Introduction: Infective endocarditis is a severe condition, characterized by the presence of valvular vege-tations, causing structural damage at this level. Infec-tive endocarditis with negative blood cultures occurs in 30% of cases of endocarditis, generating problems in diagnosis and treatment. The etiology in these cases is represented by fungus and atypical bacteria, especi-ally intracellular bacteria, their identification requiring special culture media. The following case is particular because, behind a painful lumbar symptomatology, was a much more complex case, with severe consequences if left undiagnosed.

Methods: We present the case of a 63-year-old man, smoker of 20 cigarettes/day, diabetic in treatment with oral antidiabetic agents (metformin 2 g/day), hyperten-sive, therapeutically uncontrolled, who is hospitalized for lumbar pain, intensified during the effort, which occurred few days prior the admission. Physical exami-nation revealed a patient with altered general conditi-on, with rhythmic heart sounds, with diastolic murmur grade III/VI, with normal blood pressure values at both arms, with a heart rate of 100b/min, without pulmo-nary rales or peripheral edema.

Results: Laboratory tests revealed inflammatory syn-drome, hyperglicemia and dyslipidemia. The electro-cardiogram showed sinusal rhythm, with negative T waves in V1-V3, without other changes. MRI of the lumbar spine describes changes suggestive for spon-dylodiscitis. Transthoracic echocardiography remarks hyperechogenic tissue with dimensions of 14/14 mm in diameters, attached to the aortic valve. Transeso-phageal echocardiography confirms the presence of the hyperechogenic formation attached to the right aortic cusp, with dimensions of 24/24 mm, which ca-uses severe aortic regurgitation through the right cusp flail. The results of the blood cultures were negative at 7 days. Diagnosis: Infective endocarditis with negative blood cultures. Heart failure NYHA III functional class. Acute spondylodiscitis. Treatment: Antibacteri-al – Vancomycin 30 mg/kg given intravenous in two doses per day and Gentamicin 3 mg/kg in one dose per day. Surgical treatment – complete excision of the infected valve tissue and prosthesis of the aortic valve with mechanical prostheses. Evolution: the patient was discharged hemodynamically stable, with favorable prognosis.

Discussions: In cases of infective endocarditis with ne-gative blood cultures, the guidelines recommend spe-cial tests to identify special microorganisms. Multiple studies regarding this issue, recommend the use of the polymerization chain reaction to identify the atypical bacteria.

Conclusions: We consider that the case presented is a particular one, because a patient with a simple lumbar pain was actually a much more complex and severe case. In patients with infective endocarditis with nega-tive blood cultures it is recommended to use a more de-tailed diagnostic tests, including serological and imu-nological tests to identify the microorganism. In these cases, it is also recommended to use the polymerization chain reaction for identifing the microorganism.