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Streptococcus equinus Endocarditis in a Woman With Pulmonary Histiocytosis
To the Editor: Streptococcus equinus is the predominant streptococcus in the alimentary tract of the horse.1 Although this organism occasionally has been isolated from the human intestine,2 to our knowledge it has not been reported to cause endocarditis in patients without prior cardiac disease.
Report of a Case
A 65-year-old woman was referred to us for evaluation of intermittent fever associated with nonproductive cough and weight loss. She had not undergone recent dental or invasive procedures, and she had no history of cardiac disease or murmur. The patient's body temperature was 38.2°C; her pulse, 98/min; and her blood pressure, 130/160 mm Hg. A grade 3 early diastolic murmur was audible on the left sternal border and scattered dry crackles were heard on lung auscultation. Ophthalmoscopy and examination of the mouth, ears, nose, throat, abdomen, and nervous system were normal. Laboratory tests showed anemia (hemoglobin, 97 g/L), mild leukocytosis (white blood cell count, 11,000 x 106/L), and increased erythrocyte sedimentation rate (75 mm/h). Transthoracic and transesophageal echocardiography disclosed the presence of a pedunculated and echodense mass on the posterior leaflet of the aortic valve and a small mass on the anterior leaflet of the mitral valve. Doppler ultrasonography showed severe aortic and mild mitral regurgitation with an ejection fraction of 65%. A honeycomb pattern was visible on radiographs of the chest with predominance in the middle and upper lung fields. High-resolution computed tomographic scan of the lungs showed multiple bilateral radiolucent areas with diameters from a few millimeters to 5 cm, some with thin walls. The results of pulmonary function studies were normal. Eight out of 8 blood culture bottles were positive for S equinus, which was identified with standard microbiologic criteria. Repeated searches for fecal occult blood were negative and the result of a barium enema examination with air contrast medium was normal.
Treatment with piperacillin sodium and gentamicin was begun, and the patient recovered quickly. After 6 weeks of treatment, however, an echocardiogram showed a significant deterioration of left ventricular function, and the patient underwent cardiac surgery with replacement of the aortic valve and mitral valvuloplasty. A biopsy of the lung was performed during surgery. Microscopical examination showed extensive fibrosis of the interstitium with a few Langerhans cells and lymphocytes; cystic spaces with a fibrous wall were present beneath the pleural surface together with focal areas of retraction emphysema. These findings were indicative of an organizing phase of histiocytosis X. The postsurgical course was uneventful and the patient was well 6 months after the operation.
Comment
S equinus and S bovis are included in the Lancefield group D streptococci. Both S bovis and S equinus have been isolated from the human bowel in approximately 7% of the general population.2 While S bovis bacteremia is frequently associated with carcinoma of the colon, S equinus only rarely has been described as a human pathogen. The only case of S equinus endocarditis reported in the literature occurred in a farmer.3 To our knowledge, ours is the first reported case of the occurrence of S equinus endocarditis in a patient who had no preexisting heart disease or evidence of gastrointestinal disease. This patient also had underlying pulmonary hystiocytosis X. Many abnormalities of the immune system have been described in patients with this disease, including decreased production of natural antibodies and IgM,4 and changes in T lymphocyte phenotype.5 These abnormalities can predispose patients with histiocytosis X to bacterial infections,6 and a similar mechanism might have occurred in our patient.
Leonardo A. Sechi, MD;
Rosanna Ciani, MD
University of Udine School of Medicine
Udine, Italy
1. Hardie JM. Streptococcus. In: Sneath PH, Mair NS, Sharpe ME, eds. Bergey's Manual of Systematic Bacteriology. Vol 2. Baltimore, Md: Williams & Wilkins; 1991:1069-1084.
2. Noble CJ. Carriage of group D streptococci in the human bowel. J Clin Pathol. 1978;31:1182-1186.
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3. Elliott PM, Williams H, Brooksby AB. A case of infective endocarditis in a farmer caused by Streptococcus equinus. Eur Heart J. 1993;14:1292-1293.
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4. Gonchartova SI, Poddubnyi AF, Panasiukova OR. Clinical and immunologic characteristics of patients with histiocytosis X. Probl Tuberk. 1993;2:30-32.
5. Hosmalin A, McIlroy D, Autran B, et al. Imbalanced "memory" T lymphocyte subsets and analysis of dendritic cell precursors in the peripheral blood of adult patients with Langerhans cell histiocytosis. Clin Exp Rheumatol. 1997;15:649-654.
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6. Watson LC, Mendelsohn SS, Nash J. Adult-onset Langerhans cell histiocytosis associated with severe abscesses. Clin Exp Dermatol. 1995;20:415-418.
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Letters Section Editors: Phil B. Fontanarosa, MD, Deputy Editor; Stephen J. Lurie, MD, PhD, Fishbein Fellow.
JAMA. 2000;283:1005.
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