Fluorescence in situ hybridization for identification and visualization of microorganisms in infected heart valve tissue as addition to standard diagnostic tests improves diagnosis of endocarditis

Abstract

OBJECTIVES In infective endocarditis (IE), identification of the causative organism and consecutive treatment are crucial for patient survival. Although the macroscopic aspect resembles infected tissue, standard diagnostic tests often fail to allow one to identify bacteria. Fluorescence in situ hybridization (FISH) is a molecular, culture-independent technique that allows one to identify and visualize microorganisms within tissue and to recognize their morphology, number and activity. We analysed the diagnostic benefit of FISH/polymerase chain reaction (PCR) by comparing its results to those of standard diagnostic tests. METHODS From September 2015 to April 2018, 128 patients underwent first-time or redo valve surgery to treat IE. Patients were designated according to the modified Duke criteria as definite (n = 61), possible (n = 34) or rejected (n = 33) IE. Tissue specimens obtained intraoperatively were analysed using FISH/PCR in addition to undergoing standard diagnostic testing and PCR alone. RESULTS We used blood cultures to detect microorganisms in 67/128 patients; valve cultures, in 34/128; PCR, in 67/128; histopathological diagnosis showed IE in 72/128 cases. We were able to detect microorganisms in 103/128 cases using FISH/PCR, with 55/61 in definite IE. Furthermore, we were able to identify 26 cases of bacterial biofilm using FISH/PCR, despite antibiotic treatment of 61 in the definite, 13 in the possible and 1 in the rejected group, including 8/33 patients in the rejected group with active bacteria. In all cases, the patient’s therapy was altered. CONCLUSIONS FISH/PCR was used to identify microorganisms in cases in which standard diagnostic tests failed to provide sufficient results for various reasons. Furthermore, FISH/PCR enabled us to identify bacterial biofilms and to differentiate between active versus degraded bacteria, thus indicating the impact of treatment. Therefore, we suggest FISH/PCR as an additional diagnostic tool in IE alongside standard diagnostic tests.

New Perspectives for Prosthetic Valve Endocarditis: Impact of Molecular Imaging by FISHseq Diagnostics

“…FISHseq identified PVE-causing pathogens in approximately one-third of the cases with noninformative (negative, inconclusive, or missing) BCs. In addition, in the study of Eichinger et al [ 39 ], FISHseq turned out to be the most effective diagnostic test for pathogen detection in native valve endocarditis. In this study, FISHseq identified microorganisms in 103 of 128 (80.4%) cases, whereas BCs were positive in 67 of 128 (52.3%) cases and VCs only in 34 of 128 (34%) cases.…”

Fluorescence in situ Hybridization (FISH) in the Microbiological Diagnostic of Deep Sternal Wound Infection (DSWI)

“…Fluorescence in situ hybridization (FISH) in combination with 16S RNA-directed PCR and sequencing (FISHseq) is a molecular method that has proven useful for the detection and identification of bacteria in clinical samples, in particular in biofilm-associated diseases and culture-negative infections. 22 , 23 As a microscopic technique, FISH visualizes an infection landscape of the tissue sample showing where specific microbial species are found, and in which state they are. This is important because resistant bacteria may persist in the deep tissue of the sternal wound.…”

Limiting Factors in Treatment Success of Biofilm-Forming Streptococci in the Case of Canine Infective Endocarditis Caused by Streptococcus canis

“…Multilocus sequence typing was performed via the PubMLST webtool, which revealed that this strain (denominated as IMT 49926) belongs to the ST35 type (Table 3). Fluorescence in situ hybridization (FISH) of the heart valve tissue sections was performed to visualize the microbial biofilms in situ as described before [2,3]. The heart valve sample was briefly fixated, embedded in cold polymerizing resin, and sectioned.…”

“…Fluorescence in situ hybridization (FISH) of the heart valve tissue sections was performed to visualize the microbial biofilms in situ as described before [ 2 , 3 ]. The heart valve sample was briefly fixated, embedded in cold polymerizing resin, and sectioned.…”