Mouse model of Gram-negative prosthetic joint infection reveals therapeutic targets

Abstract

Bacterial biofilm infections of implantable medical devices decrease the effectiveness of antibiotics, creating difficult-to-treat chronic infections. Prosthetic joint infections (PJI) are particularly problematic because they require prolonged antibiotic courses and reoperations to remove and replace the infected prostheses. Current models to study PJI focus on Gram-positive bacteria, but Gram-negative PJI (GN-PJI) are increasingly common and are often more difficult to treat, with worse clinical outcomes. Herein, we sought to develop a mouse model of GN-PJI to investigate the pathogenesis of these infections and identify potential therapeutic targets. An orthopedic-grade titanium implant was surgically placed in the femurs of mice, followed by infection of the knee joint with Pseudomonas aeruginosa or Escherichia coli. We found that in vitro biofilm-producing activity was associated with the development of an in vivo orthopedic implant infection characterized by bacterial infection of the bone/joint tissue, biofilm formation on the implants, reactive bone changes, and inflammatory immune cell infiltrates. In addition, a bispecific antibody targeting P. aeruginosa virulence factors (PcrV and Psl exopolysaccharide) reduced the bacterial burden in vivo. Taken together, our findings provide a preclinical model of GN-PJI and suggest the therapeutic potential of targeting biofilm-associated antigens.

Preclinical Optical Imaging to Study Pathogenesis, Novel Therapeutics and Diagnostics Against Orthopaedic Infection

“…26 We found a direct correlation between in vitro biofilm-producing ability of P. aeruginosa or E. coli and the development of a robust Gram-negative OIAI in vivo. 26 In addition, we developed a preclinical mouse model of hematogenous OIAI by first performing sterile placement of the K-wire into the femurs of mice 3 weeks prior to an intravenous inoculation of a bright and virulent community-acquired MRSA bioluminescent strain (SAP231 13 ). 27 This resulted in a marked predilection of the hematogenous-spread OIAI in post-surgical knees possessing an implant, compared with contralateral native knees or in the knees of mice that had sham surgery without placement of the implant.…”

“…Other preclinical models have used in vivo BLI to study the pathogenesis in preclinical models of OIAI caused by various types of bacteria, in different anatomical locations of the infection, and involving different types of implants. For example, given that Gram‐negative bacteria are an increasingly common cause of OIAI in humans, we used either a bioluminescent Pseudomonas aeruginosa strain (Xen41) or a bioluminescent Escherichia coli strain (Xen14) in our K‐wire mouse model of OIAI . We found a direct correlation between in vitro biofilm‐producing ability of P. aeruginosa or E. coli and the development of a robust Gram‐negative OIAI in vivo .…”

“…For example, given that Gram‐negative bacteria are an increasingly common cause of OIAI in humans, we used either a bioluminescent Pseudomonas aeruginosa strain (Xen41) or a bioluminescent Escherichia coli strain (Xen14) in our K‐wire mouse model of OIAI . We found a direct correlation between in vitro biofilm‐producing ability of P. aeruginosa or E. coli and the development of a robust Gram‐negative OIAI in vivo . In addition, we developed a preclinical mouse model of hematogenous OIAI by first performing sterile placement of the K‐wire into the femurs of mice 3 weeks prior to an intravenous inoculation of a bright and virulent community‐acquired MRSA bioluminescent strain (SAP231) .…”

“…We reported that in vivo BLI could successfully be used in our preclinical mouse model of a hematogenous OIAI model to show that a combination of mAbs targeting S. aureus α‐toxin and ClfA (which are both involved in S. aureus biofilm formation) significantly decreased the marked predilection of a hematogenous‐spread OIAI . Furthermore, we successfully used in vivo BLI to demonstrate that a novel bispecific mAb (MEDI3902) targeting P. aeruginosa virulence factors PcrV (which facilitates bacterial aggregation) and Psl (an exopolysaccharide involved in biofilm formation and maintenance) was effective in reducing the bacterial burden in our Gram‐negative P. aeruginosa (Xen41) OIAI model . Finally, in vivo BLI and FLI imaging has been combined to evaluate host‐related factors in treating OIAI.…”

“…27 Furthermore, we successfully used in vivo BLI to demonstrate that a novel bispecific mAb (MEDI3902) targeting P. aeruginosa virulence factors PcrV (which facilitates bacterial aggregation) and Psl (an exopolysaccharide involved in biofilm formation and maintenance) was effective in reducing the bacterial burden in our Gram-negative P. aeruginosa (Xen41) OIAI model. 26 Finally, in vivo BLI and FLI imaging has been combined to evaluate host-related factors in treating OIAI. For instance, Hegde et al 53 in the Kwire mouse model of OIAI found that vitamin D deficient mice had increased bacterial burden and inflammation compared with vitamin D sufficient or replenished mice.…”