Controlled release of antibiotics from coated orthopedic implants

Chronic osteomyelitis is one of the most serious complications of orthopedic open fracture treatment. The objective of this study was to develop a biodegradable implant coating with impregnated antibiotics as an adjunct to current therapy. We used a polylactic-co-glycolic acid copolymer (PLGA) as the biodegradable carrier and gentamicin as the antibiotic. Our objectives were to establish elution characteristics of the antibiotic from the polymer, and determine if the coated orthopedic implants would inhibit bacterial growth in vitro. In the elution study, coated implants were incubated in phosphate buffered saline (PBS) at 37 degrees C and sampled daily for gentamicin levels. The in vitro model consisted of test tubes containing Mueller-Hinton culture broth inoculated with 5 x 10(6) cfu of Staphylococcus aureus and incubated at 37 degrees C. The implants were switched to a new set of inoculated tubes each day. Tubes were sampled for colony counting to determine bactericidal effects. Implant coatings consisted of 40 mg of gentamicin as a 20% mixture with PLGA. The elution curve showed an average level of 138 micrograms/mL over 15 days. This local concentration would be more than adequate to kill susceptible organisms. The in vitro study showed a significant reduction in bacterial growth in the test tubes containing coated implants. Control tubes averaged 2.5 x 10(8) cfu/mL of S.aureus over 24 days. Coated implant tubes averaged 0.9 cfu/mL. This was a reduction of greater than 99.999% (p < 0.0001). This study showed that a thin biodegradable implant coating can be developed with bactericidal activity against the organisms frequently associated with osteomyelitis in cases of open fractures.

The prevention of infection in open fractures: an experimental study of the effect of fracture stability

An experimental model of a contaminated open fracture has been developed. This model has been used to test the hypothesis that stable fixation of a contaminated open fracture will reduce its susceptibility to infection. The tibiae of male New Zealand white rabbits were fractured and then fixed with either a dynamic compression plate (stable group) or a loose-fitting intramedullary rod (unstable group). The fracture site was then inoculated with a standard inoculum of Staphylococcus aureus. There were 20 rabbits in the stable group and osteomyelitis developed in seven (35 per cent); in the unstable group 15 (71 per cent) out of 21 animals developed osteomyelitis. This difference in infection rates was statistically significant (P < 0.02). This experimental study supports the concept of stabilization of open fractures in man.

Optimal duration of antibiotic therapy in vertebral osteomyelitis

OBJECTIVES

To compare the risk of relapse of vertebral osteomyelitis (VO), according to the duration of antibiotic therapy (< or =6 weeks versus >6 weeks).

METHODS

We performed a 10-year retrospective study to assess the risk of VO relapse and to verify that this risk was not enhanced in patients who received 6 weeks of antibiotic therapy (Group 1) as compared with those who received a longer treatment (Group 2). VO was diagnosed based on clinical manifestations, magnetic resonance imaging and/or computed tomography findings, and isolation of a pyogenic organism in blood cultures and/or a discovertebral biopsy. Relapse was diagnosed based on isolation of the same organism in blood cultures and/or a discovertebral biopsy. Outcome was evaluated 6 months post-treatment and in December 2004.

RESULTS

Group 1 included 36 patients (mean age, 58 +/- 15 years) and Group 2 included 84 patients (mean age, 67 +/- 15 years) (P = 0.003). Clinical data and microorganisms were comparable in the 2 groups. In the first 6 months, 6 (5%) patients died (Group 1, n = 2; Group 2, n = 4), and 5 (4%) in Group 2 relapsed, 2 with recurrent VO and 3 with recurrent bacteremia. In 2004, 91 patients were evaluated (mean follow-up, 40.6 +/- 31 months): 77 (85%) were cured, 13 (14%) died (Group 1, n = 3; Group 2, n = 10), 1 had VO due to a different microorganism (Group 2), and no long-term relapses occurred.

CONCLUSION

Our results suggest that antibiotic therapy of VO could be safely shortened to 6 weeks without enhancing the risk of relapse.

