Gentamicin for prevention of intraoperative mesh contamination: demonstration of high bactericide effect (in vitro) and low systemic bioavailability (in vivo)

Regional antibiotic delivery for sternal wound infection prophylaxis a systematic review and meta-analysis of randomized controlled trials

Despite evidence suggesting the benefit of prophylactic regional antibiotic delivery (RAD) to sternal edges during cardiac surgery, it is seldom performed in clinical practice. The value of topical vancomycin and gentamicin for sternal wound infections (SWI) prophylaxis was further questioned by recent studies including randomized controlled trials (RCTs). The aim of this systematic review and meta-analysis was to comprehensively assess the safety and effectiveness of RAD to reduce the risk of SWI.We screened multiple databases for RCTs assessing the effectiveness of RAD (vancomycin, gentamicin) in SWI prophylaxis. Random effects meta-analysis was performed. The primary endpoint was any SWI; other wound complications were also analysed. Odds Ratios served as the primary statistical analyses. Trial sequential analysis (TSA) was performed.Thirteen RCTs (N = 7,719 patients) were included. The odds of any SWI were significantly reduced by over 50% with any RAD: OR (95%CIs): 0.49 (0.35-0.68); p < 0.001 and consistently reduced in vancomycin (0.34 [0.18-0.64]; p < 0.001) and gentamicin (0.58 [0.39-0.86]; p = 0.007) groups (psubgroup = 0.15). Similarly, RAD reduced the odds of SWI in diabetic and non-diabetic patients (0.46 [0.32-0.65]; p < 0.001 and 0.60 [0.44-0.83]; p = 0.002 respectively). Cumulative Z-curve passed the TSA-adjusted boundary for SWIs suggesting adequate power has been met and no further trials are needed. RAD significantly reduced deep (0.60 [0.43-0.83]; p = 0.003) and superficial SWIs (0.54 [0.32-0.91]; p = 0.02). No differences were seen in mediastinitis and mortality, however, limited number of studies assessed these endpoints. There was no evidence of systemic toxicity, sternal dehiscence and resistant strains emergence. Both vancomycin and gentamicin reduced the odds of cultures outside their respective serum concentrations' activity: vancomycin against gram-negative strains: 0.20 (0.01-4.18) and gentamicin against gram-positive strains: 0.42 (0.28-0.62); P < 0.001. Regional antibiotic delivery is safe and effectively reduces the risk of SWI in cardiac surgery patients.

Polyglactin 910 Meshes Coated with Sustained-Release Cannabigerol Varnish Inhibit Staphylococcus aureus Biofilm Formation and Macrophage Cytokine Secretion: An In Vitro Study

Synthetic surgical meshes are commonly used in abdominal wall reconstruction surgeries to strengthen a weak abdominal wall. Common mesh-related complications include local infection and inflammatory processes. Because cannabigerol (CBG) has both antibacterial and anti-inflammatory properties, we proposed that coating VICRYL (polyglactin 910) mesh with a sustained-release varnish (SRV) containing CBG would prevent these complications. We used an in vitro infection model with Staphylococcus aureus and an in vitro inflammation model of lipopolysaccharide (LPS)-stimulated macrophages. Meshes coated with either SRV-placebo or SRV-CBG were exposed daily to S. aureus in tryptic soy medium (TSB) or macrophage Dulbecco's modified eagle medium (DMEM). Bacterial growth and biofilm formation in the environment and on the meshes were assessed by changes in optical density, bacterial ATP content, metabolic activity, crystal violet staining, spinning disk confocal microscopy (SDCM), and high-resolution scanning electron microscopy (HR-SEM). The anti-inflammatory effect of the culture medium that was exposed daily to the coated meshes was analyzed by measuring the release of the cytokines IL-6 and IL-10 from LPS-stimulated RAW 264.7 macrophages with appropriate ELISA kits. Additionally, a cytotoxicity assay was performed on Vero epithelial cell lines. We observed that compared with SRV-placebo, the segments coated with SRV-CBG inhibited the bacterial growth of S. aureus in the mesh environment for 9 days by 86 ± 4% and prevented biofilm formation and metabolic activity in the surroundings for 9 days, with respective 70 ± 2% and 95 ± 0.2% reductions. The culture medium that was incubated with the SRV-CBG-coated mesh inhibited LPS-induced secretion of IL-6 and IL-10 from the RAW 264.7 macrophages for up to 6 days without affecting macrophage viability. A partial anti-inflammatory effect was also observed with SRV-placebo. The conditioned culture medium was not toxic to Vero epithelial cells, which had an IC₅₀ of 25 µg/mL for CBG. In conclusion, our data indicate a potential role of coating VICRYL mesh with SRV-CBG in preventing infection and inflammation in the initial period after surgery.

