Probiotic Lactobacillus rhamnosus GG (LGG) restores intestinal dysbacteriosis to alleviate upregulated inflammatory cytokines triggered by femoral diaphyseal fracture in adolescent rodent model.

OBJECTIVE: The aim of the study was to examine the influence of femoral shaft fracture on systemic inflammation and gut microbiome in adolescent rats and evaluate the anti-inflammatory effect of Lactobacillus rhamnosus GG (LGG) and its regulation of intestinal flora, as well as illustrate the mechanism by which LGG ameliorates the inflammatory response and restores intestinal dysbacteriosis. MATERIALS AND METHODS: Twenty-four male Sprague Dawley rats of 5 to 6 weeks of age were subjected to a standard femoral shaft fracture and internally fixed with LGG supplementation in advance or on the same day of injury or with saline solution for 1 week. The levels of TNF-α, IL-6, IL-10, and CRP were assessed using standard protocols. Furthermore, gut microbiota composition was analyzed in the fecal samples using 16S rDNA gene sequencing, and the relationship between gut microbiota variation and inflammatory response was tested. RESULTS: The serum indices of the above-mentioned inflammatory cytokines were significantly increased, and the gut microbial balance was significantly disturbed in adolescent rats by diaphyseal fractures of the femur and surgery. Moreover, L. rhamnosus strains manipulated the gut microbiota by decreasing the relative abundance of Proteobacteria and increasing that of Firmicutes, Actinobacteria and Bacteroidetes, which in turn increased the levels of IL-10 and alleviated the levels of IL-6, CRP, and TNF-α. CONCLUSIONS: LGG exhibited anti-inflammatory effects by alleviating the inflammatory response and regulating the gut microbiota in adolescent rats who underwent skeletal fracture and surgery. Our results suggested that the L. rhamnosus strains could be considered as an alternative dietary supplement for the prevention or treatment of skeletal injury and its associated complications.

Akkermansia muciniphila promotes type H vessel formation and bone fracture healing by reducing gut permeability and inflammation.

Improving revascularization is one of the major measures in fracture treatment. Moderate local inflammation triggers angiogenesis, whereas systemic inflammation hampers angiogenesis. Previous studies showed that Akkermansia muciniphila, a gut probiotic, ameliorates systemic inflammation by tightening the intestinal barrier. In this study, fractured mice intragastrically administrated with A. muciniphila were found to display better fracture healing than mice treated with vehicle. Notably, more preosteclasts positive for platelet-derived growth factor-BB (PDGF-BB) were induced by A. muciniphila at 2 weeks post fracture, coinciding with increased formation of type H vessels, a specific vessel subtype that couples angiogenesis and osteogenesis, and can be stimulated by PDGF-BB. Moreover, A. muciniphila treatment significantly reduced gut permeability and inflammation at the early stage. Dextran sulfate sodium (DSS) was used to disrupt the gut barrier to determine its role in fracture healing and whether A. muciniphila still can stimulate bone fracture healing. As expected, A. muciniphila evidently improved gut barrier, reduced inflammation and restored the impaired bone healing and angiogenesis in DSS-treated mice. Our results suggest that A. muciniphila reduces intestinal permeability and alleviates inflammation, which probably induces more PDGF-BB+ preosteoclasts and type H vessel formation in callus, thereby promoting fracture healing. This study provides the evidence for the involvement of type H vessels in fracture healing and suggests the potential of A. muciniphila as a promising strategy for bone healing.This article has an associated First Person interview with the first author of the paper.

Paediatric infected femoral nonunion; mid-term results of a rare problem with a single-stage treatment and up to eleven and half years follow-up.

PURPOSE: Nonunion of femur fractures is a devastating disabling complication which is rare in children. The purpose of this study was to report the outcomes of treating infected femur nonunions in children by the Ilizarov fixator in one stage. PATIENTS AND METHODS: The study included 13 patients with unilateral infected nonunion of the femur with an average age of 9.1 years. The nonunion duration averaged 10.69 months. Ten cases were draining nonunions, and three patients had quiescent sinuses. Associated problems include shortening in all cases (mean 3.5 cm), joint stiffness (9 cases), and angular deformity (7 cases). The quiescent cases were treated by bloodless monofocal compression-distraction. Four draining cases were treated by debridement and compression with relengthening through nonunion site. The remaining six cases were treated by bifocal technique. RESULTS: The mean follow-up duration was 60.15 months. External fixation period averaged 5.3 months. Successful union was achieved in all patients. Recurrences of infection occurred in two cases including one with refracture and another one with late pathological fracture. Other complications included pin tract infections, one delayed union, two residual angular deformities, and 6 cm residual shortening in one patient. ASAMI bone results were excellent (8 patients), good (3 patients), fair (one patient), and poor (one patient). The functional results were excellent (9 cases), good (3cases), and fair (one case). CONCLUSIONS: The Ilizarov method provided a viable treatment option for treating paediatric infected femur nonunions in single stage of management with infection control in most cases and satisfactory outcomes.