Postoperative infection following orthopaedic surgery in human immunodeficiency virus-infected hemophiliacs with CD4 counts < or = 200/mm3

Human immunodeficiency virus-infected hemophiliacs are at risk for bacterial and opportunistic infections with worsening immunosuppression. Thus, the risk of postoperative infection following orthopaedic surgery is of considerable concern. A survey of United States hemophilia treatment centers was conducted to determine the incidence of postoperative infection in human immunodeficiency virus-positive hemophiliacs with CD4 counts of 200 mm3 or less undergoing orthopaedic surgery. A total of 115 centers from 37 states reported that postoperative infection occurred in 10 (15.1%) of 66 patients undergoing 74 orthopaedic procedures, between several weeks and 5 months following surgery. In five (50%), pre-operative infection preceded postoperative joint infection. Staphylococcus was the most common organism isolated in a prosthetic joint infection, in 6 of 10 (60.0%), and the knee was the most commonly affected joint, in 9 of 10 (90.0%). Joint arthroplasty appeared to have 10 times the risk of nonarthroplasty procedures for postoperative infection (9 of 34 [26.5%] and 1 of 40 [2.5%], respectively, P < .01). Two subjects developed chronic osteomyelitis. The rate of postoperative infection in human immunodeficiency virus-positive hemophiliacs with CD4 counts of 200/mm3 or less appears to be high, when compared with the general population. Early, vigorous treatment should be instituted for suspected infection, antibiotic prophylaxis considered for invasive procedures, and surgical intervention individualized based on the balance of risks and benefits.

The prophylactic use of antibiotic impregnated beads in open fractures

Four hundred four compound fractures were reviewed in 339 patients treated between August 1983 and November 1987. The 252 males and 87 females had a mean age of 33 years (range, 14-86). One hundred twenty-seven (31.4%) fractures were classified as Grade I, 153 (38.9%) as Grade II, and 124 (30.7%) as Grade III by Gustilo's classification. The mean Injury Severity Score was 15 (range, 9-57). Three hundred thirty-four of the open fractures (82.7%) were managed with antibiotic-impregnated bead chains (tobramycin) and systemic antibiotic prophylaxis (cefazolin, tobramycin, and penicillin). Seventy open fractures (17.3%) received systemic antibiotic prophylaxis (cefazolin, tobramycin, and penicillin) without supplemental use of the antibiotic beads. All open fractures underwent acute irrigation and debridement. In the 404 fractures 46.5% of wounds were closed primarily, 12.9% underwent delayed primary closure, 7.9% were left open, and 32.7% were temporized by the antibiotic bead pouch technique until definitive flap coverage and skin grafting were performed. Of the 404 fractures evaluated, 17 (4.2%) developed an acute wound infection. Of these wound infections, eight (11.4%) were in the group managed with systemic antibiotics alone. By comparison, nine (2.7%) of open fractures treated with combined systemic antibiotics and antibiotic-impregnated beads developed an infection. Chronic osteomyelitis developed in 18 of 404 open fractures (4.5%). Ten (14.3%) open fractures which developed osteomyelitis were managed with systemic antibiotics whereas eight (2.4%) fractures managed with systemic antibiotics and antibiotic-impregnated beads developed a chronic infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetic foot infections: state-of-the-art

Foot infections are frequent and potentially devastating complications of diabetes. Unchecked, infection can progress contiguously to involve the deeper soft tissues and ultimately the bone. Foot ulcers in people with diabetes are most often the consequence of one or more of the following: peripheral sensory neuropathy, motor neuropathy and gait disorders, peripheral arterial insufficiency or immunological impairments. Infection develops in over half of foot ulcers and is the factor that most often leads to lower extremity amputation. These amputations are associated with substantial morbidity, reduced quality of life and major financial costs. Most infections can be successfully treated with optimal wound care, antibiotic therapy and surgical procedures. Employing evidence-based guidelines, multidisciplinary teams and institution-specific clinical pathways provides the best approach to guide clinicians through this multifaceted problem. All clinicians regularly seeing people with diabetes should have an understanding of how to prevent, diagnose and treat foot infections, which requires familiarity with the pathophysiology of the problem and the literature supporting currently recommended care.