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.

Engineering biomaterials to prevent post-operative infection and fibrosis

Implantable biomaterials are essential surgical devices, extending and improving the quality of life of millions of people globally. Advances in materials science, manufacturing, and in our understanding of the biological response to medical device implantation over several decades have resulted in improved safety and functionality of biomaterials. However, post-operative infection and immune responses remain significant challenges that interfere with biomaterial functionality and host healing processes. The objectives of this review is to provide an overview of the biology of post-operative infection and the physiological response to implanted biomaterials and to discuss emerging strategies utilizing local drug delivery and surface modification to improve the long-term safety and efficacy of biomaterials.

Prosthetic meshes for hernia repair: State of art, classification, biomaterials, antimicrobial approaches, and fabrication methods

Worldwide, hernia repair represents one of the most frequent surgical procedures encompassing a global market valued at several billion dollars. This type of surgery usually requires the implantation of a mesh that needs the appropriate chemical, physical and biological properties for the type of repair. This review thus presents a description of the types of hernias, current hernia repair methods, and the state of the art of prosthetic meshes for hernia repair providing the most important meshes used in clinical practice by surgeons working in this area classified according to their biological or chemical nature, morphology and whether bioabsorbable or not. We emphasise the importance of surgical site infection in herniatology, how to deal with this microbial problem, and we go further into the future research lines on the production of advanced antimicrobial meshes to improve hernia repair and prevent microbial infections, including multidrug-resistant strains. A great deal of progress has been made in this biomedical field in the last decade. However, we are still far from an ideal antimicrobial mesh that can also provide excellent integration to the abdominal wall, mechanical performance, low visceral adhesion and minimal inflammatory or foreign body reactions, among many other problems.

Electrospun Scaffold with Sustained Antibacterial and Tissue-Matched Mechanical Properties for Potential Application as Functional Mesh

Introduction

Various materials and approaches have been used to reduce the mesh-induced inflammatory response and modify the mesh with tissue-matched mechanical properties, aiming to improve the repair of abdominal wall defects.

Materials and Methods

In this study, we fabricated a polycaprolactone (PCL)/silk fibroin (SF) mesh integrated with amoxicillin (AMX)-incorporating multiwalled carbon nanotubes (MWCNTs) via electrospinning, grafting and crosslinking, developing a sustainable antibiotic and flexible mesh. AMX was loaded into the hollow tubular MWCNTs by physical adsorption, and a nanofibrous structure was constructed by electrospinning PCL and SF (40:60 w/w). The AMX@MWCNTs were then chemically grafted onto the surfaces of the PCL/SF nanofibers by treating with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) solution for simultaneous crosslinking and coating. The incorporation of AMX into the MWCNTs (AMX@MWCNTs) and the integration of the AMX@MWCNTs with the PCL/SF nanofibers were characterized. Then, the functional mesh was fabricated and fully evaluated in terms of antibacterial activity, mechanical properties and host response.

