Targeting intracellular Staphylococcus aureus to lower recurrence of orthopaedic infection.

Staphylococcus aureus is often found in orthopaedic infections and may be protected from commonly prescribed antibiotics by forming biofilms or growing intracellularly within osteoblasts. To investigate the effect of non-antibiotic compounds in conjunction with antibiotics to clear intracellular and biofilm forming S. aureus causing osteomyelitis. SAOS-2 osteoblast-like cell lines were infected with S. aureus BB1279. Antibiotics (vancomycin, VAN; and dicloxacillin, DICLOX), bacterial efflux pump inhibitors (piperine, PIP; carbonyl cyanide m-chlorophenyl hydrazone, CCCP), and bone morphogenetic protein (BMP-2) were evaluated individually and in combination to kill intracellular bacteria. We present direct evidence that after gentamicin killed extracellular planktonic bacteria and antibiotics had been stopped, seeding from the infected osteoblasts grew as biofilms. VAN was ineffective in treating the intracellular bacteria even at 10× MIC; however in presence of PIP or CCCP the intracellular S. aureus was significantly reduced. Bacterial efflux pump inhibitors (PIP and CCCP) were effective in enhancing permeability of antibiotics within the osteoblasts and facilitated killing of intracellular S. aureus. Confocal laser scanning microscopy (CLSM) showed increased uptake of propidium iodide within osteoblasts in presence of PIP and CCCP. BMP-2 had no effect on growth of S. aureus either alone or in combination with antibiotics. Combined application of antibiotics and natural agents could help in the treatment of osteoblast infected intracellular bacteria and biofilms associated with osteomyelitis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1086-1092, 2018.

Effects of loading concentration, blood and synovial fluid on antibiotic release and anti-biofilm activity of bone cement beads.

Antibiotic loaded cement beads are commonly used for the treatment of biofilm related orthopaedic periprosthetic infections; however the effects of antibiotic loading and exposure of beads to body fluids on release kinetics are unclear. The purpose of this study was to determine the effects of (i) antibiotic loading density (ii) loading amount (iii) material type and (iv) exposure to body fluids (blood or synovial fluid) on release kinetics and efficacy of antibiotics against planktonic and lawn biofilm bacteria. Short-term release into an agar gel was evaluated using a fluorescent tracer (fluorescein) incorporated in the carrier materials calcium sulfate (CaSO4) and poly methyl methacrylate (PMMA). Different fluorescein concentrations in CaSO4 beads were evaluated. Mechanical properties of fluorescein-incorporated beads were analyzed. Efficacy of the antibiotics vancomycin (VAN) or tobramycin (TOB) alone and in combination was evaluated against lawn biofilms of bioluminescent strains of Staphylococcus aureus and Pseudomonas aeruginosa. Zones of inhibition of cultures (ZOI) were measured visually and using an in-vivo imaging system (IVIS). The influence of body fluids on release was assessed using CaSO4 beads that contained fluorescein or antibiotics and were pre-coated with human blood or synovial fluid. The spread from the beads followed a square root of time relationship in all cases. The loading concentration had no influence on short-term fluorescein release and pre-coating of beads with body fluids did not affect short-term release or antibacterial activity. Compared to PMMA, CaSO4 had a more rapid short term rate of elution and activity against planktonic and lawn biofilms. This study highlights the importance of considering antibiotic loading and packing density when investigating the clinical application of bone cements for infection management.

Best practices for centers of excellence in addressing periprosthetic joint infection.

Periprosthetic joint infection is a rare and devastating complication. Management of this complication often requires a multidisciplinary approach similar to that used for the care of patients with cancer. Several studies have reported better outcomes following total joint arthroplasties performed at specialized hospitals than those performed at general hospitals. Specialized institutions use care pathways that aid the multidisciplinary team in decision making. During the recent Musculoskeletal Infection symposium, specific issues were discussed with regard to the treatment of periprosthetic joint infection, including medical optimization, systematic approaches to infection management, and the importance of establishing registries to aid in the creation of Centers of Excellence. A Center of Excellence in periprosthetic infection could provide better overall outcomes with lower financial, physical, and emotional costs to patients.

