Electrical stimulation of bone growth with direct current

Electrical stimulation of osteogenesis was studied in rabbit femora in: (A) a transcortical electric field with a cortex-depolarizing or hyperpolarizing orientation derived from an intramedullary electrode and a ring-shaped counter electrode encircling the femoral shaft; and (B) an electric field derived from an electrode located in the medullary canal and the counter electrode in the abdominal wall. Electrodes were made of platinum. A direct current of 20 microA was applied during six weeks. Contralateral femora with dummy electrodes served as controls. Results were analyzed by optical densitometry of roentgenograms and histomorphometry of histologic slides. Under the conditions of these experiments bone growth was not stimulated by applying a cortex-depolarizing electric field. Significant stimulation of bone growth was only observed at an intramedullary cathode, when the anode was placed at a distance.     

Some effects of weak direct current and silver ions on experimental osteomyelitis and their clinical application

The effects of a weak direct current and of silver ions on experimental osteomyelitis were studied. Electrical stimulation with stainless electrodes aggravates the osteomyelitis, especially at the positive electrode. But electrically generated silver ions inhibit the growth of bacteria not only in vitro but also in vivo, and electrical callus formation occurs on infected bone. A clinical study was undertaken based on these findings. We obtained a success rate of 12 out of 14 based on the total number of cases, of which eight had a previous history of known or suspected infection, and this method proved to be an effective means of treating infected non-union.     

A new animal model for implant-related infected non-unions after intramedullary fixation of the tibia in rats with fluorescent in situ hybridization of bacteria in bone infection

There is no adequate animal model to mimic the difficult clinical situation of infected non-union of the tibia after intramedullary stabilization. The purpose was to establish an animal model of implant-related infected non-unions of the tibia in rats. Furthermore, it was evaluated if detection of bacteria by fluorescent in situ hybridisation (FISH) technique is possible in bone infection. 17 rats were used in which osteotomy of the midshaft tibia was performed and stabilized with an intramedullary device. Two groups were tested: group 1: contamination of the osteotomy site with 10(4) colony forming units (CFUs) of Staphylococcus aureus (11 animals), group 2: no bacterial contamination (6 animals). The animals were sacrificed after 42 days and bone healing and infection were assessed clinically, by X-ray, micro-CT, and microbiological methods including FISH technique using EUB and STAPHY probes. Histology and scanning electron microscopy (SEM) for biofilm formation were performed. All animals of the control group showed uneventful bone healing after 6 weeks without any signs of local infections. 10 of 11 (90.9%) animals of group 1 with bacterial contamination exhibited infected non-union formation with positive clinical, radiological and microbiological infection signs of the tibia but without any systemic infection signs. FISH technique was able to identify bacteria in the infected bone. All intramedullary implants from the infected animals showed positive biofilm formation in SEM. This work presents the first animal model for the induction of intramedullary device-related infected non-union in the tibia and detection of bacteria by FISH technique in infected bone.     

The effect of methylmethacrylate on the bacterial inhibiting properties of normal human serum.

In vitro evaluation of the effect of known concentrations of methylmethacrylate on the bacterial inhibiting properties of normal human serum has been carried out. In low concentrations, methylmethacrylate was found to abolish almost completely the growth inhibition of Staphylococcus epidermidis by normal human serum. Normal human serum did not have an effect on growth of Staphylococcus aureus. It did inhibit growth of Escherichia coli, but there was no reversal of this effect by methylmethacrylate.     

The prevention of infection in open fractures. An experimental study of the effect of antibiotic therapy

Using an experimental rabbit model of a contaminated open fracture of the tibia that was fixed with an intramedullary pin, we assessed the effect of a single dose of cephradine in preventing post-traumatic osteomyelitis in which the infecting organism was Staphylococcus aureus. We paid particular attention to the effect of a delay in giving the antibiotic. The frequency of osteomyelitis in the animals in a control group (no antibiotic) was 91 per cent. When a single injection of cephradine was given one hour before inoculation with the bacteria, the rate was 30 per cent, a statistically significant reduction (p less than 0.01). When cephradine was not administered until one to four hours after inoculation with the bacteria, the average rate of osteomyelitis was 51 per cent, a 40 per cent reduction compared with the rate for the control group. The effect of the antibiotic therefore persisted even when the initial dose was delayed for four hours after bacterial inoculation.     

