A rare case of an infected aortoiliac graft complicated with Eggerthella lenta bacteremia and septic shock.

We describe the successful medical management of an infected aorto-bi-Iliac endograft. In this case report, we provide an example of a patient with an infected aorto-bi-iliac endograft and how appropriate medical management may result in a positive outcome. We report a case of a 67-year-old man with several medical comorbidities who developed aorto-bi-iliac endograft infection one year after graft placement. The patient presented to our E.R. with fever, lethargy, tachycardia, tachypnea, and hypotension. The diagnosis of an infected endograft was established after excluding any other possible source of infection plus the strong radiological evidence by computed tomographic scan and WBCs labeled Indium-111 tropolone scan. Blood cultures revealed the development of Eggerthella lenta, Escherichia coli Extended-spectrum beta-lactamase (ESBL), and Enterococcus Faecalis. To our knowledge, this is a rare case of an infected endograft and bacteremia due to Eggerthella lenta. After the administration of vancomycin and Meropenem, no improvements were noted to the patient's clinical condition. However, upon the administration of Tigecycline, the patient's clinical condition improved. Two days later, repeat blood cultures were negative. After completion of the course of antibiotics and stabilization of other comorbidities, the patient was discharged home with long term antibiotic therapy under close control of inflammation markers.

Introduction

Infection of aortoiliac endograft is, to date, a rare complication after endovascular aneurysm repair (EVAR) [1,2,3]. Endograft infection with an aorto-duodenal fistula is usually the reported long-term complication of (EVAR) [4,5]. Staphylococcus species, Streptococcus species, and Escherichia coli were the most common isolated microorganisms [6]. Staphylococcus species are the most common responsible pathogens [7].

The diagnosis of an infected endograft is based on an association of clinical symptoms, radiologic imaging, and microbial cultures. Angio-computed tomography is currently the gold-standard technique for diagnosis. Low-grade infection sometimes requires nuclear medicine imaging to make a correct diagnosis [8]. As the number of patients with endovascular aneurysm repair has increased over the last decade, the number of patients with endograft infection might also have increased [9,10]. However, no guideline defines the treatment of endograft infection [9].

Surgical treatment with complete explantation of the infected endograft seems to be the preferred management in selected patients [1,11].

Supportive medical treatment without surgical intervention is thought to have significant associated mortality [1]. There are sporadic case reports; however, difficulties remain in ensuring prompt diagnosis and determining the optimum treatment strategy. Conservative, non-resectional management of graft infection is still a reasonable solution for selected patients, as those with significant comorbidities [12], or those where the implanted aortic graft is in a location that precludes excision without causing a high likelihood of morbidity and/or mortality [13,14].

Case presentation

The patient is a 67-year-old male with several medical comorbidities who presented to our E.D. with fever, lethargy, tachycardia, tachypnea, and hypotension. The patient had aorto-bi-iliac graft replacement placement for Abdominal Aortic Aneurysm(AAA) one year prior. AAA repair was complicated with paraplegia and graft leaking treated with embolization. On physical examination, the patient was minimally responsive unable to maintain the airway with minimal peri-umbilical tenderness with deep palpation without peritoneal signs. Emergent intubation was done, and the patient was transferred to the medical critical care unit.

White blood cell count was 17,000/μL; Hemoglobin 9.6 g/dL, platelet count 300,000/μL, BUN 66 mg/dL, Cr 2.1 mg/dL, minimal elevation of troponin and normal level of electrolytes. Diagnosis of severe sepsis and septic shock of unknown source was made. The patient received empirical treatment of vancomycin and Meropenem. Urine cultures, respiratory culture were all negative for any bacterial growth; however, blood culture demonstrated Eggerthella lenta, Escherichia coli Extended-spectrum beta-lactamase (ESBL), and Enterococcus Faecalis. A transesophageal echocardiogram was performed and revealed no vegetation. Abdominal computed tomography (C.T.) with contrast demonstrated inflammatory changes around aorto-bi-iliac graft, as shown in Figure 1 with no aortoenteric fistula. To identify the inflammation site impression, Indium-111 WBC scan was performed and showed abnormally increased activity in the mid to lower abdomen in the midline also shown in Figure 2.

