Combination of Bacteriophages and Antibiotics for Prevention of Vascular Graft Infections-An In Vitro Study.

(1) Background: Implant-associated bacterial infections are usually hard to treat conservatively due to the resistance and tolerance of the pathogens to conventional antimicrobial therapy. Bacterial colonization of vascular grafts may lead to life-threatening conditions such as sepsis. The objective of this study is to evaluate whether conventional antibiotics and bacteriophages can reliably prevent the bacterial colonization of vascular grafts. (2) Methods: Gram-positive and Gram-negative bacterial infections were simulated on samples of woven PET gelatin-impregnated grafts using Staphylococcus aureus and Escherichia coli strains, respectively. The ability to prevent colonization was evaluated for a mixture of broad-spectrum antibiotics, for strictly lytic species-specific bacteriophage strains, and for a combination of both. All the antimicrobial agents were conventionally tested in order to prove the sensitivity of the used bacterial strains. Furthermore, the substances were used in a liquid form or in combination with a fibrin glue. (3) Results: Despite their strictly lytic nature, the application of bacteriophages alone was not enough to protect the graft samples from both bacteria. The singular application of antibiotics, both with and without fibrin glue, showed a protective effect against S. aureus (0 CFU/cm2), but was not sufficient against E. coli without fibrin glue (M = 7.18 × 104 CFU/cm2). In contrast, the application of a combination of antibiotics and phages showed complete eradication of both bacteria after a single inoculation. The fibrin glue hydrogel provided an increased protection against repetitive exposure to S. aureus (p = 0.05). (4) Conclusions: The application of antibacterial combinations of antibiotics and bacteriophages is an effective approach to the prevention of bacteria-induced vascular graft infections in clinical settings.

Development of a dual-component infection-resistant arterial replacement for small-caliber reconstructions: A proof-of-concept study.

Introduction: Synthetic vascular grafts perform poorly in small-caliber (<6mm) anastomoses, due to intimal hyperplasia and thrombosis, whereas homografts are associated with limited availability and immunogenicity, and bioprostheses are prone to aneurysmal degeneration and calcification. Infection is another important limitation with vascular grafting. This study developed a dual-component graft for small-caliber reconstructions, comprising a decellularized tibial artery scaffold and an antibiotic-releasing, electrospun polycaprolactone (PCL)/polyethylene glycol (PEG) blend sleeve. Methods: The study investigated the effect of nucleases, as part of the decellularization technique, and two sterilization methods (peracetic acid and γ-irradiation), on the scaffold's biological and biomechanical integrity. It also investigated the effect of different PCL/PEG ratios on the antimicrobial, biological and biomechanical properties of the sleeves. Tibial arteries were decellularized using Triton X-100 and sodium-dodecyl-sulfate. Results: The scaffolds retained the general native histoarchitecture and biomechanics but were depleted of glycosaminoglycans. Sterilization with peracetic acid depleted collagen IV and produced ultrastructural changes in the collagen and elastic fibers. The two PCL/PEG ratios used (150:50 and 100:50) demonstrated differences in the structural, biomechanical and antimicrobial properties of the sleeves. Differences in the antimicrobial activity were also found between sleeves fabricated with antibiotics supplemented in the electrospinning solution, and sleeves soaked in antibiotics. Discussion: The study demonstrated the feasibility of fabricating a dual-component small-caliber graft, comprising a scaffold with sufficient biological and biomechanical functionality, and an electrospun PCL/PEG sleeve with tailored biomechanics and antibiotic release.

Vascular Graft Pre-Treatment with Daptomycin Prior to Implantation Prevents Graft Infection with Staphylococcus aureus in an In Vivo Model.

