Molecular Biological Methods in The Etiological Diagnostics of Infective Endocarditis.

Aim      To study the role of early blood tests using the polymerase chain reaction (PCR) (before or at initial stages of antibacterial therapy, within the first 24-48 hours after diagnosis) for the diagnosis of infective endocarditis (IE) and improvement of the etiological algorithm.Material and methods  The study included 154 patients with confirmed IE (DUKE, 2015) who underwent standard microbiological (culture) blood tests with a simultaneous molecular biological test (PCR study/sequencing) on the same type of biological material at the stage of primary diagnosis.Results In 117 (76.0%) examined patients, the etiologic agent was determined in blood samples by any of the methods used. Concordant results were obtained in 43 (36.8%) patients and discordant in 4 (3.4%) patients. In 29 (24.8%) patients, the causative agent of IE was determined only by the microbiological (cultural) examination of blood samples, and in 25 (21.4%) patients, only by the PCR study, including 3 cases of Bartonella spр. 23 patients had results of the microbiological (culture) blood tests that required clarification (70% CoNS, 26% gram-negative bacteria, one case of Enterococcus faecalis); 16 (69.6%) of 23 were not confirmed by the molecular biological method and were interpreted as contamination. In 1/3 of patients, the PCR blood study allowed increasing the accuracy of determining the causative agent of IE. Based on the integrated approach to the etiological diagnosis of IE, criteria for determining the causative pathogen were developed. This allowed reclassifying 9 (5.9%) diagnoses into the category of confirmed IE and to de-escalate the antibacterial therapy in every third examined patient. The microbiological and PCR studies of blood demonstrated comparable indexes of sensitivity, specificity and diagnostic accuracy [79.0, 86.0, 81.0% and 67.0, 93.0, 74.0%, respectively]. The PCR study of blood at the early stages of IE diagnosis (before or during the initial antibacterial therapy, within the first 24-48 hours after the IE diagnosis) is proposed as a control for Streptococcus spp., Staphylococcus aureus, CoNS, Enterococcus spр., and at the later stages of laboratory examination, especially in IE with an unspecified pathogen, as a priority method.Conclusion      The PCR study of blood samples is a highly informative method for the etiological diagnosis of IE that allows increasing the accuracy of the pathogen identification in every third patient and, thus, prescribing an effective antibacterial therapy.