Orthopedic Implant-associated Infection Research Articles

Microbiological profile of patients with orthopedic implant-associated infection in the post-COVID period

Background. The etiological structure of implant-associated infection and antibiotic resistance of pathogens are important when choosing empirical antibiotic therapy. COVID-19 pandemic and increased consumption of antibiotics by the population could provoke an increase in antibiotic resistance.The aim of the work. To compare the spectrum of leading pathogens of implantassociated infection in the pre- and post-Covid period and to assess antibiotic resistance.Materials and methods. A continuous retrospective study of biomaterial samples from traumatology and orthopedic patients with implant-associated infection was carried out for 2018–2019 and 2021–2022. The sample consisted of 548 microorganism strains (n = 237 and n = 317, respectively) in 442 cases of infectious complications. The antibiotic resistance of all isolated microorganisms, including those from microbial associations, was assessed.Results. The leading pathogen of monomicrobial implant-associated infection in both study periods was Staphylococcus epidermidis (33–37 %). In 2021–2022, the proportion of microbial associations increased (from 12.5 to 17.5 %; p = 0.147) with the appearance of fungi in the microbial landscape. In the post-Covid period, the increase in Staphylococcus aureus resistance to tetracycline and doxycycline was revealed; the isolation of methicillin-resistant strains among Staphylococcus aureus decreased from 4 cases (out of 187) to 3 (out of 232); 100 % sensitivity to rifampicin and co-trimoxazole was maintained. An increase in Staphylococcus epidermidis resistance to all tested antibiotics was detected (statistically significant increase in resistance to fluoroquinolones; p = 0.002–0.003) with the isolation of methicillin-resistant strains in 80.5% and 80.9% of cases, respectively. All staphylococcal isolates were susceptible to vancomycin and linezolid. Enterobacteriaceae representatives showed a decrease in resistance to carbapenems and an increase in resistance to co-trimoxazole; in Pseudomonas aeruginosa and Acinetobacter baumannii, there is an increase in resistance to carbapenems and fluoroquinolones. All gram-negative microorganisms were sensitive to colistin.Conclusion. The high frequency of isolation of methicillin-resistant staphylococci determines the choice of vancomycin for empirical therapy. Increasing resistance of staphylococci to fluoroquinolones may limit their use. Increasing resistance of gram-negative bacteria and a narrow spectrum of antibiotics acting on carbapenemase producers may reduce the effectiveness of therapy.

Optimal ultrasonic treatment frequency and duration parameters were used to detect the pathogenic bacteria of orthopedic implant-associated infection by ultrasonic oscillation

IntruductonThe most accurate method for detecting the pathogen of orthopedic implant-associated infections (OIAIs) is sonication fluid (SF). However, the frequency and duration of ultrasound significantly influence the number and activity of microorganisms. Currently, there is no consensus on the selection of these two parameters. Through this study, the choice of these two parameters is clarified. MethodsWe established five ultrasonic groups (40kHz/10min, 40kHz/5min, 40 kHz/1min, 20kHz/5min, and 10kHz/5min) based on previous literature. OIAIs models were then developed and applied to ultrasound group treatment. Subsequently, we evaluated the efficiency of bacteria removal by conducting SEM and crystal violet staining. The number of live bacteria in the SF was determined using plate colony count and live/dead bacteria staining. ResultsThe results of crystal violet staining revealed that both the 40kHz/5min group and the 40kHz/10min group exhibited a significantly higher bacterial clearance rate compared to the other groups. However, there was no significant difference between the two groups. Additionally, the results of plate colony count and fluorescence staining of live and dead bacteria indicated that the number of live bacteria in the 40kHz/5min SF group was significantly higher than in the other groups. Conclusion40kHz/5min ultrasound is the most beneficial for the detection of pathogenic bacteria on the surface of orthopedic implants.

Diagnostic Role of Metagenomic Next-Generation Sequencing in Tubercular Orthopedic Implant-Associated Infection.