Background: Infection of vascular grafts is a life-threatening complication in cardiovascular surgical procedures. This experimental study tested the efficacy and possible harmful effects of daptomycin pre-treatment in vivo in prevention of vascular graft infection caused by Staphylococcus aureus. Methods: Polyethylene terephthalate (PET) patches (5 × 7 mm) were sewn on the infra-renal abdominal aorta of 32 New Zealand White rabbits. Before implantation, patches either were pre-treated for 15 min with daptomycin in one group (n = 13) or left untreated in the other group (n = 13) before contamination with 100 mcL bacterial solution (1 × 1010 colony-forming units [CFU] per mL). Six animals with uninfected patches without (n = 3) or with (n = 3) daptomycin pre-treatment served as controls. On postoperative day seven, all patches were explanted, washed with phosphate buffered saline, and sonicated to release viable adherent bacteria. The CFUs were quantified and aortic tissues were histologically examined. In addition, bacterial adherence on the patches was analyzed using scanning electron microscopy (SEM). Results: In the daptomycin pre-treatment group, significantly reduced numbers of CFUs on the patches were observed, compared with non-pre-treated patches (3.21 × 102 ± 1.02 × 103 mL-1 vs. 5.18 × 105 ± 1.05 × 106 mL-1; p < 0.001). Peri-vascular abscesses were visible in all rabbits with S. aureus infected patches, whereas no signs of inflammation were found in the daptomycin pre-treatment group or the control groups. Conclusions: Daptomycin showed excellent in vivo antibacterial activity against vascular graft infection caused by S. aureus, compared with non-pre-treated grafts, resulting in a significant reduction in bacterial infection and prevention of abscess formation. No harmful effects of the antibiotic pre-treatment could be observed.

Resistance to infection of long-term cryopreserved human aortic valve allografts.

OBJECTIVE: To analyze the in vitro antimicrobial activity of 3 antibiotic regimens (group A, gentamicin-piperacillin-vancomycin-metronidazole-amphotericin B; group B, gentamicin-piperacillin-flucloxacillin-metronidazole-amphotericin B; and group C, meropenem-vancomycin-tobramycin-colistin-amphotericin B) used in the processing of cryopreserved human ascending aortic tissue and aortic valves against Staphylococcus epidermidis and Staphylococcus aureus. The results were additionally compared with the infection resistance of cryopreserved ascending aortic tissue against Escherichia coli and Pseudomonas aeruginosa. MATERIALS: Each of 10 cryopreserved human allografts (CHAs) was divided into 25 pieces (separating aortic wall and valve). Eighteen segments were microbiologically tested, and 7 pieces underwent scanning electron microscopy. A bacterial solution (4 mL; optical density, 0.20 ± 0.02) was used for contamination. After incubation, the optical density of the solution was measured. CHAs underwent sonication to release viable adherent bacteria. The number of attached bacteria was quantified by the colony forming units per square centimeter of CHA surface. RESULTS: Antibiotic regimen groups B and C were more efficient than group A in eradicating gram-positive organisms adherent to the aortic wall (P < .001). Group C showed enhanced resistance against E coli compared with group A or B (P < .001), whereas group B appeared to be more effective against P aeruginosa (P < .001). With reference to each antibiotic regimen, ascending aortic tissue showed significantly less bacterial contamination with staphylococcal bacteria than valve grafts (P ≤ .01). CONCLUSIONS: CHAs possess antibacterial activity despite long-term storage over 5 years. Antibiotic combinations applied during CHA processing have a significant influence on their infection resistance. Ascending aortic tissue shows a significantly enhanced bacterial resistance against staphylococcal bacteria compared with aortic valves.

In vitro comparison of biological and synthetic materials for skeletal chest wall reconstruction.