Figure 1.

C.T. abdomen and pelvis with IV contrast reveals an approximately 6 cm infra-renal aortic aneurysm repaired with an intra-aortic stent-graft placement (red arrow). There was noted to be a subtle peri-aortic enhancement that represents edema and would indicate an infected graft (white arrow).

Figure 2.

Indium-111 WBC scan: Autologous WBCs labeled Indium-111 tropolone administered intravenously reveals increased uptake in the mid-abdomen (Red arrow) in the region of the intra-aortic graft signifying increased inflammatory activity consistent with infection at the 24-hour scan. Increased uptake in the right lower abdomen (blue arrow) represents colitis. Otherwise, there is normal uptake in the liver, spleen, and bone marrow.

Vascular surgery extensively evaluated the patient for graft replacement surgery. However, given the unstable condition of the patient, vascular interventions were deferred. Due to the patient’s frail condition, we chose a less invasive and conservative strategy. Seven days’ course of IV antibiotics vancomycin (1 g daily) and Meropenem (1 g twice a day) were administered; however, the patient continued to have a spiking of fever and was unable to be weaned from mechanical ventilation. Repeat blood culture drawn during the same period grew the same bacteria (Eggerthella lenta, Escherichia coli Extended-spectrum beta-lactamase (ESBL), and Enterococcus Faecalis). The antibiotic regimen was changed to Tigecycline (50 mg twice a day), which was administered for 14 days. Two days after conducting Tigecycline, repeat blood cultures were negative. After completion of the course of antibiotics and stabilization of other comorbidities, the patient was discharged home with long term antibiotic therapy under close control of inflammation markers.

Discussion

The incidence of endograft infection is below 1%, with a mortality rate of 25% [15]. Publications report high mortality after conservative therapy of endograft infection. There is evidence for lower mortality in patients who underwent surgery [6,9]. The gold standard for aortic endograft infection includes the excision of infected endograft, debridement, and reconstruction. However, these methods are not always the best option for patients with poor clinical status [16]. Although the consensus is that infected graft material should always be removed [17].

This case shows that there may be a role for conservative treatment in selected cases of patients with an infected endograft [18]. Expert opinion previously suggested removal of the infected graft, anatomical revascularization, and antibiotic therapy are important for long term survival after aortic endograft infection [19]. Conservative therapy is only warranted in patients unsuitable for surgical treatment [12,20,21].

Another very important aspect, in this case, is the Eggerthella lenta bacteremia in the absence of an aortoenteric fistula. Eggerthella lenta is an anaerobic, non-sporulating, Gram-positive bacilli from the normal human gut flora that can occasionally be implicated in invasive diseases. The evidence of the presence of colitis in the Indium-111 WBC scan could be the source of Eggerthella lenta bacteremia also could be supported by the demonstration of the other two bacteria (Escherichia coli Extended-spectrum beta-lactamase (ESBL), and Enterococcus Faecalis) that all consider as normal gastrointestinal flora [22].

Nuclear medicine imaging can be used to aid and make a correct diagnosis [8,23]. In our case, C.T. abdomen and pelvis with IV contrast reveals an approximately 6 cm infra-renal aortic aneurysm repaired with an intra-aortic stent-graft placement. There was noted to be a subtle peri-aortic enhancement that represents edema and would indicate an infected graft, as shown in Figure 1. Similarly, autologous WBCs labeled Indium-111 tropolone administered intravenously reveals increased uptake in the mid-abdomen at the region of the intra-aortic graft signifying increased inflammatory activity consistent with infection at 24-hour scan, as shown in Figure 2.

Conclusion

We describe a case of successful medical management of an infected endograft in our patient. There is a role for conservative treatment in selected cases of patients with infected endograft such as our patient. We also highlight the need for a multidisciplinary approach for the management of infected endograft. Nuclear medicine imaging can be used to aid and make a correct diagnosis. Long term antibiotic therapy under close control of inflammation markers is needed post conservative treatment of infected endograft.