Hydrogen Peroxide, Povidone-Iodine and Chlorhexidine Fail to Eradicate Staphylococcus aureus Biofilm from Infected Implant Materials

Hydrogen peroxide, povidone-iodine, and chlorhexidine are antiseptics that are commonly added to irrigants to either prevent or treat infection. There are little clinical data available that demonstrate efficacy of adding antiseptics to irrigants in the treatment of periprosthetic joint infection after biofilm establishment. The objective of the study was to assess the bactericidal activity of the antiseptics on S. aureus planktonic and biofilm. For planktonic irrigation, S. aureus was exposed to different concentrations of antiseptics. S. aureus biofilm was developed by submerging a Kirschner wire into normalized bacteria and allowing it to grow for forty-eight hours. The Kirschner wire was then treated with irrigation solutions and plated for CFU analysis. Hydrogen peroxide, povidone-iodine, and chlorhexidine were bactericidal against planktonic bacteria with over a 3 log reduction (p < 0.0001). Unlike cefazolin, the antiseptics were not bactericidal (less than 3 log reduction) against biofilm bacteria but did have a statistical reduction in biofilm as compared to the initial time point (p < 0.0001). As compared to cefazolin treatment alone, the addition of hydrogen peroxide or povidone-iodine to cefazolin treatment only additionally reduced the biofilm burden by less than 1 log. The antiseptics demonstrated bactericidal properties with planktonic S. aureus; however, when used to irrigate S. aureus biofilms, these antiseptics were unable to decrease biofilm mass below a 3 log reduction, suggesting that S. aureus biofilm has a tolerance to antiseptics. This information should be considered when considering antibiotic tolerance in established S. aureus biofilm treatment

Implant orientation accuracy of a hand-held robotic partial knee replacement system over conventional technique in a cadaveric test

Unicondylar Knee Arthroplasty (UKA) is a minimally-invasive surgical procedure for treating isolated compartmental knee osteoarthritis. Accurate implant placement is crucial for a successful UKA procedure. Previous work has shown the improvement in UKA by using robotic systems. Here, we present the implant alignment accuracy of a hand-held robotic UKA system compared with a conventional manual UKA system for 12 cadaver specimens. Two surgeons carried out equal number of medial UKAs with robotic UKA on one knee and the manual UKA on the other knee. Preoperative and postoperative computed tomography (CT) scans were obtained for each cadaveric model. The final implant positions were identified in the postoperative CT scan. The implant orientations were compared with the planned implant positions to obtain femoral and tibial implant alignment errors. Our results show that the femoral flexion, varus, and rotation root mean square errors for the robotic and conventional approach were 1.23°, 2.81°, 1.62° and 7.52°, 6.25°, 5.0°, respectively. The tibial slope and varus errors for the robotic and conventional approaches were 2.41°, 2.96° and 4.06°, 1.8°, respectively. We did not find any statistical significant difference (p = .05) in the performance of the two surgeons. We conclude that the hand-held robotic UKA system offers significant improvement in the final implant placemen

Elimination of Antibiotic Resistant Surgical Implant Biofilms Using an Engineered Cationic Amphipathic Peptide WLBU2

Abstract Antibiotics are unable to remove biofilms from surgical implants. This high antibiotic tolerance is related to bacterial persisters, a sub-population of bacteria phenotypically tolerant to antibiotics secondary to a reduced metabolic state. WLBU2 is an engineered cationic amphipathic peptide designed to maximize antimicrobial activity with minimal mammalian cell toxicity. The objective of this study was to test the ability of WLBU2 to remove Staphylococcus aureus surgical implant biofilms. WLBU2 effectively treated S. aureus biofilms formed by a variety of clinical MSSA and MRSA strains and created culture-negative implants in the in vitro biofilm model. Blocking bacterial metabolism by inhibiting oxidative phosphorylation did not affect WLBU2 killing compared to decreased killing by cefazolin. In the surgical implant infection animal model, WLBU2 decreased biofilm mass as compared to control, untreated samples. WLBU2 could rapidly eliminate implants in vitro and had sufficient efficacy in vivo with minimal systemic toxicity

