Mycotic aortic aneurysm due to brucellosis.

Brucellosis is a multisystem zoonotic disease. Mycotic aneurysm due to Brucella is rare and has no clear management approach. Here, we present two cases of mycotic aortic aneurysm due to Brucella. The first patient was treated with surgical resection of a symptomatic infrarenal abdominal aortic aneurysm combined with lifelong doxycycline and rifampicin. The second patient improved with conservative treatment including a 6-month course of antibiotics and regular clinical and radiologic monitoring. Through these cases, we hope to draw attention to this serious adverse effect of Brucella and the importance of management of its local arterial complications, especially in endemic areas.

Brucellosis is the most prevalent zoonotic disease worldwide. Brucella melitensis is the most common type of Brucella bacteria transmitted to humans through unpasteurized products.1, 2, 3 Brucellosis may present with a large spectrum of clinical manifestations affecting the gastrointestinal, cardiovascular, genitourinary, hematologic, neurologic, and skeletal systems. The most common cardiovascular complication is endocarditis, which occurs in 1% to 2% of cases. Brucella arteritis or its local arterial complication is rare. Through this case series, we hope to draw attention to the absence of an optimal treatment for vascular brucellosis and mycotic aneurysm due to Brucella. The consent of the patients for publication was obtained.

Case report

First patient

A 60-year-old woman with a history of asymptomatic type III DeBakey chronic spontaneous aortic dissection for 4 years was admitted through the emergency department with severe continuous abdominal and bilateral flank pain persisting for 3 days. Her most recent thoracoabdominal computed tomography (CT) scan 6 months earlier showed stable aortic dissection without aneurysmal change (Fig 1). Physical examination on admission revealed a pulsatile abdominal mass. Urgent thoracoabdominal CT with arterial-phase administration of contrast material showed a 6- × 6-cm infrarenal abdominal aortic aneurysm that was not obvious on previous CT scans (Fig 2, A and B). She was a nonsmoker and nonalcoholic, and she had no family history of aortic aneurysm. However, she had a history of continuous low-grade fever with sweating for 8 weeks, which was accompanied by generalized joint and back pain. She was a farmer and had a history of consuming unpasteurized milk daily. Her leukocyte count was 17,000/mm3 and her C-reactive protein (CRP) level was 32 mg/dL. Results of an acid-fast bacilli test were negative, whereas those of a Brucella immunoglobulin G (IgG) serologic test were highly positive (600).

Fig 1

An axial view of computed tomography (CT) of the abdomen during arterial phase showing spontaneous infrarenal abdominal aorta dissection without change for 4 years.

Fig 2

Computed tomography (CT) of the abdomen during arterial phase showing an infrarenal abdominal aorta dissection complicated by a 6- × 6-cm mycotic aneurysm due to chronic Brucella arteritis. A, Axial view. B, Three-dimensional view. C, Coronal view of CT of the abdomen during arterial phase showing normal infrarenal abdominal aorta graft that was applied 1 year earlier for a patient with a 6- × 6-cm mycotic aneurysm due to chronic Brucella arteritis.

At this point, the infectious disease team began treatment with antibiotics, including aminoglycoside, doxycycline, and rifampicin. However, the patient's abdomen was tender and her pain was continuous. Therefore, she underwent urgent mycotic aneurysm excision with a 20- × 10-mm silver-coated aortobi-iliac in situ graft. Histopathologic examination revealed a severe degenerative aneurysm with severe arteritis. Tissue cultures after a 3-week incubation period were positive for Brucella, which was sensitive to rifampicin and doxycycline.

Regular clinical and radiologic follow-up at 6 months showed a normal erythrocyte sedimentation rate, CRP level of <10 mg/dL, gradual decrease in Brucella IgG serology titer to 80, and normal aortic graft on 1-year follow-up abdominal CT (Fig 2, C). Currently, the patient undergoes regular clinical and radiologic follow-up annually.