The diagnosis of tubercular orthopedic implant-associated infection (TB-IAI) is challenging. This study evaluated the value of metagenomic next-generation sequencing (mNGS) for the diagnosis of TB-IAI and developed a standardized diagnostic procedure for TB-IAI. The records of all patients with TB-IAI diagnosed and treated at our institution between December 2018 and September 2022 were retrospectively reviewed. Patient demographic characteristics, medical history, laboratory test, microbial culture, histopathology, and mNGS results, and time to diagnosis were recorded. The diagnostic efficiency of mNGS for TB-IAI was assessed by comparing the results and diagnostic time with that of other diagnostic modalities. Ten patients were included in the analysis, including eight with prosthetic joint infections and two with fracture-related infections. The mNGS positivity rate was 100% (10/10), which was higher than that of TB-antibody (11%, 1/9), real-time quantitative polymerase chain reaction (22%, 2/9), T-SPOT.TB (25%, 2/8), purified protein derivative (50%, 4/8), microbial culture (50%, 5/10), and histopathology (20%, 2/10). mNGS shortened the time to diagnosis of TB-IAI. A standardized diagnostic procedure for TB-IAI was developed based on the findings. mNGS is useful for the diagnosis of TB-IAI. mNGS is recommended in cases where it is difficult to identify a pathogen using routine diagnostic tests. The standardized diagnostic procedure might improve TB-IAI diagnosis. TB-IAI is a rare infection, which occurs after orthopedic surgery and hard to diagnose microbiologically. mNGS is a new detection technique not yet discussed in current literature as a means for TB-IAI diagnostics. Here we describe a cohort of patients with TB-IAI diagnosed by mNGS show high efficiency of mNGS for detection of this pathology and present a clinical algorithm supplementing conventional methods for TB-IAI assessment.

Prevalence of Infective Endocarditis among Patients with Staphylococcus aureus Bacteraemia and Bone and Joint Infections.

We aimed to evaluate the occurrence of infective endocarditis (IE) among patients with bone and joint infections (BJIs) and Staphylococcus aureus bacteraemia. This observational study was conducted at Lausanne University Hospital, Switzerland, from 2014 to 2023, and included episodes involving BJI, S. aureus bacteraemia, and cardiac imaging studies. The endocarditis team defined IE. Among the 384 included episodes, 289 (75%) involved native BJI (NBJI; 118 septic arthritis, 105 acute vertebral or non-vertebral osteomyelitis, 101 chronic osteitis), and 112 (29%) involved orthopedic implant-associated infection (OIAI; 78 prosthetic joint infection and 35 osteosynthesis/spondylodesis infection). Fifty-one episodes involved two or more types of BJI, with 17 episodes exhibiting both NBJI and OIAI. IE was diagnosed in 102 (27%) episodes. IE prevalence was 31% among patients with NBJI and 13% among patients with OIAI (p < 0.001). The study revealed a high prevalence of IE among S. aureus bacteraemic patients with NBJI, with notably lower prevalence among those with OIAI.

Recent Advances in the Evaluation of Antimicrobial Materials for Resolution of Orthopedic Implant-Associated Infections In Vivo

While orthopedic implant-associated infections are rare, revision surgeries resulting from infections incur considerable healthcare costs and represent a substantial research area clinically, in academia, and in industry. In recent years, there have been numerous advances in the development of antimicrobial strategies for the prevention and treatment of orthopedic implant-associated infections which offer promise to improve the limitations of existing delivery systems through local and controlled release of antimicrobial agents. Prior to translation to in vivo orthopedic implant-associated infection models, the properties (e.g., degradation, antimicrobial activity, biocompatibility) of the antimicrobial materials can be evaluated in subcutaneous implant in vivo models. The antimicrobial materials are then incorporated into in vivo implant models to evaluate the efficacy of using the material to prevent or treat implant-associated infections. Recent technological advances such as 3D-printing, bacterial genomic sequencing, and real-time in vivo imaging of infection and inflammation have contributed to the development of preclinical implant-associated infection models that more effectively recapitulate the clinical presentation of infections and improve the evaluation of antimicrobial materials. This Review highlights the advantages and limitations of antimicrobial materials used in conjunction with orthopedic implants for the prevention and treatment of orthopedic implant-associated infections and discusses how these materials are evaluated in preclinical in vivo models. This analysis serves as a resource for biomaterial researchers in the selection of an appropriate orthopedic implant-associated infection preclinical model to evaluate novel antimicrobial materials.

