The expanding horizon of prosthetic joint infections

Antibiotic Tolerance of Staphylococcus aureus Biofilm in Periprosthetic Joint Infections and Antibiofilm Strategies

The need for bone and joint prostheses is currently growing due to population aging, leading to an increase in prosthetic joint infection cases. Biofilms represent an adaptive and quite common bacterial response to several stress factors which confer an important protection to bacteria. Biofilm formation starts with bacterial adhesion on a surface, such as an orthopedic prosthesis, further reinforced by matrix synthesis. The biofilm formation and structure depend on the immediate environment of the bacteria. In the case of infection, the periprosthetic joint environment represents a particular interface between bacteria, host cells, and the implant, favoring biofilm initiation and maturation. Treating such an infection represents a huge challenge because of the biofilm-specific high tolerance to antibiotics and its ability to evade the immune system. It is crucial to understand these mechanisms in order to find new and adapted strategies to prevent and eradicate implant-associated infections. Therefore, adapted models mimicking the infectious site are of utmost importance to recreate a relevant environment in order to test potential antibiofilm molecules. In periprosthetic joint infections, Staphylococcus aureus is mainly involved because of its high adaptation to the human physiology. The current review deals with the mechanisms involved in the antibiotic resistance and tolerance of Staphylococcus aureus in the particular periprosthetic joint infection context, and exposes different strategies to manage these infections.

Preoperative joint aspiration culture results and causative pathogens in total hip and knee prosthesis infections: mind the gap

OBJECTIVES

In prosthetic joint infections (PJIs), there is no consensus about the utility of the preoperative joint aspiration culture to guide antimicrobial treatment. The main objective of this retrospective study was to investigate the value of these preoperative samples to narrow immediate postoperative empirical antimicrobial treatment in patients with a knee or hip PJI.

METHODS

Adult patients admitted for an exchange procedure between June 2007 and July 2016 for whom a preoperative joint aspiration within 6 months prior to the procedure was available and with an antibiotic-free interval before sampling, were eligible. Per PJI, taking both preoperative joint aspiration and intraoperative deep samples into account, causative pathogen(s) were assessed by the current Infectious Diseases Society of America (IDSA) guidelines. Per PJI, agreement of preoperative joint aspiration cultures corresponding to the causative pathogen(s) was investigated both on species and on Gram/fungi level.

RESULTS

From the 85 PJIs, on species level, the total agreement was found in 58 (68%) PJIs. On Gram/fungi level, when preoperative joint aspiration cultures yielded exclusively Gram-positive microorganisms (n = 61), a 100% predictive value for Gram positive causing pathogens was attained. Insufficient predictive value was observed in PJIs with preoperative joint aspiration yielding Gram-negative microorganisms (n = 4), a fungus (n = 1) or with sterile results (n = 19).

CONCLUSION

In the immediate postoperative setting, the treating team might consider a broad spectrum empirical antibiotic regime, guided by the local epidemiology and susceptibility, which can be narrowed to Gram-positive coverage if preoperative joint aspiration cultures yield exclusively Gram-positive microorganisms.

Bacterial Extracellular DNA Production Is Associated with Outcome of Prosthetic Joint Infections

In a retrospective study the association of the production of extracellular DNA (eDNA) in biofilms of clinical staphylococcal isolates from 60 patients with prosthetic joint infection (PJI) and the clinical outcome were investigated. Data from a previous study on eDNA production determined in 24-hour biofilms of staphylococcal isolates (Staphylococcus aureus n=30, Staphylococcus epidermidis n=30) was correlated with the patients' clinical outcome after 3 and 12 months. Statistical analysis was performed using either the Spearman's rank correlations test or the t-test. eDNA production of S. epidermidis in 24-hour biofilms correlated with the patients' outcome ‘not cured‘ after 12 months. For S. aureus no such correlation was detected. Thus, eDNA may be a virulence factor of S. epidermidis. Quantification of eDNA production as a surrogate marker for biofilm formation might be a potential predictive marker for the management of PJI.

Not all approved antibiotic-loaded PMMA bone cement brands are the same: ranking using the utility materials selection concept

In the literature on in vitro characterization of approved antibiotic-loaded poly(methyl methacrylate) bone cement brands, there is no information on the basis for selection of a given brand for use in cemented arthroplasties. This shortcoming is addressed in the present study. It involved determining four key properties (fatigue limit, fracture toughness, polymerization rate, and phosphate buffered saline diffusion coefficient) for six brands and then using the mean property values, in conjunction with a materials selection methodology, called the utility concept, to rank the brands. It is emphasized that the present work is an illustration of a rational approach to selection of a cement brand and, as such, the study findings are not intended to be recommendations regarding clinical use or otherwise of a brand.