Evaluation of PCR in the molecular diagnosis of endocarditis.
OBJECTIVE
Infective endocarditis (IE) is diagnosed by the Duke criteria, which can be inconclusive particularly when blood cultures are negative. This study investigated the application of polymerase chain reaction (PCR) to identify bacterial DNA in excised valvular tissue, and its role in establishing the diagnosis of IE.


METHODS
Ninety-eight patients undergoing valve replacement surgery were studied. Twenty-eight patients were confirmed as definite for endocarditis by the Duke criteria; nine were considered as possible and 61 had no known or previous microbial infection of the endocardium. A broad-range PCR technique was used to amplify prokaryotic 16S rRNA genes present within homogenised heart valve tissue. Subsequent DNA sequencing of the PCR amplicon allowed identification of the infecting microorganism.


RESULTS
PCR results demonstrated the presence of bacterial DNA in the heart valves obtained from 14 out of 20 (70%) definite IE patients with positive blood cultures preoperatively. The causative microorganism for one patient with definite culture negative endocarditis was identified by PCR. Two out of nine (22%) of the valves from possible endocarditis patients also had bacterial DNA present converting them into the definite criteria whereas in the valves of seven out of nine (78%) of these patients no bacterial DNA was detected.


CONCLUSIONS
The application of PCR to the explanted valves in patients with possible or confirmed diagnosis can augment the Duke criteria thereby improving post-surgical antimicrobial therapeutic options.
Lang
S
S
Microbiology Research, Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK. s.lang@aston.ac.uk
Watkin
R W
RW
Lambert
P A
PA
Bonser
R S
RS
Littler
W A
WA
Elliott
T S J
TS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004269:DNA, Bacterial / Q000032:analysis*; D004697:Endocarditis, Bacterial / Q000175:diagnosis* / Q000382:microbiology; D005188:False Negative Reactions; D005260:Female; D006351:Heart Valves / Q000382:microbiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity
D004269:DNA, Bacterial