Bacteriophage-Delivering Hydrogels: Current Progress in Combating Antibiotic Resistant Bacterial Infection

Antibiotic resistance remains as an unresolved global challenge in the health care system, posing serious threats to global health. As an alternative to antibiotics, bacteriophage (phage) therapy is rising as a key to combating antibiotic-resistant bacterial infections. In order to deliver a phage to the site of infection, hydrogels have been formulated to incorporate phages, owing to its favorable characteristics in delivering biological molecules. This paper reviews the formulation of phage-delivering hydrogels for orthopedic implant-associated bone infection, catheter-associated urinary tract infection and trauma-associated wound infection, with a focus on the preparation methods, stability, efficacy and safety of hydrogels as phage carriers.

Value of D-Dimer as a Diagnostic Marker of Infection Associated with Orthopedic Implants.

Background:Recently, the D-dimer biomarker has gained the researchers' attention for predicting infections. We aimed to determine the relationship between this marker and other inflammatory markers involved in orthopedic implant-associated infections.Materials and Methods:In this study, all patients diagnosed with an orthopedic implant-associated infection were investigated in 3 years. The serum level of D-dimer, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) was measured. Infection was diagnosed based on the clinical and culture results of biopsy samples.Results:The cultured microorganisms, detected in 26 patients with infections, included Staphylococcus aureus (n = 13, 50%), Staphylococcus epidermidis (n = 2, 7.7%), Klebsiella aerogenes (n = 8, 30.8%), and Pseudomonas aeruginosa (n = 3, 11. 5%). Based on laboratory findings, there was a significant difference in the CRP level and ESR (P = 0.001). Although the level of D-dimer was higher in infected patients, compared to the controls (992.6 ± 667.2 vs. 690.1 ± 250.2 ng/mL), the difference was not statistically significant. There was no significant correlation between the elevated D-dimer level and CRP level, whereas ESR had a positive correlation with the elevated D-dimer level (r = 0.6, P = 0.03). The sensitivity, specificity, and positive predictive value (PPV) of D-dimer in the prediction of infection were 65%, 57%, and 45%, respectively. Furthermore, the sensitivity, specificity, and PPV of CRP were 100%, 92.3%, and 95%, respectively, whereas the corresponding values for ESR were 85%, 69.2%, and 62%, respectively.Conclusion:Measurement of the serum D-dimer level is not efficient for the diagnosis of orthopedic implant-associated infections due to its low predictive value. Furthermore, there was no significant correlation between the serum D-dimer level and CRP.

A Rat Model of Orthopedic Implant-Associated Infection for Identification of Staphylococcal Biofilm Proteins.

Secreted bacterial proteins are difficult to identify directly from an infection site due to a limited amount of bacteria and presence of a large quantity of host proteins. Here we describe a rat model of orthopedic implant that allows us to harvest bacterial biofilm materials sufficient for identification of bacterial proteins in the biofilm matrix by liquid chromatography-tandem MS (GeLC-MS/MS) analysis.

Antimicrobial hydroxyapatite and its composites for the repair of infected femoral condyle