BACKGROUND: Various biological and synthetic materials have been proposed for use in skeletal chest wall reconstruction (SCWR). Because of the lack of studies allowing a direct comparison of SCWR materials, their clinical use often depends on the surgeon's preference and experience. The aim of this study was to analyze 6 synthetic and 3 biological materials frequently used in SCWR with respect to their cytotoxicity, bacterial adhesion, surface characteristics, and mechanical properties to facilitate data-driven decisions. METHODS: The effect of the SCWR materials and their extracts on the metabolism of human skeletal muscle cells (SkMCs), dermal fibroblasts, adipose cells, and osteoblasts was analyzed in vitro. Bacterial adhesion was quantified by incubating samples in bacterial suspensions (Staphylococcus epidermidis, S aureus, and Escherichia coli), followed by counting colony-forming units and performing scanning electron microscopy. Moreover, the mechanical properties of the materials were analyzed under uniaxial tensile loading to failure. RESULTS: The metabolism of all cell types seeded on the SCWR materials was reduced compared with untreated cells. With the exception of Vypro (Ethicon, Somerville, NJ), whose extracts significantly reduced fibroblast viability, no cytotoxic leachable substances were detected. Biological materials were less cytotoxic compared with synthetic ones, but they demonstrated increased bacterial adhesion. Synthetic materials demonstrated higher elongation to failure than did biological materials. CONCLUSIONS: Biological and synthetic SCWR materials showed significant differences in their cytotoxicity, bacterial adhesion, and biomechanical properties, suggesting that they may be used for different indications in SCWR. Further comparable in vivo studies are needed to analyze their performance in different indications of clinical application.

Prevention of pacemaker infections with perioperative antimicrobial treatment: an in vitro study.

AIMS: The antimicrobial treatment of pacemaker casings with antiseptics (povidone-iodine or octenidine dihydrochloride) or antibiotics (vancomycin, daptomycin, cefuroxime, Tazobac, or nebacetin) was analysed in vitro for its biocompatibility and efficacy in preventing the bacterial adhesion of Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli to cardiac-implantable electrophysiological devices (CIEDs). METHODS AND RESULTS: Titan platelets (0.4 cm²) cut from pacemaker casings were impregnated with seven different antimicrobial solutions: two antiseptics and five antibiotics. Subsequently, they were challenged with bacterial contamination by four test strains over a 24 h incubation period. Bacterial adherence was quantified using the colony-forming-unit method after cell recovery with sonication and examined with confocal laser scanning electron microscopy. Simultaneously, the biocompatibility of the antimicrobial impregnation was assessed using pre-treated titan platelets in a culture of human fibroblasts, skeletal myoblasts, and microvascular endothelial cells. After a 48 h incubation, cell vitality was measured using the 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H/tetrazolium monosodium (WST-8) assay. The immersion of pacemaker casings in antiseptic or antibiotic solutions applies an antimicrobial coating that can significantly reduce bacterial adhesion. The studied impregnations differed in their antimicrobial efficacy and toxicity. CONCLUSION: Compared with the two antiseptics and the other tested antibiotics, nebacetin showed the best ratio of efficacy to toxicity. Nebacetin showed good in vitro antibacterial activity against both Gram-positive and Gram-negative pathogens without impairing human cell vitality. It is a safe and effective candidate for CIED impregnation.

Microbial adhesion on membrane oxygenators in patients requiring extracorporeal life support detected by a universal rDNA PCR test.

Extracorporeal membrane oxygenation (ECMO) represents a temporary life-saving therapy for respiratory or circulatory failure, but infections during ECMO support are a life-threatening complication. Surface-related infections of ECMO are mentioned, but rarely described in the literature. A universal rDNA polymerase chain reaction (PCR) test was used to investigate the potential microbiological colonization of membrane oxygenators (MOs) in 20 patients undergoing ECMO. The overall patient-based positivity by PCR was 45%. Gram-positive bacteria (71%) represented the most abundant microorganisms on MO surfaces, followed by Gram-negative bacteria (22%) and fungi (7%). The most frequently detected causative pathogens were staphylococci (58%). Bacterial mixed infections represented 56% of all infections. In four PCR-positive cases, the pathogens detected on the MO surfaces were also found by blood culture or by culture of specimens obtained from the infectious focus. In conclusion, hollow fiber membranes of MOs can be colonized by microorganisms and appear to be a potential source of bacterial and fungal infections in ECMO patients. These infections may pose an increased risk for clinical worsening. As a consequence, persistent septic complications have to be discussed as an indication for MO exchange. The initial results suggest that the applied PCR assay is a valuable tool to investigate MOs.