NExt-Generation Sequencing and Cell Culture-based Characterization of S. Aureus in Infective Endocarditis

Overview

Infective endocarditis is a deadly disease with a mortality rate between 20 and 40%. Antibiotic therapy is of utmost importance. It is primarily guided by microbial results from positive blood culture. However, culture-based microbiological diagnostic can identify the species, but not the strain or the genotypic characteristics of a pathogen. Identifying the strain can be of utmost clinical significance. S. aureus is the most common causative organism of IE worldwide (16%-32%). This pathogen causes massive valve destruction and abscesses, which is strongly dependent on the expression of virulence factors that vary between different S. aureus strains. Functional characterization of S. aureus and determination of virulence factors can currently be achieved through cell culture-based assays (CCBA). However, these tests are very time consuming and cannot be performed as routine clinical diagnostics. Next Generation Sequencing (NSG) has the potential to identify the genotypic characteristics of the pathogen, which is important to determine its virulent potential. The aim of this study is to evaluate the possible utilization of NGS in the prediction of virulence factors of S. aureus and to compare it to the virulence factors determined using CCBA. Hopefully, by comparing the NGS and CCBA, the investigators will get a faster way of determining the possible virulence factors. The NGS method can be further utilized to describe the prevalence of different strains of bacteria in infected valve tissue and blood culture samples. The collected data will serve as a basis for further evaluation of the potentials of NGS-based Diagnosis of IE, as well as a comparison between NGS-guided antibiotic treatment and the standard of care antibiotic treatment.

The ability of the Staphylococcus aureus to produce massive valve destruction as well as abscesses and to switch from acute to chronic infection and vice versa is a significant issue in the modern treatment of infective endocarditis. Furthermore, the ability to produce different virulence factors to evade the immune defense mechanisms proves the treatment more difficult. Another conundrum is the proof of different S. aureus strains isolated from Blood culture samples and infected valve samples. This makes a possible treatment of S. aureus-based endocarditis more difficult than expected. Isolation of Bacteria in the Blood culture samples can take much time (3-14 days), and Cell Culture-based assays (CCBA) are not regularly implemented as a diagnostic procedure. CCBA is not regularly used in the clinical setting due to the time consumption and high cost. The significance of the CCBA method lies in the determination of the possible virulence factors. Utilizing the Next Generation Sequence (NGS) method, it might be possible to gain this information about the culprit microorganism faster and to identify the different strains and virulence factors. To date, such correlations between genetic information about virulence factors gained by NGS and phenotypic information obtained by cell culture-based assays have not yet been performed.If proven, the NGE based analysis of the pathogens and their phenotypical behavior could guide antimicrobial therapy and make it individualized. Blood culture and infected tissue valve samples will be examined using the NGS and CCBA. The investigators aim to compare the differences in virulence factor results in these two methods, to characterize the prevalence of different strains of S. aureus in the blood culture and valve samples and to evaluate the possible potentials of NGS-based diagnosis of IE and to compare the effects of the NGS-guided antimicrobial therapy to the standard of care therapy.