Microbiological Approach in Diagnosing Native and Heart Valves Prosthesis Infections

Background: Traditional culturing approaches either on native (NV) or on prosthetic valves (PV) are still not efficient in detecting pathogens responsible of infection. In fact, despite the continuous development of microbiological technologies, a truly valid technique that could be used as reference has yet to be found. Here we present a revised version of traditional culture methods based on a pre-treatment of both NVs and PVs by DL–dithiothreitol (DTT). Methods and findings: A total of 79 specimens were included in the study: 54 were NVs and 25 were PVs. We compared the results of both culturing methods and molecular assays performed on NVs/PVs collected in two different periods named pre-DTT and post-DTT, respectively. The protocol consisted in treating NV/PV by an appropriate volume of DTT, following which the suspension of bacteria/DTT was used for culture and molecular assay. In pre-DTT period five specimens were culture-positive and one was positive by molecular assay only (1/20; 5%), showing a culture positivity rate of 25% (5/20). In the post-DTT period, of 59 specimens processed, 19 were culture positive (19/59; 32%). Moreover, PCRs performed on specimens treated with DTT contributed to the identification of six additional positive specimens plus an identification of poly-microbial infection lost by culture (7/59; 12%). Conclusion: Our findings show that the use of DTT can be helpful in increasing the identification of microorganisms involved in NV/PV infections. Given its simple and cost-effective use and considering the issue that this technique does not require any specific instrumentation, it could easily be introduced in any laboratories. However, since our study included a limited number of specimens, more extensive studies are needed to further confirm our results.