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Zielstellung: Ziel dieser Studie war es herauszustellen, ob die Notwendigkeit einer strikten räumlichen oder zeitlichen Trennung von septischen und aseptischen Operationen bezüglich einer möglichen Patientengefährdung durch freigesetzte aerogene Mikroflora besteht. Methode: Über einen Zeitraum von acht Wochen wurden 14 aseptische und 16 septische Operationen der Allgemein- und Viszeralchirurgie in zwei baulich vergleichbaren OP-Sälen ohne RLTA hinsichtlich der Art und Menge der mikrobiellen Raumluftbelastung untersucht. Für den Vergleich der Luftqualität wurden drei Arten von Messungen durchgeführt, Luftkoloniezahlmessungen mittels Air-Sampler, Sedimentationsuntersuchungen und Kontaktkulturuntersuchungen mittels Blutagarplatten. Die Unterschiede im Erregerspektrum beider Gruppen waren mit Ausnahme der für die Risikobewertung irrelevanten aeroben Sporenbildner nicht signifikant. Die Anzahl bei septischen Eingriffen in die Raumluft freigesetzter Gram-negativer Bakterien war so gering (durchschn. KbE pro min bei Proteus mirabilis 0,095, Escherichia coli 0,077, Enterococcus faecalis 0,016), dass in keinem Fall deren Nachweis auf Umgebungsflächen (OP-Wände) gelang. Selbst in 1 m Entfernung vom OP-Feld gelang nur einmal der Nachweis von 2 KbE E. coli, aber nicht von anderen Gram-negativen Bakterien. Ein Nachweis Gram-negativer Bakterien 30 min nach dem Ende einer OP in der Raumluft gelang nur in geringen Mengen (insg. 16 KbE/m³). Bei der Interpretation der Ergebnisse ist zu berücksichtigen, dass sie in einem OP ohne RLTA generiert wurden. Da bei zwei OP´s, wenn auch in geringen Mengen, Gram-negative Bakterien 30 min nach dem OP-Ende in der Raumluft nachweisbar waren, ist in Operationseinrichtungen ohne RLTA die räumliche Trennung septischer und aseptischer Operationen aus Sicherheitsgründen zu empfehlen. Sofern allerdings die deklarierte Einwirkungszeit der Flächendesinfektion eingehalten wird, ist bei Verzicht auf räumliche Trennung eine Wechselzeit nach septischen Eingriffen > 30 min als ausreichend anzusehen. Aufgrund der Leistungsfähigkeit moderner RLTA, potentiell infektiösen Erreger in der Raumluft in weniger als 25 min auf 1 % der Ausgangsmenge zu reduzieren, ist in OP-Einheiten mit RLTA keine Notwendigkeit zur räumlichen Trennung von septischen und aseptischen Operationen gegeben. Ergebnisse: Luftkoloniezahlmessungen (KbE/m³ septisch 401,8 vs. aseptisch 388,2) und Sedimentationsuntersuchungen (KbE/min/m² septisch 53,4 vs. aseptisch 54,4) sowie Kontaktkulturuntersuchungen wiesen in der quantitativen Gesamtbetrachtung der Erregerfreisetzung keine signifikanten Unterschiede auf. Bezüglich der Luftkoloniezahlmessungen konnten zu gewissen OP-Zeitpunkten Unterschiede beim Erregervorkommen zwischen beiden OP-Gruppen beobachtet werden. Das betraf besonders kurze Operationen.
