Autoimmunohistochemistry: a new method for the histologic diagnosis of infective endocarditis.
BACKGROUND
Although the pathologic examination of cardiac valves remains the reference standard for the diagnosis of infective endocarditis, the detection of microorganisms often poses a challenge for pathologists. This can be done by use of nonspecific histochemical stains or by immunohistochemical analysis, but specific antibodies are often not available. We describe a novel method for the detection of microorganisms in valve specimens from patients with infective endocarditis.


METHODS
Detection of microorganisms was performed in valve specimens from patients with endocarditis caused by gram-positive cocci (25 specimens), blood culture-negative endocarditis (15 specimens: 6 cases caused by Coxiella burnetii, 5 caused by Tropheryma whipplei, and 4 caused by Bartonella species), or noninfective degenerative damage (30 specimens, used as negative controls), using the patients' own serum. This technique, called "autoimmunohistochemistry," is an immunohistochemical peroxidase-based method that we compared with results of culture and polymerase chain reaction (PCR) assay.


RESULTS
Bacteria were detected by autoimmunohistochemistry in 20 (80%) specimens from patients with endocarditis caused by gram-positive cocci and in 15 (100%) specimens from patients with blood culture-negative endocarditis but in no control specimens. The rate of detection of bacteria by autoimmunohistochemistry was significantly higher than that by culture but was similar to that by PCR.


CONCLUSIONS
Autoimmunohistochemistry may be useful for the detection of microorganisms in samples of valves from patients with infective endocarditis. This new diagnostic tool may be particularly useful in cases of blood culture-negative endocarditis.
Lepidi
Hubert
H
Unite des Rickettsies et des Pathogenes Emergents, Centre National de la Recherche Scientifique, Unite Mixte de Recherche 6020, Institut Federatif de Recherche 48, Universite de la Mediterranee, Marseille, France. hubert.lepidi@medecine.univ-mrs.fr
Coulibaly
Bema
B
Casalta
Jean-Paul
JP
Raoult
Didier
D
D000192:Actinomycetales / Q000276:immunology / Q000302:isolation & purification; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000276:immunology; D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D001473:Bartonella / Q000276:immunology / Q000302:isolation & purification; D016997:Coxiella burnetii / Q000276:immunology / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000032:analysis; D004697:Endocarditis, Bacterial / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006095:Gram-Positive Cocci / Q000302:isolation & purification; D006351:Heart Valves / Q000382:microbiology*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial