Following distribution to various organ sites via the bloodstream, the pathogen recruits large numbers of neutrophils and other innate immune cells to the site of infection. targets for antibiotics and immunotherapies. Keywords:Staphylococcus aureus, osteomyelitis, adaptive immunity, immune proteome, orthopaedic infections, canalicular invasion == Introduction == Hard-to-treat, deep infections such as osteomyelitis remain a significant healthcare problem in the United NG52 States and around the world [1]. Even with major advances in surgical procedures, and novel antimicrobial therapies, the treatment failure rate remains high [24]. The cost to treat prosthetic joint associated osteomyelitis is projected to rise to $1.62 billion a year by 2020 due to the aging population in the United States [1,5,6]. Unfortunately, there has been little or no reduction in infection-related outcomes in several decades as the current standard of care treatments, developed in NG52 the 1970s, are still being employed in the US hospitals [7*9*]. Osteomyelitis, defined as an infection of the bone, can occur by: 1) the local spread of the bacteria from a contaminated bone to an adjacent uninfected bone, 2) contamination of the bone via the hematogenous route, and 3) bacterial invasion of the bone from an infected implant [10,11]. There are five distinct classes of osteomyelitis. These include: 1) prosthetic joint infection (PJI), the post-operative infection that occurs after a prosthetic joint has been placed, typically in the knee or hip; 2) fracture-related infection (FRI), a common complication in trauma surgery where patients typically present with open fractures; 3) acute hematogenous osteomyelitis (AHO), that arises due to seeding bacteria circulating in NG52 blood to the long bones; 4) diabetic NG52 foot infections (DFI), frequently observed as a polymicrobial infection of a diabetic foot ulcer that spreads contiguously to the underlying bone; and 5) osteomyelitis of the spine (OMS), that usually occurs postoperatively [1,10,11,12*,13,14]. The incidence rate of all classes of orthopaedic infections range from 0.1%30%, and treatment can cost up to $150,000 per patient in the US [7*]. The rate of PJI in primary arthroplasty remains between 1% and 2%, though re-infection rates remain far higher for these patients: 8% for hips and knees. Unfortunately, due to the aging population in the US, and the increased number of elective total knee and hip arthroplasties in the last two decades, the anticipated incidence rate of PJI will likely increase in the near future. Moreover, there is increasing incidence of arthroplasty procedures for other joints such as the ankle and shoulder, that could also affect the overall incidence of PJI [1,6,15]. The incidence rate for FRIs is much higher, from 10% to 50% depending on the fracture type [12,16]. Rabbit Polyclonal to C/EBP-alpha (phospho-Ser21) Typically, monomicrobial AHO represents about 20% of all osteomyelitis cases and is most prevalent in children and related to rapid bone growth; about 85% of AHO patients are under 17 years of age [1719]. Recently, AHO rates have increased in adults due to secondary conditions such as bacteremia induced by intravenous drug abuse associated with the opioid abuse crisis in the US [20,21]. Among the osteomyelitis patients, DFI patients have the highest mortality risk. Their five-year mortality rate is reported to be 50%, equal to that of the most life-threatening cancers [22]. Moreover, their quality of life is among the poorest of the osteomyelitis patients as two-thirds of lower extremity amputations are associated with DFI [13,23,24]. Finally, the post-operative occurrence rate of OMS is between 0.3 and 20%, a prevalence rate that is higher than all of the other classes of orthopaedic infections [14]. Most research on bone infections has centered onStaphylococcus aureus(S. aureus) due to its frequency, plasticity and resistance, and because it causes the majority of osteomyelitis cases.S. aureusis a gram-positive coccus, first isolated by Alexander Ogston from the pus of surgical wound infections in the1880s. An astounding 50% of the prosthetic joint-related orthopaedic infections are caused by.