Viable adhered Staphylococcus aureus highly reduced on novel antimicrobial sutures using chlorhexidine and octenidine to avoid surgical site infection (SSI)

Background Surgical sutures can promote migration of bacteria and thus start infections. Antiseptic coating of sutures may inhibit proliferation of adhered bacteria and avoid such complications. Objectives This study investigated the inhibition of viable adhering bacteria on novel antimicrobially coated surgical sutures using chlorhexidine or octenidine, a critical factor for proliferation at the onset of local infections. The medical need, a rapid eradication of bacteria in wounds, can be fulfilled by a high antimicrobial efficacy during the first days after wound closure. Methods As a pretesting on antibacterial efficacy against relevant bacterial pathogens a zone of inhibition assay was conducted with middle ranged concentrated suture coatings (22 mu g/cm). For further investigation of adhering bacteria in detail the most clinically relevant Staphylococcus aureus (ATCC (R) 49230 (TM)) was used. Absorbable braided sutures were coated with chlorhexidine-laurate, chlorhexidine-palmitate, octenidine-laurate, and octenidine-palmitate. Each coating type resulted in 11, 22, or 33 mu g/cm drug content on sutures. Scanning electron microscopy (SEM) was performed once to inspect the coating quality and twice to investigate if bacteria have colonized on sutures. Adhesion experiments were assessed by exposing coated sutures to S. aureus suspensions for 3 h at 37 degrees C. Subsequently, sutures were sonicated and the number of viable bacteria released from the suture surface was determined. Furthermore, the number of viable planktonic bacteria was measured in suspensions containing antimicrobial sutures. Commercially available sutures without drugs (Vicryl (R), PGA Resorba (R), and Gunze PGA), as well as triclosan-containing Vicryl (R) Plus were used as control groups. Results Zone of inhibition assay documented a multispecies efficacy of novel coated sutures against tested bacterial strains, comparable to most relevant S. aureus over 48 hours. SEM pictures demonstrated uniform layers on coated sutures with higher roughness for palmitate coatings and sustaining integrity of coated sutures. Adherent S. aureus were found via SEM on all types of investigated sutures. The novel antimicrobial sutures showed significantly less viable adhered S. aureus bacteria (up to 6.1 log) compared to Vicryl (R) Plus (0.5 log). Within 11 mu g/cm drug-containing sutures, octenidine-palmitate (OL11) showed the highest number of viable adhered S. aureus (0.5 log), similar to Vicryl (R) Plus. Chlorhexidine-laurate (CL11) showed the lowest number of S. aureus on sutures (1.7 log), a 1.2 log greater reduction. In addition, planktonic S. aureus in suspensions were highly inhibited by CL11 (0.9 log) represents a 0.6 log greater reduction compared to Vicryl (R) Plus (0.3 log). Conclusions Novel antimicrobial sutures can potentially limit surgical site infections caused by multiple pathogenic bacterial species. Therefore, a potential inhibition of multispecies biofilm formation is assumed. In detail tested with S. aureus, the chlorhexidine-laurate coating (CL11) best meets the medical requirements for a fast bacterial eradication. This suture coating shows the lowest survival rate of adhering as well as planktonic bacteria, a high drug release during the first-clinically most relevant-48 hours, as well as biocompatibility. Thus, CL11 coatings should be recommended for prophylactic antimicrobial sutures as an optimal surgical supplement to reduce wound infections. However, animal and clinical investigations are important to prove safety and efficacy for future applications

Local Application of BMP-2 Specific Plasmids in Fibrin Glue does not Promote Implant Fixation

<p>Abstract</p> <p>Background</p> <p>BMP-2 is known to accelerate fracture healing and might also enhance osseointegration and implant fixation. Application of recombinant BMP-2 has a time-limited effect. Therefore, a gene transfer approach with a steady production of BMP-2 appears to be attractive. The aim of this study was to examine the effect of locally applied BMP-2 plasmids on the bone-implant integration in a non-weight bearing rabbit tibia model using a comparatively new non-viral copolymer-protected gene vector (COPROG).</p> <p>Methods</p> <p>Sixty rabbits were divided into 4 groups. All of them received nailing of both tibiae. The verum group had the nails inserted with the COPROG vector and BMP-2 plasmids using fibrin glue as a carrier. Controls were a group with fibrin glue only and a blank group. After 28 and 56 days, these three groups were sacrificed and one tibia was randomly chosen for biomechanical testing, while the other tibia underwent histomorphometrical examination. In a fourth group, a reporter-gene was incorporated in the fibrin glue instead of the BMP-2 formula to prove that transfection was successful.</p> <p>Results</p> <p>Implant fixation strength was significantly lower after 28 and 56 days in the verum group. Histomorphometry supported the findings after 28 days, showing less bone-implant contact.</p> <p>In the fourth group, successful transfection could be confirmed by detection of the reporter-gene in 20 of 22 tibiae. But, also systemic reporter-gene expression was found in heterotopic locations, showing an undesired spreading of the locally applied gene formula.</p> <p>Conclusion</p> <p>Our results underline the transfecting capability of this vector and support the idea that BMP-2 might diminish osseointegration. Further studies are necessary to specify the exact mechanisms and the systemic effects.</p

Novel High Efficient Coatings for Anti-Microbial Surgical Sutures Using Chlorhexidine in Fatty Acid Slow-Release Carrier Systems