Orthopedic implant-associated infection constitutes one of the most devastating and challenging symptoms in the clinic. Implants without antimicrobial properties may become the harbourage for microbial colonization and biofilm formation, thus hindering normal bone regeneration processes. We had previously developed tannin modified HA (THA) as well as silver and tannin modified hydroxyapatite (HA) (Ag-THA) via a facile one-step and scalable process, and proven their antimicrobial performance in vitro. Herein, by compositing with non-antimicrobial polyurethane (PU), the in vivo anti-bacterial activity, osteoconductivity and osteoinductivity of PU/Ag-THA composite were investigated using an infected femoral condyle defect model on rat. PU/Ag-THA exhibited excellent in vivo antimicrobial activity, with the calculated bacteria fraction being reduced to lower than 3% at week 12 post operation. Meanwhile, PU/Ag-THA is also promising for bone regeneration under the bacteria challenge, evidenced by a final bone mineral density (BMD) ~0.6 times higher than that of the blank control at week 12. A continuous increase in BMD over time was observed in the PU/Ag-THA group, but not in the blank control and its non- or weak-antimicrobial counterparts (PU/HA and PU/THA), in which the growth rate of BMD declined after 8 weeks of operation. The enhanced osteoinductivity of PU/Ag-THA relative to blank control, PU/HA and PU/THA was also confirmed by the Runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) immunohistochemical staining. The above findings suggest that antimicrobial Ag-THA may serve as a promising and easy-to-produce antimicrobial mineral for the development of antimicrobial orthopedic composite implants to address the challenges in orthopedic surgeries, especially where infection may become a challenging condition to treat.

Interleukin-1β and tumor necrosis factor are essential in controlling an experimental orthopedic implant-associated infection.

Orthopedic implant-associated infection (OIAI) is a major complication that leads to implant failure. In preclinical models of Staphylococcus aureus OIAI, osteomyelitis and septic arthritis, interleukin-1α (IL-1α), IL-1β, and tumor necrosis factor (TNF) are induced, but whether they have interactive or distinctive roles in host defense are unclear. Herein, a S. aureus OIAI model was performed in mice deficient in IL-1α, IL-1β, or TNF. Mice deficient in IL-1β or TNF (to a lesser extent) but not IL-1α had increased bacterial burden at the site of the OIAI throughout the 28-day experiment. IL-1β and TNF had a combined and critical role in host defense as mice deficient in both IL-1R and TNF (IL-1R/TNF-deficient mice) had a 40% mortality rate, which was associated with markedly increased bacterial burden at the site of the OIAI infection. Finally, IL-1α- and IL-1β-deficient mice had impaired neutrophil recruitment whereas IL-1β-, TNF-, and IL-1R/TNF-deficient mice all had impaired recruitment of both neutrophils and monocytes. Therefore, IL-1β and TNF contributed to host defense against S. aureus OIAI and neutrophil recruitment was primarily mediated by IL-1β and monocyte recruitment was mediated by both IL-1β and TNF.

Significant Suppression of Staphylococcus aureus Colonization on Intramedullary Ti6Al4V Implants Surface-Grafted with Vancomycin-Bearing Polymer Brushes.

Orthopedic implant-associated bacterial infection presents a major health threat due to tendency for periprosthetic bacterial colonization/biofilm formation that protects bacteria from host immune response and conventional antibiotic treatment. Using surface-initiated atom transfer radical polymerization and copper-catalyzed azide-alkyne cycloaddition (CuAAC), alkynylated vancomycin is conjugated to azido-functionalized side chains of polymethacrylates grafted from Ti6Al4V. High-efficiency CuAAC across the substrate is confirmed by complete surface conversion of azides by X-ray photoelectron spectroscopy (XPS) and elemental mapping of changing characteristic elements. The vancomycin-modified surface (Ti-pVAN) significantly reduces in vitro adhesion and colonization of Staphylococcus aureus (S. aureus), a main bacterial pathogen responsible for periprosthetic infection and osteomyelitis, compared to untreated Ti6Al4V, supporting retained antibacterial properties of the covalently conjugated antibiotics. When the surface-modified intramedullary Ti-pVAN pins are inserted into mouse femoral canals infected by bioluminescent Xen29 S. aureus, significantly reduced local bioluminescence along with mitigated blood markers for infection are detected compared to untreated Ti6Al4V pins over 21 days. Ti-pVAN pins retrieved after 21 days are confirmed with ∼20-fold reduction in adherent bacteria counts compared to untreated control, supporting the ability of surface-conjugated vancomycin in inhibiting periprosthetic S. aureus adhesion and colonization.

