Mouse model of Gram-negative prosthetic joint infection reveals therapeutic targets
John M. Thompson, … , Daniel L.J. Thorek, Lloyd S. Miller
John M. Thompson, … , Daniel L.J. Thorek, Lloyd S. Miller
Published September 6, 2018
Citation Information: JCI Insight. 2018;3(17):e121737. https://doi.org/10.1172/jci.insight.121737.
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Research Article Infectious disease Therapeutics

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.

Authors

John M. Thompson, Robert J. Miller, Alyssa G. Ashbaugh, Carly A. Dillen, Julie E. Pickett, Yu Wang, Roger V. Ortines, Robert S. Sterling, Kevin P. Francis, Nicholas M. Bernthal, Taylor S. Cohen, Christine Tkaczyk, Li Yu, C. Kendall Stover, Antonio DiGiandomenico, Bret R. Sellman, Daniel L.J. Thorek, Lloyd S. Miller

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Figure 5

In vitro biofilm-producing activity and the development of an in vivo Gram-negative prosthetic joint infection.

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In vitro biofilm-producing activity and the development of an in vivo Gr...
(A) In vitro biofilm formation of P. aeruginosa (P.a.) and E. coli (E.c.) strains in an in vitro microtiter biofilm assay, as measured by absorbance (550 nm) ± SEM (n = 15 replicate wells/strain). The in vivo mouse model of Gram-negative prosthetic joint infection (GN-PJI) was performed with a high in vitro biofilm-producing E. coli strain 25922 (E.c. 25922) or no bacteria (Un, uninfected). (B and C) Mean CFU ± SEM recovered from tissue samples for E. coli strain 25922 (E.c. 25922) (n = 15) vs. uninfected (n = 10) (B) and implants vs. uninfected (n = 10/group) (C). (D) Percentage of tissue and implant samples with the presence of bacterial growth using the groups from B and C. (E) Representative anteroposterior X-ray images: yellow bars indicate femoral width. (F) Mean femoral width (mm) ± SEM and mean femoral area (mm2) ± SEM (n = 10–15/group). (G) Representative low- (scale bars: 100 μm) and high-magnification (scale bars: 10 μm) scanning electron microscopy images of the intra-articular portion of the implant (n = 5/group). LOD, limit of detection. †P < 0.01, ‡P < 0.001 between indicated groups, as calculated by 1-way ANOVA model with heterogeneous within-group variance (P values from multiple comparisons were adjusted by step-up Bonferroni method) (A), nonparametric exact Wilcoxon rank-sum test (B and C), Fisher’s exact test (D), or two-sample t test (2 tailed) (F).