gms | German Medical Science

Objectives: The low number of planktonic bacteria in clinical samples poses a challenge in the diagnosis of chronic implant infections in orthopaedics, traumatology, cardiology and other fields. With the objective to dislodge bacteria from prosthesis-associated biofilms, sonication and – more recently – the chemical pretreatment of implants and tissue biospies with dithiothreitol (DTT) has been introduced in clinical practice.

Methods: The available clinical studies in the period 2013 to 2017 were analysed (Medline, Embase, PubMed), in order to compare the diagnostic value of DTT-pretreatment of samples with sonication & culture of native biopsies or swabs

Results: 2 studies from orthopaedic centers in Italy, with in total n=106 patients (48 with presumed aseptic condition & 58 with prosthesis infection) compared the culture of samples after either prior sonication or prior DTT-pretreatment of explanted prosthesis material. The number of true positive cultures was higher in the DTT than in the sonication group in both studies (sensitivity: +14,5% and +12,3%; specificity: comparable). In particular S. epidermidis was more frequently detected in the DTT group. 1 study from a septic orthopaedic unit with n=70 patients (45 non-infected & 25 prosthesis infections) randomly allocated tissue samples from the same site either to DTT or saline pretreatment before culture. The sensitivity & specificity of the diagnosis was higher when DTT-pretreated tissues were plated on agar plates compared to native biopsies (+16% & +6,7%). 1 study from a trauma department enrolled 30 patients with presumed septic conditions (post-traumatic complications, implant infections or osteomyelitis) and compared the number of positive and negative samples using the specific MicroDTTect device or swabs. The DTT-based method showed a much higher sensitivity compared to swabs (+31%) and was associated with more positive results (+15%). There were also significant differences in the type of microorganisms isolated with both methods. 1 case report described the successful detection of S. aureus & P. mirabilis from the biofilm of an aortic valve as culprits of the endocarditis case using the DTT method.

Conclusions: DTT-pretreatment of samples taken from the site of a possible chronic implant infection may improve the identification of biofilm-embedded pathogens. If combined with a completely closed system of sample processing, the number & considerable costs of false negative & false positive results will be reduced. Further trials and larger studies are needed to validate this diagnostic procedure.