The Musculoskeletal Infection Society symposium includes ten articles presented, in part, at the annual 2005 meeting in Snowmass, CO, August 5-6, 2005. The first three articles focus on basic issues. Olson et al studied the adherence of Staphylococcus epidermidis to different bio-materials. The authors hypothesized polysaccharide inter-cellular adhesin (PIA) helps facilitate initial adherence to biomaterials in addition to mediating multicellular aggregation. On all biomaterials tested (Zirconia, ultra-high molecular weight polyethylene, polymethylmethacrylate, cobalt chromium, titanium, stainless steel, and silastic), polysaccharide intercellular adhesion-positive Staphylococcus epidermidis 1457 exhibited greater levels of adherence than the isogenic mutant, polysaccharide intercellular adhesion-negative Staphylococcus epidermidis 1457 M10 stain, or the negative control strain, Staphylococcus carnosus TM300. The authors concluded polysaccharide intercellular adhesion appears to play a critical role in the adherence of Staphylococcus epidermidis to orthopaedic biomaterials and may serve as an important virulence determinant in orthopaedic prosthetic device infections. In the second article, McLaren et al compared Xylitol (a naturally occurring sweetener with direct antibiofilm properties) to glycine to determine its effectiveness in increasing antibiotic release. The authors' data suggested Xylitol is more effective than glycine as a filler to enhance daptomycin release. Additionally, because of its antibiofilm activity, it may be a more advantageous filler. The third basic article by Heijink et al tested the in vitro compatibility of vancomycin and gentamicin with three biodegradable materials that could be used for local delivery. The materials were OsteoSet®, DBX-putty®, and Colla-graft®. The authors were also interested in determining the in vitro release of vancomycin and gentamicin from these materials. The authors reported vancomycin and gentamicin were released quickly and reproducibly from all three carriers, leading them to conclude that OsteoSet®, DBX-putty®, and Collagraft® are potentially suitable biodegradable carriers for local delivery of vancomycin and gentamicin.
The second section of the symposium includes six clinical manuscripts. Daptomycin is a novel cyclic glycopep-tide which has been approved by the FDA for use in the treatment of Gram-positive pathogens which include Staphylococcus aureus. Daptomycin does have a unique mechanism of action and the advantages of a rapid bactericidal activity and a long half-life, but its use for prosthetic joint infections has not been established. Rao and Regalla prospectively monitored 12 patients with identified Gram-positive prosthetic joint infections who were treated with Daptomycin. Methicillin-resistant Staphylococcus was present in seven patients and methicillin-resistant coagulase-negative Staphylococcus aureus in four. Five of the 12 patients had failure of treatment with persistent methicillin-resistant staphylococcal infections. Two of these patients had failure of treatment despite prosthetic joint removal. The authors' study reminds us of the difficulty in treating patients with methicillin-resistant infections. Zalavras et al reported 147 adult patients with septic knee arthritis, of whom 29 of the patients had persistence or recurrence of symptoms after surgical drainage. Adjacent osteomyelitis was present in 31 of the 33 knees. Diabetes and intravenous drug abuse were factors pre-disposing patients to this contiguous and/or persistent infection.
Mehta et al retrospectively reviewed all patients admitted to their institution with musculoskeletal infection and identified 52 patients with septic large joints of the upper extremity. The authors concluded a high index of suspicion for infection is necessary and a joint aspirate with a differential white cell count is an important diagnostic study. Zalavras et al reviewed 19 patients with human immunodeficiency virus and septic arthritis. Interestingly, Staphylococcus aureus was the most common pathogen followed by oxacillin resistant Staphylococcus aureus and others. Microbacterial infections were present in three patients.
Intraarticular steroid injection for patients with arthritis is a common diagnostic and therapeutic intervention. A risk associated with intraarticular steroid injection is sepsis. McIntosh et al respectively reviewed 224 primary total hip arthroplasties in 217 patients implanted within one year after an intraarticular steroid injection and compared them to a control of 224 primary total hip arthroplasties without an injection. The authors concluded an ipsilateral intraarticular steroid injection before total hip arthroplasty did not affect the development of deep or superficial infection. Despite their conclusion, the authors encourage caution and judgment before performing an intraarticular steroid injection when arthroplasty is anticipated.
The final two articles by Marculescu et al describe the association of unusual microorganisms (aerobic Gram positive, aerobic Gram negative and anaerobic) and prosthetic joint infection. These unusual pathogens are not susceptible to the antimicrobials used to treat the bacteria that typically cause prosthetic joint infection. The two articles are thorough and should serve as a reference for physicians treating patients with prosthetic joint infection. The comprehensive articles describe the unusual pathogens and review the literature describing the course of treatment for patients who have developed infection caused by these pathogens.
In summary, we believe readers will find this symposium helpful in their practices as we all strive to lessen the risk of developing infection, as well as improve the treatment of this often devastating occurrence.