Sonication of Extracted Implants Improves Microbial Detection in Patients With Orthopedic Implant-Associated Infections

BackgroundWe assessed whether combining the conventional culture and implant sonicate fluid culture (SFC) methods increased the diagnostic accuracy of orthopedic implant-associated infection (OIAI). MethodsConsecutive patients (n = 66) undergoing implant removal (OIAI, 17; non-OIAI, 49) were evaluated prospectively. We analyzed 493 samples (39 preoperative joint aspirates, 243 peri-implant tissue specimens, 124 implant sonication, 67 controls, and 20 water bath samples). OIAI was preoperatively evaluated based on clinical evidence of infection or aspirate culture (AC). Conventional methods required positive results in either preoperative ACs or intraoperative tissue cultures (TCs), whereas the combination method required at least 1 positive culture among 3 sources (AC, TC, or SFC). The application of SFC and the detection rate, sensitivity, and specificity of the diagnostic methods were assessed. ResultsNo controls or water bath samples harbored bacteria. Three patients (18%) were detected by SFC only and Peptostreptococcus and Corynebacterium species were isolated by SFC only. The OIAI detection rate attributable to SFC was significantly higher than that of TC (61% vs 36%; P = .02). The sensitivities of AC, TC, and SFC at a cutoff point of 1 colony-forming unit/plate and 1 positive culture were 60%, 59%, and 71%, respectively. At a cutoff point of 2 positive cultures, the combination (vs conventional) method showed significantly greater sensitivity (71% vs 47%; P = .008). ConclusionBy incorporating SFCs into conventional culture methods, the diagnostic accuracy in the context of OIAI was significantly improved.

Orthopedic Implant-Associated Infection by Multidrug Resistant Enterobacteriaceae

Introduction: Orthopedic implant-associated infections caused by multidrug-resistant Enterobacteriaceae are a growing challenge for healthcare providers due to their increasing incidence and the difficulties of medical and surgical treatment. Material and Methods: A retrospective observational study of all cases of multidrug resistant Enterobacteriaceae orthopedic implant-associated infection diagnosed in a tertiary European hospital from December 2011 to November 2017 was carried out. Clinical records were reviewed using a previously designed protocol. Data analysis was performed with IBM® SPSS®, version 22. Results: 25 patients met inclusion criteria. The infected implants included 10 prosthetic joints, seven osteosyntheses, six combinations of prosthetic joint and osteosynthesis material, and two spacers. Of the multidrug resistant Enterobacteriaceae obtained on culture, 12 were extended-spectrum beta-lactamase-producing Escherichia coli, three OXA-48-producing Klebsiella pneumoniae, nine extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, and one extended-spectrum beta-lactamase-producing Proteus mirabilis. Combination antimicrobial therapy was employed in all cases but two. Overall, 16 (64%) patients underwent implant removal. The rate of infection control in the overall implant removal group was 100% compared to 33% in the implant retention group. A strong relationship between implant removal and infection control was observed (p = 0.001). Discussion: Implant removal is strongly associated with infection control. However, in some cases, patient age and comorbidity contraindicate hardware extraction. Potential objectives for future studies should be geared towards targeting the population in which debridement, antibiotic therapy, and implant retention can be used as a first-line therapeutic strategy with a reasonable probability of achieving infection control.

Fluorescence lateral flow immunoassay based point-of-care nanodiagnostics for orthopedic implant-associated infection

Detection of implant-associated infection at the earliest is necessary to prevent, treat or monitor further complications. In this work, the lateral flow immunoassay (LFIA) based on double antibody sandwich technique is developed using bright fluorescent cadmium telluride quantum dots (CdTe QDs). This point-of-care (POC) nanodiagnostics technique utilizes CdTe QDs for detection of orthopedic implant-associated infection biomarkers such as C-reactive protein (CRP) and interleukin-6 (IL-6). Staphylococcal protein A (SPA) was conjugated with CdTe QDs (SPA-QDs) and antibodies i.e. anti-CRP, anti-IL-6, and anti-rabbit IgG were bound separately on SPA-QDs complex to develop the biosensor mixture. LFIA was developed on the nitrocellulose strip with test and control spot. Color sensor based portable fluorescence strip reader (PorFloR™) was developed and calibrated. The detection range was found to be 1–300 μg/ml and 1-1000 pg/ml for CRP and IL-6, respectively. Limit of detection was found to be 0.3 μg/ml and 0.9 pg/ml for CRP and IL-6, respectively. Developed LFIA was compared with standard ELISA technique and it showed excellent accuracy, sensitivity, reproducibility, and stability. PorFloR™ device provides the quantitative approach to POC nanodiagnostics and has the potential to be utilized for early detection of implant-associated infection and assist surgeons regarding the status of an implanted device.

