Staphylococcus aureus surface attachment selectively influences tolerance against charged antibiotics

The threat of infection during implant placement surgery remains a considerable burden for millions of patients worldwide. To combat this threat, clinicians employ a range of anti-infective strategies and practices. One of the most common interventions is the use of prophylactic antibiotic treatment during implant placement surgery. However, these practices can be detrimental by promoting the resilience of biofilm-forming bacteria and enabling them to persist throughout treatment and re-emerge later, causing a life-threatening infection. Thus, it is of the utmost importance to elucidate the events occurring during the initial stages of bacterial surface attachment and determine whether any biological processes may be targeted to improve surgical outcomes. Using gene expression analysis, we identified a cellular mechanism of S. aureus which modifies its cell surface charge following attachment to a medical grade titanium surface. We determined the upregulation of two systems involved in the d-alanylation of teichoic acids and the lysylation of phosphatidylglycerol. We supported these molecular findings by utilizing synchrotron-sourced attenuated total reflection Fourier-transform infrared microspectroscopy to analyze the biomolecular properties of the S. aureus cell surface following attachment. As a direct consequence, S. aureus quickly becomes substantially more tolerant to the positively charged vancomycin, but not the negatively charged cefazolin. The present study can assist clinicians in rationally selecting the most potent antibiotic in prophylaxis treatments. Furthermore, it highlights a cellular process that could potentially be targeted by novel technologies and strategies to improve the outcome of antibiotic prophylaxis during implant placement surgery. STATEMENT OF SIGNIFICANCE: The antibiotic tolerance of bacteria in biofilm is a well-established phenomenon. However, the physiological adaptations employed by Staphylococcus aureus to increase its antibiotic tolerance during the early stages of surface attachment are poorly understood. Using multiple techniques, including gene expression analysis and synchrotron-sourced Fourier-transform infrared microspectroscopy, we generated insights into the physiological response of S. aureus following attachment to a medical grade titanium surface. We showed that this phenotypic transition enables S. aureus to better tolerate the positively charged vancomycin, but not the negatively charged cefazolin. These findings shed light on the antibiotic tolerance mechanisms employed by S. aureus to survive prophylactically administered antibiotics and can help clinicians to protect patients from infections.

The efficacy and safety of intra-articular dual-acting antibacterial agent (TNP-2092) for implant infection-associated MRSA

Owing to the presence of microbial biofilm on the implant, the eradication of biofilm-associated infections poses a challenge for antibiotic therapies. The study aimed to investigate the efficacy and safety of the novel antibiotic agent TNP-2092 in the context of implant infections. In vivo, the periprosthetic joint infection (PJI) rats treated with antibiotics showed an increase in body weight and decrease in swelling, temperature, and width of knee, versus control group. Meanwhile, inflammatory markers in synovium and serum were decreased in TNP-2092 group, consistent with the pathological results. Moreover, TNP-2092 was effective in eliminating bacteria and disruption biofilm formation, and further alleviated the abnormal bone absorption and reactive bone changes around the prosthesis. In conclusion, intra-articular injection of TNP-2092 is effective and safety in treating knee PJI in rat. The study provides a foundation for the future utilization of TNP-2092 in the management of implant-related infections.

Multifunctional nanocoating for enhanced titanium implant osseointegration

Preventing bacterial infection and promoting osseointegration are essential for the long-term success of titanium (Ti) implants. In this study, we developed a multifunctional nanocoating on Ti mini-implants to simultaneously address these challenges. The nanocoating consists of self-assembled antimicrobial peptides GL13K and silver nanoparticles, referred to as Ag-GL. Our results showed that the Ag-GL coating did not alter the surface morphology of the mini-implants. Ag-GL coated mini-implants demonstrated a two orders of magnitude reduction in colony-forming unit (CFU) values compared to the noncoated eTi group, resulting in minimal inflammation and no apparent bone destruction in a bacterial infection in vivo model. When evaluating osseointegration properties, micro-CT analysis, histomorphometric analysis, and pull-out tests revealed that the Ag-GL coating significantly enhanced osseointegration and promoted new bone formation in vivo.

