In Vitro Inflammatory Cell-Induced Corrosion Using a Lymphocyte and Macrophage Coculture.

BACKGROUND: Cobalt-chromium-molybdenum (CoCrMo) and titanium alloys have been used for orthopaedic implants for decades. However, recent evidence has shown that inflammatory cell-induced corrosion (ICIC) can damage these metal alloys. This study aimed to investigate the mechanisms of ICIC by coculturing macrophages with lymphocytes. We hypothesized that macrophages would be able to alter the surface oxide layer of CoCrMo and titanium alloy (Ti6Al4V) disks, with greater oxide layer damage occurring in groups with a coculture compared to a macrophage monoculture and in groups with inflammatory activators compared to nonactivated groups. METHODS: Murine macrophages were cultured on American Society for Testing and Materials F1537 CoCrMo and F136 Ti6Al4V disks for 30 days and activated with interferon gamma and lipopolysaccharide. Interferon gamma and lipopolysaccharide were added to the culture medium to simulate local inflammation. Macrophages were either cultured alone or in a coculture with T helper lymphocytes. After the 30-day experiment, scanning electron microscopy was used to examine the disk surfaces, and oxide levels were found using energy dispersive x-ray spectroscopy. RESULTS: Pitting features consistent with previous reports of ICIC were found on disks cultured with cells. Both CoCrMo and Ti6Al4V disks had significantly lower oxide levels in all groups with cells compared to control groups with no cells (P < .01). Additionally, CoCrMo disks had significantly lower oxide levels when cultured with activated macrophages and lymphocytes compared to nonactivated macrophages alone (P < .001), activated macrophages alone (P < .01), and nonactivated macrophages and lymphocytes (P < .05). No differences in the oxide levels were found among the Ti6Al4V groups. CONCLUSIONS: This study demonstrates the ability of macrophages to alter the surface chemistry of commonly used orthopaedic alloys. We found that the addition of lymphocytes and a simulated local inflammatory response may contribute to the ICIC of CoCrMo implants.

Staphylococcal infection prevention using antibiotic-loaded mannitol-chitosan paste in a rabbit model of implant-associated osteomyelitis.

Antibiotic-loaded chitosan pastes have shown advantages in the treatment and coverage of complex musculoskeletal defects. We added mannitol, previously shown to increase antibiotic susceptibility of biofilm, to an injectable chitosan/polyethylene glycol paste for delivery of antibiotics. Ground sponges (0.85% acetic acid solution, 1% chitosan, 0% or 2% mannitol, 1% polyethylene glycol) were hydrated using phosphate-buffered saline with 10 mg/ml amikacin and 10 mg/ml vancomycin added to form pastes. We inoculated rabbit radial defects with 105 colony-forming units of Staphylococcus aureus (UAMS-1) and inserted titanium pins into the cortical bone. Groups compared included mannitol blend pastes, non-mannitol blends, antibiotic-loaded bone cement, vancomycin powder, and no treatment controls. We harvested tissue samples and retrieved the pins retrieved at 3 weeks. All antibiotic-loaded groups lowered bacterial growth and colony-forming unit counts in soft and bone tissue and on titanium pins in in vivo studies. The results indicate this biomaterial is capable of eluting active antibiotics at concentrations that reduce bacterial growth on biomaterials and tissue, which, in turn, may prevent biofilm formation. Blends of chitosan and mannitol may be useful in prevention and treatment of osteomyelitis and implant-associated infections.

Impact of COVID-19 Pandemic on a Regional Stroke Thrombectomy Service in the United Kingdom.

INTRODUCTION: We examined the impact of the coronavirus disease 2019 (COVID-19) pandemic on our regional stroke thrombectomy service in the UK. METHODS: This was a single-center health service evaluation. We began testing for COVID-19 on 3 March and introduced a modified "COVID Stroke Thrombectomy Pathway" on 18 March. We analyzed the clinical, procedural and outcome data for 61 consecutive stroke thrombectomy patients between 1 January and 30 April. We compared the data for January and February ("pre-COVID," n = 33) versus March and April ("during COVID," n = 28). RESULTS: Patient demographics were similar between the 2 groups (mean age 71 ± 12.8 years, 39% female). During the COVID-19 pandemic, (a) total stroke admissions fell by 17% but the thrombectomy rate was maintained at 20% of ischemic strokes; (b) successful recanalization rate was maintained at 81%; (c) early neurological outcomes (neurological improvement following thrombectomy and inpatient mortality) were not significantly different; (d) use of general anesthesia fell significantly from 85 to 32% as intended; and (e) time intervals from onset to arrival, groin puncture, and recanalization were not significantly different, whereas internal delays for external referrals significantly improved for door-to-groin puncture (48 [interquartile range (IQR) 39-57] vs. 33 [IQR 27-44] minutes, p = 0.013) and door-to-recanalization (82.5 [IQR 61-110] vs. 60 [IQR 55-70] minutes, p = 0.018). CONCLUSION: The COVID-19 pandemic has had a negative impact on the stroke admission numbers but not stroke thrombectomy rate, successful recanalization rate, or early neurological outcome. Internal delays actually improved during the COVID-19 pandemic. Further studies should examine the effects of the COVID-19 pandemic on longer term outcome.

