Biofilm Growth on Simulated Fracture Fixation Plates Using a Customized CDC Biofilm Reactor for a Sheep Model of Biofilm-Related Infection

In vitro antibiofilm efficacy of ertapenem, tobramycin, and moxifloxacin against biofilms grown in a glass bead or CDC Biofilm Reactor®

Laboratory grown biofilms are used to simulate bacterial growth in diverse environmental conditions and screen the effectiveness of anti-biofilm therapies. Recently, we developed a glass bead biofilm reactor that utilizes low broth volume to provide high-throughput biofilm growth for testing and translation across the research continuum (e.g., benchtop assays to preclinical models). Bioburden per mm2 surface area of Staphylococcus aureus and Pseudomonas aeruginosa biofilms were comparable on beads and CDC Biofilm Reactor® coupons. In this study, we hypothesized that biofilms grown on beads would be more susceptible to ertapenem, moxifloxacin, and tobramycin than those grown on coupons. Results indicated a significant reduction in S. aureus bioburden on glass beads compared to glass coupons following treatment with ertapenem (p = 0.005) and tobramycin (p = 0.014). P. aeruginosa biofilms had smaller differences in antibiotic response between the two systems. There was a significantly greater reduction in bead P. aeruginosa biofilm than coupon when treated with tobramycin (p = 0.035). This work offered insight into how the bead biofilm reactor could be used as a tool for antibiotic screening and translation across the continuum of in vitro to in vivo systems that support development of antimicrobial technology.

Alternating magnetic fields (AMF) and linezolid reduce Staphylococcus aureus biofilm in a large animal implant model

OBJECTIVES

We aimed to evaluate the effectiveness of alternating magnetic fields (AMF) combined with antibiotics in reducing Staphylococcus aureus biofilm on metal implants in a large animal model, compared to antibiotics alone.

METHODS

Metal plates were inoculated with a clinical MRSA strain and then implanted into thirty-three ewes divided into three groups: positive control, linezolid only, and a combination of linezolid and AMF. Animals had either titanium or cobalt-chrome plates and were sacrificed at 5 or 21 days post-implantation. Blood and tissue samples were collected at various time points post-AMF treatment.

RESULTS

In vivo efficacy studies demonstrated significant biofilm reduction on titanium and cobalt-chrome implants with AMF-linezolid combination treatment compared to controls. Significant bacterial reductions were also observed in surrounding tissues and bones. Cytokine analysis showed improved inflammatory responses with combination therapy, and histopathology confirmed reduced inflammation, necrosis, and bacterial presence, especially at 5 days post-implantation.

CONCLUSIONS

This study demonstrates that combining AMF with antibiotics significantly reduces biofilm-associated infections on metal implants in a large animal model. Numerical simulations confirmed targeted heating, and in vivo results showed substantial bacterial load reduction and reduced inflammatory response. These findings support the potential of AMF as a non-invasive treatment for prosthetic joint infections.

A Bead Biofilm Reactor for High-Throughput Growth and Translational Applications

Bacteria in natural ecosystems such as soil, dirt, or debris preferentially reside in the biofilm phenotype. When a traumatic injury, such as an open fracture, occurs, these naturally dwelling biofilms and accompanying foreign material can contaminate the injury site. Given their high tolerance of systemic levels of antibiotics that may be administered prophylactically, biofilms may contribute to difficult-to-treat infections. In most animal models, planktonic bacteria are used as initial inocula to cause infection, and this might not accurately mimic clinically relevant contamination and infection scenarios. Further, few approaches and systems utilize the same biofilm and accompanying substrate throughout the experimental continuum. In this study, we designed a unique reactor to grow bacterial biofilms on up to 50 silica beads that modeled environmental wound contaminants. The data obtained indicated that the reactor system repeatably produced mature Staphylococcus aureus and Pseudomonas aeruginosa biofilms on the silica beads, with an average of 5.53 and 6.21 log10 colony-forming units per mm2, respectively. The bead substrates are easily manipulable for in vitro or in vivo applications, thus improving translatability. Taken together, the bead biofilm reactor presented herein may be a useful system for repeatably growing established biofilms on silica beads that could be used for susceptibility testing and as initial inocula in future animal models of trauma-related injuries.

Advances in Animal Models for Studying Bone Fracture Healing

Fracture is a common traumatic injury that is mostly caused by traffic accidents, falls, and falls from height. Fracture healing is a long-term and complex process, and the mode of repair and rate of healing are influenced by a variety of factors. The prevention, treatment, and rehabilitation of fractures are issues that urgently need to be addressed. The preparation of the right animal model can accurately simulate the occurrence of fractures, identify and observe normal and abnormal healing processes, study disease mechanisms, and optimize and develop specific treatment methods. We summarize the current status of fracture healing research, the characteristics of different animal models and the modeling methods for different fracture types, analyze their advantages and disadvantages, and provide a reference basis for basic experimental fracture modeling.