A case of mediastinal abscess and infected aortic aneurysm caused by dissemination of Mycobacterium abscessus subsp. massiliense pulmonary disease

An 81-year-old man was admitted to our hospital because of fever and malaise that had persisted for 3 months. The patient had undergone two aortic valve replacements, 10 and 5 years previously, because of aortic valve regurgitation and infectious endocarditis. He also had had asymptomatic Mycobacterium abscessus complex (MABC) pulmonary disease for the two previous years. Contrast-enhanced computed tomography showed a mediastinal abscess and an ascending aortic aneurysm. Mycobacterium abscessus subsp. massiliense was cultured from his blood, suggesting the aortic aneurysm was secondary to infection of an implanted device. After enlargement over only a few days, a leakage of contrast medium to the mediastinal abscess was found on computed tomography. The patient was diagnosed with rupture of an infectious aortic aneurysm, and emergency aortic replacement and drainage of the mediastinal abscess were successful. The patient was treated with several antibiotics, including meropenem, amikacin, and clarithromycin, and his general condition improved. Cultures from both the mediastinal abscess and a pericardial patch that was placed at the time of surgery 5 years previously revealed MABC. In our case, the infected aortic aneurysm most likely resulted from MABC pulmonary disease rather than from previous intraoperative contamination. This route of infection is rare. Physicians should be aware of the possibility of dissemination and subsequent infection of implants related to MABC pulmonary disease.

Transition metal complex laminated bioactive implant alleviates Methicillin Resistant Staphylococcus aureus virulence

Orthopedic implant infections cause a serious threat after implantation. The major source of implant infection is biofilms which are highly tolerant to antibiotics due to the presence of rigid biofilm matrix. Hence to overcome biofilm mediated implant infections, we developed a novel antibiofilm agent, palladium (II) thiazolinyl picolinamide complex (Pd(II)-E). From our study, it was found that Pd(II)-E have profound biofilm inhibition activity and also reduced various virulence factors of Methicillin resistant Staphylococcus aureus (MRSA) including slime synthesis, Phenol soluble modulin (PSM) mediated spreading, Exopolysaccharides production and staphyloxanthin synthesis. Further, Pd(II)-E was coated over the titanium plates which was confirmed using EDX (Energy Dispersive X-Ray) analysis. The Pd(II)-E coated plates were able to prevent the biofilm formation on them which was evident under a Scanning electron microscope (SEM) and several virulent genes were found to be downregulated in the biofilms on the coated titanium plates which confirmed by qPCR. From our findings, it was found that Pd(II)-E coated titanium implants would be an effective alternate approach for preventing biofilm mediated implant infections.

Are late hernia mesh complications linked to Staphylococci biofilms?

Purpose

The purpose of this study was to investigate the link between bacterial biofilms and negative outcomes of hernia repair surgery. As biofilms are known to play a role in mesh-related infections, we investigated the presence of biofilms on hernia meshes, which had to be explanted due to mesh failure without showing signs of bacterial infection.

Methods

In this retrospective observational study, 20 paraffin-embedded tissue sections from explanted groin hernia meshes were analysed. Meshes have been removed due to chronic pain, hernia recurrence or mesh shrinkage. The presence and bacterial composition of biofilms were determined. First, specimens were stained with fluorescence in situ hybridisation (FISH) probes, specific for Staphylococcus aureus and coagulase-negative staphylococci, and visualised by confocal laser scanning microscopy. Second, DNA was extracted from tissue and identified by S. aureus and S. epidermidis specific PCR.

Results

Confocal microscopy showed evidence of bacterial biofilms on meshes in 15/20 (75.0%) samples, of which 3 were positive for S. aureus, 3 for coagulase-negative staphylococci and 9 for both species. PCR analysis identified biofilms in 17/20 (85.0%) samples, of which 4 were positive for S. aureus, 4 for S. epidermidis and 9 for both species. Combined results from FISH/microscopy and PCR identified staphylococci biofilms in 19/20 (95.0%) mesh samples. Only 1 (5.0%) mesh sample was negative for bacterial biofilm by both techniques.

Conclusion

Results suggest that staphylococci biofilms may be associated with hernia repair failure. A silent, undetected biofilm infection could contribute to mesh complications, chronic pain and exacerbation of disease.

