Koscianski, Christina

AbstractTo minimize periprosthetic joint infection (PJI) risk, some clinicians prescribe extended antibiotic prophylaxis (EAP) following total joint arthroplasty (TJA). Given the limited evidence supporting EAP, we sought to evaluate impact of prophylactic antibiotic duration on PJI risk in a murine TJA model. A titanium prosthesis was implanted into the proximal tibia of 89 mice and inoculated with 102 colony forming units (cfu) of Staphylococcus aureus Xen36. Control mice (n = 20) did not receive antibiotics. Treated mice received either 24 h (n = 35) or 4 days (n = 34) of cefazolin prophylaxis. Cultures were obtained from the prostheses, tibia, femur, and knee tissues 3 weeks after surgery. All mice in the control group developed PJI. Both prophylaxis regimens reduced the rate of PJI relative to the control, with only 2/35 mice in the 24‐h cohort (p < 0.0001) and 1/34 in 4‐day cohort developing PJI (p < 0.0001). CFU counts from the prostheses, bone and knee tissues were reduced for the 24‐h and 4‐day prophylaxis cohorts relative to the control (p < 0.0001 for both). There was no difference in rates of PJI or CFU counts between the two prophylaxis cohorts (p = 0.58). Prophylactic cefazolin profoundly reduced rates of PJI in a murine model of TJA in which all control animals developed PJI. Extending cefazolin prophylaxis duration from 24 h to 4 days did not result in improved PJI rates or decreased bacterial loads in infected cases. While these results strongly support use of antibiotic prophylaxis for TJA, EAP did not appear to add benefit in the described mouse model.

ABSTRACT Phage therapy has not been established in the clinical routine, in part due to uncertainties concerning efficacy and immunogenicity. Here, three rabbits were immunized against staphylococcal phage K to assess viral potency in the presence of immunized serum. Three rabbits received weekly intramuscular injections of ~10 10±1 pfu/mL phage K. Phage K-specific IgG formation was measured by an enzyme-linked immunosorbent assay (ELISA); phage inactivation was assessed by calculating K-rates. Using transmission electron microscopy (TEM) and immunogold labeling, antibody binding to phage K was visualized. This was numerically assessed by objective imaging analysis comparing the relative distances of each gold particle to the nearest phage head and tail structure. Immunization led to a strong IgG response, plateauing 7 days after the last phage injection. There was no significant correlation between K-rate and antibody titer over time. TEM showed IgG binding to the head structure of phage K. Image analysis showed a significant reduction in relative distances between antibodies and phage head structures when comparing samples from day 0 and day 28 ( P < 0.0001). These results suggest that while individual serum analysis for antibodies against therapeutic phage bears consideration prior to and with prolonged therapy, during phage application, the formation of specific antibodies against phage may only partially explain decreased phage potency in the presence of immunized serum. Instead, other factors may contribute to an individual’s “humoral receptiveness” to phage therapy. Future investigations should be directed toward the identification of the humoral factors that have the most significant predictive value on phage potency in vivo .

ABSTRACT The growing threat of antibiotic-resistant bacterial pathogens necessitates the development of alternative antimicrobial approaches. This is particularly true for chronic wound infections, which commonly harbor biofilm-dwelling bacteria. A novel electrochemical bandage (e-bandage) delivering low-levels of hypochlorous acid (HOCl) was evaluated against Pseudomonas aeruginosa murine wound biofilms. 5 mm skin wounds were created on the dorsum of mice and infected with 10 6 colony-forming units (CFU) of P. aeruginosa . Biofilms were formed over 2 days, after which e-bandages were placed on the wound beds and covered with Tegaderm. Mice were administered Tegaderm-only (control), non-polarized e-bandage (no HOCl production), or polarized e-bandage (using an HOCl-producing potentiostat), with or without systemic amikacin. Purulence and wound areas were measured before and after treatment. After 48 hours, wounds were harvested for bacterial quantification. Forty-eight hours of polarized e-bandage treatment resulted in mean biofilm reductions of 1.4 log 10 CFUs/g ( P = 0.0107) vs non-polarized controls and 2.2 log 10 CFU/g ( P = 0.004) vs Tegaderm-only controls. Amikacin improved CFU reduction in Tegaderm-only ( P = 0.0045) and non-polarized control groups ( P = 0.0312) but not in the polarized group ( P = 0.3876). Compared to the Tegaderm-only group, there was less purulence in the polarized group ( P = 0.009). Wound closure was neither impeded nor improved by either polarized or non-polarized e-bandage treatment. Concurrent amikacin did not impact wound closure or purulence. In conclusion, an HOCl-producing e-bandage reduced P. aeruginosa in wound biofilms with no impairment in wound healing, representing a promising antibiotic-free approach for addressing wound infection.