Silver ion doped ceramic nano-powder coated nails prevent infection in open fractures: In vivo study

BackgroundDespite improvement in operative techniques and antibiotic therapy, septic complications still occur in open fractures. We developed silver ion containing ceramic nano powder for implant coating to provide not only biocompatibility but also antibacterial activity to the orthopaedic implants.Questions/purposesWe hypothesised silver ion doped calcium phosphate based ceramic nano-powder coated titanium nails may prevents bacterial colonisation and infection in open fractures as compared with uncoated nails.Methods33 rabbits divided into three groups. In the first group uncoated, in the second group hydroxyapatite coated, and in the third group silver doped hydroxyapatite coated titanium nails were inserted left femurs of animals from knee regions with retrograde fashion. Before implantation of nails 50 μl solution containing 10⁶ CFU/ml methicillin resistance Staphylococcus aureus (MRSA) injected intramedullary canal. Rabbits were monitored for 10 weeks. Blood was taken from rabbits before surgery and on 2nd, 6th and 10th weeks. Blood was analysed for biochemical parameters, blood count, C-reactive protein and silver levels. At the end of the 10 weeks animals were sacrificed and rods were extracted in a sterile fashion. Swab cultures were taken from intramedullary canal. Bacteria on titanium rods were counted. Liver, heart, spleen, kidney and central nervous tissues samples were taken for determining silver levels. Histopathological evaluation of bone surrounding implants was also performed.ResultsNo significant difference was detected between the groups from hematologic, biochemical, and toxicological aspect. Microbiological results showed that less bacterial growth was detected with the use of silver doped ceramic coated implants compared to the other two groups (p = 0.003). Accumulation of silver was not detected. No cellular inflammation was observed around the silver coated prostheses. No toxic effect of silver on bone cells was seen.ConclusionSilver ion doped calcium phosphate based ceramic nano powder coating to orthopaedic implants may prevents bacterial colonisation and infection in open fractures compared with those for implants without any coating.     

Experimental efficacy study of coated VICRYL plus antibacterial suture in guinea pigs challenged with Staphylococcus aureus

BACKGROUND: This study evaluated the ability of coated polyglactin 910 suture with triclosan (Coated VICRYL Plus Antibacterial) suture to inhibit the colonization of bacteria on the suture after direct in vivo inoculation challenge with Staphylococcus aureus utilizing a guinea pig model. METHODS: One control suture (4-5 cm) and one test suture (4-5 cm) were implanted subcutaneously in the dorsal-lateral regions (control on the left side, test on the right side, approximately 5 cm apart) in 16 female Hartley guinea pigs (300-400 g) via a 20-gauge catheter. Each implantation site was challenged directly with 2.1 x 10(4) colony forming units (cfu) of Staphylococcus aureus through the indwelling catheter. The test material was coated polyglactin 910 suture with triclosan (2-0, dyed), and the control material was coated polyglactin 910 suture (2-0, undyed). At 48 h, suture articles were explanted and a bacterial enumeration assay was performed. RESULTS: There was a significant difference (p < 0.05) in the number of bacteria recovered between the study groups at 48 h post-implantation. The mean recovery for test sutures was 559 cfu, and the mean recovery for control sutures was 16,831 cfu. Coated polyglactin 910 suture with triclosan provided a 30.5-fold (96.7%) reduction in the number of recovered bacteria compared to standard coated polyglactin 910 suture. CONCLUSIONS: This study demonstrates that coated polyglactin 910 suture with triclosan inhibits bacterial colonization of suture after direct in vivo challenge with S. aureus in a guinea pig model.     

Study on experimental suppurative osteomyelitis--influence of an intramedullary nail on infection in open fractures

Studies were conducted on temporary intramedullary fixation of open fractures containing pathogens to determine the degree of involvement of metal splints in the "establishment of infection" and whether or not there is a so-called "golden hour" for antibiotic administration. An open fracture was experimentally produced in the tibia of mice and inoculated with 10(2) or 10(3) cells of staphylococcus aureus. Two separate groups of intramedullary fixation and plaster cast fixation were compared. In the intramedullary fixation group, infection was established in 77.8% of the mice inoculated with 10(2) bacteria and in 100% of those inoculated with 10(3) cells, compared with 35.0% and 70.0% in the plaster cast fixation group. When antibiotic administration was started 12 hours after the inoculation, 4 of 5 mice of the intramedullary fixation group inoculated with 10(3) cells showed abundant bacterial cells after 2 weeks. Antibiotic administration started 6 hours after the inoculation achieved bacterial elimination in all mice.     