Long-term antibacterial properties of a nanostructured titanium alloy surface: An in vitro study

The demand for joint replacement and other orthopedic surgeries involving titanium implants is continuously increasing; however, 1%-2% of surgeries result in costly and devastating implant associated infections (IAIs). Pseudomonas aeruginosa and Staphylococcus aureus are two common pathogens known to colonise implants, leading to serious complications. Bioinspired surfaces with spike-like nanotopography have previously been shown to kill bacteria upon contact; however, the longer-term potential of such surfaces to prevent or delay biofilm formation is unclear. Hence, we monitored biofilm formation on control and nanostructured titanium disc surfaces over 21 days following inoculation with Pseudomonas aeruginosa and Staphylococcus aureus. We found a consistent 2-log or higher reduction in live bacteria throughout the time course for both bacteria. The biovolume on nanostructured discs was also significantly lower than control discs at all time points for both bacteria. Analysis of the biovolume revealed that for the nanostructured surface, bacteria was killed not just on the surface, but at locations above the surface. Interestingly, pockets of bacterial regrowth on top of the biomass occurred in both bacterial species, however this was more pronounced for S. aureus cultures after 21 days. We found that the nanostructured surface showed antibacterial properties throughout this longitudinal study. To our knowledge this is the first in vitro study to show reduction in the viability of bacterial colonisation on a nanostructured surface over a clinically relevant time frame, providing potential to reduce the likelihood of implant associated infections.

Zinc alloy-based bone internal fixation screw with antibacterial and anti-osteolytic properties

There is no targeted effective treatment for patients undergoing internal fixation surgery/two-stage total joint revision surgery with a high risk of postoperative infection and osteolysis, while the rate of reoperation due to infection and osteolysis remains high. In this study, we report a pioneering application of implants made of biodegradable Zn–Ag alloy with active antibacterial and anti-osteolytic properties in three classical animal models, illustrating antibacterial, anti-osteolysis, and internal fixation for fractures. The antibacterial activity of the Zn–2Ag alloy was verified in a rat femur osteomyelitis prevention model, while the anti-osteolytic properties were evaluated using a mouse cranial osteolysis model. Moreover, the Zn–2Ag based screws showed similar performance in bone fracture fixation compared to the Ti–6Al–4V counterpart. The fracture healed completely after 3 months in the rabbit femoral condyle fracture model. Furthermore, the underlying antibacterial mechanism may include inhibition of biofilm formation, autolysis-related pathways, and antibiotic resistance pathways. Osseointegration mechanisms may include inhibition of osteoclast-associated protein expression, no effect on osteogenic protein expression, and no activation of related inflammatory protein expression. The empirical findings here reveal the great potential of Zn–Ag-based alloys for degradable biomaterials in internal fixation surgery/two-stage total joint revision surgery for patients with a high risk of postoperative infection and osteolysis.

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Zn–2Ag alloy is designed for orthopedic applications.

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Zn–2Ag alloy exhibit outstanding antibacterial properties in a rat femur osteomyelitis prevention model.

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Zn–2Ag alloy exhibit outstanding anti-osteolytic properties in a mouse cranial osteolysis model.

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Zn-2Ag based screws showed reliable performance in bone fracture fixation in the rabbit femoral condyle fracture model.

Efficacy of short-term antibiotic prophylaxis in immediate two-stage breast reconstruction after mastectomy: A retrospective monocentric study

BACKGROUND

Infective complications following implant-based breast reconstruction range from 2,5 to 24% and are often associated with high morbidity and poor outcome. Many authors still employ long-term antibiotic prophylaxis even though there is no conclusive evidence on the impact on infection-rate reduction. In the present study, we report we report our single-shot short-term prophylaxis protocol for surgical site infection prevention in immediate two-stage implant breast reconstruction.

METHODS

We retrospectively compared clinical data from two groups of women undergoing immediate two-stage breast reconstruction with tissue expander. Group 1 (n = 391) was administered with long-term prophylaxis, and Group 2 (n = 89) was administered with short-term prophylaxis associated with early drains removal (21 days maximum). We evaluated risk factors for infection, clinical preoperative data, time before drain removal, and clinical feature of the diagnosed infections (early or late onset) and compared the reconstructive outcome between the two groups (infection rate, implant loss rate).

