Abstract
To the Editor:
Infected abdominal aortic aneurysm (IAAA) is a special type of aneurysm caused by infection of various pathogenic bacteria. The occurrence of IAAA is relatively rare, accounting for only 0.6% to 2% of the all aortic aneurysms [1,2]. The common pathogenic bacteria are Salmonella, Staphylococcus, Streptococcus, and Escherichia coli; rare pathogens include Mycobacterium tuberculosis, Treponema pallidum, Candida, Aspergillus, and rickettsia. In extremely rare cases, Brucella can cause IAAA. Here, we describe a case of primary IAAA caused by Brucella.
A 72-year-old male presented to the hospital with fever, abdominal pain, and sweating of 10 days' duration. He denied history of hypertension, diabetes mellitus, or any infectious disease. The patient said he was a farmer, but after his diagnosis was confirmed, we again asked about the epidemiologic history and he admitted that he had eaten sheep placenta a month ago.
On physical examination, a mass measuring 4 × 5 cm was found in the upper abdomen, with a pulsating sensation. Results of laboratory studies showed that the white blood cell count was 11.5 × 109/L, neutrophil count was 7.1 × 109/L, neutrophil rate was 87.1%, D2 polymer was 6.03 mcg/mL, procalcitonin was 5.47 ng/mL. Computed tomography (CT) scans demonstrated dilated lower abdominal aorta lumen (Fig. 1A and 1B), aortic computed tomography angiography (CTA) showed the lower segment of the abdominal aorta and bilateral common iliac aneurysms expanded, the aorta and bilateral common iliac arteries were scattered with atheromatous plaques (Fig. 1C).
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The diagnosis of IAAA was made. An initial antibiotic, piperacillin/sulbactam was administered intravenously every eight hours. On the third day after admission, blood culture showed growth of gram-negative coccobacilli; bacteria was identified as Brucella malta, which was sensitive to rifampicin and doxycycline. The antibiotic regimen was then changed to doxycycline and rifampicin. After anti-infection treatment, the patient's fever gradually improved, but intermittent abdominal pain persisted. On the tenth day after admission, he underwent surgical treatment. Tissue cultures after a 10-day incubation period were positive for Brucella. The patient's abdominal pain disappeared on post-operative day six. The patient was discharged on post-operative day 10 and continued taking oral doxycycline and rifampin for six months. At the six-month follow-up, the abdominal aneurysm had disappeared almost completely and normal aortic graft on CT and CTA. Currently, there is no evidence of recurrence or complications; the patient undergoes regular clinical and radiologic follow-up.
Brucella is a rare pathogen of IAAA and the diagnosis can be challenging because of the atypical clinical manifestations and long incubation time of blood and tissue cultures. There should be awareness of this disease in patients who have a history of brucellosis-related epidemiology. Definitive treatment by open surgery and antimicrobial therapy needs to be performed for full control of the infection.