High prevalence of bacteria in clinically aseptic non-unions of the tibia and the femur in tissue biopsies.

PURPOSE: There are several hints that bacterial colonization might be an often overseen cause of non-union. Modern procedures like PCR have been reported to diagnose bacterial colonization with a high degree of accuracy. While PCR is not ubiquitously available, we hypothesize that biopsies from the non-union site are comparable to PCR results reported in the literature. METHODS: Retrospective analysis of microbiological results of biopsies from non-unions (femoral or tibial, history of revision surgery, and/or open fracture) with stable osteosynthesis, no clinical signs of local infection were analysed. CRP and leucocyte count were taken on admission. Multiple tissue samples (soft tissue and bone) were from the non-union (1-4 cm incision). Samples were cultivated for 2 weeks and tested following EUCAST protocols using VITEK® 2. RESULTS: 11 tibia- and 7 femur non-union (44 ± 23.9 years), 11 open fractures (1 I°, 6 II°, 4 III° Gustillo Anderson), 0-5 revisions, and 4.1 (± 1.8) tissue samples were taken 8.5 (± 1.7) months after trauma. Cultures were positive in 8/18 (44,4%) (3/18 Propionibacterium acnes, 1/18 S. capitis, and 4/18 S. epidermidis). There was neither a correlation between number of biopsies taken and positive culture results (Pearson R: - 0.0503, R2 0.0025), nor between positive culture results and leucocytes counts (Pearson R: - 0.0245, R2 0.0006) or CRP concentration (Pearson R: 0.2823, R2 0.0797). CONCLUSION: The results confirm that the presence of bacteria in cases with no clinical signs of infection is a relevant issue. The prevalence of bacteria reported here is comparable that reported from cohorts tested with PCR or sonication. In most cases, there was only one positive biopsy, raising the question whether a contamination has been detected. Thus, to better understand the problem, it is necessary to gather more knowledge regarding the sensitivities and specificities of the different diagnostic procedures.

Does the induced membrane have antibacterial properties? An experimental rat model of a chronic infected nonunion.

INTRODUCTION: The Masquelet procedure proved its efficiency in treating infected nonunion filling bony gaps up to 25 cm. Yet the use of local antibiotics is still questionable in the daily practice with lack of evidence regarding its usefulness in controlling infection. An experimental rat model is put in place to study the antibacterial properties of the induced membrane produced during the first stage of Masquelet. METHOD: Twenty-three-month-old wistar male rats are inoculated with a 0.5 mL solution of 10^8 CFU/mL MRSA over a critical fracture done on the right femur. Six weeks later, remaining 11 rats exhibiting signs of a chronic infection with a sinus tract and oozing pus along with radiological nonunion are used for a first stage Masquelet procedure. They are randomly divided into two groups with six rats having no local antibiotic in the cement mixture and five rats having 3 g of vancomycin mixed with gentamycin loaded cement. Six weeks later (twelve weeks from baseline), all eleven rats are euthanized and blood samples for C-reactive protein are withdrawn. The induced membrane is identified and resected along with bone fragments and sent for cultures and pathology. RESULTS: MRSA is isolated in the cultures of all six rats in the first group where no local antibiotic was added. Altered polymorphonuclears with abscess and pus are noted on four of six pathology samples. However in the second group where local antibiotics were added, three out of five rats exhibited eradication of MRSA (p = 0.034) and all samples did not exhibit clear infection signs on pathology. A pyo-epithelioid over a foreign body reaction is seen predominantly in this group demonstrating a regenerative process. DISCUSSION: The induced membrane does not have antimicrobial properties capable of overcoming an infected nonunion on its own. When local antibiotics were added during the first stage of the Masquelet procedure, new bone formation occurred indicating the need to control an infection in order for bone union to occur. CONCLUSION: Local antibiotics use in adjunction to extensive debridement is advisable during the first stage of a Masquelet procedure for an infected nonunion.

