Hernia, mesh, and topical antibiotics, especially gentamycin: seeking the evidence for the perfect outcome…

Identification of mixed anaerobic infections after inguinal hernia repair based on metagenomic next-generation sequencing: A case report

Infection following inguinal hernia repair (IHR) is uncommon. Rational use of antibiotics can significantly improve the prognosis of patients. However, accurately identifying the pathogen involved is usually challenging. This case report describes a patient who developed intermittent fever after undergoing open preperitoneal tension-free repair of a bilateral inguinal hernia. The scrotal fluid specimen was cultured and subjected to metagenomic next-generation sequencing (mNGS). Culture revealed the presence of Enterococcus faecalis (a facultative anaerobe). However, mNGS detected E. faecalis along with multiple anaerobic bacteria including Bacteroides thetaiotaomicron, Parabacteroides distasonis, and Levyella massiliensis. The patient was finally diagnosed with a mixed infection of E. faecalis and multiple anaerobes, and his condition was effectively controlled after timely adjustment of the antibiotic regimen. Treating postoperative infections with multiple concurrent conditions can be challenging. mNGS is valuable for the accurate diagnosis and treatment of infections, as it not only can further verify the culture results, but also assist clinicians in ruling out pulmonary infection caused by hematogenous dissemination after IHR in patients.

In vitro and Ex vivo Assessments of the Compatibility of Fibrin Sealant with Antimicrobial Compounds

Background: Fibrin sealants are used as antimicrobial-releasing carriers for preventing surgical site infections; however, it is important to determine the release kinetics and antimicrobial effects of drugs added to fibrin sealants and the effects of drugs on clot/clotting properties. Materials and Methods: The antimicrobial and antibiofilm activity of cefazolin, colistin, gentamicin, oxacillin, tobramycin, and silver nitrate released from fibrin sealant were characterized using in vitro and ex vivo assays against bacteria commonly found on the skin. The effects of antimicrobial agents on the physical structure of the fibrin sealant were assessed with scanning electron microscopy (SEM) and on the clotting rate and strength of fibrin clots using run-off tests and rheology. Results: Generally, antibiotic agents were released gradually from fibrin sealant and were stable after release, with antimicrobial effects evident up to three days. Cefazolin, gentamicin, and oxacillin prevented biofilm formation of Staphylococcus aureus in porcine skin explants; gentamicin and colistin prevented biofilm formation of Pseudomonas aeruginosa. Gentamicin, cefazolin, colistin, and tobramycin did not affect the structural integrity or viscoelastic properties of fibrin sealant; changes were observed with oxacillin (SEM) and particularly silver nitrate (SEM and rheology). No antimicrobial agents caused deterioration of clotting time (run-off tests). Conclusions: From the antimicrobial agents tested, gentamicin and cefazolin showed prolonged release from fibrin sealant, sustained antimicrobial activity, and biofilm prevention properties against Staphylococcus aureus; similar results were observed for gentamicin and colistin against Pseudomonas aeruginosa. For each of these findings, the physical structure of the fibrin sealant, clotting rate, and strength of fibrin clots were unaffected.

Tailor-Made 3D Printed Meshes of Alginate-Waterborne Polyurethane as Suitable Implants for Hernia Repair

Hernia injuries are the main condition where mesh implants are needed to provide a suitable reinforcement of the damaged tissue. Mesh implants made of polypropylene (PP) are widely used for this application, however complications related to lack of flexibility, elasticity, and mesh infection have been reported. The development of mesh implants from safer materials adaptable to patient necessities can suppose an alternative for conventional PP meshes. In this work, personalized mesh implants made of alginate and waterborne-polyurethane (A-WBPU) are developed using 3D printing technology. For that purpose, five waterborne polyurethane ink formulations with different amounts of alginate are developed and rheologically characterized. All ink formulations are 3D printed showing good printability, manufacturing surgical mesh implants with suitable morphological characteristics customizable to patient injury through computer-aided design (CAD) mesh model adaptation. A calcium chloride (CaCl₂ ) coating is applied after 3D printing as mesh reinforcement. Mechanical analysis revealed that CaCl₂ coated meshes containing 6 wt % of alginate in their formulation are the most suitable to be used as implants for small and groin hernias under physiological tensile strength value of 16 N cm^-1 , and presenting proper elasticity to cover physiological corporal movements (42.57 %). Moreover, an antibiotic-loaded A-WBPU formulation suitable for 3D printing of meshes are developed as strategy to avoid possible mesh infection.

Complex Abdominal Wall Hernia Repair in Contaminated Surgical Fields: Factors Affecting the Choice of Prosthesis

To compare patients with complex abdominal wall hernias undergoing surgical repair using synthetic nonabsorbable or biologic meshes in contaminated fields. Retrospective review of 62 patients with complex abdominal wall hernia with surgical repair in an elective setting and in the context of a clean-contaminated or contaminated fields (January 2009–April 2015). Two groups according to the prosthesis (synthetic nonabsorbable, n = 48 or biologic, n = 14). Mean follow-up was 24.6 (15.8) months. Clean-contaminated wounds were significantly more frequent in the synthetic group. Contaminated wounds were significantly more frequent in the biologic group. Enterocutaneous fistula, recurrent hernia, and removal of chronic infected mesh were significantly more frequently in the biologic group. Differences in postoperative complications and surgical site infections were not found. Recurrence was higher in the biologic group (35.7% vs 8.3%, P = 0.03). In the elective repair of complex hernia, the level of contamination, a recurrent hernia, an enterocutaneous fistula or removal of chronic infected mesh were the factors affecting the choice of prosthesis. In the clean-contaminated setting, the use of a synthetic nonabsorbable mesh versus a biologic mesh did not increase the rate of postoperative infections. Recurrences are significantly higher with biologic meshes.

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.