Table 3.

Mouse models of orthopedic infections.

Model/Strain	Gender	Age/Weight	Microorganism/Concentration	Disease Model	Site of Inoculum	Timepoint	Aim of the Study	Results	Ref.
CD1	na	>6 months	S. aureus ATTC 49230. 2 to 3 mm length of 4–0 suture seeded with S. aureus.	Chronic osteomyelitis	Proximal tibia	2 h–28 days	To investigate the role of interleukin 4 in osteoclast activation and development of chronic osteomyelitis	IL4 may help to block the osteoclast reaction, which leads to more bone loss.	[139]
C3H/HeJ	na	8–10 weeks; 20–25 g	S. aureus LS-1. 5 × 107 UFC (injected into the tail vein).	Acute hematogenous osteomyelitis	Tibia (incomplete cartilaginous fracture)	7 days	To study the immunological responses to S. aureus bone infection	An increase of splenic B lymphocytes and in lymph–node CD4+ T lymphocytes was observed.	[145]
ICR	F	5–weeks; 25 g	S. aureus E-31461. 4.6 × 105 CFU/suture	Tibial osteomyelitis	Tibia	28 days	To evaluate local levels of IL-1 β, IL–4, IL-6, and TNF–α, in a model of murine osteomyelitis due to S. aureus	Levels of IL-1β and IL-6 in infected bone were elevated in the early post–infection period and then decreased. TNF levels remained elevated 3 to 28 days post–infection, while IL–4 levels were elevated late in the infection.	[185]
C57BL/6	F	6–8 weeks	S. aureus UAMS-1 ATCC 49230 and S. aureus Xen29 (derived from ATCC 12600). 9.5 ± 3.7 × 105 CFU/pin of UAMS-1 and 4.2 ± 0.5 × 105 CFU/pin of Xen29.	Implant–associated osteomyelitis	Tibial metaphysis	18 days	To develop a novel murine model of implant–associated osteomyelitis using steel pin coated with S. aureus	Histology confirmed all the characteristics of the associated implant. After one week, the mice produced IgM, which converted to IgG 11 days after implantation.	[181]
C57BL/6 wildtype and LysEGFP	M	12–weeks	S. aureus SH1000 strain, ALC2906 (contains the shuttle plasmid pSK236 with the penicillin–binding protein 2 promoter fused to the luxABCDE reporter cassette). 5 × 102, 5 × 103 and 5 × 104 CFU/mouse	Post–arthroplasty infections	Knee joint	7 and 14 days	To develop a model of post–arthroplasty Infection combining the use of bioluminescent bacteria and genetically engineered mice that possess fluorescent neutrophils (LysEGFP mice)	Chronic osteomyelitis was developed in mice infected with a low bacterial load, while acute osteomyelitis was developed in those who received 103 and 104. In vivo bioluminescence EGFP–neutrophil signals and fluorescence of LysEGFP mice are highly correlated with Ex vivo bacterial counts.	[182]
BALB/c	M	12 weeks; 20–25 g	S. aureus Xen-29. 1.0 × 108 CFU	Osteomyelitis	Femur	Not necessary	To establish a real–time quantitative mouse model of osteomyelitis using bioluminescence imaging	In infected mice, serum levels of interleukin–6, interleukin–1β and C–reactive protein were significantly higher.	[183]
C57BL/6 and LysEGFP	M	12–weeks	S. aureus ALC2906 S. aureus Xen29 (derived from the pleural fluid isolate ATCC 12600 with an antibiotic marker), S. aureus Xen40 (derived from the osteomyelitis isolate UAMS–1, inside chromosome) and S. aureus Xen36 (derived from the bacteremia isolate ATCC 49525, integrated into a stable plasmid). 1 × 102, 1 × 103 and 1 × 104 CFU.	Post–arthroplasty infections	Femur	42 days	To study the pathogenesis of post–arthroplasty infections with the use of bioimaging and non–invasive technology	A chronic post–arthroplasty infection model was developed. Up until day 10 ALC2906 had an increase in bioluminescent signals. On day 42, biofilms were detected on the implants inoculated with ALC2906. These results suggest that the construct was lost during in vivo replication.	[184]
NOD/ShiLtJ	F	23.3 ± 1.3 g	S. aureus. 103 CFU/mouse	Implant related infection	Femoral canal	28 days	To investigate the effect of a PGE1 vasodilator on the incidence of surgical infections in diabetic mice	Limited signs of infection were identified in mice treated with the combination of a PGE1 and an antibiotic using micro–CT and histological analysis.	[180]
C57BL/6	M	8 weeks	S. aureus USA300 LAC. 103 CFU	Orthopaedic biofilm infection	Femur	28 days	To examine the functional role of Myeloid–derived suppressor cells in shaping the anti–inflammatory milieu during S. aureus orthopedic biofilm infection	Increased expression of Arg–1, iNOS and IL-10. Bacterial clearance was improved due to the targeted depletion of MDSC and neutrophils using mAb 1A8 (antiLy6G).	[186]
C57BL/6NCr	M	8 weeks	S. aureus isolate USA300 LAC. 103 CFU	Orthopaedic implant infection	Femur	28 days	To study the pro–inflammatory ability of IL-12 in myeloid–derived suppressor cell recruitment and bacterial persistence	Several cytokines (IL-12p40, IL-1β, TNF–α, and G–CSF) and chemokines (CXCL2, CCL5) were significantly elevated. In both p40 and p35 KO Mice MDSC recruitment was significantly reduced.	[187]
C57BL/6	M	8 weeks	S. aureus. 2 × 103 CFU	Implant–associated osteomyelitis	Mid–diaphysis of the femur	3 days	To develop a model of implant–associated S. aureus osteomyelitis to study the expression of osteomyelitis associated genes (ERBB2, TWIST1, and NANOG)	Around the infected implant, an upregulation of TWIST1 in macrophages and an accumulation of macrophages was observed. In addition, the expression of TWIST1, MMP9, and MMP13, together with the migration and phagocytosis function of 264.7 cells were increased.	[188]
(NOD)–scid IL2Rγnull (NSG) mice	F	na	S. aureus. 5 × 105 CFU/mL	Orthopaedic implant infection	Tibia	14 days	To study the response of human immune cells during chronic S. aureus bone infections engrafting mice with hematopoietic stem cells (huNSG)	Compared to the control group, huNSG mice have increased weight loss, osteolysis, and bacterial spread to internal organs. Moreover, through flow cytometry and immunohistochemistry, more human T cells are present in infected huNGS mice than in uninfected ones.	[189]

Abbreviations: na = not available.