Acute shortening versus bone transport for the treatment of infected femur non-unions with bone defects.

BACKGROUND: The bone transport technique has been a well-known method in the treatment of osteomyelitis of the long bones with large segmental bone defects. However, one of the major drawbacks with this traditional technique is the long-lasting consolidation period, which may entail infectious and non-infectious complications. To overcome this drawback, several techniques were developed, one of which is acute shortening and re-lengthening. The aims of this study were: 1) to present our experience with a new modified technique of acute shortening and re-lengthening using a monolateral external fixator combined with a retrograde intramedullary nail, and 2) to compare its results with the classic Ilizarov bone transport method in the management of infected non-unions of the distal femur with bone loss. METHODS: This retrospective study compared these two techniques. 17 patients were treated using our modified technique of acute shortening and re-lengthening (Group A); 15 patients were treated using segmental bone transport (Group B). The average follow-up was 66 months (range: 24-180) in Group A and 70 months (range: 24-240) in Group B. The mean bone loss was 5.5 cm (range: 3-10) in Group A and 5.9 cm (range: 3-10) in Group B. The primary outcome of the present study was to compare the external fixator time (EFT) and external fixation index (EFI) between the two groups. The bone and functional status were also assessed. RESULTS: The mean EFI was lower in Group A (mean: 31.8 days/cm; range: 24-50) than in Group B (mean 48.7 days/cm; range: 40-100) (p = 0.02). The mean EFT was shorter in Group A (mean: 120 days; range: 100-150) than in Group B (mean: 290 days; range: 100-400) (p = 0.0003). With respect to the bone and functional results, no difference was observed. CONCLUSIONS: Although both techniques could be employed safely in the treatment of infected non-union of the distal femur with size defects ranging between 3 cm and 10 cm, our modified technique of acute shortening and re-lengthening may confer greater patient satisfaction because of shorter EFI.

The AMANDUS Project-Advanced Microperfusion Assessed Non-Union Diagnostics With Contrast-Enhanced Ultrasound (CEUS) for the Detection of Infected Lower Extremity Non-Unions.

The pre-operative determination of infection plays a decisive role in non-union treatment. This study investigated in a large cohort the diagnostic potential of contrast-enhanced ultrasound (CEUS) as stand-alone method for the differentiation between aseptic and infected non-unions. Of 109 patients with lower extremity non-unions (tibia n = 78, femur n = 31) osseous perfusion with CEUS was prospectively assessed before revision surgery. The perfusion was quantified via time-intensity curves and peak enhancement (PE) (arbitrary unit [au]). Significant perfusion differences between aseptic and infected non-unions were evident (PE, p < 0.001). The sensitivity and specificity for the detection of infected tibial and femoral non-unions could be determined with 85.1% and 88.7% (cutoff PE: 81.2 au). CEUS illustrates tibial and femoral non-union perfusion in real time and discriminates reliably between aseptic and infected non-unions. Consequently, when CEUS is integrated into the diagnostic routine algorithm, non-union revision surgery can be planned more accurately as a single or multistep procedure.

Effect of antibiotic infused calcium sulfate/hydroxyapatite (CAS/HA) insets on implant-associated osteitis in a femur fracture model in mice.