Results

Our results demonstrated that the PCL/SF nanofibrous structure was fabricated successfully by electrospinning. After integrating with AMX@MWCNT by grafting and crosslinking, the functional mesh showed undeformed structure, modified surface hydrophilicity and biocompatible interfaces, abdominal wall-matched mechanical properties, and a sustained-release antibiotic profile in E. coli growth inhibition compared to those of PCL/SF mesh in vitro. In a rat model with subcutaneous implantation, the functional mesh incited less mesh-induced inflammatory and foreign body responses than PCL/SF mesh within 14 days. The histological analysis revealed less infiltration of granulocytes and macrophages during this period, resulting in the loosely packed collagen deposition on the functional mesh and prominent collagen incorporation.

Discussion

Therefore, this designed PCL/SF-AMX@MWCNT nanofibrous mesh, functionalized with antibacterial and tissue-matched mechanical properties, provides a promising alternative for the repair of abdominal wall defects.

Thermo-Responsive Antimicrobial Hydrogel for the In-Situ Coating of Mesh Materials for Hernia Repair

The prophylactic coating of prosthetic mesh materials for hernia repair with antimicrobial compounds is commonly performed before implantation of the mesh in the abdominal wall. We propose a novel alternative, which is a rifampicin-loaded thermo-responsive hydrogel formulation, to be applied on the mesh after its implantation. This formulation becomes a gel in-situ once reached body temperature, allowing an optimal coating of the mesh along with the surrounding tissues. In vitro, the hydrogel cytotoxicity was assessed using rabbit fibroblasts and antimicrobial efficacy was determined against Staphylococcus aureus. An in vivo rabbit model of hernia repair was performed; implanted polypropylene meshes (5 × 2 cm) were challenged with S. aureus (10⁶ CFU), for two study groups—unloaded (n = 4) and 0.1 mg/cm² rifampicin-loaded hydrogel (n = 8). In vitro, antibacterial activity of the hydrogel lasted for 5 days, without sign of cytotoxicity. Fourteen days after implantation, meshes coated with drug-free hydrogel developed a strong infection and resulted in poor tissue integration. Coating meshes with the rifampicin-loaded hydrogel fully prevented implant infection and permitted an optimal tissue integration. Due to its great performance, this, degradable, thermo-responsive antimicrobial hydrogel could potentially be a strong prophylactic armamentarium to be combined with prosthesis in the surgical field.

An in vitro study on the biocompatibility of fibroblasts in sterile and non-sterile low-cost and commercial meshes

INTRODUCTION

Despite several successful studies with low-cost meshes (LCM) for the treatment of inguinal hernias in India and Africa, a nationwide application has not been possible for a variety of reasons. One problem is the special preparation and sterilization of these meshes-naturally, they should comply with international standards and demands, which is often difficult to achieve in Africa. Our primary approach was to determine whether there are differences in the biocompatibility of fibroblasts between non-sterile and sterile LCMs and commercial meshes (CM).

MATERIALS AND METHODS

Two polyester CMs with different pore size and a polyester LCM were examined as both sterile and non-sterile. LCM was plasma sterilized at 60 °C and steam sterilized at 134 °C. Sterile and non-sterile meshes were soaked with an antibiotic (penicillin/streptomycin) and antimycotic solution (amphotericin B). Human fibroblasts from healthy subcutaneous tissue were used. Various tests for evaluating the growth behavior and cell morphology of human fibroblasts were conducted. Semiquantitative (light microscopy) and qualitative (scanning electron microscopy) analyses were performed after 1 week and again after 12 weeks. The metabolism of fibroblasts was checked by pH measurements and glucose analyses. Biocompatibility of fibroblasts on sterile and non-sterile meshes was carried out by luminescence methods (cell viability and apoptosis) as well as calorimetric methods for proliferation determination (BrDU assay) and cytotoxicity (LDH assay).

