Antibiotic-loaded synthetic calcium sulfate beads for prevention of bacterial colonization and biofilm formation in periprosthetic infections.

Periprosthetic infection (PI) causes significant morbidity and mortality after fixation and joint arthroplasty and has been extensively linked to the formation of bacterial biofilms. Poly(methyl methacrylate) (PMMA), as a cement or as beads, is commonly used for antibiotic release to the site of infection but displays variable elution kinetics and also represents a potential nidus for infection, therefore requiring surgical removal once antibiotics have eluted. Absorbable cements have shown improved elution of a wider range of antibiotics and, crucially, complete biodegradation, but limited data exist as to their antimicrobial and antibiofilm efficacy. Synthetic calcium sulfate beads loaded with tobramycin, vancomycin, or vancomycin-tobramycin dual treatment (in a 1:0.24 [wt/wt] ratio) were assessed for their abilities to eradicate planktonic methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis relative to that of PMMA beads. The ability of the calcium sulfate beads to prevent biofilm formation over multiple days and to eradicate preformed biofilms was studied using a combination of viable cell counts, confocal microscopy, and scanning electron microscopy of the bead surface. Biofilm bacteria displayed a greater tolerance to the antibiotics than their planktonic counterparts. Antibiotic-loaded beads were able to kill planktonic cultures of 10(6) CFU/ml, prevent bacterial colonization, and significantly reduce biofilm formation over multiple days. However, established biofilms were harder to eradicate. These data further demonstrate the difficulty in clearing established biofilms; therefore, early preventive measures are key to reducing the risk of PI. Synthetic calcium sulfate loaded with antibiotics has the potential to reduce or eliminate biofilm formation on adjacent periprosthetic tissue and prosthesis material and, thus, to reduce the rates of periprosthetic infection.

A new acoustic method to determine the setting time of calcium sulfate bone cement mixed with antibiotics.

A new method is described which can be used to determine the setting times of small amounts of high value bone cements. The test was developed to measure how the setting times of a commercially available synthetic calcium sulfate cement (Stimulan, Biocomposites, UK) in two forms (standard and Rapid Cure) varies with the addition of clinically relevant antibiotics. The importance of being able to accurately quantify these setting times is discussed. The results demonstrate that this new method, which is shown to correlate to the Vicat needle, gives reliable and repeatable data with additional benefits expressed in the article. The majority of antibiotics mixed were found to retard the setting reaction of the calcium sulfate cement.