Cerament (Bonesupport Holding, Lund, Sweden) is a bioresorbable synthetic bone substitute consisting of calcium sulfate and hydroxyapatite which is successfully used as a bone graft in bone defects or in delayed and non-unions after fractures. Besides, calcium sulfate/ hydroxyapatite (CAS/HA) could have, attributed to its composition and osteoinductive properties, have great importance in the treatment of bone infections with critical size defects (CSD). Aim of the study was to evaluate the effects of antibiotic infused CAS/HA on inflammation and bone healing in an implant-associated osteitis mice model. In a standardized murine model, the left femur of 72 BALB/c mice were osteotomized, generating a CSD (2,5 mm) with stabilization through a 6-hole titanium locking plate. Osteitis has been induced through inoculation of Staphylococcus aureus (SA) into the fracture gap. To analyze the effect of CAS/HA, following groups were generated with either CAS/HA, CAS/HA with gentamycin (CAS/ HA-G) or CAS/HA with vancomycin (CAS/HA-V) insets placed into the osteotomy. Debridément and lavages were progressed on day 7 and 42 to determine the local bacterial growth and the immune reaction. Fracture healing was quantified on day 7 and 42 by x-ray and bone healing markers from blood samples. Progression of infection was assessed by estimation of colony-forming units (CFU) and immune response was analyzed by determination of Interleukin (IL)- 6 and polymorphonuclear neutrophils (PMN) in lavage samples. Osteitis induced higher IL-6 and PMN-levels in the lavage samples on day 7. Both parameters showed a reduction in all groups on day 42. CAS/HA-V revealed a significant reduction of CFU and PMNs in lavage samples on day 42. A positive effect on bone healing could only be shown in non-infected mice. Whereas, application of mere CAS/HA in infected mice did show tendencies of bone destruction and lysis, independent of impregnation with antibiotics or not. Thus, application of CAS/HA in acute implant-associated infections is not recommended. In non-infectious environments or after infect-convalescence CAS/HA could albeit serve as a suggestive tool in trauma and orthopedic surgery.

Antibiotic coated hinged threaded rods in the treatment of infected nonunions and intramedullary long bone infections.

INTRODUCTION: Local delivery of high dose antibiotics in the form of antibiotic impregnated polymethyl methacrylate (PMMA) cement beads or coated rods is commonly used in the management of long bone infections. The downsides of antibiotic cement beads for intramedullary long bone infections are associated with difficulty in removal from the medullary canal, bead breakage, and lack of stability. Antibiotic cement-coated smooth flexible guide wires, rods and nails can have complications such as delamination or debonding of the cement. In addition, the current techniques for cement rod insertion have a risk of iatrogenic joint contamination. To improve upon this technique and decrease potential complications, we propose the use of an antibiotic cement-coated hinged threaded rod as a temporary intramedullary spacer. This technique utilizes both an antegrade and retrograde insertion of the threaded rod into the medullary canal through the bony defect site with connection at the hinge to treat intramedullary long bone infections and infected nonunions. MATERIAL AND METHODS: A total of 40 patients were included in the study. The details in making the cement rod were well documented. The shape of cement rod and the integrity of the cement at the time of rod insertion and rod removal were compared to identify any cement debonding or delamination. Potential postoperative complications including iatrogenic joint infection, displacement or breakage of the threaded cement rods, and fracture displacement were all carefully documented. The preliminary biological effect of the initial debridement and antibiotic cement rod placement was determined using the negative conversion rate of intraoperative cultures. RESULTS: A single antibiotic coated threaded rod was inserted in 18 cases. Two separate antibiotic coated threaded rods were inserted and connected via hinge in 22 cases. There were zero cases of rod breakage and no secondary loss of reduction from antibiotic rod placement to the definitive staged operation. There were zero iatrogenic joint infections. There were zero cases of cement debonding or delamination from the rod. The conversion rate to a negative culture after initial debridement and antibiotic rod placement was 85% (34/40 cases). CONCLUSIONS: The use of an antibiotic coated cement threaded rod with a hinge as an intramedullary spacer provides the benefits of local antibiotic delivery, offers improved construct stability, makes implant removal easier without delamination of the cement mantle, and utilizes the versatility of a hinge to prevent violation of native joints when treating infected nonunions and intramedullary long bone infections.

CSA-90 Promotes Bone Formation and Mitigates Methicillin-resistant Staphylococcus aureus Infection in a Rat Open Fracture Model.