Sutures can cause challenging surgical site infections, due to capillary effects resulting in bacteria permeating wounds. Antimicrobial sutures may avoid these complications by inhibiting bacterial pathogens. Recently, first triclosan-resistances were reported and therefore alternative substances are becoming clinically relevant. As triclosan alternative chlorhexidine, the "gold standard'' in oral antiseptics was used. The aim of the study was to optimize novel slow release chlorhexidine coatings based on fatty acids in surgical sutures, to reach a high anti-microbial efficacy and simultaneously high biocompatibility. Sutures were coated with chlorhexidine laurate and chlorhexidine palmitate solutions leading to 11, 22 or 33 mu g/cm drug concentration per length. Drug release profiles were determined in aqueous elutions. Antibacterial efficacy against Staphylococcus aureus was assessed in agar diffusion tests. Biocompatibility was evaluated via established cytotoxicity assay (WST-1). A commercially triclosan-containing suture (Vicryl Plus), was used as anti-microbial reference. All coated sutures fulfilled European Pharmacopoeia required tensile strength and proved continuous slow drug release over 96 hours without complete wash out of the coated drug. High anti-microbial efficacy for up to 5 days was observed. Regarding biocompatibility, sutures using 11 mg/cm drug content displayed acceptable cytotoxic levels according to ISO 10993-5. The highest potential for human application were shown by the 11 mg/cm chlorhexidine coated sutures with palmitic acid. These novel coated sutures might be alternatives to already established anti-microbial sutures such as Vicryl Plus in case of triclosan-resistance. Chlorhexidine is already an established oral antiseptic, safety and efficacy should be proven for clinical applications in anti-microbial sutures

Influence of Absorbable Calcium Sulfate-Based Bone Substitute Materials on Human Haemostasis-In Vitro Biological Behavior of Antibiotic Loaded Implants

Calcium sulfate (CS) formulations are frequently implanted as antibiotically impregnated bone substitutes in orthopedic and trauma surgery to prevent or treat bone infections. Calcium ions have been discussed as candidates to accelerate blood coagulation. The goal of this study is to evaluate substance-specific influences of CS formulations on blood coagulation. Specific ELISAs were conducted to determine markers of activated blood coagulation after incubation of human blood with CS beads. Additionally, wettability with freshly drawn human blood was measured. Three different types of CS bone substitute beads were compared (CS dihydrate with tripalmitin, containing Gentamicin (Herafill&reg;-G: Group A) or Vancomycin (CaSO4-V: Group B); and a CS hemihydrate with Tobramycin (Osteoset&reg;: Group C)). Examinations were performed by ELISA assays for F1+2, FXIIa and C3a. Our results prove that none of the CS preparations accelerated single specific assays for activated coagulation markers. This allows the conclusion that neither Herafill&reg;-G (CaSO4-G) nor CaSO4-V alter haemostasis negatively. Blood samples incubated with Osteoset&reg; display an elevated F1+2-activity. The addition of tripalmitin in Herafill&reg;-G shifts the original into a significantly hydrophobic formulation. This was additionally proven by contact angle examination of the three substances with freshly drawn human blood, showing that acceleration of plasmatic coagulation is hindered by lipids and induced by surface effects caused by presence of rapidly soluble calcium ions in the Osteoset&reg; preparation

Elution profiles of chlorhexidine coated sutures.

<p>Released chlorhexidine in PBS buffer at 37°C for A) chlorhexidine-laurate coatings and B) chlorhexidine-palmitate coated sutures. Elution profiles were determined for each carrier at drug content 11, 22 or 33 µg/cm. The horizontal lines depict the limit of drug release for each concentration, the normalized content of chlorhexidine on coated sutures.</p

Mean tensile strength values of surgical sutures (USP 1).

<p>Mean values of the maximum force F_max (n = 5) for uncoated, commercial and novel coated sutures CL22 and CP22 in example are given above. The required minimum for USP 1 surgical sutures at 50.8 N according to European Pharmacopoeia, was reached for all tested sutures.</p

Measuring anti-bacterial efficacy of coated sutures via zones of inhibition.

<p>A) Principle of measuring inhibition zones in a longitudinal analysis on the example of a Vicryl Plus suture, in order to achieve anti-microbial effectiveness over several days. B) Anti-microbial efficacies on Agar plates with <i>S. aureus</i> lawns (2×10⁸ cfu/ml) for a) chlorhexidine lauric acid and b) chlorhexidine palmitic acid coated sutures. Coated suture samples with three different chlorhexidine concentrations 11, 22 and 33 µg/cm. c) Vicryl Plus as reference for commercial anti-microbial sutures.</p

Percentage of chlorhexidine released after 96

<p>Percentage of chlorhexidine release related to the drug content on coated sutures per cm length at 96) chlorhexidine-laurate and B) chlorhexidine-palmitate coated sutures.</p

Numbers of viable bacteria in suspension incubated for 3 hours with novel antimicrobial sutures.

<p>An initial <i>S</i>. <i>aureus</i> concentration of 1.3 x 10⁸ cfu/ml was used for bacterial suspensions. Chlorhexidine- or octenidine-coated sutures showed a strong inhibition of pathogens in the surrounding suspensions. The triclosan-coated suture Vicryl^® Plus (VP) and the uncoated Gunze suture (G) were used as controls. Fatty acid-coated sutures (PA80, LA80) and commercial sutures without any drug content (V: Vicryl^®, R: PGA Resorba^®) were tested within the non-antimicrobial suture group. Significance levels are p<0.05 (*), p<0.01 (**) and p<0.001 (***); n.s.: not significant, n.a.: not applicable.</p

Rating levels used for comparative antimicrobial suture evaluation.

<p>Rating levels used for comparative antimicrobial suture evaluation.</p