RESULTS

Light and electron microscopy revealed a moderate growth of fibroblasts on all investigated mesh types. The results of glycolysis and the pH value were within the normal range for all sterile and non-sterile meshes. In biocompatibility studies, no elevated level of apoptosis was detected. The viability measurement of mitochondrial activity of fibroblasts showed a 50% inhibition of mitochondria in all nets, with the exception of non-sterile CM, whereas mitochondrial activity was increased in the non-sterile CM. A proliferation measurement (BrdU test) revealed different growth inhibition in the sterile and non-sterile meshes. This growth inhibition was significantly stronger, particularly for non-sterile CM light meshes, than it was for the non-sterile LCM.

CONCLUSION

Again, our studies show no significant differences in biocompatibility of fibroblasts between expensive and low-cost meshes. In addition, we detected fibroblast growth even in sterile meshes, independent of the mesh group. To our knowledge, the present study is the first of its kind in terms of qualitative equivalence of sterile and non-sterile in vitro mesh samples. We do not wish to create future patient studies with non-sterilized meshes saturated with antibiotics/antimycotics. However, perhaps we can prove in future studies that under semi-sterile conditions with certain LCMs, wound infection rates can be acceptable.

Experimental study on the use of a chlorhexidine-loaded carboxymethylcellulose gel as antibacterial coating for hernia repair meshes

PURPOSE

Biomaterials with an antimicrobial coating could avoid mesh-associated infection following hernia repair. This study assesses the use of a chlorhexidine-loaded carboxymethylcellulose gel in a model of Staphylococcus aureus mesh infection.

METHODS

A 1% carboxymethylcellulose gel containing 0.05% chlorhexidine was prepared and tested in vitro and in vivo. The in vitro tests were antibacterial activity (S. aureus; agar diffusion test) and gel cytotoxicity compared to aqueous 0.05% chlorhexidine (fibroblasts; alamarBlue). For the in vivo study, partial abdominal wall defects (5 × 2 cm) were created in New Zealand white rabbits (n = 15) and inoculated with 0.25 mL of S. aureus (10⁶ CFU/mL). Defects were repaired with a lightweight polypropylene mesh (Optilene) without coating (n = 3) or coated with a carboxymethylcellulose gel (n = 6) or chlorhexidine-loaded carboxymethylcellulose gel (n = 6). Fourteen days after surgery, bacterial adhesion to the implant (sonication, immunohistochemistry), host tissue incorporation (light microscopy) and macrophage reaction (immunohistochemistry) were examined.

RESULTS

Carboxymethylcellulose significantly reduced the toxicity of chlorhexidine (p < 0.001) without limiting its antibacterial activity. While control and gel-coated implants were intensely contaminated, the chlorhexidine-gel-coated meshes showed a bacteria-free surface, and only one specimen showed infection signs. The macrophage reaction in this last group was reduced compared to the control (p < 0.05) and gel groups.

CONCLUSIONS

When incorporated in the carboxymethylcellulose gel, chlorhexidine showed reduced toxicity yet maintained its bactericidal effect at the surgery site. Our findings suggest that this antibacterial gel-coated polypropylene meshes for hernia repair prevent bacterial adhesion to the mesh surface and have no detrimental effects on wound repair.

Mesh implants for hernia repair: an update

INTRODUCTION

Today the use of textile meshes has become a standard for the treatment of abdominal wall hernias and for the reinforcement of any tissue repair as the strength of the implant decreases the recurrence rates. With increasing use, side effects of the textile implants became apparent, as well.

AREAS COVERED

Based on publications in Medline over the past decade, general and specific benefits, as well as risks, are discussed with the challenge to define individual risk-benefit ratios. For meshes, certain high-risk or low-risk conditions can be defined. In an attempt to eliminate mesh-related risks, quality control for medical devices has meanwhile been revised. In both the USA and the EU post-market surveillance studies are required to keep medical devices approved.

EXPERT COMMENTARY

The impact of material on the complication rate will vary depending on the patient's co-morbidity or the risks of the procedure. Even the best material can end up with disappointing results in case of poor healing or poor surgery. On the other hand, when using high-risk devices, most of the complications after excellent surgery with excellent indication can be supposed to be mesh-related. Thus, the use of low-risk devices is recommended even though its advantage may not be demonstrable in clinical studies.