BACKGROUND: Infection of open fractures remains a significant cause of morbidity and mortality to patients worldwide. Early administration of prophylactic antibiotics is known to improve outcomes; however, increasing concern regarding antimicrobial resistance makes finding new compounds for use in such cases a pressing area for further research. CSA-90, a synthetic peptidomimetic compound, has previously demonstrated promising antimicrobial action against Staphylococcus aureus in rat open fractures. However, its efficacy against antibiotic-resistant microorganisms, its potential as a therapeutic agent in addition to its prophylactic effects, and its proosteogenic properties all require further investigation. QUESTIONS/PURPOSES: (1) Does prophylactic treatment with CSA-90 reduce infection rates in a rat open fracture model inoculated with S aureus, methicillin-resistant S aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis (MRSE) as measured by survival, radiographic union, and deep tissue swab cultures? (2) Does CSA-90 reduce infection rates when administered later in the management of an open fracture as measured by survival, radiographic union, and deep tissue swab cultures? (3) Does CSA-90 demonstrate a synergistic proosteogenic effect with bone morphogenetic protein 2 (BMP-2) in a noninfected rat ectopic bone formation assay as assessed by micro-CT bone volume measurement? (4) Can CSA-90 elute and retain its antimicrobial efficacy in vitro when delivered using clinically relevant agents measured using a Kirby-Bauer disc diffusion assay? METHODS: All in vivo studies were approved by the local animal ethics committee. In the open fracture studies, 12-week-old male Wistar rats underwent open midshaft femoral fractures stabilized with a 1.1-mm Kirschner wire and 10 µg BMP-2 ± 500 µg CSA-90 was applied to the fracture site using a collagen sponge along with 1 x 10 colony-forming units of bacteria (S aureus/MRSA/MRSE; n = 10 per group). In the delayed treatment study, débridement and treatment with 500 µg CSA-90 were performed at Day 1 and Day 5 after injury and bacterial insult (S aureus). All animals were reviewed daily for signs of local infection and/or sepsis. An independent, blinded veterinarian reviewed twice-weekly radiographs, and rats showing osteolysis and/or declining overall health were culled at his instruction. The primary outcome of both fracture studies was fracture infection, incorporating survival, radiographic union, and deep tissue swab cultures. For the ectopic bone formation assay, 0 to 10 µg BMP-2 and 0 to 500 µg CSA-90 were delivered on a collagen sponge into bilateral quadriceps muscle pouches of 8-week-old rats (n = 10 per group). Micro-CT quantification of bone volume and descriptive histologic analysis were performed for all in vivo studies. Modified Kirby-Bauer disc diffusion assays were used to quantify antimicrobial activity in vitro using four different delivery methods, including bone cement. RESULTS: Infection was observed in none of the MRSA inoculated open fractures treated with CSA-90 with 10 of 10 deep tissue swab cultures negative at the time of cull. Median survival was 43 days (range, 11-43 days) in the treated group versus 11 days (range, 8-11 days) in the untreated MRSA inoculated group (p < 0.001). However, delayed débridement and treatment of open fractures with CSA-90 at either Day 1 or Day 5 did not prevent infection, resulting in early culls by Day 21 with positive swab cultures (10 of 10 for each time point). Maximal ectopic bone formation was achieved with 500 µg CSA-90 and 10 µg BMP-2 (mean volume, 9.58 mm; SD, 7.83), creating larger bone nodules than formed with 250 µg CSA-90 and 10 µg BMP-2 (mean volume, 1.7 mm; SD, 1.07; p < 0.001). Disc diffusion assays showed that CSA-90 could successfully elute from four potential delivery agents including calcium sulphate (mean zone of inhibition, 11.35 mm; SD, 0.957) and bone cement (mean, 4.67 mm; SD, 0.516). CONCLUSIONS: CSA-90 shows antimicrobial action against antibiotic-resistant Staphylococcal strains in vitro and in an in vivo model of open fracture infection. CLINICAL RELEVANCE: The antimicrobial properties of CSA-90 combined with further evidence of its proosteogenic potential make it a promising compound to develop further for orthopaedic applications.

Influence of fracture stability on Staphylococcus epidermidis and Staphylococcus aureus infection in a murine femoral fracture model.

Fracture-related infection (FRI) is a major complication in surgically fixed fractures. Instability of the fracture after fixation is considered a risk factor for infection; however, few experimental data are available confirming this belief. To study whether stable fractures led to higher infection clearance, mouse femoral osteotomies were fixed with either stable or unstable fixation and the surgical site was contaminated with either Staphylococcus epidermidis (S. epidermidis)or Staphylococcus aureus (S. aureus)clinical isolates. Infection progression was assessed at different time points by quantitative bacteriology, total cell counts in spleen and lymph node and histological analysis. Operated, non-inoculated mice were used as controls. Two inbred mouse strains (C57BL/6 and BALB/c) were included in the study to determine the influence of different host background in the outcome. Stable fixation allowed a higher proportion of C57BL/6 mice to clear S. epidermidis inoculation in comparison to unstable fixation. No difference associated with fixation type was observed for BALB/c mice. Inoculation with S. aureus resulted in a more severe infection for both stable and unstable fractures in both mouse strains; however, significant osteolysis around the screws rendered the stable group functionally unstable. Our results suggested that fracture stability could have an influence on S. epidermidis infection, although host factors also played a role. No differences were observed when using S. aureus, due to a more severe infection, leading to osteolysis and loss of stability in both groups. Further studies are required in order to address the biological features underlying the differences observed.