RESULTS

We did not find any statistically significant difference in the infection rate (11,51% overall) and implant loss rate (4,49% overall) between the two groups. We found a difference in the implant loss to infection ratio (46.67% in group 1 and 20% in group 2, p < 0,05) and in the time before drain removal (19 days in group 1 and 15 days in group 2, p < 0.001). We finally found an association between prolonged time before drain removal and increased infection rate (p = 0.004).

CONCLUSIONS

Short-term single-shot perioperative antibiotic prophylaxis associated with early drain removal (within 21 days postop) represents a safe approach in terms of prevention of local infective surgical complication and allows a more effective treatment of the diagnosed SSI.

Biological activity and antimicrobial property of Cu/a-C:H nanocomposites and nanolayered coatings on titanium substrates

Infection associated with titanium based implants remains the most serious problem in implant surgery hence it is important to find optimal strategies to prevent infections. In the present study, we investigated the surface properties, antibacterial activity and biocompatibility of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) film containing copper nanoparticles (CuNPs) deposited on Ti discs via a gas aggregation cluster source. Three different Cu/a-C:H coatings with approximately the same amount of embedded CuNPs with and without barrier a-C:H layer were fabricated. The obtained results revealed that different structures of the produced coatings have significantly different release rates of Cu ions from the coatings into the aqueous media. This subsequently influences the antibacterial efficiency and osteoblast cell viability of the treated coatings. Coatings with the highest number of CuNPs resulted in excellent antibacterial activity exhibiting approximately 4 log reduction of E.coli and S.aureus after 24 h incubation. The cytotoxicity study revealed that after 7 day cell seeding, even the coating with the highest Cu at.% (4 at.%) showed a cell viability of ̴90%. Consequently, the coating, formed with a properly tailored number of CuNPs and a-C:H barrier thickness offer a strong antibacterial effect without any harm to osteoblast cells.

Risk factors and outcome of patients with periprosthetic joint infection admitted to intensive care unit

INTRODUCTION

Prosthetic joint infection (PJI) is a severe complication after total joint replacement surgery. The current study analyzes the outcome and mortality of patients admitted to an intensive care unit following PJI.

METHODS

Retrospective analysis of all patients treated between 2012 and 2016 due to PJI in the surgical intensive care unit of a university hospital.

RESULTS

A total of 124 patients were included. The mean age was 75 ± 11 years. Of those 124 patients, 85 patients (68.5%) suffered a prosthetic infection of the hip, 33 patients (27.3%) of the knee, six patients (4.8%) of hip and knee. 52 patients were male (40.9%). The assessed mean Simplified Acute Physiology Score II (SAPSII) was 29.6 ± 5.9. The mortality rate was 21% (26/124). Of surviving patients, 53.1% were discharged home, 25.5% were transferred to a nursing home, and 21.4% were transferred to a geriatric rehabilitation center. Comparing survivors to non-survivors, the non-survivor group showed a higher incidence of renal replacement therapy (46.1 vs 3.0%; p < 0.01), higher SAPSII on admission (35.7 vs. 29.0; p = 0.01) and higher Charlson Comorbidity Indices (CCI) (5.5 vs. 2.82; p < 0.01). The multivariate regression identified CCI (odds ratio 1.49; p < 0.01) and renal replacement therapy (odds ratio 12.4; p < 0.01) as independent risk factors for increased mortality.

CONCLUSIONS

Admission to an intensive care unit was associated with a mortality rate of 21%. Factors associated with poor outcomes included renal replacement therapy, higher admission SAPII scores, and higher admission Charlson comorbidity index. These factors could be used for individual risk assessment on admission to the ICU.

Salvaging the infected breast implant: results of a retrospective series of 80 consecutive cases

BACKGROUND

Breast implants are widely used in reconstruction after breast cancer. Infection after implant reconstruction is a major complication, with rates ranging from 5 to 30%. This rate is less for pure cosmetic augmentation. Historically, infection of an implant mandated implant removal for sepsis control. An alternative is to attempt to salvage the infected implant. This path can be a long one, requiring surgery for washouts and prolonged antibiotic therapy. This article documents our experience of infected implant salvage over the last 13 years.

METHODS

We conducted a retrospective analysis of all patients who developed a breast implant infection between January 2005 and January 2018. All patients had both clinical signs of infection and a positive bacteriological sample. Patients were divided into two groups: upfront medical therapy (including those requiring secondary surgical salvage) and primary surgery. The salvage procedure was defined as successful when the implant was still in place three months after the initial reconstruction.

