Disseminated melioidosis presenting with multifocal thoracic aortic mycotic aneurysms: A case report

Abstract

BACKGROUND

Melioidosis, caused by Burkholderia pseudomallei (B. pseudomallei), is endemic to Southeast Asia and northern Australia, with clinical manifestations ranging from localized infection to life-threatening disseminated disease. Mycotic aneurysm is a rare but serious complication of disseminated melioidosis, associated with high morbidity and mortality.

CASE SUMMARY

We describe a case of a 67-year-old man with diabetes mellitus who presented with B. pseudomallei bacteremia complicated by multiple deep-seated abscesses and multifocal mycotic aneurysms of the descending thoracic aorta. Despite appropriate antimicrobial therapy, serial imaging demonstrated progressive aneurysmal enlargement. Surgical repair was recommended but declined by the patient. He was managed conservatively with prolonged antimicrobial therapy and close clinical and radiological monitoring.

CONCLUSION

This case illustrates the aggressive nature of disseminated melioidosis with vascular involvement and highlights the need for early diagnosis and multidisciplinary management to improve outcomes.

Key Words: Splenic abscess; Descending aorta; Mycotic aneurysm; Burkholderia pseudomallei; Melioidosis; Case report

Core Tip: Melioidosis is a potentially severe infectious disease caused by Burkholderia pseudomallei, with clinical manifestations ranging from localized infection to fulminant disseminated disease. Although vascular involvement is an uncommon complication, mycotic aneurysm represents a particularly severe manifestation. Involvement of the thoracic aorta is especially rare and carries a high risk of morbidity and mortality. This case highlights disseminated melioidosis complicated by multifocal mycotic aneurysms of the descending thoracic aorta, emphasizing the need for early recognition, serial imaging, and multidisciplinary management to improve patient outcomes.

INTRODUCTION

Melioidosis is an infectious disease caused by the Gram-negative bacterium Burkholderia pseudomallei (B. pseudomallei), which is endemic to Southeast Asia and northern Australia. The clinical manifestations of melioidosis are diverse, ranging from localized skin and soft tissue infections to pneumonia, genitourinary involvement, visceral abscesses, septic arthritis, and neurological melioidosis. The disease carries a high mortality rate, particularly in cases presenting with acute fulminant sepsis[1,2].

Individuals with frequent exposure to soil and surface water are at greatest risk, with diabetes mellitus, hazardous alcohol consumption, chronic kidney disease, immunosuppressive therapy, and thalassemia recognized as major predisposing factors[3]. The primary routes of transmission are believed to be percutaneous inoculation, inhalation, and ingestion. Person-to-person transmission is exceedingly rare, with sexual transmission proposed but not definitively established[4].

Melioidosis-related mycotic aneurysm is an uncommon but life-threatening complication, associated with high morbidity and mortality. In Malaysia, reports of mycotic aneurysms secondary to B. pseudomallei are limited[5]. Here, we describe a rare case of melioidosis-related mycotic aneurysm involving the descending thoracic aorta, accompanied by splenic and prostate abscesses.

CASE PRESENTATION

Chief complaints

A 67-year-old man presented with a two-week history of persistent fever, reduced oral intake, and vague lower abdominal discomfort.

History of present illness

Fever for two weeks associated with reduced oral intake and vague lower abdominal discomfort. He denied dysuria, urinary frequency, haematuria, chest pain, cough, or shortness of breath. There was no recent history of travel or contact with unwell individuals. He reported engaging in home gardening but denied recent soil exposure or skin injuries.

He was initially admitted to a district hospital, where blood cultures grew B. pseudomallei, identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing demonstrated sensitivity to ceftazidime, meropenem, and trimethoprim–sulfamethoxazole. Intravenous ceftazidime was initiated, and he was subsequently transferred to a tertiary hospital for further management.

History of past illness

The patient had underlying type 2 diabetes mellitus, hypertension, and a prior ischemic stroke. There was no history of chronic kidney disease, malignancy, or immunosuppressive therapy.

Personal and family history

He was retired and lived independently. He denied smoking, alcohol consumption, and recreational drug use. There was no significant family history of infectious or hereditary diseases.

Physical examination

On admission, the patient was febrile with a temperature of 38.4 °C, heart rate of 96 beats per minute, blood pressure of 138/76 mmHg, and oxygen saturation of 98% on room air. He appeared comfortable at rest. Abdominal examination revealed mild lower abdominal tenderness without guarding or palpable masses. Cardiovascular and respiratory examinations were unremarkable. There was no peripheral oedema or skin lesion suggestive of an inoculation site.

Laboratory examinations

Blood cultures were positive for B. pseudomallei, identified by MALDI-TOF MS. Antimicrobial susceptibility testing showed susceptibility to ceftazidime, meropenem, and trimethoprim-sulfamethoxazole.

