Aim

The aim of this study was to investigate the clinical relevance of an isolated positive sonication fluid culture (SFC) in patients who underwent revision surgery of a prosthetic joint. We hypothesized that cases with a positive SFC have a higher rate of infection and prosthesis failure during follow-up compared to controls with a negative SFC.

Implant-related infections pose a severe economical and societal burden, hence solutions capable of exerting suitable efficacy while not causing toxicity and/or development of resistant bacterial strains are needed. Thus, inorganic antibacterial coatings, and in particular silver coatings, have been extensively studied and used in the clinical practice. However, some drawbacks such as scarce adhesion to the substrate, delamination, or scarce control over silver release have been evidenced. Here, antibacterial nanostructured silver thin films have been developed by a novel plasma-assisted technique. The technique allows deposition on several substrates, including heat sensitive materials and objects of complex shape. Thanks to nanostructured surface, a tuned release can be achieved, preventing citoxicity. Composition (grazing incidence XRD, XPS) and morphology (SEM, AFM, ASTM) of the obtained coatings were characterized, then, their efficacy was validated in vitro against relevant bacterial strains (gram+ S. Aureus and gram– E. Coli). Live/dead kit and confocal microscopy were used to evaluate antibacterial efficacy. Super resolution imaging in the Structured Illumination Microscopy (SIM) setup was used to investigate damage to the bacterial wall. Results indicate that the coatings are composed of nanosized aggregates of metallic silver, indicating a perfect transfer of composition from the deposition target to the coating. Because of the sub-micrometric thickness, they do not alter the micro- and macro- morphology and surface finishing of the implants, developed by the manufacturers to ensure optimal integration in the host bone. Finally, remarkable efficacy was found against both gram+ and gram- bacteria, indicating that the developed coatings are promising for antibacterial applications.

Introduction: The aim of study was to evaluate the prevalence of microbiological isolates obtained from patients admitted to a 308-bed university-affiliated adult and children orthopaedic hospital of northern Italy (with more than 16.000 admissions per year), during a three year period (2000–2002), and, to analyze modifications during this period with regard to the prevalence of methicillin-resistant staphylococci strains.

Material and Methods: A retrospective study was conducted using laboratory records from 2000 to 2002 (2003 in progress) concerning bacterial and yeast isolates from all specimens sent to microbiological laboratory for culture. The specimens came from 8 surgical, 1 intensive care, 1 oncologie and 1 physiotherapy wards and included samples taken at surgical intervention, as like as at patient bed. Antimicrobial susceptibility testing results were also collected. All data were stored in an electronic database for statistical analysis.

Results: Between 2000 and 2002 a total of 8302 clinical specimens have been cultured and they yielded to 2978 isolates from 2653 positive samples. The prevalence of positive cultures form 24.8% in 2000 to 36.7% in 2002 and the isolated organisms are shown in table 1. Gram positive bacteria represent more than 70% of isolates and staphylococci are the most common organism (almost 50%). Staphylococcus epidermidis and other coagulase-negative staphylococci prevalence raised during the period 2000–2002 (respectively 25.4% to 33.4%, and 3.3% to 6.5%). Methicillin resistance rate resulted, 27.1% to 34.9% for Staphylococcus aureus, 37.6% to 28% for Staphylococcus epidermidis, and 33.3% to 42.1% for other coagulase-negative staphylococci. No difference in methicillin sensitivity was found between staphylococci isolated from surgical sites and other samples (urine, blood, sputum, throat swab).

Conclusions: Knowledge of the local epidemiology of pathogens in a surgical/orthopaedic hospital is critical in formulating policies on infection control. Amongst these rules the choice of antibiotic prophylaxis should be taken after analysis of bacteria prevalence and their antibiotic sensitivity.