f Identification of the causative pathogen of infective endocarditis (IE) is crucial for adequate management and therapy. A broadrange PCR-electrospray ionization mass spectrometry (PCR-ESI-MS) technique was compared with broad-spectrum 16S rRNA PCR and amplicon sequencing (16S rRNA PCR) for the detection of bacterial pathogens in 40 heart valves obtained from 34 definite infective endocarditis patients according to the modified Duke criteria and six nonendocarditis patients. Concordance between the two molecular techniques was 98% for being positive or negative, 97% for concordant identification up to the genus level, and 77% for concordant identification up to the species level. Sensitivity for detecting the causative pathogen (up to the genus level) in excised heart valves was 88% for 16S rRNA PCR and 85% for PCR-ESI-MS; the specificity was 83% for both methods. The two molecular techniques were significantly more sensitive than valve culture (18%) and accurately identified bacteria in excised heart valves. In eight patients with culture-negative IE, the following results were obtained: concordant detection of Coxiella burnetii (n ؍ 2), Streptococcus gallolyticus (n ؍ 1), Propionibacterium acnes (n ؍ 1), and viridans group streptococci (n ؍ 1) by both molecular tests, detection of P. acnes by PCR-ESI-MS whereas the 16S rRNA PCR was negative (n ؍ 1), and a false-negative result by both molecular techniques (n ؍ 2). In one case of IE caused by viridans streptococci, PCR-ESI-MS was positive for Enterococcus spp. The advantages of PCR-ESI-MS compared to 16S rRNA PCR are its automated workflow and shorter turnaround times.
Diagnosis of infective endocarditis (IE) remains challenging. A multidisciplinary approach by microbiologists, infectiologists, surgeons, and cardiologists is needed for adequate management. Identification of the pathogen is crucial for selecting appropriate antimicrobial therapy (1-4). According to the modified Duke criteria, positive blood cultures (BCs) remain the cornerstone of the microbiological diagnosis of IE (4). Three sets of BCs, taken before starting antimicrobial therapy, detect 96% to 98% of bacteremia (5, 6). Unfortunately, BCs are negative in 2% to 31% of IE patients due to prior antimicrobial therapy or fastidious (Brucella spp., fungi) or intracellular (Coxiella burnetii, Bartonella spp., or Tropheryma whipplei) microorganisms, resulting in obscured diagnoses (7-9). During the last decade, molecular techniques performed directly on excised heart valves have emerged. Broad-range PCR, targeting the 16S rRNA gene, followed by subsequent sequencing of the amplicon proved to be superior to the culture of excised valves (VC) (8, 10-12). The sensitivity and specificity of 16S rRNA PCR for detecting the causative microorganism ranged from 61% to 90% and 97% to 100%, respectively, whereas the sensitivity and specificity of VC ranged from 23% to 31% and 67% to 87%, respectively (10-12). The use of different or no criteria for defining the definite microbiological cause of IE ...