The Toxin-Antitoxin MazEF Drives Staphylococcus aureus Biofilm Formation, Antibiotic Tolerance, and Chronic Infection

Surgical infections are one of the most common types of infections encountered in a hospital. Staphylococcus aureus is the most common pathogen associated with this infection. These infections are resilient and difficult to eradicate, as the bacteria form biofilm, a community of bacteria held together by an extracellular matrix. Compared to bacteria that are planktonic, bacteria in a biofilm are more resistant to antibiotics. The mechanism behind how bacteria develop this resistance and establish a chronic infection is unknown. We demonstrate that mazEF, a toxin-antitoxin gene, inhibits biofilm formation and promotes biofilm antibiotic tolerance which allows S. aureus to transition from an acute to chronic infection that cannot be eradicated with antibiotics but is less virulent. This gene not only makes the bacteria more tolerant to antibiotics but makes the bacteria more tolerant to the host.Staphylococcus aureus is the major organism responsible for surgical implant infections. Antimicrobial treatment of these infections often fails, leading to expensive surgical intervention and increased risk of mortality to the patient. The challenge in treating these infections is associated with the high tolerance of S. aureus biofilm to antibiotics. MazEF, a toxin-antitoxin system, is thought to be an important regulator of this phenotype, but its physiological function in S. aureus is controversial. Here, we examined the role of MazEF in developing chronic infections by comparing growth and antibiotic tolerance phenotypes in three S. aureus strains to their corresponding strains with disruption of mazF expression. Strains lacking mazF production showed increased biofilm growth and decreased biofilm antibiotic tolerance. Deletion of icaADBC in the mazF::Tn background suppressed the growth phenotype observed with mazF-disrupted strains, suggesting the phenotype was ica dependent. We confirmed these phenotypes in our murine animal model. Loss of mazF resulted in increased bacterial burden and decreased survival rate of mice compared to its wild-type strain demonstrating that loss of the mazF gene caused an increase in S. aureus virulence. Although lack of mazF gene expression increased S. aureus virulence, it was more susceptible to antibiotics in vivo. Combined, the ability of mazF to inhibit biofilm formation and promote biofilm antibiotic tolerance plays a critical role in transitioning from an acute to chronic infection that is difficult to eradicate with antibiotics alone

Revision Total Knee Arthroplasty With an Imageless, Second-Generation Robotic System

Robotic-assisted total knee arthroplasty (RA-TKA) is increasingly used in revision TKA (rTKA), with imageless systems recently receiving Food and Drug Administration (FDA) approval. However, there remains a paucity of literature on the use of robotic assistance in revision TKA. This paper describes the imageless surgical technique for robotic revision TKA using a second-generation robotic system and details both intraoperative and 90-day outcomes. This was a retrospective review of 115 robotic revision TKAs from March 2021 to May 2023 at three tertiary academic centers. Patient demographics, perioperative surgical data, and 90-day outcomes were collected. Pain and Patient-Reported Outcomes Measurement Information System (PROMIS) scores pre- and post-operatively were recorded. All-cause reoperations at the final follow-up were detailed. The mean patient age was 65 years (range, 43 to 88), and 58% were women. The mean follow-up time was 13 months (range, 3 to 51). The most common indications for rTKA were instability (n = 37, 32%) and aseptic loosening (n = 42, 37%). There were 83 rTKAs to a posterior-stabilized liner, 22 to a varus-valgus constrained liner, and five to a hinged construct. The median polyethylene size was 11 (IQR [interquartile range], 10 to 13), and 93% of patients had their joint line restored within five millimeters of the native contralateral knee. Within the 90-day postoperative window, there were eight Emergency Department visits and two readmissions. At the final follow-up, there were five reoperations and two manipulations under anesthesia. There were four patients who required irrigation and debridement after superficial wound dehiscence, and one had an arthrotomy disruption after a fall. This review demonstrates favorable intraoperative and 90-day outcomes and suggests that imageless robotic surgery is a promising modality in rTKA. Further studies comparing the longitudinal outcomes after robotic and conventional rTKA are warranted