Culture negative endocarditis: the value of 16S rDNA PCR and sequencing

Abstract number: 1134_03_60

Zwet A.A., Riemens S., Laterveer L., Kooistra M.

Objectives:  

An essential element in the diagnosis of bacterial endocarditis is the finding of positive bloodcultures. In patients with endocarditis successive negative bloodcultures can be misleading and finally at best, by exclusion, the inadequate diagnosis of a so-called ‘culture negative endocarditis’ is made. In these special cases 16S rDNA PCR and sequencing of a blood sample can be of great value as is demonstrated in the following case history.

Patient and Methods:  

A 64 years old man presented himself at our hospital with complaints of fatigue, fever and weight loss since a couple of weeks. Eight years ago he had received an aortic valve bioprosthesis. Under the working diagnosis of a bacterial endocarditis several blood- and a bone marrow samples were taken for culture. Incubation time was extended, however, all cultures remained negative. Since trans-esophageal-echoscopy of the valves could not confirm the diagnosis of an endocarditis, uncertainty concerning the diagnosis was growing.

Finally, a 3 ml EDTA blood sample was taken for 16S rDNA PCR and sequencing.

DNA was extracted from the sample by a bead-beating/silica/guanidinium thiocyanate procedure. Amplification was performed with universal bacterial primers. A positive signal was found and subsequent sequencing revealed a Bartonella species. A positive Bartonella serology (IgG titer 500) confirmed our 16S rDNA PCR finding and the diagnosis of a Bartonella endocarditis was made. Patient was treated with a combination of antibiotics.

Conclusion:  

Direct detection of bacterial DNA in an EDTA blood sample using broad-range PCR and subsequent DNA sequencing is an important diagnostic tool, particularly helpful in cases where bacteraemia is suspected but bloodcultures nevertheless remain negative.