Imaging examinations

Abdominal ultrasonography demonstrated no intra-abdominal collections. In view of persistent fever and the high risk of deep-seated infection associated with B. pseudomallei bacteraemia, a contrast-enhanced computed tomography (CT) scan of the thorax, abdomen, and pelvis was performed. This revealed multifocal saccular aneurysmal dilatations of the descending thoracic aorta at the T5 and T11 vertebral levels, with associated periaortic inflammatory changes and collections, consistent with mycotic aneurysms (Figures 1 and 2). Additional findings included multiple splenic abscesses, a prostatic abscess, and a thick-walled cavitary lesion in the left upper lobe consistent with pulmonary melioidosis.

Figure 1 Sagittal view of computed tomography angiography of the thoracic aorta in maximum intensity projection showing three saccular aneurysms (*) along the descending thoracic aorta. Background atherosclerotic changes of the visualized aorta are also noted.

Figure 2 Axial view of computed tomography angiography of the thoracic aorta. A: Upper thoracic axial section demonstrating a saccular aneurysm (*) arising from the descending thoracic aorta; B: Lower thoracic axial section showing additional saccular aneurysms (*) along the descending thoracic aorta.

FINAL DIAGNOSIS

Disseminated melioidosis complicated by multifocal mycotic aneurysms of the descending thoracic aorta, splenic abscesses, prostatic abscess, and pulmonary involvement.

TREATMENT

Intravenous ceftazidime 2 g every six hours was continued. Oral trimethoprim–sulfamethoxazole was added during the second week of therapy. Cardiothoracic surgical consultation initially recommended conservative management with antimicrobial therapy. Despite radiological progression of the aortic aneurysms, the patient declined surgical intervention. He received eight weeks of intravenous ceftazidime while in the hospital and was discharged on lifelong oral trimethoprim-sulfamethoxazole because melioidosis-associated aortitis is associated with a high risk of relapse, particularly if surgery is not performed to remove the infected tissue.

OUTCOME AND FOLLOW-UP

Repeat contrast-enhanced CT imaging demonstrated progressive enlargement of the multifocal thoracic aortic mycotic aneurysms despite interval reduction in the size of the splenic and prostatic abscesses. Clinically, the patient showed symptomatic improvement with resolution of fever and stabilization of vital signs. Surgical intervention was again recommended; however, he declined operative management. He was discharged with plans for close outpatient follow-up and serial imaging. Unfortunately, the patient did not attend scheduled follow-up appointments and remained uncontactable despite multiple attempts.

DISCUSSION

Melioidosis is a potentially life-threatening infection caused by B. pseudomallei, which is endemic to Southeast Asia and northern Australia. The disease is associated with diverse clinical manifestations, ranging from localized abscesses to severe pneumonia, septicaemia, and disseminated infection with visceral abscess formation. Among its rarer but recognized complications is mycotic aneurysm, which poses significant diagnostic and management challenges[1].

Melioidosis-related mycotic aneurysm is an uncommon entity, but its true incidence is likely underestimated, particularly in endemic areas where awareness and routine screening may be limited. This complication results from hematogenous seeding of the vascular endothelium by B. pseudomallei, leading to inflammation, destruction of the arterial wall, and subsequent aneurysm formation[6,7]. The abdominal aorta is the most common site of mycotic aneurysm in melioidosis, as demonstrated in a case series from China, where six of eight patients had abdominal aortic involvement, while the remaining cases involved the left iliac artery and the mesenteric artery, respectively[8]. The descending thoracic aorta, as seen in our patient, is a less commonly reported site of involvement.

Several case series have highlighted the severe morbidity and mortality associated with melioidosis-related mycotic aneurysm. Azizi et al[9] described three cases of pseudoaneurysm secondary to melioidosis, all of whom underwent aneurysmectomy and graft placement. Despite surgical intervention, one patient died, presumably due to post-operative complications. In a larger series, Wu et al[8] reported eight cases of melioidosis-related mycotic aneurysm in Hainan province, China. Six patients survived following a combination of surgical repair and antimicrobial therapy, resulting in a mortality rate of 25%.

In our case, the patient presented with B. pseudomallei bacteremia complicated by multiple deep-seated abscesses and descending thoracic aortic mycotic aneurysms. Despite initial appropriate antimicrobial therapy, follow-up imaging demonstrated progressive enlargement of the aneurysms, reflecting the aggressive nature of the infection. Surgical repair was indicated; however, the patient declined operative intervention after extensive discussion regarding the risks and benefits.

The management of melioidosis-related mycotic aneurysm typically involves prolonged antimicrobial therapy alongside timely surgical or endovascular intervention. The recommended intensive phase includes intravenous ceftazidime, meropenem, or imipenem for at least eight weeks, followed by an eradication phase with oral trimethoprim-sulfamethoxazole for six months[10]. Lifelong suppressive therapy may be considered in select cases, particularly when surgical intervention is not feasible or there is residual infected vascular tissue[6,10].

CONCLUSION

Melioidosis-related mycotic aneurysm remains a rare but serious complication. The descending thoracic aorta is an uncommon site for vascular involvement in melioidosis. Multidisciplinary involvement, including infectious disease specialists, radiologists, and vascular or cardiothoracic surgeons, is critical in guiding individualized treatment strategies.