Eubacterium moniliforme Bacteremia in a Woman with Fractures.

E. moniliforme infections in humans have not been reported previously. We firstly described blood-stream infections caused by E. moniliforme in an elder woman with fractures of her left thigh. This study highlights the strategies to detect this anaerobic pathogen and the importance of investigating its molecular epidemiology in humans.

Bone penetrance of locally administered vancomycin powder in a rat femur fracture model.

INTRODUCTION: Locally delivered, crystalline vancomycin has been suggested as a potential prophylactic measure against the development of deep and superficial surgical site infection. Clinical expectations regarding the duration and peak of drug concentration in local tissues following administration are unknown. Our goal was to develop concentration vs time curves for locally administered vancomycin powder in a high-energy, open femur fracture rat model in local tissues and to compare that data to two well performed similar, systemic administration studies. METHODS: After approval for animal research, 24 adult Sprague-Dawley rats sustained closed, midshaft femoral fracture under anesthesia. Fractures were caused via blunt guillotine with 750g metal rod dropped 50cm. Injured hindlimbs were surgically opened at fracture to simulate open injury and stabilized using 0.054 Kirschner wires. Vancomycin powder was administered using weight-based protocol (goal: 25mg/kg). Rats were sacrificed in groups of 4 at 4, 8, 24, 48, 72, 96h. Samples harvested included rat-tail venous blood prior to sacrifice, and femoral bone and anterior thigh soft-tissue were harvested post-mortem. High Performance Liquid Chromatography (HPLC) was performed on all samples. RESULTS: Concentration vs. time curves demonstrated that the surrounding soft-tissues demonstrated highest maximum concentration (1.5mg vancomycin/g muscle). Bone reached maximum average of 199µg vancomycin/g femur: approximately 13% of maximal soft-tissue absorption. Plasma reached maximum concentration of 1.8µg/mL plasma. All peaks at t=4h. Within 48h, average muscle vancomycin concentration dropped to 3µg/g muscle (0.2% maximum muscle concentration) and the average bone concentration dropped to 1.9µg/g femur (0.9% maximum bone concentration). Vancomycin was undetectable on all samples at 96h. Comparison to classical animal studies suggest local delivery to bone exceeds that of IV dosing for approximately 48h and may peak near concentrations of 102 multiples. CONCLUSIONS: Locally administered vancomycin provides drug delivery in excess of IV dosing for approximately 48h after intervention. Exponential decay demonstrates rapid removal of drug to near undetectable levels in bone, plasma, and local soft tissue thereafter in a rat model. Local delivery may generate concentrations exceeding that achievable by steady state systemic dosing for 48h.

Effects of Local Antibiotic Delivery from Porous Space Maintainers on Infection Clearance and Induction of an Osteogenic Membrane in an Infected Bone Defect.

Reconstruction of large bone defects can be complicated by the presence of both infection and local antibiotic administration. This can be addressed through a two-stage reconstructive approach, called the Masquelet technique, that involves the generation of an induced osteogenic membrane over a temporary poly(methyl methacrylate) (PMMA) space maintainer, followed by definitive reconstruction after the induced membrane is formed. Given that infection and antibiotic delivery each have independent effects on local tissue response, the objective of this study is to evaluate the interaction between local clindamycin release and bacterial contamination with regards to infection prevention and the restoration of pro-osteogenic gene expression in the induced membrane. Porous PMMA space maintainers with or without clindamycin were implanted in an 8 mm rat femoral defect model with or without Staphylococcus aureus inoculation for 28 days in a full-factorial study design (four groups, n = 8/group). Culture results demonstrated that 8/8 animals in the inoculated/no antibiotic group were infected at 4 weeks, which was significantly reduced to 1/8 animals in the inoculated/antibiotic group. Quantitative polymerase chain reaction analysis demonstrated that clindamycin treatment restores inflammatory cytokine and growth factor expression to the same levels as the no inoculation/no antibiotic group, demonstrating that clindamycin can ameliorate the negative effects of bacterial inoculation and does not itself negatively impact the expression of important cytokines. Main effect analysis shows that bacterial inoculation and clindamycin treatment have independent and interacting effects on the gene expression profile of the induced membrane, further highlighting that antibiotics play an important role in the regeneration of infected defects apart from their antimicrobial properties.