Comparing PMMA and calcium sulfate as carriers for the local delivery of antibiotics to infected surgical sites.

Antibiotic-loaded bone cement is a primary option for treatment of orthopedic infections. Poly(methyl methacrylate) (PMMA) is a widely used cement that, when loaded with antibiotics in spacer or bead form, has been shown to reduce infection rates. However, PMMA is not resorbable and requires a second surgery for removal, while also acting as a potential foreign body for bacterial colonization. Alternatively, resorbable bone cements, such as calcium sulfate, have been proposed and present the advantage of being completely reabsorbed. It is unknown whether the antibiotic elution characteristics of absorbable bone cements are similar to PMMA. This study (1) characterized antibiotic elution from synthetic, highly purified calcium sulfate cement beads of varying sizes against pathogenic bacteria both in liquid culture and seeded on agar plates, (2) tested calcium sulfate beads against PMMA beads loaded with the same antibiotics, and (3) analyzed the structural differences between how PMMA and calcium sulfate bind to antibiotics. In every assay, the calcium sulfate beads performed as well as, or better than, the PMMA beads in inhibition of bacterial growth and elution of vancomycin in vitro with complete elution observed from calcium sulfate within three days. These data suggest that calcium sulfate, functions, as well as PMMA in the patient setting for infection control.

Biofilms in periprosthetic orthopedic infections.

As the number of total joint arthroplasty and internal fixation procedures continues to rise, the threat of infection following surgery has significant clinical implications. These infections may have highly morbid consequences to patients, who often endure additional surgeries and lengthy exposures to systemic antibiotics, neither of which are guaranteed to resolve the infection. Of particular concern is the threat of bacterial biofilm development, since biofilm-mediated infections are difficult to diagnose and effective treatments are lacking. Developing therapeutic strategies have targeted mechanisms of biofilm formation and the means by which these bacteria communicate with each other to take on specialized roles such as persister cells within the biofilm. In addition, prevention of infection through novel coatings for prostheses and the local delivery of high concentrations of antibiotics by absorbable carriers has shown promise in laboratory and animal studies. Biofilm development, especially in an arthoplasty environment, and future diagnostic and treatment options are discussed.

Size and composition of synthetic calcium sulfate beads influence dissolution and elution rates in vitro.

Treatments of osteomyelitis lag behind bacterial resistance to antibiotics. We tested different-sized calcium sulfate beads and their ability to elute multiple antibiotics in vitro as a possible method to improve the therapeutic delivery in patients. Two sizes of calcium sulfate beads (4.8 and 3.0 mm diameter) that contained vancomycin, tobramycin, or both were dissolved in phosphate-buffered saline, and the rate of dissolution by weight and antibiotic elution by the disc diffusion assay and high-pressure liquid chromatography were measured. The 4.8 mm beads showed significantly higher dissolution rates relative to the 3.0 mm beads (2.3 mg/day vs. 1.3 mg/day). While the vancomycin-loaded 4.8 mm beads eluted for a longer time relative to the 3.0 mm beads (20 days vs. 10 days), the smaller beads had threefold higher elution for the first 2 days, before dropping to near zero elution by day 4. The presence of tobramycin extended the elution of the vancomycin to day 40, which closely matches the recommended 6 weeks to treat orthopedic staphylococcus infections. These data suggest that size and content of the bead are variables that could affect their clinical success, and both could be exploited to tailor treatments of specific infections and injuries.

A rabbit osteomyelitis model to simulate multibacterial war wound infections.