Intramuscular versus oral antibiotic therapy for the prevention of meningitis and other bacterial sequelae in young, febrile children at risk for occult bacteremia

Because studies of the treatment of children with occult bacteremia have yielded conflicting results, we compared ceftriaxone with amoxicillin for therapy. Inclusion criteria were age 3 to 36 months, temperature > or = 39 degrees C, an acute febrile illness with no focal findings or with otitis media (6/10 centers), and culture of blood. Subjects were randomly assigned to receive either ceftriaxone, 50 mg/kg intramuscularly, or amoxicillin, 20 mg/kg/dose orally for six doses. Of 6733 patients enrolled, 195 had bacteremia and 192 were evaluable: 164 Streptococcus pneumoniae, 9 Haemophilus influenzae type b, 7 Salmonella, 2 Neisseria meningitidis, and 10 other. After treatment, three patients receiving amoxicillin had the same organism isolated from their blood (two H. influenzae type b, one Salmonella) and two from the spinal fluid (two H. influenzae type b), compared with none given ceftriaxone. Probable or definite infections occurred in three children treated with ceftriaxone and six given amoxicillin (adjusted odds ratio 0.43, 95% confidence interval 0.08 to 1.82, p = 0.31). The five children with definite bacterial infections (three meningitis, one pneumonia, one sepsis) received amoxicillin (adjusted odds ratio 0.00, 95% confidence interval 0.00 to 0.52, p = 0.02). Fever persisted less often with ceftriaxone (adjusted odds ratio 0.52, 95% confidence interval 0.28 to 0.94, p = 0.04). Although the difference in total infections was not significant, ceftriaxone eradicated bacteremia, prevented significantly more definite focal bacterial complications, and was associated with less persistent fever.

Mycobacterium bovis BCG vaccination as prophylaxis against Mycobacterium ulcerans osteomyelitis in Buruli ulcer disease

Mycobacterium ulcerans disease, or Buruli ulcer (BU), causes significant morbidity in West Africa. Clinically, the disease presents in the skin as either nonulcerative or ulcerative forms and often invades bones either subjacent to the skin lesion (contiguous osteomyelitis) or remote from the skin lesion (metastatic osteomyelitis). Osteomyelitis represents a severe form of the disease that often requires numerous surgical interventions, even amputations. Surgery is accepted as the present definitive treatment for BU. In the absence of an effective drug treatment, the need for the development of preventive and control strategies becomes paramount. No specific vaccine, however, is presently available for BU. Of 372 consecutive patients in Benin presenting with BU (confirmed by microbiological and histopathological analyses) whose Mycobacterium bovis BCG scar statuses were known, 196 children (<15 years old) and 108 adults had neonatal BCG vaccination scars. Of 196 children with BCG scars, 17 (8.7%) had osteomyelitis, while 7 of 28 children without BCG scars (25.0%) had osteomyelitis. Of 108 adults with BCG scars, 17 (15.7%) had osteomyelitis, while 14 of 40 adults without BCG scars (35.0%) had osteomyelitis. Our results show that effective BCG vaccination at birth provides significant protection against the development of M. ulcerans osteomyelitis in children and adults. Therefore, health authorities should give attention to the enhancement of neonatal BCG vaccination coverage in all countries of Africa where BU is endemic. Protection against severe forms of BU and childhood tuberculosis would likewise be improved by this intervention.

Systemic versus local application of gentamicin in prophylaxis of implant-related osteomyelitis in a rat model

Administration of perioperative antibiotic prophylaxis is a routine procedure in orthopedic surgery. Besides systemic prophylaxis, only few techniques are established for local application of antibiotics to reduce infection related to orthopedic implants. The aim of this study was to evaluate the efficacy of locally versus systemically applied gentamicin in a rat model (n = 60). For local application, the antibiotic was delivered from a biodegradable poly(D,L-lactide) (PDLLA) coating of titanium implants. The efficacy of local prophylaxis was compared to a systemic single shot application of gentamicin as well as a combination of both administrations. Half of the animals received a weight-adopted single shot application of gentamicin 30 min prior to surgery. At surgery, the medullary cavities of the tibiae were contaminated with Staphylococcus aureus (10(2) colony forming units /CFU) and titanium Kirschner wires were implanted into the medullary canals. The implants were either uncoated, PDLLA coated, or coated with PDLLA + 10% w/w gentamicin. The animals were followed up for 42 days. X-ray examinations were performed; body weight, temperature, and the clinical condition were determined. After sacrifice, infection was evaluated by histological and microbiological analysis. All animals treated with uncoated or PDLLA-coated Kirschner wires without systemic application of the antibiotic developed osteomyelitis and all cultures of implants were tested positive on S. aureus. Implant-related osteomyelitis could be prevented by prophylaxis of systemically applied gentamicin in 15% of animals. In contrast, local application of gentamicin delivered from a PDLLA coating was more effective. Onset of infection could be prevented in 90% of animals treated with gentamicin coated Kirschner wires, and in 80% of the animals that were treated with a combination of local and systemic application. The local application from PDLLA-coated implants might support systemic antibiotic prophylaxis in preventing implant-associated osteomyelitis.