Second patient

An 83-year-old man was referred by his primary care physician because of continuous abdominal pain persisting for 3 days. He also had a history of consuming unpasteurized milk with a history of generalized joint and low back pain and low-grade fever for 3 months. On admission, his CRP level was 28 mg/dL, and results of a Brucella IgG serologic test were positive (320). Abdominal CT with arterial-phase administration of contrast material showed a 3.8-cm infrarenal abdominal aortic aneurysm surrounded by retroperitoneal fat stranding and inflammatory change. The other parts of the aorta appeared to have normal wall thickness surrounded by normal fatty layers (Fig 3). There was no previous abdominal CT scan because the patient did not have such symptoms previously. All of these clinical findings are highly suggestive of mycotic aneurysm.

Fig 3

Computed tomography (CT) of the abdomen during arterial phase showing an infrarenal abdominal aorta aneurysm of 31 × 38 mm; the arrow shows wall thickening and inflammatory fat stranding changes localized at the aneurysm wall in a patient who had high Brucella serology titer. A, Axial view. B, Coronal three-dimensional view.

Treatment with antibiotics including doxycycline and rifampicin was initiated. Within 3 days, his symptoms were completely resolved. Because of the patient's dramatic clinical response to antibiotic treatment and the small size of the aneurysm, we leaned toward conservative management, including a 6-month course of antibiotics and close clinical and radiologic monitoring.

Regular clinical and radiologic follow-up at 6 months showed a CRP level of <10 mg/dL, gradual decrease in Brucella IgG serology titer to 80, and no change in aneurysm size on abdominal CT.

Discussion

Mycotic aneurysm may be caused by either local extension of an adjacent soft tissue infection or embolization of an infectious source. It is postulated that in the case of embolization, emboli reach the adventitia through the vasa vasorum, and the inflammatory response disrupts both the muscularis and adventitia, resulting in blood vessel wall weakness and pseudoaneurysm formation.

Mycotic aneurysm involving the aorta or large arteries due to Brucella is very rare. According to a literature search, the ascending aorta, superior mesenteric artery, subclavian artery, or axillary artery may be affected. Thirty-four cases of Brucella endarteritis have been published. In a previous review of 25 published cases of aortic brucellosis, Kakkos et al reported that the infrarenal abdominal aorta (65%) was most affected, followed by the ascending thoracic aorta (23%).

The chronic form of brucellosis usually is manifested with either local disease or constitutional symptoms in the form of generalized bone pain, back pain, low-grade fever, or sweating. However, Brucella endarteritis usually has no specific clinical symptoms that may guide immediate diagnosis. Abdominal pain appears to be the most common symptom of aortic brucellosis, and it was the main presenting complaint for both of our patients. In endemic areas, we believe that brucellosis should be included in the differential diagnosis or as the leading cause of the main disease. We routinely screen for Brucella infection in all cases of mycotic aneurysm in addition to other suspected causes, such as tuberculosis, syphilis, and salmonellosis. Brucella serologic testing by enzyme-linked immunosorbent assay is the usual method of diagnosis.4, 5, 6 The sensitivity of Brucella IgG serology is 92% or more for Brucella endarteritis, which may be due to the long period of disease formation. Enzyme-linked immunosorbent assay and tissue histopathology also have high sensitivity for Brucella infection.

There is no specific management approach for Brucella arteritis or its local complication of mycotic aneurysm. Herrick et al reported a case of brucellosis presenting as bacteremia and aortic ulcer 18 years after Brucella exposure, which was treated successfully by combined surgical repair and lifelong doxycycline and rifampicin. Doxycycline (200 mg) plus rifampicin (600-900 mg) daily for a minimum of 6 weeks is the recommended treatment for brucellosis.7, 8 A literature search on the optimal treatment for Brucella infection and its local complication of endocarditis revealed no reliable data regarding choice or duration of antibiotic therapy; however, there seems to be unanimous agreement that therapy should be prolonged.6, 7, 8 Medical treatment alone for Brucella endocarditis has a high mortality rate (33%) compared with combined medical and surgical treatment (7%).6, 7, 8, 9, 10 However, there is no comparative study on the various treatments for Brucella arteritis or its local arterial complications.

Conclusions

Through these cases, we hope to draw attention to this serious adverse effect of Brucella and the importance of management of its local arterial complications, especially in endemic areas.