Unlike the native surface of the implant material (Ti6Al4V), oxidation with H2O2 leads to increased binding of the effective antimicrobial agent poly(hexamethylene) biguanide [PHMB]. However, treating with NaOH instead results in an even higher PHMB mass coverage. After oxidation with H2O2, strong differences in the PHMB adsorption capability between polished and corundum-blasted surfaces appear, indicating a roughness dependence. After NaOH treatment, no such effect was observed. The wetting properties of specimens treated with either H2O2 or NaOH prior to PHMB exposure clearly varied. To unravel the nature of this interaction, widespread in silico and in vitro experiments were performed. Methods: By X-ray photoelectron spectroscopy, scanning electron microscopy, water contact angle measurements and MD simulations, we characterized the interplay between the polycationic antimicrobial agent and the implant surface. A theoretical model for PHMB micelles is tested for its wetting properties and compared to carbon contaminated TiO2. In addition, quantitation of anionic functional group equivalents, the binding properties of PHMB with blocked amino end-group, and the ability to bind chlorhexidine digluconate (CHG) were investigated. Ultimately, the capability of osteoblasts to build calcium apatite, and the activity of alkaline phosphatase on PHMB coated specimens, were determined. Results: Simulated water contact angles on carbon contaminated TiO2 surfaces and PHMB micelle models reveal little influence of PHMB on the wetting properties and point out the major influence of remaining and recovering contamination from ambient air. Testing PHMB adsorption beyond the critical micelle concentration and subsequent staining reveals an island-like pattern with H2O2 as compared to an evenly modified surface with NaOH. Both CHG and PHMB, with blocked amino end groups, were adsorbed on the treated surfaces, thus negating the significant influence of PHMB’s terminal groups. The ability of osteoblasts to produce calcium apatite and alkaline phosphatase is not negatively impaired for PHMB mass coverages up to 8 μg/specimen. Conclusion: Differences in PHMB adsorption are triggered by the number of anionic groups and carbon contaminants, both of which depend on the specimen pre-treatment. With more PHMB covering, the implant surface is protected against the capture of new contamination from the ambient air, thus building a robust antimicrobial and biocompatible surface coating.
Aim
Periprosthetic joint infections are a devastating complication after arthroplasty, leading to rejection of the prosthesis. The prevention of septic loosening may be possible by an antimicrobial coating of the implant surface. Poly (hexamethylene) biguanide hydrochloride [PHMB] seems to be a suitable antiseptic agent for this purpose since previous studies revealed a low cytotoxicity and a long-lasting microbicidal effect of Ti6Al4V alloy coated with PHMB. To preclude an excessive activation of the immune system, possible inflammatory effects on macrophages upon contact with PHMB-coated surfaces alone and after killing of S. epidermidis and P. aeruginosa are analyzed.
Methods
THP-1 monocytes were differentiated to M0 macrophages by phorbol 12-myristate 13-acetate and seeded onto Ti6Al4V surfaces coated with various amounts of PHMB. Next to microscopic immunofluorescence analysis of labeled macrophages after adhesion on the coated surface, measurement of intracellular reactive oxygen species and analysis of cytokine secretion at different time points without and with previous bacterial contamination were conducted.
Results
No influence on morphology of macrophages and only slight increases in iROS generation were detected. The cytokine secretion pattern depends on the surface treatment procedure and the amount of adsorbed PHMB. The PHMB coating resulted in a high reduction of viable bacteria, resulting in no significant differences in cytokine secretion as reaction to coated surfaces with and without bacterial burden.
Conclusion
Ti6Al4V specimens after alkaline treatment followed by coating with 5–7 μg PHMB and specimens treated with H2O2 before PHMB-coating (4 μg) had the smallest influence on the macrophage phienotype and thus are considered as the surface with the best cytocompatibility to macrophages tested in the present study.
Abstract
Antimicrobial coating of implant material with poly(hexamethylene biguanide) hydrochloride (PHMB) may be an eligible method for preventing implant‐associated infections. In the present study, an antibacterial effective amount of PHMB is adsorbed on the surface of titanium alloy after simple chemical pretreatment. Either oxidation with 5% H2O2 for 24 hr or processing for 2 hr in 5 M NaOH provides the base for the subsequent formation of a relatively stable self‐assembled PHMB layer. Compared with an untreated control group, adsorbed PHMB produces no adverse effects on SaOs‐2 cells within 48 hr cell culture, but promotes the initial attachment and spreading of the osteoblasts within 15 min. Specimens were inoculated with slime‐producing bacteria to simulate a perioperative infection. Adsorbed PHMB reacts bactericidally against Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa after surface contact. Adhered SaOs‐2 cells differentiate and produce alkaline phosphatase and deposit calcium within 4 days in a mineralization medium on PHMB‐coated Ti6Al4V surfaces, which have been precontaminated with S. epidermidis. The presented procedures provide a simple method for generating biocompatibly and antimicrobially effective implant surfaces that may be clinically important.