Antibiotic Irrigation of the Surgical Site Decreases Incidence of Surgical Site Infection after Open Ventral Hernia Repair

Surgical site infections (SSI) are common complications after open ventral hernia repair (OVHR), potentially requiring further intervention. Antibiotic lavage before abdominal closure has been shown to lower the incidence in intra-abdominal and soft tissue SSI. A retrospective review of OVHR was performed with mesh at Greenville Health System Hernia Center between 2008 and 2017. Patients were divided into three groups, receiving no antibiotic irrigation (Grp 1, n = 260), gentamicin alone (Grp 2, n = 263), or gentamicin 1 clindamycin (G 1 C) irrigation (Grp 3, n = 299). Differences in categorical variables among the three groups were tested using chi-squared or Fischer's exact test (for n < 5). Analysis of continuous variables was performed using analysis of variance or Kruskal-Wallis test for differences in length of stay. Logistic regression was performed using all clinically relevant variables to determine the effects of irrigation on SSI. Incidence of surgical site occurrence was significantly lower after G 1 C irrigation (Grp 1, 28.1%; Grp 2, 35.4%; Grp 3, 19.7%; P < 0.001). Incidence of SSI was significantly lower after G 1 C irrigation, but not G alone (Grp 1, 16.5%; Grp 2, 15.2%; and Grp 3, 5.4%; P < 0.001). Multivariate logistic regression demonstrated significantly increased SSI with contaminated wounds (OR 2.96; 95% confidence interval (CI) 1.39–6.21), dirty wounds (OR 3.84; 95% CI 1.49–9.69), and chronic obstructive pulmonary disease (OR 3.70; 95% CI 2.16–6.38), as expected. Use of G 1 C was an independent predictor of decreased SSI (OR 0.33; 95% CI 0.16–0.67). Irrigation with a combined G 1 C antibiotic irrigation significantly reduces the incidence of surgical site infection after OVHR with mesh.

First Year Preliminary Results on the Use of a Monofilament Polyester Mesh With a Collagen Barrier for Primary and Incisional Ventral Hernia Repair

Aim:

The SymCHro study objective is to assess patient outcomes and surgeon satisfaction following ventral hernia repair with a three-dimensional (3D) monofilament polyester mesh (Symbotex composite mesh) that contains an absorbable collagen barrier on 1 side to minimize tissue attachment.

Methods:

SymCHro is a multicenter observational study of 100 consecutive patients in the French Club Hernie registry who underwent primary and incisional ventral hernia repair with a Symbotex composite mesh. The primary objective is to assess recurrences and complications within 2 years of repair. This analysis reports 1-year results from the ongoing study.

Results:

A total of 105 hernias (37.1% primary, 62.9% incisional) in 100 patients were repaired by open or laparoscopic surgery. The patient follow-up rate at 1 year was 94%. A total of 6 (6.0%) low-grade seromas; 3 (3.0%) cases of low-grade transitory ileus; and 1 (1.0%) recurrence, which was asymptomatic but was repaired, occurred within 1-year follow-up. No serious adverse events were reported. All surgeons responded as satisfied with mesh flexibility and ease of insertion. Relative to baseline, patient pain reduced significantly at day 1 through month 3 postoperatively. At 1 year, 88.3% (83/94) patients assessed the hernia operation results as “good” or “excellent.”

Conclusion:

At this 1-year analysis, 94% of patients were followed up and experienced minimal pain and low complication rates, suggesting that Symbotex composite mesh provides an effective and safe repair for primary and incisional ventral hernias.

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.