An electrified catheter to resist encrustation by Proteus mirabilis biofilm

PURPOSE: We investigated the effect of iontophoresis produced by passing an electric current through silver electrodes attached to catheters on catheter encrustation by crystalline Proteus mirabilis biofilm. MATERIALS AND METHODS: Four glass bladder models were catheterized with 16Fr silicone catheters, of which 3 had 0.25 mm silver wires running through and beside the lumen. Two wired catheters had the silver wires connected to a 9 V direct current source supplying a steady current of 150 microA via a self-regulating circuit. Artificial urine, which had been inoculated with a clinical strain of P. mirabilis isolated from an encrusted catheter, was instilled into the bladder model at 0.5 ml per minute. The models were operated until the test catheters became blocked. Mean blockage time was statistically analyzed by ANOVA. Bacterial colony count, silver ions and pH were assessed every 24 hours. RESULTS: The experiment was repeated 3 times. Time to blockage, colony count, pH and scanning electron microscopy was used to assess encrustation in electrified and control catheters. Time to blockage in electrified vs control catheters was 156 vs 22 hours. The difference in blockage times was statistically significant (p <0.002). The viable bacterial cell count in urine with test catheters vs that in controls was 1.12 x 10(4) vs 2.73 x 10(9) cfu/ml. The pH increased to 9 in control models, whereas it remained less than 6.5 in test models for about 100 hours. CONCLUSIONS: Electrified catheters released ions in urine that have the oligodynamic property of inhibiting bacterial growth. The application of electric current to catheters fitted with silver electrodes significantly decreased the rate at which these devices became encrusted by P. mirabilis. This principle could be used to prevent encrustation on long-term catheters.     

Development of an infection-resistant LVAD driveline: a novel approach to the prevention of device-related infections.

BACKGROUND: Infection remains the single most important challenge to extended left ventricular assist device (LVAD) use and often arises from the percutaneous driveline exit site. We evaluated the ability of an LVAD driveline prototype impregnated with chlorhexidine, triclosan, and silver sulfadiazine to resist bacterial and fungal colonization. METHODS: The spectrum and duration of antimicrobial activity were evaluated in vitro by daily transfer of driveline segments embedded on agar plates inoculated with 10(8) colony-forming units (CFU) of Staphylococcus aureus (S. aureus), Staphlococcus epidermidis, Enterobacter aerogenes, Psuedomonas aeruginosa, and Candida albicans, and then measuring zones of inhibition around the sample subsequent to 24 hours of incubation at 37 degrees C. Antimicrobial activity was demonstrated against all organisms for greater than 14 days, and for over 21 days for gram-positive bacteria. To demonstrate in vivo efficacy of the treated driveline, 3-cm segments of driveline were implanted in the dorsal and ventral surface of rats. The exit site was inoculated with 10(6) CFU of S. aureus. After 7 days, driveline segments were aseptically explanted and assayed for bacterial colonization and retention of antimicrobial activity. One hundred percent of control segments were colonized (10(5) CFU S. aureus/cm) as against 13% of the test explants (< or = 330 CFU/cm; p < 0.0001). RESULTS: Subcultures of the insertion site and driveline pocket tissue resulted in 10(3) to 10(5) CFU per swab culture for control rats and 0 to 10(2) CFU/swab for test animals. Test drivelines retained 80% of anti-S. aureus activity. Gross and histological examination of the driveline and surrounding pocket revealed minimal tissue reactivity with positive signs of tissue ingrowth. CONCLUSION: An antimicrobial driveline may prevent early infections and facilitate ingrowth of tissue to provide long-term stability and protection against late infection.     

A historical review of the use of silver in the treatment of burns. II. Renewed interest for silver

In 1965, Moyer revived interest in silver nitrate solution. He concluded on the basis on in vitro and in vivo studies that a 0.5% solution represented the lowest concentration at which antibacterial action (against Staphylococcus aureus, haemolytic streptococci and generally against Pseudomonas aeruginosa and E. coli) was obtained. Mafenide acetate was introduced a short time after the reintroduction of silver nitrate, followed a few years later by silver sulphadiazine. Thus, in a short period of time three medicaments appeared on the market which represented a radical change in the topical treatment of burns. The action of silver sulphadiazine has been intensively studied. Since silver sulphadiazine does not offer sufficient protection to prevent or retard the growth of gram-negative bacteria in patients with burns covering more than 50% of body surface, Monafo introduced the combined preparation silver sulphadiazine and cerium nitrate. Although various attempts have been made to develop more effective silver compounds, so far silver sulphadiazine still remains the most widely used substance of this type.     