Proteomics of Staphylococcus aureus biofilm matrix in a rat model of orthopedic implant-associated infection.

The matrix proteins of Staphylococcus aureus biofilm have not been well defined. Previous efforts to identify these proteins were performed using in vitro systems. Here we use a proteomic approach to identify biofilm matrix proteins directly from infected bone implants using a rat model of orthopedic implant-associated S. aureus infection. Despite heavy presence of host proteins, a total of 28 and 105 S. aureus proteins were identified during acute infection and chronic infection, respectively. Our results show that biofilm matrix contains mostly intracellular cytoplasmic proteins and, to a much less extent, extracellular and cell surface-associated proteins. Significantly, leukocidins were identified in the biofilm matrix during chronic infection, suggesting S. aureus is actively attacking the host immune system even though they are protected within the biofilm. The presence of two surface-associated proteins, Ebh and SasF, in the infected bone tissue during acute infection was confirmed by immunohistochemistry. In addition, a large number of host proteins were found differentially expressed in response to S. aureus biofilm formed on bone implants.

Orthopedic-Implant Associated Infection due to Gram-Negative Bacilli: The Worrisome Impact of Acinetobacter baumannii Multidrug Resistance in a Brazilian Center

Background Orthopedic implant-associated surgical site infection (SSI) is a severe complication presenting a treatment challenge. Recently, Gram-negative bacteria orthopedic infections have become a global concern.Objectives:To describe the bacterial profile of orthopedic implant-associated Gram-negative infections and specific outcome of Acinetobacter baumannii infections.Methods A single-center, retrospective cohort study analyzing the infection control database on the year 2016. Cases selected were those osteosynthesis or prosthetic joint, which evolved with SSI and Gram-negative bacterial growth in bone tissue or periprosthetic cultures.ResultsIn 2016, 4001 clean surgeries with orthopedic implant placement were performed; of which 84 fulfillled the criteria for SSI, according to CDC/NHSH definitions (54 cases of open fracture reduction, 24 of hip arthroplasty, five of knee arthroplasty). Main agent of infections was Staphylococcus aureus (29.9%); Gram-negative bacteria however were responsible for 57.3% of infections (Enterobacter ssp. 22.4%; Acinetobacter baumannii 14.9%; Klebsiella pneumoniae 10%; Pseudomonas aeruginosa 10%). Among them, 100% Enterobacter ssp. were sensitive to carbapenems and 75% to ciprofloxacin. Klebsiella pneumoniae showed sensitivity to carbapenems in 85.7%, Pseudomonas aeruginosa showed sensitivity in 85.7% to carbapenems and 100% to ciprofloxacin. However, Acinetobacter baumannii showed the least favorable profile amongst Gram-negatives since only 12.5% of strains were sensitive to carbapenems, 28.6% to Ampicilin-sulbactam, 22.2% to ciprofloxacin, while showing 100% sensitivity to polymyxins. From 13 patients in whom Acinetobacter baumannii was isolated, none presented sepsis related to this infection, yet four of them died as result of hospitalization-related complications (30.7% mortality rate). Among these deaths, two were related to total hip arthroplasty, one to knee arthroplasty and one to open fracture fixation. Among the survivors, two remain in antimicrobial use and seven showed remission/cure.Conclusion SSI caused by carbepenem-resistant Acinetobacter baumannii represents great impact on morbi-mortality in patients who undergo surgery with placement of orthopedic implants.Disclosures All authors: No reported disclosures.

Concentration of Sonication Fluid through Centrifugation Is Superior to Membrane Filtration for Microbial Diagnosis of Orthopedic Implant-Associated Infection.