Risk-adjusted procedure tailoring leads to uniformly low complication rates in ventral and incisional hernia repair: a propensity score analysis and internal validation of classification criteria

BACKGROUND

The usual approach in hernia surgery is to select the ideal repair method independent of the patient's characteristics. In the present study, we change the approach to ask which technique is best for the individual patient`s risk profile. For this, two criteria are important: does the patient need reconstruction of the abdominal wall? or does he or she need treatment of symptoms without being exposed to unnecessarily high perioperative risks?

METHODS

In a heuristic selection procedure, 486 consecutive patients were classified according to their characteristics as low-risk or high-risk for postoperative complications. Low-risk patients preferentially underwent open abdominal wall reconstruction with mesh (MFR + mesh), high-risk patients mainly a bridging-mesh procedure, either by laparoscopic (Lap.-IPOM) or open approach (Open-IPOM). Primary outcome was the incidence of postoperative complications. Secondary outcome was the recurrence-free interval. The propensity score was used for covariate adjustment analyzing recurrence rate as well as postoperative complications using Cox regression and logistic regression, respectively.

RESULTS

Comparison of all surgical procedures showed risk factors had no independent influence on occurrence of complications (p = 0.110). Hernial gap width was an independent factor for occurrence of complications (p = 0.002). Propensity score adjustment revealed Lap.-IPOM to have a significantly higher recurrence rate than MFR + mesh (HR 2.367, 95% CI 1.123-4.957, p = 0.024). Three or more risk factors were protective against recurrence (HR 0.454, 95% CI 0.221-0.924, p = 0.030). In the univariate Cox regression analysis for recurrence, age >50 years was a protective prognostic factor (HR 0.412, 95% CI 0.245-0.702, p = 0.002).

CONCLUSIONS

The classification criteria applied were internally validated. The heuristic algorithm ensured that patients at high-risk of complications did not have a higher perioperative complication rate than patients at low-risk.

In vitro assessment of an antibacterial quaternary ammonium-based polymer loaded with chlorhexidine for the coating of polypropylene prosthetic meshes

PURPOSE

This study assesses the use of an absorbable polymer loaded with chlorhexidine (CHX) as an antibacterial coating for polypropylene (PP) meshes employed in hernia repair.

METHODS

The polymer N,N-dimethyl-N-benzyl-N-(2-methacryloyloxyethyl) ammonium bromide was loaded with CHX (1 % w/w). Fragments (1 cm²) of Optilene^® Mesh Elastic were coated either with the unloaded (POL) or CHX-loaded polymer (POL-CHX). Uncoated fragments (PP) served as controls. The release kinetics of the POL-CHX coating was monitored by HPLC. Sterile fragments were placed on agar plates previously contaminated with 10⁶ CFU of Staphylococcus aureus (Sa) ATCC25923, Staphylococcus epidermidis (Se) ATCC12228, or Escherichia coli (Ec) ATCC25922 and incubated at 37 °C for 1/2/7 days. At each time point, inhibition halos were measured and bacterial adhesion to the meshes quantified by sonication and scanning electron microscopy. Coating cytotoxic effects were examined on cultured fibroblasts.

RESULTS

The polymer coating gradually released CHX over 3 days. Inhibition halos were produced only around the POL-CHX-coated meshes and these were significantly smaller for Ec than Sa or Se (p < 0.01). While POL-CHX prevented bacterial adhesion to the mesh, the reduced bacterial yields over time were observed for the POL-coated versus control PP meshes (p < 0.001). By day 7, only Ec remained attached to the surface of control meshes. The POL coating was not cytotoxic, yet POL-CHX reduced the viability of cultured fibroblasts.

CONCLUSIONS

When loaded with the antiseptic CHX, this quaternary ammonium-based polymer coating released its contents in a controlled manner indicating its potential prophylactic use to reduce the risk of infection following PP mesh implantation.

Predictors of mesh infection and explantation after abdominal wall hernia repair

BACKGROUND

The main objective was to identify predictive factors associated with prosthesis infection and mesh explantation after abdominal wall hernia repair (AWHR).

