Universal Automated Molecular Diagnosis of Infectious Endocarditis

Objectives: Surgical therapy of infective endocarditis (IE) is often a technically complex therapy that depends on an adequate postoperative antibiotic therapy to prevent early prosthetic valve infection. Conventional microbiological tests are often negative due to fastidious growth requirements or inhibition of strains from antibiotic-treated patients. Moreover, cultural tests can take more than 1 week prior to obtaining results. Direct molecular testing does not depend on growth of pathogens, but can generate false-positive results because of potential microbial DNA contamination during handling. Therefore, we used automated approach for molecular biological diagnostics and compared it with the culture methods.

Methods: Specimens included blood, excised valves, pacemakers, hematomas, pericardial abscesses, and thrombi were processed on the SelectNAplus robot using Micro-Dx kit (Molzym, Bremen, Germany). In total, 97 samples from 52 patients suspected for IE were tested via universal 16S and 18S PCR assays with sequencing.

Results: The molecular biological method allowed us to diagnose IE within maximal 2 days versus time to a positive culture up to 7 to 14 days. Only 22 patients (42.3%) were diagnosed as IE using conventional culture methods, whereas 30 (57.7%) positives were obtained with Micro-Dx. Positive results by both methods were in 19 cases. Consequently, the sensitivity of the PCR-based method against culture was 86.4%. However, two positive samples differed by identified pathogen. In 11 culture-negative patients, Micro-Dx identified strains that were regarded true or possible by clinical consideration or repeated occurrence in other samples.

Conclusion: The broad-range 16S/18S PCR and sequencing is faster than conventional culture methods for IE diagnostics. The use of Micro-Dx leads to faster and more adequate therapy of IE, especially in cases of culture-negative IE.

No conflict of interest has been declared by the author(s).