Wound bioburden and infection-related complications in diabetic foot ulcers

The identification and diagnosis of diabetic foot ulcer (DFU) infections remains a complex problem. Because inflammatory responses to microbial invasion may be diminished in persons with diabetes, clinical signs of infection are often absent in persons with DFUs when infection is limited to localized tissue. In the absence of these clinical signs, microbial load is believed to be the best indicator of infection. Some researchers, however, believe microbial load to be insignificant and type of organism growing in the ulcer to be most important. Previous studies on the microbiology of DFUs have not provided enough evidence to determine the microbiological parameters of importance.Infection-related complications of DFUs include wound deterioration, osteomyelitis, and amputation. Risk factors for amputation include age, peripheral vascular disease, low transcutaneous oxygen, smoking, and poor glycemic control. These risk factors are best measured directly with physiological measures of arterial perfusion, glycemic control, sensory neuropathy, plantar pressures, and activity level and by controlling off-loading. DFU bioburden has not been examined as a risk factor for infection-related complications. To address the relationship between wound bioburden and the development of infection-related complications in DFUs, tightly controlled prospective studies based on clearly defined, valid measures of wound bioburden and wound outcomes are needed. This article reviews the literature and proposes a model of hypothesized relationships between wound bioburden-including microbial load, microbial diversity, and pathogenicity of organisms-and the development of infection-related complications.

Nonremovable, windowed, fiberglass cast boot in the treatment of diabetic plantar ulcers: efficacy, safety, and compliance

OBJECTIVE

To compare the efficacy, safety, and compliance of a nonremovable fiberglass cast boot and off-loading shoes in the treatment of diabetic plantar ulcers.

RESEARCH DESIGN AND METHODS

Patients (n = 93) with noninfected, nonischemic plantar ulcers were included in this prospective nonrandomized study. Treatment used a nonremovable fiberglass cast boot for longer standing and deeper ulcers (n = 42) and a half shoe or heel-relief shoe for other ulcers (n = 51). We evaluated off-loading therapy, compliance, and complications in both groups.

RESULTS

The healing rate was significantly higher with the cast boot than with the off-loading shoe (81 vs. 70%, P = 0.017), with healing times of 68.6 +/- 35.1 vs. 134.2 +/- 133.0 days, respectively, and hazard ratio 1.68 (95% CI 1.04-2.70); complete compliance with treatment was 98 vs. 10% (P = 0.001), respectively. Secondary osteomyelitis developed in 3 patients in the cast boot group and 13 patients in the off-loading shoe group (P = 0.026).

CONCLUSIONS

A nonremovable fiberglass cast boot was effective in healing diabetic plantar ulcers and in decreasing the risk of secondary osteomyelitis. The cast boot forced compliance with off-loading, thus promoting healing.

Bioactivity in glass/PMMA composites used as drug delivery system

Gentamicin sulfate has been incorporated in composites prepared from a SiO2-CaO-P2O5 bioactive glass and polymethylmethacrylate. Data showed that these materials could be used as drug delivery system, keeping the bioactive behavior of the glass. The composites supply high doses of the antibiotic during the first hours when they are soaked in simulated body fluid (SBF). Thereafter, a slower drug release is produced, supplying 'maintenance' doses until the end of the experiment. The gentamicin release rate is related with the ionic Ca2+ and H3O+ exchange between composite and SBF. The porous structure of the composites allows the growth of hydroxycarbonate apatite on the surface and into the pores.

The role of environment and management on leg abnormalities in meat-type fowl

Continuous light with 1 h of darkness at midnight is a common photoperiod for raising meat-type fowl. The logic behind the 1 h of darkness, usually provided between midnight and 0100 h, is to acclimate the birds to darkness in the event of a power failure. Increasing evidence from several research laboratories indicates that lighting regimens other than continuous light, such as intermittent or step-up lighting, can lower the incidence of leg abnormalities in meat-type fowl. Some evidence suggests that increased exercise contributes in part to the reduction in lameness due to lighting. Management can influence the incidence of leg and foot problems via effects on rate of gain, flooring systems, and litter moisture. Rapid weight gains have been correlated with tibial dyschondroplasia (TD), although more evidence is needed to determine whether other types of leg deformities, such as long bone distortion, are related to rapid growth rates. Using low intensity X-ray imaging (hand-held lixiscope), live breeders with TD lesions can be identified and the incidence of TD can be reduced in breeder flocks through genetic selection. In addition, turkeys can be selected for wider shanks to improve walking ability. Slippery surfaces should be avoided to prevent spraddled legs. With the exception of TD, broilers reared in cages have more leg deformities than floor-reared birds. Dry litter conditions can help prevent foot pad dermatitis caused by Staphylococcus aureus and other bacteria.