Characterization and Antibiofilm Activity of Mannitol-Chitosan-Blended Paste for Local Antibiotic Delivery System.

Mannitol, a polyalcohol bacterial metabolite, has been shown to activate dormant persister cells within bacterial biofilm. This study sought to evaluate an injectable blend of mannitol, chitosan, and polyethylene glycol for delivery of antibiotics and mannitol for eradication of Staphylococcal biofilm. Mannitol blends were injectable and had decreased dissociation and degradation in the enzyme lysozyme compared to blends without mannitol. Vancomycin and amikacin eluted in a burst response, with active concentrations extended to seven days compared to five days for blends without mannitol. Mannitol eluted from the paste in a burst the first day and continued through Day 4. Eluates from the mannitol pastes with and without antibiotics decreased viability of established S. aureus biofilm by up to 95.5% compared to blends without mannitol, which only decreased biofilm when loaded with antibiotics. Cytocompatibility tests indicated no adverse effects on viability of fibroblasts. In vivo evaluation of inflammatory response revealed mannitol blends scored within the 2-4 range at Week 1 (2.6 ± 1.1) and at Week 4 (3.0 ± 0.8), indicative of moderate inflammation and comparable to non-mannitol pastes (p = 0.065). Clinically, this paste could be loaded with clinician-selected antibiotics and used as an adjunctive therapy for musculoskeletal infection prevention and treatment.

Imaging Membrane Curvature inside a FcεRI-Centric Synapse in RBL-2H3 Cells Using TIRF Microscopy with Polarized Excitation.

Total internal reflection fluorescence microscopy with polarized excitation (P-TIRF) can be used to image nanoscale curvature phenomena in live cells. We used P-TIRF to visualize rat basophilic leukemia cells (RBL-2H3 cells) primed with fluorescent anti-dinitrophenyl (anti-DNP) immunoglobulin E (IgE) coming into contact with a supported lipid bilayer containing mobile, monovalent DNP, modeling an immunological synapse. The spatial relationship of the IgE-bound high affinity IgE receptor (FcεRI) to the ratio image of P-polarized excitation and S-polarized excitation was analyzed. These studies help correlate the dynamics of cell surface molecules with the mechanical properties of the plasma membrane during synapse formation.

Effect of Educational Debt on Emergency Medicine Residents: A Qualitative Study Using Individual Interviews.

STUDY OBJECTIVE: In 2001, less than 20% of emergency medicine residents had more than $150,000 of educational debt. Our emergency medicine residents anecdotally reported much larger debt loads. Surveys have reported that debt affects career and life choices. Qualitative approaches are well suited to explore how and why such complex phenomena occur. We aim to gain a better understanding of how our emergency medicine residents experience debt. METHODS: We conducted individual semistructured interviews with emergency medicine residents. We collected self-reported data related to educational debt and asked open-ended questions about debt influence on career choices, personal life, future plans, and financial decisions. We undertook a structured thematic analysis using a qualitative approach based in the grounded theory method. RESULTS: Median educational debt was $212,000. Six themes emerged from our analysis: (1) debt influenced career and life decisions by altering priorities; (2) residents experienced debt as a persistent source of background stress and felt powerless to change it; (3) residents made use of various techniques to negotiate debt in order to focus on day-to-day work; (4) personal debt philosophy, based on individual values and obtained from family, shaped how debt affected each individual; (5) debt had a normative effect and was acculturated in residency; and (6) residents reported a wide range of financial knowledge, but recognized its importance to career success. CONCLUSION: Our emergency medicine residents' debt experience is complex and involves multiple dimensions. Given our current understanding, simple solutions are unlikely to be effective in adequately addressing this issue.