Challenges in the Microbiological Diagnosis of Implant-Associated Infections: A Summary of the Current Knowledge

Abstract

Implant-associated infections are characterized by microbial biofilm formation on implant surface, which renders the microbiological diagnosis challenging and requires, in the majority of cases, a complete device removal along with a prolonged antimicrobial therapy. Traditional cultures have shown unsatisfactory sensitivity and a significant advance in the field has been represented by both the application of the sonication technique for the detachment of live bacteria from biofilm and the implementation of metabolic and molecular assays. However, despite the recent progresses in the microbiological diagnosis have considerably reduced the rate of culture-negative infections, still their reported incidence is not negligible. Overall, several culture- and non-culture based methods have been developed for diagnosis optimization, which mostly relies on pre-operative and intra-operative (i.e., removed implants and surrounding tissues) samples. This review outlines the principal culture- and non-culture based methods for the diagnosis of the causative agents of implant-associated infections and gives an overview on their application in the clinical practice. Furthermore, advantages and disadvantages of each method are described.

Keywords: BioTimer Assay; biofilm; culture-based methods; diagnosis; implant-associated infection; metabolic assays; molecular methods; sonication.

FIGURE 1

Overview of sonication method for the diagnosis of implant-associated infections.

FIGURE 2

Correlation lines obtained by BioTimer Assay with the reagent containing both Phenol Red and Resazurin as indicators in order to enumerate fermenting (color switch from violet-to-yellow) and non-fermenting (color switch from violet-to-orange) microorganisms. The correlation lines show the relationship between the time (X-axis) required for color switch and the initial number of microorganisms (Y-axis). The equations and the linear correlation coefficients describing the correlation lines for both fermenting and non-fermenting microorganisms are reported in parenthesis.