Deep infection in Charnley low-friction arthroplasty. Comparison of plain and gentamicin-loaded cement

A retrospective review of 1542 Charnley low-friction arthroplasties was carried out to compare the incidence of deep infection arising after plain and gentamicin-containing acrylic cement. There was no significant difference between the two series in primary operations, the infection rate being 1.72% and 1.65% respectively. However, in secondary operations (conversions and revisions) the gentamicin-containing cement gave significantly better results--a 0.81% infection rate as compared with 3.46%. All operations were performed in a clean air enclosure using total-body exhaust suits. Radiological diagnosis of deep infection was possible within one year of operation in all cases. Late haematogenous infection occurred in one case and was related to a skin lesion.

A doxycycline-loaded polymer-lipid encapsulation matrix coating for the prevention of implant-related osteomyelitis due to doxycycline-resistant methicillin-resistant Staphylococcus aureus

Implant-associated bone infections caused by antibiotic-resistant pathogens pose significant clinical challenges to treating physicians. Prophylactic strategies that act against resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are urgently required. In the present study, we investigated the efficacy of a biodegradable Polymer-Lipid Encapsulation MatriX (PLEX) loaded with the antibiotic doxycycline as a local prophylactic strategy against implant-associated osteomyelitis. Activity was tested against both a doxycycline-susceptible (doxy(S)) methicillin-susceptible S. aureus (MSSA) as well as a doxycycline-resistant (doxy(R)) methicillin-resistant S. aureus (MRSA). In vitro elution studies revealed that 25% of the doxycycline was released from the PLEX-coated implants within the first day, followed by a 3% release per day up to day 28. The released doxycycline was highly effective against doxy(S) MSSA for at least 14days in vitro. A bolus injection of doxycycline mimicking a one day release from the PLEX-coating reduced, but did not eliminate, mouse subcutaneous implant-associated infection (doxy(S) MSSA). In a rabbit intramedullary nail-related infection model, all rabbits receiving a PLEX-doxycycline-coated nail were culture negative in the doxy(S) MSSA-group and the surrounding bone displayed a normal physiological appearance in both histological sections and radiographs. In the doxy(R) MRSA inoculated rabbits, a statistically significant reduction in the number of culture-positive samples was observed for the PLEX-doxycycline-coated group when compared to the animals that had received an uncoated nail, although the reduction in bacterial burden did not reach statistical significance. In conclusion, the PLEX-doxycycline coating on titanium alloy implants provided complete protection against implant-associated MSSA osteomyelitis, and resulted in a significant reduction in the number of culture positive samples when challenged with a doxycycline-resistant MRSA.

Local and systemic levels of tobramycin delivered from calcium sulfate bone graft substitute pellets

We asked if tobramycin-loaded calcium sulfate pellets could be used to maintain high local site antibiotic concentrations for an extended period with minimal systemic levels and without adverse effects on vital organs. Calcium sulfate pellets loaded with 10% tobramycin were implanted in contained medullary defects in the proximal humeri of canines. The number of pellets implanted was calculated to yield an equivalent human maximum prescribed dose, and 1.8-fold this dose. These doses converted to approximately 20 mg/kg, and 36 mg/kg, respectively, for the canine. Local and systemic tobramycin levels, pellet resorption, bone response, clinical pathology parameters, and histopathologic responses of potential target organs were analyzed to determine if there was any adverse response for a 28-day period. Serum tobramycin was elevated for less than one day while local levels remained elevated for at least 14 days, and in some animals, 28 days. Tobramycin delivered locally from calcium sulfate pellets had no apparent adverse effect on clinical pathology parameters or on any of the organs that were analyzed. In addition, bone formation and pellet resorption followed patterns typically seen with calcium sulfate materials.