RESULTS

Eighty patients were included: 77 in the medical group and 3 in the surgical group. Overall, implant salvage was achieved in 88.8% of women (n=71). Of these, 73.8% (n=59) underwent medical treatment alone and 15% (n=12) underwent medical treatment followed by surgical management. The main causative organism was staphylococcus in 81.2%. When the infection was caused by a coagulase-negative staphylococcus, the rate of success was 98% (p<0.003).

CONCLUSIONS

This case series reports that salvage of an infected breast implant was achievable in up to 90% of women presenting with a documented infection, the majority requiring antibiotic management only. Early intervention is central to success.

Rapid diagnostics of orthopedic implant-associated infections using Unyvero ITI implant and tissue infection application is not optimal for Staphylococcus species identification

Objectives

This pilot study aimed to compare the commercial Unyvero ITI multiplex PCR application (U-ITI, Curetis GmbH) with conventional culturing concerning (a) detection of pathogens, (b) time to detection of pathogens and (c) time to and quality of antibiotic treatment recommendation in diagnostics of orthopedic implant-associated infections (OIAI).

Results

72 tissue biopsies from 15 consecutive patients with deep OIAI infections were analyzed with conventional culturing including phenotypic antibiotic susceptibility testing and the U-ITI. U-ITI showed lower sensitivity than conventional culturing concerning detection of pathogens (73% vs 93%). 4/15 patients would have been given false negative results by U-ITI, all of which were culture-positive for Staphylococcus species. Median time to detection of pathogens was 47 h and antibiotic resistance 89 h by conventional methods compared to 13.5 h with the U-ITI. The U-ITI did not detect antibiotic resistance, whereas conventional culturing showed resistance to antibiotics covered by the U-ITI panel in 2 patients. Time to detection of pathogens was improved, but the detection limit for staphylococci was unsatisfactory. Although the time to antibiotic treatment recommendation was significantly reduced, the U-ITI would have resulted in incorrect antibiotic recommendation in 2 patients. Our data do not support use of this assay in diagnostics.

A novel fixation method for panfacial fracture using an Ilizarov-type external fixator. Trauma Case Rep. 2019;22:100214. [PMID: 31294071 PMCID: PMC6595467 DOI: 10.1016/j.tcr.2019.100214]

In general, internal plate fixation is mainly performed in order to reduce multiple facial bone fractures and rarely uses an external fixator. Although it would be ideal to successfully achieve or preserve the occlusal relationship of the upper and lower jaws, it is difficult to successfully manage multiple bone fragments in order to use them to achieve internal fixation, especially when treating a severely comminuted facial fracture. In addition, it is also important to prevent the onset of severe infection after sub-periosteal dissection, due to the presence of avascular bony fragments and an internal fixation implant which thus represents a foreign body. In order to treat extensive comminuted fracture without internal plate fixation, we performed external fixation using an Ilizarov-type external fixator. The Ilizarov-type external fixator is characterized by a few circular external structures and threaded rods. This device can be modified for use in the field of orthopedic surgery to correct three-dimensional deformities caused by fragile complicated fractures and bone defects. The advantages of the Ilizarov-type external fixator for treating panfacial fractures include a low invasiveness, utility in various fracture situations, easy adjustment of threaded rods, and a low potential cost. We herein report the first case of a severe panfacial fracture that was successfully treated using an Ilizarov-type external fixator.

Biomaterial surfaces self-defensive against bacteria by contact transfer of antimicrobials

Despite extensive engineering of tissue-contacting biomedical devices to control healing, these devices remain susceptible to bacterial colonization, biofilm formation, and chronic infection. The threat of selecting for resistance genes largely precludes sustained antimicrobial elution as a wide-spread clinical solution. In response, self-defensive surfaces have been developed where antimicrobial is released only when and where there is a bacterial challenge. We explore a new self-defensive approach using anionic microgels into which small-molecule cationic antimicrobials are loaded by complexation. We identify conditions where antimicrobial remains sequestered within the microgels for periods as long as weeks. However, bacterial contact triggers release and leads to local bacterial killing. We speculate that the close proximity of bacteria alters the local thermodynamic environment and interferes with the microgel-antimicrobial complexation. The contact-transfer approach does not require bacterial metabolism but instead appears to be driven by differences between the microgels and the bacterial cell envelope where there is a high concentration of negative charge and hydrophobicity. Contact with metabolizing macrophages or osteoblasts is, however, insufficient to trigger antimicrobial release, indicating that contact transfer can be specific to bacteria and suggesting an avenue to biomedical device surfaces that can simultaneously promote healing and resist infection.

