The results show that S. aureus adheres more readily to acellular dermal matrix material than to synthetic material. The resazurin assay provides a standard method for evaluating surgical materials with regard to bacterial adherence and potential propensity for biofilm development.

The effect of bacterial infection on the biomechanical properties of biological mesh in a rat model

BACKGROUND

The use of biologic mesh to repair abdominal wall defects in contaminated surgical fields is becoming the standard of practice. However, failure rates and infections of these materials persist clinically. The purpose of this study was to determine the mechanical properties of biologic mesh in response to a bacterial encounter.

METHODS

A rat model of Staphylococcus aureus colonization and infection of subcutaneously implanted biologic mesh was used. Samples of biologic meshes (acellular human dermis (ADM) and porcine small intestine submucosa (SIS)) were inoculated with various concentrations of methicillin-resistant Staphylococcus aureus [10(5), 10(9) colony-forming units] or saline (control) prior to wound closure (n = 6 per group). After 10 or 20 days, meshes were explanted, and cultured for bacteria. Histological changes and bacterial recovery together with biomechanical properties were assessed. Data were compared using a 1-way ANOVA or a Mann-Whitney test, with p<0.05.

RESULTS

The overall rate of staphylococcal mesh colonization was 81% and was comparable in the ADM and SIS groups. Initially (day 0) both biologic meshes had similar biomechanical properties. However after implantation, the SIS control material was significantly weaker than ADM at 20 days (p = 0.03), but their corresponding modulus of elasticity were similar at this time point (p>0.05). After inoculation with MRSA, a time, dose and material dependent decrease in the ultimate tensile strength and modulus of elasticity of SIS and ADM were noted compared to control values.

CONCLUSION

The biomechanical properties of biologic mesh significantly decline after colonization with MRSA. Surgeons selecting a repair material should be aware of its biomechanical fate relative to other biologic materials when placed in a contaminated environment.

Bacterial clearance of biologic grafts used in hernia repair: an experimental study

BACKGROUND

Biologic grafts used in ventral hernia repair are derived from various sources and undergo different post-tissue-harvesting processing, handling, and sterilization techniques. It is unclear how these various characteristics impact graft response in the setting of contamination. We evaluated four materials in an infected hernia repair animal model using fluorescence imaging and quantitative culture studies.

METHODS

One hundred seven rats underwent creation of a chronic hernia. They were then repaired with one synthetic polyester control material (n = 12) and four different biologic grafts (n = 24 per material). Biologic grafts evaluated included Surgisis (porcine small intestinal submucosa), Permacol (crosslinked porcine dermis), Xenmatrix (noncrosslinked porcine dermis), and Strattice (noncrosslinked porcine dermis). Half of the repairs in each group were inoculated with Staphylococcus aureus at 10(4) CFU/ml and survived for 30 days without systemic antibiotics. Animals then underwent fluorescence imaging and quantitative bacterial studies.

RESULTS

All clean repairs remained sterile. Rates of bacterial clearance were as follows: polyester synthetic 0%, Surgisis 58%, Permacol 67%, Xenmatrix 75%, and Strattice 92% (P=0.003). Quantitative bacterial counts had a similar trend in bacterial clearance: polyester synthetic 1×10(6) CFU/g, Surgisis 4.3×10(5) CFU/g, Permacol 1.7×10(3) CFU/g, Xenmatrix 46 CFU/g, and Strattice 31 CFU/g (P=0.001). Fluorescence imaging was unable to detect low bacterial fluorescence counts observed on bacterial studies.

CONCLUSION

Biologic grafts, in comparison to synthetic material, are able to clear a Staphylococcus aureus contamination; however, they are able to do so at different rates. Bacterial clearance correlated to the level of residual bacterial burden observed in our study. Post-tissue-harvesting processing, handling, and sterilization techniques may contribute to this observed difference in ability to clear bacteria.

The use of human acellular dermal matrix for chest wall reconstruction

BACKGROUND

Reconstruction of chest wall defects has evolved, but challenges remain. This is particularly true when defects are large or contamination is present. Although numerous materials are available for reconstruction, acellular dermal matrix has the advantage of becoming vascularized and incorporated autologously. By its resistance to infection and lack of adhesion formation, it is a promising although expensive alternative to synthetic materials in some circumstances. This report examines our experience with human acellular dermal matrix (HADM) in reconstruction of major chest wall and diaphragmatic defects.

METHODS

A retrospective study was conducted of all patients who underwent thoracic reconstruction using HADM between March 2007 and March 2010 at Harbor-University of California-Los Angeles Medical Center. Data acquisition included demographics, surgical indications, operative details, complications, and follow-up evaluation.

RESULTS

Ten patients were identified. Indications included thoracic tumor resection in 5, Clagett procedure modification for postpneumonectomy empyema in 2, resection of chest wall osteomyelitis in 2, and pneumonectomy for multiple aspergillomata in 1. Complications occurred in 4 patients and included respiratory failure, pneumonia, and wound seromas. All wounds healed without need to remove or revise the HADM, and sound chest wall closure was achieved in every case.