Interventions in the management of infection in the foot in diabetes: a systematic review

The expert panel on diabetic foot infection (DFI) of the International Working Group on the Diabetic Foot conducted a systematic review seeking all published reports relating to any type of treatment for infection of the foot in persons with diabetes published as of 30 June 2014. This review, conducted with both PubMed and EMBASE, was used to update an earlier one undertaken on 30 June 2010 using the same search string. Eligible publications included those that had outcome measures reported for both a treated and a control population that were managed either at the same time, or as part of a before-and-after case design. We did not include studies that contained only information related to definition or diagnosis, but not treatment, of DFI. The current search identified just seven new articles meeting our criteria that were published since the 33 identified with the previous search, making a total of 40 articles from the world literature. The identified articles included 37 randomised controlled trials (RCTs) and three cohort studies with concurrent controls, and included studies on the use of surgical procedures, topical antiseptics, negative pressure wound therapy and hyperbaric oxygen. Among the studies were 15 RCTs that compared outcomes of treatment with new antibiotic preparations compared with a conventional therapy in the management of skin and soft tissue infection. In addition, 10 RCTs and 1 cohort study compared different treatments for osteomyelitis in the diabetic foot. Results of comparisons of different antibiotic regimens generally demonstrated that newly introduced antibiotic regimens appeared to be as effective as conventional therapy (and also more cost-effective in one study), but one study failed to demonstrate non-inferiority of a new antibiotic compared with that of a standard agent. Overall, the available literature was both limited in both the number of studies and the quality of their design. Thus, our systematic review revealed little evidence upon which to make recommendations for treatment of DFIs. There is a great need for further well-designed trials that will provide robust data upon which to make decisions about the most appropriate treatment of both skin and soft tissue infection and osteomyelitis in diabetic patients.

Multifunctional pH sensitive 3D scaffolds for treatment and prevention of bone infection

Multifunctional-therapeutic three-dimensional (3D) scaffolds have been prepared. These biomaterials are able to destroy the S. aureus bacterial biofilm and to allow bone regeneration at the same time. The present study is focused on the design of pH sensitive 3D hierarchical meso-macroporous 3D scaffolds based on MGHA nanocomposite formed by a mesostructured glassy network with embedded hydroxyapatite nanoparticles, whose mesopores have been loaded with levofloxacin (Levo) as antibacterial agent. These 3D platforms exhibit controlled and pH-dependent Levo release, sustained over time at physiological pH (7.4) and notably increased at infection pH (6.7 and 5.5), which is due to the different interaction rate between diverse Levo species and the silica matrix. These 3D systems are able to inhibit the S. aureus growth and to destroy the bacterial biofilm without cytotoxic effects on human osteoblasts and allowing an adequate colonization and differentiation of preosteoblastic cells on their surface. These findings suggest promising applications of these hierarchical MGHA nanocomposite 3D scaffolds for the treatment and prevention of bone infection.

STATEMENT OF SIGNIFICANCE

Multifunctional 3D nanocomposite scaffolds with the ability for loading and sustained delivery of an antimicrobial agent, to eliminate and prevent bone infection and at the same time to contribute to bone regeneration process without cytotoxic effects on the surrounding tissue has been proposed. These 3D scaffolds exhibit a sustained levofloxacin delivery at physiological pH (pH 7.4), which increasing notably when pH decreases to characteristic values of bone infection process (pH 6.7 and pH 5.5). In vitro competitive assays between preosteoblastic and bacteria onto the 3D scaffold surface demonstrated an adequate osteoblast colonization in entire scaffold surface together with the ability to eliminate bacteria contamination.

Osteomyelitis prevention in rabbits using antimicrobial peptide hLF1-11- or gentamicin-containing calcium phosphate cement

OBJECTIVES

The efficacy of prophylactic treatment with human lactoferrin 1-11 (hLF1-11), a broad-spectrum antimicrobial peptide, was studied in a rabbit model of femur infection.

METHODS

Calcium phosphate cement with 50 mg/g hLF1-11 or gentamicin was injected into the femoral canal, after inoculation with Staphylococcus aureus. Three weeks later, slices of the proximal femora were sawn for quantitative bacterial culture and histology.

RESULTS

Treatment with hLF1-11 (P<0.038) or gentamicin (P<0.008) caused a reduction of cfu compared with the untreated control rabbits. The number of sterile cultures was higher in hLF1-11- (3/7) and gentamicin- (5/6) treated animals than in controls (1/7). Radiological and histological analysis showed early bone ingrowth into the cement cracks, and only moderate pathological changes in rabbits with positive cultures.