Systemic and Local Administration of Antimicrobial and Cell Therapies to Prevent Methicillin-Resistant Staphylococcus epidermidis-Induced Femoral Nonunions in a Rat Model.

S. epidermidis is responsible for biofilm-related nonunions. This study compares the response to S. epidermidis-infected fractures in rats systemically or locally injected with vancomycin or bone marrow mesenchymal stem cells (BMSCs) in preventing the nonunion establishment. The 50% of rats receiving BMSCs intravenously (s-rBMSCs) died after treatment. A higher cytokine trend was measured in BMSCs locally injected rats (l-rBMSCs) at day 3 and in vancomycin systemically injected rats (l-VANC) at day 7 compared to the other groups. At day 14, the highest cytokine values were measured in l-VANC and in l-rBMSCs for IL-10. µCT showed a good bony bridging in s-VANC and excellent both in l-VANC and in l-rBMSCs. The bacterial growth was lower in s-VANC and l-VANC than in l-rBMSCs. Histology demonstrated the presence of new woven bone in s-VANC and a more mature bony bridging was found in l-VANC. The l-rBMSCs showed a poor bony bridging of fibrovascular tissue. Our results could suggest the synergic use of systemic and local injection of vancomycin as an effective treatment to prevent septic nonunions. This study cannot sustain the systemic injection of BMSCs due to high risks, while a deeper insight into local BMSCs immunomodulatory effects is mandatory before developing cell therapies in clinics.

Time-Dependent Effectiveness of Locally Applied Vancomycin Powder in a Contaminated Traumatic Orthopaedic Wound Model.

OBJECTIVES: To evaluate the effectiveness of locally applied vancomycin powder at different times postinfection in a contaminated traumatic animal model. METHODS: This study used an established segmental defect rat femur model contaminated with Staphylococcus aureus UAMS-1 followed by treatment at 6 or 24 hours postinfection. Three treatments were evaluated: debridement and irrigation alone (control group) or in combination with either vancomycin powder or vancomycin-impregnated poly(methyl methacrylate) beads. Serum vancomycin levels were determined at scheduled time points over 14 days; bone, surrounding muscle, and implants were harvested for bacterial and inflammatory analyses. RESULTS: Locally applied vancomycin powder and impregnated beads significantly reduced bacteria both within the bone and implant when treatment was performed at 6 hours. Delaying treatment to 24 hours significantly reduced the therapeutic efficacy of locally applied vancomycin of both groups. Serum vancomycin levels were detectable in all animals treated with vancomycin powder at 24 hours, but absorption was negligible from beads. At 14 days, vancomycin was detectable in the surrounding musculature of all animals and in serum of 20% of animals treated with vancomycin powder. CONCLUSIONS: This study suggests that vancomycin powder is a promising adjunctive therapy for preventing infection in traumatic wounds when treatment is performed early. This time-dependent effectiveness of vancomycin powder is similar to that observed with systemic and other local delivery adjuncts, which is likely attributable to biofilm formation after contamination, conferring intrinsic recalcitrance to antimicrobials.

Increased infection risk after hip hemiarthroplasty in institutionalized patients with proximal femur fracture.

In patients undergoing hip hemiarthroplasty (HHA) secondary to proximal femur fracture, acute periprosthetic joint infection (PJI) is one of the most important complications. We have detected an increased risk of PJI in chronic institutionalized patients (CIPs), and a higher number of early postoperative infections are caused by Gram-negative bacteria (GNB), not covered by the current prophylaxis (cefazolin in noninstitutionalized patients (NIPs) and cotrimoxazole in CIPs). We sought to compare infection characteristics between NIPs and CIPs, analyzing predisposing factors, causative pathogens, and antibiotic prophylaxis-related microbiological characteristics. We performed a retrospective review of our prospective institutional database to identify all patients consecutively admitted for HHA to treat proximal femur fracture at our centre between 2011 and 2013. PJI was diagnosed in 21 of 381 (5.51%) patients, with 10 of 105 (9.52%) in the CIP group and 11 of 276 (3.99%) in the NIP group, and statistical significance was achieved. GNB accounted for PJI in 14 (66.67%) patients. We detected a single case of methicillin-resistant Staphylococcus aureus (MRSA) infection in the NIP group. We confirm a higher risk of acute PJI among institutionalized patients, commonly caused by Gram-negative microorganisms, which are not covered by the current prophylaxis. New prophylactic strategies should be investigated in order to reduce this problem.

