Phage K exposure generates phage-neutralizing activity in a rabbit model-humoral receptiveness may impact efficacy of phage therapy.

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 ~1010±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.

HOCl-producing electrochemical bandage for treating Pseudomonas aeruginosa-infected murine wounds.

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 106 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 log10 CFUs/g (P = 0.0107) vs non-polarized controls and 2.2 log10 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.

Duration of cefazolin prophylaxis did not impact infection risk in a murine model of joint arthroplasty.

To 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.

HOCl-producing Electrochemical Bandage is Active in Murine Polymicrobial Wound Infection.

Wound infections, exacerbated by the prevalence of antibiotic-resistant bacterial pathogens, necessitate innovative antimicrobial approaches. Polymicrobial infections, often involving Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), present formidable challenges due to biofilm formation and antibiotic resistance. Hypochlorous acid (HOCl), a potent antimicrobial agent produced naturally by the immune system, holds promise as an alternative therapy. An electrochemical bandage (e-bandage) that generates HOCl in situ was evaluated for treatment of murine wound biofilm infections containing both MRSA and P. aeruginosa with "difficult-to-treat" resistance. Previously, the HOCl-producing e-bandage was shown to reduce wound biofilms containing P. aeruginosa alone. Compared to non-polarized e-bandage (no HOCl production) and Tegaderm only controls, the polarized e-bandages reduced bacterial loads in wounds infected with MRSA plus P. aeruginosa (MRSA: vs Tegaderm only - 1.4 log10 CFU/g, p = 0.0015, vs. non-polarized - 1.1 log10 CFU/g, p = 0.026. P. aeruginosa: vs Tegaderm only - 1.6 log10 CFU/g, p = 0.0015, vs non-polarized - 1.6 log10 CFU/g, p = 0.0032), and MRSA alone (vs Tegaderm only - 1.3 log10 CFU/g, p = 0.0048, vs. non-polarized - 1.1 log10 CFU/g, p = 0.0048), without compromising wound healing or causing tissue toxicity. Addition of systemic antibiotics did not enhance the antimicrobial efficacy of e-bandages, highlighting their potential as standalone therapies. This study provides additional evidence for the HOCl-producing e-bandage as a novel antimicrobial strategy for managing wound infections, including in the context of antibiotic resistance and polymicrobial infections.

HOCl-producing Electrochemical Bandages for Treating Pseudomonas aeruginosa -Infected Murine Wounds.

A novel electrochemical bandage (e-bandage) delivering low-level hypochlorous acid (HOCl) was evaluated against Pseudomonas aeruginosa murine wound biofilms. 5 mm skin wounds were created on the dorsum of Swiss-Webster mice and infected with 10 6 colony forming units (CFU) of P. aeruginosa . Biofilms were formed over two 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 concurrently administered systemic amikacin. Purulence and wound areas were measured before and after treatment. After 48 hours, animals were sacrificed, and 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 (9.0 vs 7.6 log 10 ; p = 0.0107) vs non-polarized controls, and 2.2 log 10 CFU/g (9.8 vs 7.6 log 10 ; p = 0.004) vs Tegaderm only controls. Systemic 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 more purulence reduction in the polarized group (p = 0.009), but not in the non-polarized group (p = 0.064). Wound closure was not impeded or 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 infections.