The impact of thermal cycling on Staphylococcus aureus biofilm growth on stainless steel and titanium orthopaedic plates

Background

Orthopaedic implant infections are difficult to eradicate because bacteria adhering to implant surfaces inhibit the ability of the immune system and antibiotics to combat these infections. Thermal cycling is a temperature modulation process that improves performance and longevity of materials through molecular structural reorientation, thereby increasing surface uniformity. Thermal cycling may change material surface properties that reduce the ability for bacteria to adhere to the surface of orthopaedic implants. This study aims to determine whether thermal cycling of orthopaedic implants can reduce bacterial growth.

Methods

In a randomized, blinded in-vitro study, titanium and stainless steel plates treated with thermal cycling were compared to controls. Twenty-seven treated and twenty-seven untreated plates were covered with 10 ml tryptic soy broth containing ~ 10⁵ colony forming units (CFU)/ml of bioluminescent Staphylococcus aureus (S. aureus)Xen29 and incubated at 37 °C for 14d. Quantity and viability of bacteria were characterized using bioluminescence imaging, live/dead staining and determination of CFUs.

Results

Significantly fewer CFUs grow on treated stainless steel plates compared to controls (p = 0.0088). Similar findings were seen in titanium plates (p = 0.0048) following removal of an outlier. No differences were evident in live/dead staining using confocal microscopy, or in metabolic activity determined using bioluminescence imaging (stainless steel plates: p = 0.70; titanium plates: p = 0.26).

Conclusion

This study shows a reduction in CFUs formation on thermal cycled plates in-vitro. Further in-vivo studies are necessary to investigate the influence of thermal cycling on bacterial adhesion during bone healing. Thermal cycling has demonstrated improved wear and strength, with reductions in fatigue and load to failure. The added ability to reduce bacterial adhesions demonstrates another potential benefit of thermal cycling in orthopaedics, representing an opportunity to reduce complications following fracture fixation or arthroplasty.

Pedicle screw loosening is correlated to chronic subclinical deep implant infection: a retrospective database analysis

PURPOSE

Spinal fusion is used for treatment of spinal deformities, degeneration, infection, malignancy, and trauma. Reduction of motion enables osseous fusion and permanent stabilization of segments, compromised by loosening of the pedicle screws (PS). Deep implant infection, biomechanical, and chemical mechanisms are suspected reasons for loosening of PS. Study objective was to investigate the frequency and impact of deep implant infection on PS loosening.

METHODS

Intraoperative infection screening from wound and explanted material sonication was performed during revision surgeries following dorsal stabilization. Case history events and factors, which might promote implant infections, were included in this retrospective survey.

RESULTS

110 cases of spinal metal explantation were included. In 29.1% of revision cases, infection screening identified a germ, most commonly Staphylococcus (53.1%) and Propionibacterium (40.6%) genus. Patients screened positive had a significant higher number of previous spinal operations and radiologic loosening of screws. Patients revised for adjacent segment failure had a significantly lower rate of positive infection screening than patients revised for directly implant associated reasons. Removal of implants that revealed positive screening effected significant pain relief.

CONCLUSIONS

Chronic implant infection seems to play a role in PS loosening and ongoing pain, causing revision surgery after spinal fusion. Screw loosening and multiple prior spinal operations should be suspicious for implant infection after spinal fusion when it comes to revision surgery. These slides can be retrieved under Electronic Supplementary Material.

A new model for biofilm formation and inflammatory tissue reaction: intraoperative infection of a cranial implant with Staphylococcus aureus in rats

BACKGROUND

Implant failure is a severe and frequent adverse event in all areas of neurosurgery. It often involves infection with biofilm formation, accompanied by inflammation of surrounding tissue, including the brain, and bone loss. The most common bacteria involved are Staphylococcus aureus. We here test whether intraoperative infection of intracranial screws with Staphylococcus aureus would lead to biofilm formation and inflammatory tissue reaction in rats.