Indolent infection in nonunion of the distal femur.

In the treatment of nonunions of the distal femur, infection should be excluded. However, it is difficult to determine whether the nonunion is infected or not with negative history and signs of infection. The purpose of this study was to investigate indolent infection as a cause of presumptive aseptic distal femur nonunion. All presumptive aseptic distal femur nonunions treated from 1998 to 2008 were retrospectively reviewed. Any patient with suspected of having an infection clinically was excluded. Multiple tissue cultures were performed at the nonunion site. The main outcomes were to analyze the rate of positive cultures in presumptive aseptic distal femur nonunion and to compare the rate of secondary surgery in positive and negative culture groups. Of the 22 patients, 3 (13.6%) had positive culture results. The organisms cultured were Staphylococcus aureus, Staphylococcus epidermidis, and Enterobacter cloacae. The overall rate of infection was 9.1% (2/22), and one patient underwent a secondary procedure. In the open fracture group, 2 of 10 patients (20%) had positive cultures; all developed infection. In the closed fracture group, 1 of 12 patients (8.3%) had positive culture results, but Infection did not occur in the patient with a 3-week intravenous antibiotic treatment. The postoperative infection rate was 67% (2/3) in patients with positive intraoperative cultures, while 0% (0/18) in the group with negative intraoperative cultures (p<0.001). The presence of indolent infection can be verified in patients with presumptive aseptic nonunion of distal femoral fractures by obtaining intraoperative biopsy tissue cultures. Positive intraoperative culture results were related with postoperative infection.

Local bismuth thiols potentiate antibiotics and reduce infection in a contaminated open fracture model.

OBJECTIVE: This proof-of-concept study tested the hypothesis that combining bismuth thiols (BTs) with systemic antibiotics will more effectively reduce infection in an animal model of contaminated open fracture than systemic antibiotics alone. METHODS: An implant-stabilized segmental defect rat model was contaminated with Staphylococcus aureus and then treated with surgical debridement 6 hours after injury and 3 days of systemic cefazolin. A single dose of BTs suspended in a hydrogel was administered to the wound immediately after debridement. After 14 days, the bone and implant were harvested for microbiological analysis. RESULTS: A single local dose of 0.05 mg of BT (MB-8-2), when combined with systemically administered cefazolin, decreased infection, without any noticeable local or systemic toxicity, from 60% to 10% (P = 0.002), with only 0.02% of the recovered bacteria quantity of the cefazolin-only group (P < 0.001). Higher doses were less effective and caused side-effects. CONCLUSIONS: BTs administered locally to infected open fracture wounds at an appropriate dose potentiate the effect of systemically administered antibiotics and reduce infection rate and bacteria quantity associated with bone and orthopaedic implants. Local delivery of BTs is a promising strategy for increasing the efficacy of systemically administered antibiotics in preventing and treating infections of open fractures.

Bacterial translocation induces proinflammatory responses and is associated with early death in experimental severe injury.

OBJECTIVE: An experimental model of severe injury with great lethality was studied to define the impact of bacterial translocation on survival and on inflammatory response. METHODS: Forty-one rabbits were divided into two groups: A, femur myotomy; and B, myotomy and fracture of the femoral bone. Vital signs and survival were recorded. Serum circulating endotoxins (lipopolysaccharides; LPS) were determined and tissue cultures were performed at necropsy. A subgroup of animals was sacrificed at 48 h post injury; LPS was determined in abdominal aorta and portal vein, apoptosis of spleen cells was assessed by flow cytometry, and ex vivo production of tumor necrosis factor alpha by splenocytes was measured. RESULTS: Tissue bacterial burden was increased in animals that died early (i.e., within 48 h after injury) versus rabbits that died later. Portal vein LPS at 48 h was increased in group B compared with group A, whereas circulating LPS did not differ. No difference in apoptosis of either lymphocytes or macrophages of the spleen was found in group B compared with group A. Following stimulation with LPS or phytohemagglutinin, tumor necrosis factor α production by splenocytes of group B was greater than that of group A. CONCLUSIONS: Bacterial translocation primes enhanced proinflammatory responses and it is associated with early death in severe trauma.