Abstract Background Periprosthetic joint infection (PJI) is a devastating complication following joint replacement, associated with morbidity and mortality. Here, we established a clinically representative murine model of knee arthroplasty and determined the ideal bacterial inoculum that would result in PJI without causing significant limb compromise.Figure 1.An example of an uninfected titanium prosthesis osseointegrated into the tibia of a mouse. Methods A titanium tibial prosthesis designed for the murine knee was 3D printed and surgically implanted into the proximal tibia (Figure 1) of 38 C57BL/6 mice. The prosthesis is designed to osseointegrate into the tibia and has a smooth articular surface to allow for immediate weight bearing and range of motion. At the time of surgery, the arthroplasty was inoculated with five inocula of Staphylococcus aureus Xen36, ranging from 29 to 14,000 colony forming units (CFU) (Table 1). Mice were sacrificed at 3 weeks, or earlier if necessary due to infectious sequelae, and the joint tissue, tibia, femur, and prosthesis quantitatively cultured. Results All mice inoculated with 181 to 14,000 CFU developed PJI as did 90% inoculated with 29 CFU. Bacterial loads from joint tissues and tibial prostheses are shown in Table 1. All mice inoculated with 14,000 and 760 CFU had overt findings of infection (abscesses, sinus tracts, significant limb dysfunction) requiring early euthanasia (Table 2). Mice inoculated with 640 CFU had swelling, redness, and small sores in first 3 days, and 1 death, but otherwise appeared well; only 2/9 had a visible abscess at 3-week sacrifice. 2/10 mice receiving 181 CFU had small sores that resolved in the first week; all limbs functioned well prior to sacrifice. Mice receiving 29 CFU had no external evidence of infection, however 9/10 had purulence within the joint at sacrifice. Conclusion This study demonstrates that inoculum size directly impacts clinical manifestations of infection in a murine model of S. aureus PJI. An inoculum of 181 CFU resulted in universal infection without significantly compromising the limb. The ability of this model to create PJI without overt infectious sequela will allow for evaluation of therapeutics, including those locally delivered. Disclosures Robin Patel, MD, Abbott Laboratories: Advisor/Consultant|Adaptive Phage Therapeutics: Grant/Research Support|Adaptive Phage Therapeutics: Mayo Clinic has a royalty-bearing know-how agreement and equity in Adaptive Phage Therapeutics.|BIOFIRE: Grant/Research Support|CARB-X: Advisor/Consultant|ContraFect: Grant/Research Support|Day Zero Diagnostics: Advisor/Consultant|HealthTrackRx: Advisor/Consultant|Mammoth Biosciences: Advisor/Consultant|Netflix: Advisor/Consultant|Oxford Nanopore Technologies: Advisor/Consultant|PhAST: Advisor/Consultant|See details: Patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic|See details: continued, patent on an anti-biofilm substance issued|TenNor Therapeutics Limited: Grant/Research Support|Torus Biosystems: Advisor/Consultant|Trellis Bioscience, Inc.: Advisor/Consultant Nicholas Bedard, MD, Stryker: Advisor/Consultant