METHODS

This is a retrospective review of all patients who underwent AWHR from January 2004 to May 2014 at a tertiary center. Multivariate analysis identified predictors of mesh infection and explantation after AWHR.

RESULTS

From 3,470 cases of AWHR, we reported 66 cases (1.9%) of mesh infection, and 48 repairs (72.7%) required mesh explantation. Steroid or immunosuppressive drugs use (odds ratio [OR] 2.22; confidence interval [CI] 1.16 to 3.95), urgent repair (OR 5.06; CI 2.21 to 8.60), and postoperative surgical site infection (OR 2.9; CI 1.55 to 4.10) were predictive of mesh infection. Predictors of mesh explantation were type of mesh (OR 3.13; CI 1.71 to 5.21), onlay position (OR 3.51; CI 1.23 to 6.12), and associated enterotomy in the same procedure (OR 5.17; CI 2.05 to 7.12).

CONCLUSIONS

Immunosuppressive drugs use, urgent repair, and postoperative surgical site infection are predictive of mesh infection. Risk factors of prosthesis explantation are polytetrafluoroethylene mesh, onlay mesh position, and associated enterotomy in the same procedure.

[Technical principles of incisional hernia surgery]

Many publications are available on the best surgical techniques and treatment of incisional hernias with reports of experiences and randomized clinical studies at the two extremes of the evidence scale. The ultimate proof of the best operative technique has, however, not yet been achieved. In practically no other field of surgery are the variability and the resulting potential aims of surgery so great. The aim of surgery is to provide patients with the optimal recommendation out of a catalogue of possibilities from a holistic perspective. This article describes the surgical techniques using meshes for strengthening (in combination with an anatomical reconstruction) and for replacement of the abdominal wall (with bridging of the defect).

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.

Inhibition of Staphylococcus aureus Adhesion to the Surface of a Reticular Heavyweight Polypropylene Mesh Soaked in a Combination of Chlorhexidine and Allicin: An In vitro Study

INTRODUCTION

Presoaking meshes for hernia repair with antiseptics prior to implantation could decrease the adhesion of microorganisms to the material surface and reduce the risk of antibiotic resistances. In this work, we evaluate chlorhexidine and allicin (natural antiseptic not yet tested for these purposes) against vancomycin as antiseptics to be used in the pretreatment of a heavyweight polypropylene mesh using an in vitro model of bacterial contamination.

METHODS

Solutions of saline, vancomycin (40 µg/mL), allicin (1,000 µg/mL), chlorhexidine (2%-0.05%) and the combination allicin-chlorhexidine (900 µg/mL-0.05%) were analyzed with agar diffusion tests in the presence of 106 CFU Staphylococcus aureus ATCC25923. Additionally, sterile fragments of Surgipro (1 cm2) were soaked with the solutions and cultured onto contaminated agar plates for 24/48/72 h. The antimicrobial material DualMesh Plus was utilized as positive control. At every time, the inhibition zones were measured and the bacterial adhesion to the mesh surface quantified (sonication, scanning electron microscopy). Cytotoxicity of the treatments was examined (alamarBlue) using rabbit skin fibroblasts.

RESULTS

The largest zones of inhibition were created by allicin-chlorhexidine. Chlorhexidine was more effective than vancomycin, and allicin lost its effectiveness after 24 h. No bacteria adhered to the surface of the DualMesh Plus or the meshes soaked with vancomycin, chlorhexidine and allicin-chlorhexidine. On the contrary, saline and allicin allowed adherence of high loads of bacteria. Vancomycin had no toxic effects on fibroblasts, while allicin and chlorhexidine exerted high toxicity. Cytotoxicity was significantly reduced with the allicin-chlorhexidine combination.

CONCLUSIONS

The use of antiseptics such as chlorhexidine, alone or combined with others like allicin, could represent an adequate prophylactic strategy to be used for hernia repair materials because soaking with these agents provides the mesh with similar antibacterial properties to those observed after soaking with vancomycin, similar to the effect of DualMesh Plus.