盐酸昂丹司琼体外抑菌作用的实验研究

目的观察盐酸昂丹司琼在体外对大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌抑菌作用的影响。。方法将盐酸昂丹司琼注射液用无菌生理盐水稀释至终浓度分别为0.5、0.25、0.125和0.0625 mg/mL,与大肠埃希杆菌、金黄色葡萄球菌、和铜绿假单胞菌培养,每个实验重复三遍,所有菌株的稀释的系列测定均进行两次。结果昂丹司琼对大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌均有明显的抑菌作用,昂丹司琼对大肠埃希菌的抑菌作用随着昂丹司琼浓度的增加而增加,至0.0625 mg/mL时仍有明显的抑菌作用(P<0.05)。昂丹司琼对金黄色葡萄球菌和铜绿假单胞菌的抑菌作用在昂丹司琼浓度为0.125 mg/mL时消失。结论昂丹司琼在体外可以抑制大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌的生长,对于预防麻醉相关的感染可能有一定的临床意义。     

盐酸格拉司琼体外抑菌作用的实验研究

目的观察盐酸格拉司琼在体外对大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌抑菌作用的影响。方法将盐酸格拉司琼注射液用无菌生理盐水稀释至终浓度分别为0.5、0.25、0.125和0.0625 mg/mL,与大肠埃希杆菌、金黄色葡萄球菌、和铜绿假单胞菌培养,每个实验重复三遍,所有菌株的稀释的系列测定均进行两次。结果格拉司琼对大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌均有明显的抑菌作用,格拉司琼对大肠埃希菌的抑菌作用随着格拉司琼浓度的增加而增加,至0.0625 mg/mL时仍有明显的抑菌作用(P<0.05)。格拉司琼对金黄色葡萄球菌和铜绿假单胞菌的抑菌作用在格拉司琼浓度为0.125 mg/mL时消失。结论格拉司琼在体外可以抑制大肠埃希菌、金黄色葡萄球菌、铜绿假单胞菌的生长,对于预防麻醉相关的感染可能有一定的临床意义。     

Antibacterial activity of remifentanil and mixtures of remifentanil and propofol

STUDY OBJECTIVE: To investigate the antibacterial activity of glycine, which is contained in remifentanil, when combined with propofol. DESIGN: Prospective study. SETTING: Departments of anesthesiology and microbiology of a university hospital. MEASUREMENTS: Growth of the microorganisms Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans in propofol 1%; saline dilutions of remifentanil at one-, 10-, and 100-microg/mL concentrations; and 1:1 mixtures of propofol with remifentanil solutions was determined. MAIN RESULTS: Remifentanil inhibits bacterial growth in a concentration-dependent manner. The antibacterial effects were more pronounced with Staphylococcus aureus and Pseudomonas aeruginosa at cultures obtained at the fifth hour. The inhibition of bacterial growth was less influenced with Escherichia coli and Candida albicans. CONCLUSIONS: Propofol and remifentanil mixtures decreased bacterial growth, and combinations may reduce the infectious complications from accidentally contaminated propofol.     

Comparative evaluation of silver-containing antimicrobial dressings and drugs

Wound dressings containing silver as antimicrobial agents are available in various forms and formulations; however, little is understood concerning their comparative efficacy as antimicrobial agents. Eight commercially available silver-containing dressings, Acticoat 7, Acticoat Moisture Control, Acticoat Absorbent, Silvercel, Aquacel Ag, Contreet F, Urgotol SSD and Actisorb, were tested to determine their comparative antimicrobial effectiveness in vitro and compared against three commercially available topical antimicrobial creams, a non treatment control, and a topical silver-containing antimicrobial gel, Silvasorb. Zone of inhibition and quantitative testing was performed by standard methods using Escherichia coli, Pseudomonas aeruginosa, Streptococcus faecalis and Staphylococcus aureus. Results showed all silver dressings and topical antimicrobials displayed antimicrobial activity. Silver-containing dressings with the highest concentrations of silver exhibited the strongest bacterial inhibitive properties. Concreet F and the Acticoat dressings tended to have greater antimicrobial activity than did the others. Topical antimicrobial creams, including silver sulfadiazine, Sulfamylon and gentamicin sulfate, and the topical antimicrobial gel Silvasorb exhibited superior bacterial inhibition and bactericidal properties, essentially eliminating all bacterial growth at 24 hours. Silver-containing dressings are likely to provide a barrier to and treatment for infection; however, their bactericidal and bacteriostatic properties are inferior to commonly used topical antimicrobial agents.     

Adhesion of Staphylococcus to orthopaedic metals, an in vivo study.