A challenge facing military caregivers is the presence of multidrug-resistant infection in extremity wounds. Most frequently identified resistant strains are methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae (KP), Pseudomonas aeruginosa (PA), and Acinetobacter baumannii (AB). We adapted an existing osteomyelitis model to simulate an infected extremity wound for antibiotic testing. New Zealand White Rabbits (n = 95) were divided into 6 inoculation groups for infection with MRSA, KP, PA, and AB alone, and in multibacteria infections. Sodium morrhuate was injected into the left tibia to simulate blast wound trauma, then the respective bacteria or combination of pathogens, and finally sterile saline were injected. Colony-forming units for the mono-organism groups showed that AB, KP, or PA alone at 10(7) colony-forming units per mL (CFUs/mL) was effective for rabbit osteomyelitis induction. Colony-forming units for the multiorganism groups showed that the combination of AB (10(7) CFUs/mL)/KP (10(7) CFUs/mL)/PA (10(7) CFUs/mL)/MRSA (10(5) CFUs/mL) yielded a 100% osteomyelitis induction rate. At 8 weeks, however, only one mono-bacterial group and one multibacterial group showed significant radiographic improvement (p < 0.05). The rabbit model of osteomyelitis can be adapted to study infected blast wounds typical of those seen in veterans. To our knowledge, this is the first demonstration of the model simulating multibacterial infections with multidrug-resistant organisms.

Medical comorbidities are independent preoperative risk factors for surgical infection after total joint arthroplasty.

BACKGROUND: Surgical site infection (SSI) after total joint arthroplasty (TJA) is a major cause of morbidity. Multiple patient comorbidities have been identified as SSI risk factors including obesity, tobacco use, diabetes, immunosuppression, malnutrition, and coagulopathy. However, the independent effect of multiple individual patient factors on risk of subsequent periprosthetic infection is unclear. QUESTIONS/PURPOSES: The purposes of this study are (1) to collect data on several preestablished infection risk factors in addition to SSI-related data on a large TJA cohort; and (2) to use multivariate modeling on previously established patient risk factors to determine independent preoperative predictors of SSI. METHODS: We reviewed records of patients undergoing TJA from January 1, 2010, to July 30, 2012. Confirmation of SSI followed published guidelines for superficial, deep, and periprosthetic. A total of 29 culture-positive SSIs (1.5% total) and 1846 controls were identified. The prevalence of known patient-specific infection risk factors was determined for both infected cases and healthy control subjects followed by multiple regression analysis to determine independent risk. RESULTS: Isolated organisms consisted of methicillin-resistant Staphylococcus aureus (MRSA; 34.5%) followed by gram-negative rods (31.0%). After adjusting for anatomic site, independent risk factors for infection include: revision surgery (odds ratio [OR], 2.28; confidence interval [CI], 1.26-3.98), super obesity (body mass index>50 kg/m2; OR, 5.28; CI, 1.38-17.1), diabetes mellitus (OR, 1.83; CI, 1.02-3.27), tobacco abuse (OR, 2.96; CI, 1.65-5.11), MRSA colonization or infection (OR, 4.17; CI, 1.63-9.66), and current or prior bone cancer (OR, 3.86; CI, 1.21-12.79). CONCLUSIONS: Multiple patient comorbidities independently contribute to infection risk after TJA. Preoperative TJA infection risk stratification may be feasible and should be investigated further. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Executive summary: Guidelines for the prevention of infections associated with combat-related injuries: 2011 update: endorsed by the Infectious Diseases Society of America and the Surgical Infection Society.

Despite advances in resuscitation and surgical management of combat wounds, infection remains a concerning and potentially preventable complication of combat-related injuries. Interventions currently used to prevent these infections have not been either clearly defined or subjected to rigorous clinical trials. Current infection prevention measures and wound management practices are derived from retrospective review of wartime experiences, from civilian trauma data, and from in vitro and animal data. This update to the guidelines published in 2008 incorporates evidence that has become available since 2007. These guidelines focus on care provided within hours to days of injury, chiefly within the combat zone, to those combat-injured patients with open wounds or burns. New in this update are a consolidation of antimicrobial agent recommendations to a backbone of high-dose cefazolin with or without metronidazole for most postinjury indications and recommendations for redosing of antimicrobial agents, for use of negative pressure wound therapy, and for oxygen supplementation in flight.

Guidelines for the prevention of infections associated with combat-related injuries: 2011 update: endorsed by the Infectious Diseases Society of America and the Surgical Infection Society.