METHODS

Two titanium screws were implanted in the cranium of Sprague-Dawley rats, anesthetized with xylazine (4 mg/kg) and ketamine (75 mg/kg). Prior to the implantation of the screws, Staphylococcus aureus was given in the drill holes; controls received phosphate-buffered saline (PBS). Rats were euthanized 2, 10 and 21 days after surgery to remove the screws for analysis of biofilm formation with a confocal laser scanning microscope. The surrounding tissue composed of soft tissue and bone, as well as the underlying brain tissue, was evaluated for inflammation, bone remodeling, foreign body reaction and fibrosis after H&E staining.

RESULTS

Intraoperative application of Staphylococcus aureus leads to robust and stable biofilm formation on the titanium implants on days 10 and 21 after surgery, while no bacteria were found in controls. This was accompanied by a substantial inflammatory response of peri-implant tissue after infection, also affecting the underlying brain tissue.

CONCLUSIONS

Intraoperative infection of implants with Staphylococcus aureus in rats may be useful as a tool to model new implant materials and surfaces on biofilm formation and inflammatory tissue reaction in vivo.

Clinical impact of positive Propionibacterium acnes cultures in orthopedic surgery

BACKGROUND

The clinical significance of a positive culture to Propionibacterium acnes in orthopedic specimens remains unclear, whether about its role as a contaminant or a pathogen, or its impact as a coinfectant. Therefore, we performed a retrospective study to provide a more accurate description of the clinical impact of P. acnes in an orthopedic population aiming to determine: 1) if there is a clinical difference between P. acnes infection and contamination? 2) If there is a clinical difference between P. acnes monoinfection, and coinfection.

HYPOTHESIS

There is a clinical difference between P. acnes infection and contamination.

MATERIALS AND METHODS

Patients were selected over a five-year period, and those with a minimum of one positive culture for P. acnes, from any intraoperative orthopedic tissue sample, were included in the study. P. acnes infection was defined as the isolation of P. acnes from≥2 specimens, or in only one specimen, in the presence of typical perioperative findings and/or local signs of infection.

RESULTS

A total of 68 patients had a positive P. acnes culture, 35 of which were considered to be infected. The infections affected mostly males (29/35-83%), occurred mostly in shoulders (22/35-63%), and at a site already containing an orthopedic implant (32/35-91%). Local inflammatory signs were present in half of the cases when an infection was diagnosed. Coinfection with other pathogens was present in 31% of patients (11/35). When comparing patients coinfected with P. acnes, and those who were monoinfected, the latter presented less often with local inflammatory signs. Recurrence rate was 24% (8/35) and the only risk factor for recurrence was the presence of a monoinfection.

DISCUSSION

This study confirms the pathogenicity of P. acnes in an orthopedic population, as it is present in multiple samples in the same patient, and because it is present in cultures from cases with clinical recurrence. Our study showed that monoinfections differ from coinfections mainly by their higher risk of recurrence.

LEVEL OF EVIDENCE

Level IV retrospective case series.

Staphylococcal orthopaedic device-related infections in older patients

INTRODUCTION

Staphylococci are the most common pathogens causing orthopaedic device-related infections (ODRI). The treatment of these infections often involves multiple surgical procedures combined with systemic antibiotic therapy to treat the infection and restore functionality. Older patients frequently present with a compromised health-status and/or low bone quality, and despite growing importance their outcomes are not well described to date. The primary aim of the current study is to describe outcomes in older patients with ODRIs and to determine if they demonstrate lower cure rates and greater risk for complications in contrast to younger patients.

PATIENTS AND METHODS

Patients treated with an ODRI of the lower extremity at our institution were included in this study. Demographic data, comorbidities and infecting organisms were recorded. Older adult patients were defined as those aged 60 and older. At two-year follow-up post-discharge, we recorded the clinical course, the Lower-Extremity-Functional-Score, the patient reported general health status (SF-12-questionnaire) and the status of infection. The antibiotic resistance pattern of the disease causing pathogens was analysed and compared between the two age groups.

