Modified Stain for Identification of Staphylococcus aureus in Osteomyelitis

Periprosthetic joint infections occur in about 2% of patients who undergo primary total joint arthroplasty, a procedure performed over 1 million times in the U.S. The gold standard of treatment is a two‐stage revision. This study aimed to establish a two‐stage procedure in a preclinical small animal model (rat) to test and compare the efficacy of an antibiotic‐eluting material in managing infection. Joint replacement was simulated by transchondylarly implanting a polyethylene (PE) plug into the distal femur and a titanium screw in the proximal tibia. Methicillin‐sensitive Staphylococcus aureus (MSSA) 108 CFU/mL was injected into the tibial canal and the joint space before wound closure. The control groups were sacrificed on post‐operative day (POD) 18 (n=12) and on POD 42 (n=4) to assess both early and later‐stage outcomes in the control group. The test group underwent revision surgery on POD 18 for treatment using gentamicin‐eluting polyethylene (GPE, n=4) and was observed until POD 42 to evaluate the efficacy of treatment. Our results showed that the bone loss for the treatment group receiving GPE was significantly less than that of the control (p < 0.05), which was supported by the histology images and an AI‐tool assisted infection rate evaluation. Gait metrics duty factor imbalance and hindlimb temporal symmetry were significantly different between the treatment and control groups on day 42. This animal model was feasible for evaluating treatments for peri‐prosthetic joint infections (PJI) with a revision surgery and specifically that revision surgery and local antibiotic treatment largely hindered the peri‐prosthetic bone loss.This article is protected by copyright. All rights reserved.

Section: Methodsmentioning

confidence: 99%

Section: Histological Analysismentioning

confidence: 99%

The efficacy of antibiotic‐eluting material in a two‐stage model of periprosthetic joint infection

Fan,

McCanne,

Yuh

et al. 2023

Treatment of experimental osteomyelitis by surgical debridement and the implantation of bioerodable, polyanhydride‐gentamicin beads

Nelson¹,

Hickmon²,

Skinner³

1997

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Osteomyelitis was induced in the radius in 77 rabbits and confirmed by histological examination and culture. At 4 weeks, the wounds were debrided and the animals were treated with (a) fatty acid dimer-sebacic acid beads (a bioerodable composite) impregnated with 20% or (b) 10% gentamicin sulfate, (c) placebo beads and intramuscular gentamicin sulfate, (d) placebo beads alone, or (e) debridement only. After 4 weeks, eradication of infection was determined by histological examination and culture. Osteomyelitis was eradicated in 93% of the animals treated with the beads and 20% gentamicin, in 67% of those treated with the beads and 10% gentamicin, in 25% of those treated with placebo beads and intramuscular gentamicin, in 7% of those treated with placebo beads alone, and in 12.5% of those treated with debridement only (p values from < 0.001 to 0.02). Fatty acid dimer-sebacic acid beads with gentamicin were then implanted in noninfected rabbits, and gentamicin sulfate concentrations in bone, serum, urine, and wound exudate were measured. Gentamicin sulfate was detectable in bone for as long as 8 weeks after implantation. Levels as high as 4,746 micrograms/ml were present in the wound exudate for the first 7 days. Levels in the serum peaked at 1.03 micrograms/ml. Urine levels peaked at 135 micrograms/ml.

Characterization of a rabbit model of staphylococcal osteomyelitis

Smeltzer

Thomas

Hickraon

et al. 1997

Self Cite

181

139

We previously described a rabbit osteomyelitis model that involved the direct introduction of Staphylococcus aureus into devascularized bone. To further evaluate the model, we performed experiments aimed at correlating the microbiological, radiographic, and histologic parameters involved in the development of experimental osteomyelitis. Using the strain UAMS-1, we achieved an infection rate of 75% with an inoculum as small as 2 x 10(3) colony-forming units. However, development of significant radiographic and histologic signs of disease required an inoculum of at least 2 x 10(4) colony-forming units. Radiographic signs were minimal 1 week after infection and progressed steadily to a maximum 3 weeks after infection. In contrast, histologic signs of disease were observed within 1 week and remained essentially unchanged throughout the 4-week evaluation period. Unlike the results obtained with UAMS-1, rabbits infected with the heavily encapsulated Staphylococcus aureus strain Smith diffuse exhibited little evidence of disease even when infected with 2 x 10(6) colony-forming units. The reduced virulence of strain Smith diffuse was surprising given its greatly enhanced virulence (relative to UAMS-1) in a murine peritonitis model of staphylococcal disease. These results suggest that UAMS-1 expresses virulence factors that are important in the pathogenesis of osteomyelitis and that some or all of these virulence factors are either absent or are not expressed in strain Smith diffuse. Most importantly, the results suggest that our model may be appropriate for the identification and characterization of these virulence factors.