1028. The Contribution of Molecular Diagnostic Techniques in the Etiologic Diagnosis of Infective Endocarditis
Session: Poster Abstract Session: Diagnosis of Bloodstream / Cardiovascular Infections
Saturday, October 22, 2011
Room: Poster Hall B1

Background: The microbial diagnosis of infective endocarditis (IE) requires the incorporation of routine blood and valve tissue cultures along with interpretation of tissue pathology in patients with a high clinical suspicion for disease. Molecular microbiological techniques are increasingly being utilized, particularly in patients with negative routine cultures.

Methods: We evaluated all patients at our facility who had heart valve specimens tested by universal PCR (followed by sequencing) after valve surgery for suspected IE between January 1, 2010 and April 1, 2011. The electronic medical record for each patient was reviewed to examine specific aspects of their diagnostic process and to determine the contribution of blood culture, valve culture, and valve PCR to the etiologic diagnosis of IE.

Results: Among the 61 patients who were included in the study, 52 were considered to have definite IE based on microbiology, histopathology and clinical picture. Histopathological examination found evidence of inflammation (either acute or chronic) in 37 (71%) patients, and microorganisms on special staining in 26 (50%) patients. Among those with definite IE, 40 (77%) had positive valve tissue PCR results, 27 (52%) had positive blood cultures and 20 (38%) had positive valve cultures. The relative contributions of valve PCR, valve culture and blood culture to the etiological diagnosis of IE are displayed in the Venn diagram (Figure). In 13 patients (25% of patients with definite IE), a positive valve PCR was the only clue to the microbiologic diagnosis. The pathogens identified solely by PCR included viridans streptococcus, Bartonella species, Propionibacterium acnes, Enterococcus faecalis and Streptococcus agalactiae. There were 2 patients with discrepant results wherein a different pathogen was isolated from blood or valve cultures than that found on PCR.

Conclusion: Molecular techniques are a valuable addition to the diagnostic armamentarium for the diagnosis of IE. When used systematically this may be the only method that provides an etiologic diagnosis.

Figure. Venn diagram showing the number of patients who had positive PCR, valve culture and blood culture results (all negative in 13 patients).

Subject Category: D. Diagnostic microbiology

Christopher S. Ledtke, MD1, Thomas G. Fraser, MD2, Steven Gordon, MD, FIDSA1, Gosta B. Pettersson, MD, PhD3 and Nabin K. Shrestha, MD, MPH1, (1)Infectious Disease, Cleveland Clinic, Cleveland, OH, (2)Cleveland Clinic Foundation, Cleveland, OH, (3)Cardiothoracic Surgery, Cleveland Clinic, Cleveland, OH


C. S. Ledtke, None

T. G. Fraser, None

S. Gordon, None

G. B. Pettersson, On-X Life Technologies, Inc.: Consultant, Consulting fee

N. K. Shrestha, Astellas: Consultant, Consulting fee
Cubist: Grant Investigator, Grant recipient
Forest: Speaker's Bureau, Speaker honorarium

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.