Microbial identification of orthopedic implant-associated infections using sonication fluid (SF) submitted to a concentration step by membrane filtration (SMF) was compared with the standard centrifugation (SC) method. Among 33 retrieved infected implants, sonication identified microorganisms in 26 (78.8%). The sensitivity of SC was higher than that of SMF (78.8% versus 30.3%; P < 0.001).

Orthopedic implant-associated infection: the main etiological agents, local resistance and antimicrobial therapy recommendations

Surgical site infections remain a major complication of arthroplasty, spinal stabilization or other orthopedic surgeries. The pathogenesis of these complications is related to use orthopedic implants. This retrospective study investigated the microbiological etiology of implant-associated infection after orthopedic surgery over a 3-year period (2010-2012). The antibiotic resistance profiles of 1350 clinical microbial isolates were determined. The biofilm forming capacity of 394 staphylococcal strains was tested. Statistical analysis was performed using Z-criterion. From a results of the microbiological culture, Staphylococcus aureus and Staphylococcus epidermidis were isolated in 49,9% of cases, followed by: Enterococcus faecalis - 6,4%, Pseudomonas aeruginosa - 5,9%, Acinetobacter spp - 5,1% and members of the family Enterobacteriaceae - 4.1%. MRSA amounted to 23,9% and MRSE - 56,6% (p

Implant sonication for the diagnosis of prosthetic elbow infection

Periprosthetic infection is a potentially devastating complication of elbow arthroplasty, associated with formation of microbial biofilm on the implant surface. The definitive microbiologic diagnosis of periprosthetic infection after elbow arthroplasty may be difficult to establish. Our study aim was to compare the diagnostic accuracy of conventional periprosthetic tissue culture and culture of fluid derived from vortexing and bath sonication of the explanted hardware (a biofilm-sampling strategy). Patients undergoing revision elbow arthroplasty at our institution between July 2007 and July 2010, from each of whom 2 or more periprosthetic tissue cultures and 1 implant sonicate culture were obtained, were studied. A standardized definition of orthopedic implant-associated infection was applied. We identified 27 subjects with aseptic failure and 9 with prosthetic elbow infection. Rheumatoid arthritis was the most common underlying disorder. The Coonrad-Morrey prosthesis was the most common type of implant used. The sensitivities of implant sonicate and periprosthetic tissue culture were 89% and 55%, respectively (P = .18), and the specificities were 100% and 93%, respectively (P = .16). Coagulase-negative staphylococci (n = 7) and Staphylococcus aureus (n = 2) were isolated in cases of infection. Culture of the implant by sonication is at least as sensitive as periprosthetic tissue culture to detect prosthetic elbow infection.

Effects of Staphylococcus epidermidis on osteoblast cell adhesion and viability on a Ti alloy surface in a microfluidic co-culture environment

A microfluidic device was used for real time imaging of MC3T3-E1 murine calvarial pre-osteoblasts (osteoblasts) in response to very small numbers of Staphylococcus epidermidis inoculated on the surface of a polished TiAl6V4 alloy in a serum-based medium. The Ti alloy surface was integrated to a poly(dimethylsiloxane) fluidic housing with eight 10 μl channels for high-throughput, cross-contamination-free co-culture. In the absence of S. epidermidis osteoblasts were able to adhere, spread, proliferate and remain viable on the Ti alloy surface during a 25 h culture period. With 10(2) or 10(5) colony forming units (cfu) ml(-1) S. epidermidis inoculated on the alloy surface osteoblast adhesion, spreading and proliferation were not adversely affected during the early stages of culture. However, osteoblasts became damaged by the end of culture, as S. epidermidis actively proliferated in the co-culture channels and formed small clusters on the alloy surface. These observations suggest that the small numbers of S. epidermidis did not necessarily compete with osteoblasts for the alloy surface during initial host cell development, but rapid proliferation of the bacteria might have changed the microenvironment, making it unfavorable to sustain the viability of osteoblasts. The results provide a new insight in projecting the potential utility of the microfluidic co-culture approach to developing physiologically and clinically relevant in vitro models of orthopedic implant-associated bacterial infection.