CONCLUSIONS

HADM is an effective but expensive alternative to synthetic mesh in reconstruction of chest wall and diaphragmatic defects. It is particularly attractive for use under conditions of potential or overt contamination.

Early biocompatibility of crosslinked and non-crosslinked biologic meshes in a porcine model of ventral hernia repair

PURPOSE

Biologic meshes have unique physical properties as a result of manufacturing techniques such as decellularization, crosslinking, and sterilization. The purpose of this study is to directly compare the biocompatibility profiles of five different biologic meshes, AlloDerm(®) (non-crosslinked human dermal matrix), PeriGuard(®) (crosslinked bovine pericardium), Permacol(®) (crosslinked porcine dermal matrix), Strattice(®) (non-crosslinked porcine dermal matrix), and Veritas(®) (non-crosslinked bovine pericardium), using a porcine model of ventral hernia repair.

METHODS

Full-thickness fascial defects were created in 20 Yucatan minipigs and repaired with the retromuscular placement of biologic mesh 3 weeks later. Animals were euthanized at 1 month and the repair sites were subjected to tensile testing and histologic analysis. Samples of unimplanted (de novo) meshes and native porcine abdominal wall were also analyzed for their mechanical properties.

RESULTS

There were no significant differences in the biomechanical characteristics between any of the mesh-repaired sites at 1 month postimplantation or between the native porcine abdominal wall without implanted mesh and the mesh-repaired sites (P > 0.05 for all comparisons). Histologically, non-crosslinked materials exhibited greater cellular infiltration, extracellular matrix (ECM) deposition, and neovascularization compared to crosslinked meshes.

CONCLUSIONS

While crosslinking differentiates biologic meshes with regard to cellular infiltration, ECM deposition, scaffold degradation, and neovascularization, the integrity and strength of the repair site at 1 month is not significantly impacted by crosslinking or by the de novo strength/stiffness of the mesh.

Novel in vitro model for assessing susceptibility of synthetic hernia repair meshes to Staphylococcus aureus infection using green fluorescent protein-labeled bacteria and modern imaging techniques

BACKGROUND

Mesh infection complicating hernia repair is a major cause of patient morbidity and results in substantial healthcare expenditures. The various constructs of prosthetic mesh may alter the ability of bacteria to attach and form a biofilm. Few data exist evaluating biofilm formation. Using the Maestro in-Vivo Imaging System (CRi, Inc., Woburn, MA) to detect green fluorescent protein (GFP)-expressing Staphylococcus aureus, we studied the ability of synthetic mesh to withstand bacterial biofilm formation in an in vitro model.

METHODS

We included four meshes: Polypropylene (PP), polypropylene/expanded PTFE (PX), compressed PTFE (cPTFE), and polyester/polyethylene glycol and collagen hydrogel (PE). Five samples of each mesh were exposed to GFP-expressing S. aureus for 18 h at 37°C. Next, green fluorescence was measured using the Maestro Imaging System, with the results expressed in relative fluorescence units (RFU), subtracting the fluorescence of uninfected mesh (control). Each mesh subsequently underwent sonication and quantitative culture of the released bacteria, with the results expressed in colony-forming units (CFU). Analysis of variance was performed to compare the mean values for the different meshes.

RESULTS

There was a statistically significant difference in bacterial fluorescence for the four meshes: PE (49.9 ± 25.5 [standard deviation] RFU), PX (30.8 ± 9.4 RFU), cPTFE (10.1 ± 4.0 RFU), and PP (5.8 ± 7.5 RFU)(p = 0.001). Bacterial counts also were significantly different: PE (2.2 × 10(8) CFU), PX (8.6 × 10(7) CFU), cPTFE (3.7 × 10(7) CFU), and PP (9.1 × 10(7) CFU)(p < 0.001).

CONCLUSION

Using novel imaging technology, this study documented significantly different amounts of S. aureus biofilm formation and proliferation on different mesh constructs, with good agreement between imaging and culture results. A multifilament woven mesh (PE) had the highest degree of biofilm formation. These findings are being evaluated in a clinical infection model.

Salvage of an infected titanium mesh in a large incisional ventral hernia using medicinal honey and vacuum-assisted closure: a case report and literature review

The overall reported percentage of mesh infections is 1.3%. Infections after incisional ventral hernia repair depend on many factors. Salvaging an infected mesh should be the priority, because serious complications are reported following mesh removal. In this case report, a methicillin-resistant Staphylococcus aureus (MRSA)-infected titanium mesh was salvaged by a novel technique, not requiring removal. The combination of vacuum-assisted closure (VAC™ therapy) of the wound and medical honey (L-Mesitran™) proved to be successful in leaving the mesh in situ. We report the successful management of this infected titanium mesh and review the literature regarding the possible pathogenetic mechanisms and treatment options.