CONCLUSIONS

Local prophylaxis with hLF1-11 effectively reduced development of osteomyelitis in a rabbit model, but gentamicin resulted in a larger number of sterile femora.

Prevention and management of infection after total joint replacement

Prophylactic antimicrobial regimens providing adequate drug levels in tissue during surgery and for periods of 24 hours to 14 days are of proven effectiveness in reducing infection rates after joint arthroplasty. Although most surgeons employ short regimens of < 24 hours' duration, their efficacy has not been clearly established for joint replacement in placebo-controlled trials. Careful preparation of the patient before surgery and attention to operating room asepsis are also important. In early postoperative infections, surgical debridement and antibiotic treatment may allow conservation of the prosthetic components. In established infection in which the components have become loose, radical surgical debridement must include removal of all prosthetic material as well as involved bone and soft tissue; reconstruction by exchange arthroplasty has an acceptable success rate. For infections caused by organisms of low virulence, exchange arthroplasty has been successful as a one-stage procedure, but no comparative trial with two-stage exchange has yet been reported.

In vivo efficacy of antimicrobial-coated devices

BACKGROUND

Since device colonization is a prelude to infection, an antimicrobial-coated device that reduces bacterial colonization can potentially protect against infection. The objective of this animal study was to assess the efficacy of a coating with minocycline and rifampin to prevent colonization of a grit-blasted titanium implant and subsequent osteomyelitis.

METHODS

Twenty-five rabbits underwent implantation of a titanium-alloy pin, either coated with minocycline and rifampin (thirteen rabbits) or uncoated (twelve rabbits), into the right femoral medullary canal. The implanted devices were inoculated with 500 CFU (colony-forming units) of Staphylococcus aureus prior to wound closure. The rabbits were killed one week later, and the removed device, femoral bone, a specimen obtained by swabbing the track surrounding the device, and blood were cultured. The rates of device colonization, osteomyelitis, and device-related osteomyelitis were compared between the two groups of rabbits.

RESULTS

The antimicrobial-coated devices had a significantly lower rate of colonization than the uncoated devices (five of thirteen compared with twelve of twelve, p = 0.0016) and were associated with significantly lower rates of osteomyelitis (six of thirteen compared with twelve of twelve, p = 0.005) and device-related osteomyelitis (five of thirteen compared with twelve of twelve, p = 0.0016). Bacteremia did not develop in any rabbit.

CONCLUSIONS

Orthopaedic devices coated with minocycline and rifampin significantly protected against device colonization and infection due to Staphylococcus aureus in this in vivo rabbit model.

CLINICAL RELEVANCE

It is possible that orthopaedic devices coated with this unique combination of antimicrobial agents may protect against the development of clinical infection in humans.

Intra-operative antibiotic prophylaxis in neurosurgery. A prospective, randomized, controlled study on cefotiam

In this prospective, randomized and controlled study the effect of cefotiam for the prevention of wound infections following trepanations was investigated. The main interest was centered on the rate of post-operative bone flap infections requiring operative revision. Administration of cefotiam was randomized for patients undergoing major craniotomies. The antibiotic was administered intravenously in a single dose of 2 g with induction of anaesthesia. Only clean or clean contaminated cases were included. Excluded were contaminated cases, operations with a transnasal-transsphenoidal approach, shunt-operations and patients with any other preoperative infection or antibiotic therapy. Outpatients were excluded due to difficulties in obtaining sufficient clinical information. From originally 918 consecutive patients operated on 711 fulfilled the entry criteria. With regard to age, sex, diagnosis and the site of te trepanation, control patients (n = 355) and cefotiam treated patients (n = 356) were shown to be comparable. In the various subgroups formed for different primary diagnoses, concomitant steroidal therapy and concomitant severe internal medical diseases cefotiam treated patients and controls were comparable as well. A highly significant difference for bone flap infection could be shown with 0.3% in the cefotiam group versus 5.1% in the control group (p less than 0.001). The overall rate of post-operative deep wound infections including meningitis and abscesses was also significantly (p less than 0.005) different with 3.1% in the cefotiam versus 9.0% in the control group. Thus it was concluded that a single dose of cefotiam significantly reduces post-operative deep wound infection.