Despite advances in resuscitation and surgical management of combat wounds, infection remains a concerning and potentially preventable complication of combat-related injuries. Interventions currently used to prevent these infections have not been either clearly defined or subjected to rigorous clinical trials. Current infection prevention measures and wound management practices are derived from retrospective review of wartime experiences, from civilian trauma data, and from in vitro and animal data. This update to the guidelines published in 2008 incorporates evidence that has become available since 2007. These guidelines focus on care provided within hours to days of injury, chiefly within the combat zone, to those combat-injured patients with open wounds or burns. New in this update are a consolidation of antimicrobial agent recommendations to a backbone of high-dose cefazolin with or without metronidazole for most postinjury indications, and recommendations for redosing of antimicrobial agents, for use of negative pressure wound therapy, and for oxygen supplementation in flight.

Prevention of infections associated with combat-related extremity injuries.

During combat operations, extremities continue to be the most common sites of injury with associated high rates of infectious complications. Overall, ∼ 15% of patients with extremity injuries develop osteomyelitis, and ∼ 17% of those infections relapse or recur. The bacteria infecting these wounds have included multidrug-resistant bacteria such as Acinetobacter baumannii, Pseudomonas aeruginosa, extended-spectrum ß-lactamase-producing Klebsiella species and Escherichia coli, and methicillin-resistant Staphylococcus aureus. The goals of extremity injury care are to prevent infection, promote fracture healing, and restore function. In this review, we use a systematic assessment of military and civilian extremity trauma data to provide evidence-based recommendations for the varying management strategies to care for combat-related extremity injuries to decrease infection rates. We emphasize postinjury antimicrobial therapy, debridement and irrigation, and surgical wound management including addressing ongoing areas of controversy and needed research. In addition, we address adjuvants that are increasingly being examined, including local antimicrobial therapy, flap closure, oxygen therapy, negative pressure wound therapy, and wound effluent characterization. This evidence-based medicine review was produced to support the Guidelines for the Prevention of Infections Associated With Combat-Related Injuries: 2011 Update contained in this supplement of Journal of Trauma.

Biographical sketch: Fuller Albright, MD 1900-1969.

This biographical sketch on Fuller Albright corresponds to the historic text, The Classic: The Metabolic Effects of Steroid Hormones in Osteoporosis, available at DOI 10.1007/s11999-011-1832-z .

Biographical sketch: William S. Baer (1872-1931).

This biographical sketch on William S. Baer corresponds to the historic text, The Classic: The Treatment of Chronic Osteomyelitis With the Maggot (Larva of the Blow Fly), available at DOI 10.1007/s11999-010-1416-3.

Biographical sketch: Ruth Jackson, MD, FACS 1902-1994.

This biographical sketch on Ruth Jackson corresponds to the historic text, The Classic: The Cervical Syndrome, available at DOI 10.1007/s11999-010-1278-8 .

Biographical sketch: royal whitman, 1857-1946.

This biographical sketch of Royal Whitman corresponds to the historic text, The Classic: A Study of the Weak Foot, with Reference to its Causes, its Diagnosis, and its Cure; with an Analysis of a Thousand Cases of So-Called Flat-Foot, available at DOI 10.1007/s11999-009-1130-1 .

Treatment of war wounds: a historical review.

The treatment of war wounds is an ancient art, constantly refined to reflect improvements in weapons technology, transportation, antiseptic practices, and surgical techniques. Throughout most of the history of warfare, more soldiers died from disease than combat wounds, and misconceptions regarding the best timing and mode of treatment for injuries often resulted in more harm than good. Since the 19th century, mortality from war wounds steadily decreased as surgeons on all sides of conflicts developed systems for rapidly moving the wounded from the battlefield to frontline hospitals where surgical care is delivered. We review the most important trends in US and Western military trauma management over two centuries, including the shift from primary to delayed closure in wound management, refinement of amputation techniques, advances in evacuation philosophy and technology, the development of antiseptic practices, and the use of antibiotics. We also discuss how the lessons of history are reflected in contemporary US practices in Iraq and Afghanistan.