RESULTS

In total, 163 patients (age: 19-94 years) with a staphylococcal ODRI were included. Sixty-four of these infections occurred in older patients, which showed a significantly higher mortality rate (9%). Within follow-up period recurrence of infection occurred significantly more frequently in younger patients (41%) than in older patients (17%). At two-years follow-up cure, which was defined as eradication of infection and terminated therapy, was achieved in 78% of younger and 75% of older patients. However, an ODRI resulted in older patients in a significantly worse functional outcome and impaired physical quality of live, as well as more frequently in an on-going infection, such as a persisting fistula (14% versus 3% in younger patients). Disease causing staphylococci, isolated from older patients showed more frequently a methicillin or multi-drug resistance than those associated with infections in younger patients.

CONCLUSIONS

ODRIs in older patients demonstrated higher morality rates rate, poor functional outcome and higher rates of persistent infections. A compromised health status and a poor bone quality may play a crucial role in this specific patient cohort.

(68)Ga-DOTA-Siglec-9 PET/CT imaging of peri-implant tissue responses and staphylococcal infections

Background

Staphylococcus epidermidis (S. epidermidis) has emerged as one of the leading pathogens of biomaterial-related infections. Vascular adhesion protein-1 (VAP-1) is an inflammation-inducible endothelial molecule controlling extravasation of leukocytes. Sialic acid-binding immunoglobulin-like lectin 9 (Siglec-9) is a leukocyte ligand of VAP-1. We hypothesized that ⁶⁸Ga-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-conjugated Siglec-9 motif containing peptide (⁶⁸Ga-DOTA-Siglec-9) could detect inflammatory response due to S. epidermidis peri-implant infection by positron emission tomography (PET).

Methods

Thirty Sprague-Dawley rats were randomized into three groups. A sterile catheter was implanted into the medullary canal of the left tibia. In groups 1 and 2, the implantation was followed by peri-implant injection of S. epidermidis or Staphylococcus aureus (S. aureus) with adjunct injections of aqueous sodium morrhuate. In group 3, sterile saline was injected instead of bacteria and no aqueous sodium morrhuate was used. At 2 weeks after operation, ⁶⁸Ga-DOTA-Siglec-9 PET coupled with computed tomography (CT) was performed with the measurement of the standardized uptake value (SUV). The presence of the implant-related infection was verified by microbiological analysis, imaging with fluorescence microscope, and histology. The in vivo PET results were verified by ex vivo measurements by gamma counter.

Results

In group 3, the tibias with implanted sterile catheters showed an increased local uptake of ⁶⁸Ga-DOTA-Siglec-9 compared with the intact contralateral bones (SUV_ratio +29.5%). ⁶⁸Ga-DOTA-Siglec-9 PET detected inflammation induced by S. epidermidis and S. aureus catheter-related bone infections (SUV_ratio +58.1% and +41.7%, respectively). The tracer uptake was significantly higher in the S. epidermidis group than in group 3 without bacterial inoculation, but the difference between S. epidermidis and S. aureus groups was not statistically significant. The difference between the S. aureus group and group 3 was neither statistically significant.

Conclusion

PET/CT imaging with novel ⁶⁸Ga-DOTA-Siglec-9 tracer was able to detect inflammatory tissue response induced by catheter implantation and staphylococcal infections.

Titania nanotubes with adjustable dimensions for drug reservoir sites and enhanced cell adhesion

This study aims to generate a bactericidal agent releasing surface via nanotube layer on titanium metal and to investigate how aspect ratio of nanotubes affects drug elution time and cell proliferation. Titania nanotube layers were generated on metal surfaces by anodic oxidation at various voltage and time parameters. Gentamicin loading was carried out via simple pipetting and the samples were tested against S. aureus for the efficacy of the applied modification. Drug releasing time and cell proliferation were also tested in vitro. Titania nanotube layers with varying diameters and lengths were prepared after anodization and anodizing duration was found as the most effective parameter for amount of loaded drug and drug releasing time. Drug elution lasted up to 4 days after anodizing for 80 min of the samples, whereas release completed in 24 h when the samples were anodized for 20 min. All processed samples had bactericidal properties against S. aureus organism except unmodified titanium, which was also subjected to drug incorporation step. The anodization also enhanced water wettability and cell adhesion results. Anodic oxidation is an effective surface modification to enhance tissue-implant interactions and also resultant titania layer can act as a drug reservoir for the release of bactericidal agents. The use of implants as local drug eluting devices is promising but further in vivo testing is required.