INTRODUCTION AND OBJECTIVES
Campylobacter fetus is an uncommon organism with a propensity to infect vascular and joint spaces in both immunodeficient and immunocompetent hosts. Our objectives are (1) to report the case of a patient with C. fetus bacteremia complicated by infectious aortitis and a septic joint, (2) review the pathogenesis of C. fetus infection, and (3) remind clinicians that immunocompetent patients with endovascular lesions including thrombus and dissection are at particular risk for sustained blood-borne infections including C. fetus.
A 51-year-old man with hypertension and obesity presented with 5 days of fever, shoulder pain, and watery, brown, non-bloody diarrhea. On the week before presentation, the patient developed nonradiating left shoulder pain with lifting. On admission, he was febrile to 101.9°F and was hemodynamically stable. His abdomen was obese but nontender without masses or peritoneal signs. His shoulder was warm and tender over the left sternoclavicular joint. His white blood count was 10.8 × 109/L with 87% neutrophils, and 4 of 4 aerobic blood cultures grew small, curved gram-negative rods which were later speciated as C. fetus. Attempted sternoclavicular joint aspiration failed. High-resolution computed tomographic angiogram revealed a 5.3 × 4.8 cm descending thoracic aneurysm with intramural thrombus and dissection ending at the level of the diaphragm (Fig. 1). The patient's blood pressure was controlled, and surgical intervention was delayed until his active infection resolved. An extended course of antibiotics including meropenem and gentamicin was initiated for a presumed endovascular infection. His joint symptoms improved throughout his hospital course and resolved after 2 weeks of antibiotic therapy. He was discharged on hospital day 28. In clinical follow-up 1 month later, the patient felt well, and physical examination failed to reveal any evidence of active joint inflammation. Six weeks later the patient required an uncomplicated surgical repair for a contained rupture of his known aortic aneurysm.
Campylobacter, Greek for "curved rod," is a motile, gram-negative, comma-shaped, microaerophilic bacilli transmitted through the fecal-oral route. C. fetus causes bacteremia, meningitis, endovascular infections, septic arthritis, and cellulitis in immunocompromised hosts with comorbid conditions including alcoholism, malignancy, cirrhosis, diabetes, and immunosuppression.1 The propensity of C. fetus to enter the circulation is attributed to its capsulelike protein structure that inhibits complement 3 binding, making it resistant to immune clearance in the bloodstream.2 Although it usually strikes immunocompromised patients, privileged sites of colonization such as atherosclerotic plaques or vascular abnormalities may allow infection of otherwise healthy individuals.
This patient had multiple foci of active infection including a suspected septic joint and a descending dissecting thoracic aneurysm. Joint symptoms have been reported in up to 12% of C. fetus cases, most commonly affecting the knees and hips.3 Although synovial fluid was not isolated from this patient, joint examination, early onset of monoarthritis, and resolution of symptoms after antibiotic therapy suggest a septic etiology rather than a reactive process. This is the first report of C. fetus infecting the sternoclavicular joint, a site often seeded in bacteremic patients.
C. fetus also has a vascular tropism which has been reported in the literature with more than 20 reports of endocarditis and 20 cases of mycotic aneurysm.4,5 The pre-pathological diagnosis of bacterial aortitis is difficult to confirm, but an actively dissecting or enlarging aortic aneurysm with concomitant bacteremia strongly suggests the diagnosis. Because this patient did not demonstrate any active clinical evidence of dissection and no interval changes were noted on serial abdominal imaging, it was concluded that a preexisting lesion, consistent with the patient's known hypertension, served as a substrate for bacterial colonization and spread.
This case serves to remind clinicians that immunocompetent patients are at risk for serious systemic infections, including C. fetus, which are more commonly considered as pathogens of immunodeficient hosts. Immunocompetent patients with endovascular lesions including thrombus and dissection are at particular risk for sustained blood-borne infections. Only by recognizing the presentation of and understanding the associated risks of C. fetus bacteremia will clinicians be able to diagnose and treat this infection effectively.
The authors thank Mykol Larvie, MD, of the MGH Department of Radiology for his technical assistance preparing the radiological figure for publication. The authors also thank Dr James Versalovic of Texas Children's Hospital Medical Center in Houston, Tex, for identifying the microbiological isolate.
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