الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
IE has long been described as a disease with polymorphic manifestations, and while its incidence has not decreased, its clinical and microbiologic profile is changing continuously and rapidly.
Despite the introduction of improved blood culture systems, an etiologic agent could not be identified in 2.5% to 31% of IE cases. These negative cultures result in the classification of such cases as CNIE.
Two main reasons account for CNIE. First, in many critical clinical situations, empirical antibiotic therapy is administered prior to diagnosis or even before the patient is suspected of having IE. Second, fastidious or yet uncultured microorganisms that are regularly missed by routine culture methods may be involved in CNIE cases.
The study was carried out to estimate the prevalence of CNIE among definite IE cases, to describe the epidemiologic and clinical characteristics of CNIE patients and to diagnose the microbial etiology of CNIE using molecular and serological techniques.
Sixty five definite IE cases were enrolled in a prospective observational study, in AUMH, between January and December 2010. CNIE cases were tested by 16SrRNA and SN-PCR for 35 blood samples, serological tests for Coxiella, Bartonella, Brucella, and Chlamydia, and the study of ten valve tissue specimens.
Causative agents were detected by blood cultures in 26 cases (40%) while 39 cases (60%) constituted the CNIE. The mean age of CNIE patients was 31 years. Male to female ratio was 2.9:1. HCA-IE accounted for 15.4% of cases. NVE accounted for 66.7%, while PVE accounted for 30.8% of cases. The mitral valve was the most frequently involved, affecting 56.4% of cases. The most common underlying heart disease was RHD, which was responsible for 64.1% of all CNIE. IVDA accounted for 20.5% of cases. All CNIE patients (100%) had received a previous antibiotic course before being admitted to our hospital. Fever was the most common symptom (100%) at initial evaluation. Complications were found in 43.6% of patients. The endocarditis associated mortality was observed in 12.8% of CNIE cases.
Out of the 39 CNIE, 23 had an etiologic agent implicated while 16 remained unresolved. Semi-nested blood PCR detected 12 positive cases as follow; eight S. aureus, two CONS and two streptococci. Six cases (three staphylococci and three streptococci) were positive by analysis of valve tissue. Six cases were positive by PCR analysis of valve tissue (of those 5 were concomitantly positive by valve culture). Five cases were reactive by serology (three Bartonella, one Coxiella, and one Brucella). Thus, the combined results of all diagnostic tools used in our study decreased the percentage of non-identified causes of CNIE from 60% to 24.6%.