This study describes a new model of biofilm study in rabbits. The primary focus of this study was to assess biofilm adhesion to orthopaedic metals in their first 48 h in a femoral intramedullary implantation model. Two previous inoculation methods i.e. that of pre- and direct inoculation were studied with two bacterial isolates namely Staphylococcus aureus and epidermidis, on titanium and stainless steel metallic implants. A method of sonication and log dilution/plating was used to assess biofilm bacteria adhering to implants. Silver coated metals were then compared with their respective control metals in the new model. The direct inoculation model gave larger and more reproducible biofilm adhesion to implanted metals. Staphylococcus epidermidis shows lower adhesion ability to metals, and biofilms adhere in greater numbers to stainless steel over titanium. Silver coated metals show no statistical difference over control metals when exposed to orthopaedic biofilms.     

Experimental acute hematogenous osteomyelitis in mice. I. Histopathological and immunological findings.

This study investigated immunological responses to Staphylococcus aureus bone infection. Because considerable immunological information is available on the mouse, a murine model of acute hematogenous osteomyelitis was established. Osteomyelitis was created in the proximal tibia of C3H/HeJ mice by a tibial epiphyseal fracture followed by intravenous bacterial inoculation with Staphylococcus aureus (strain LS-1). Swelling and warmth of the limb was found, and following limb exposure, abscess formation was evident in the proximal tibia. Histological examination revealed distortion primarily at the hypertrophic zone of the physis and polymorphonuclear leukocyte infiltration throughout the damaged area of the proximal tibia. Local infection was demonstrated at the fracture site, evidenced by the recovery of Staphylococcus aureus following microbiological analysis of tissue specimens. Polymerase chain reaction was utilized to detect 16S ribosomal prokaryotic nucleic acid to demonstrate that the diagnosis of osteomyelitis could be established in the absence of conventional microbiological techniques. The infected mice had an increase of circulating large leukocytes (granulocytes) and an elevation of total serum immunoglobulin. Flow cytometry revealed significant increases in splenic B lymphocytes and in lymph-node CD4+ T lymphocytes. These results indicate that an experimental model of acute hematogenous osteomyelitis that closely resembles the pathology of the disease in humans may be consistently induced in mice. Furthermore, marked immunological changes may be observed in response to the Staphylococcus aureus bone infection.     

ICU病区临床用药与金黄色葡萄球菌分离率之间宏观量化关系的研究

目的:分析我院ICU病区2007-2009年临床用药与金黄色葡萄球菌(金葡菌)临床分离率之间的宏观量化关系,为临床调整用药提供依据.方法:收集并统计我院ICU病区2007年1月-2009年12月每季度用药消耗情况,将其换算成国际上相关研究所共同采用的药物使用强度指标--每100住院人天所消耗的限定日剂量(DDD/100...     

Effects of isoflurane on bacterial growth

Anaesthetic agents have been implicated in the development of postoperative pneumonia, but the direct effect of volatile anaesthetics on bacterial growth has given contradictory results. The effects of isoflurane on the growth of Staphylococcus aureus and Escherichia coli were investigated under conditions similar to those of clinical practice, using standardized microbiological methods. An open anaesthetic circuit was adjusted to the normal ventilatory settings of an adult patient. A spray, installed on the inspiratory side of the circuit, ensured the delivery of isoflurane at 1.5 minimal alveolar concentration. The bacterial strains studied were both wild-type and reference strains. Bacterial inoculums were prepared to obtain a bacterial exponential growth of 10(3) colony-forming units per mL in 10 mL of nutritive broth. Each strain was studied with and without exposure to isoflurane and measured by the usual criteria of bacterial growth, and by bacterial regrowth after exposure to isoflurane. Under experimental conditions close to clinical practice, exposure to isoflurane did not alter bacterial growth of S. aureus and E. coli, or their bacterial regrowth when isoflurane exposure is over.     

Staphylococcal biofilms impair wound healing by delaying reepithelialization in a murine cutaneous wound model

Bacterial biofilms have gained increasing visibility in recent years as a ubiquitous form of survival for microorganisms in myriad environments. A number of in vivo models exist for the study of biofilms in the setting of medically relevant implanted foreign bodies. Growing evidence has demonstrated the presence of bacterial biofilms in the setting of a number of chronic wound states including pressure sores, diabetic foot ulcers, and venous stasis ulcers. Here we present a novel murine cutaneous wound system that directly demonstrates delayed reepithelialization caused by the presence of a bacterial biofilm. We established biofilms using either Staphylococcus aureus or Staphylococcus epidermidis in splinted cutaneous punch wounds created on the backs of normal C57Bl6/J mice. Wound reepithelialization was significantly delayed by bacterial biofilms. This effect was specifically dependent on the ability of the bacteria to form biofilms as demonstrated by exogenous administration of biofilm inhibiting peptides and the use of mutant Staphylococcus spp. deficient in biofilm formation. This represents the first direct evidence for the effect of bacterial biofilms on cutaneous wound healing.