Enterococcus Spp: a rare cause for infectious endocarditis of the aortic conduit

Introduction: Infectious endocarditis is still a diagnostic and therapeutic challenge. The annual incidence is 3-7/100000. The mortality and rate of complications remain high despite the progress made in its management.
Enterococcus Spp is the third most common etiology of infectious endocarditis. It is responsible for up to 20% of cases involving a native valve and 15% of cases affecting a prosthetic one. It is more commonly found in elders that have multiple comorbidities, affects the mitral or aortic valve and the source of infection is urinary, gastrointestinal or various catheters. It has a mortality rate of 20%. Approximately 30% of cases re-viewed involved a prosthetic valve and had a high rate of prosthetic abscesses.
Concerning the patients with a history of Bentall procedure and endocarditis, most of them developed the infection 2-17 months after the surgery. In the majority of cases the etiologic agent was part of the Staphylococcus Spp and the most common site of infection was the junction between the aortic annulus and the prosthetic valve and aortic conduit.
Case presentation: A 76 years old male, with a history of cardiovascular disease: severe aortic regurgitation secondary to bicuspid aortic valve and ascending aorta aneurysm repaired using the Bentall procedure 2 years ago and a history of gastrointestinal pathology (colonic diverticulosis and an endoscopic resection of a malignant colonic polyp in 2017) was transferred from the Neurology department with the diagnosis of recurrent ischemic stroke in the left carotid artery territory.
The clinical examination revealed rhythmic mechanical valve sounds, a diastolic aortic murmur, with no pulmonary or systemic stasis, BP=90/60 mmHg, HR=70/min, dysarthria, right central facial palsy, posi-tive paresis tests on the right side, hyporeflexia with Ba-binski sign present on the right side, febrile (t=38° C).
The laboratory tests showed a slight anemia, renal impairment with a Cr clearance of 42 ml/min/m2, an inflammatory syndrome and a negative urine culture. Two blood cultures were performed, 12 hours apart, both positive for Enterococcus Spp. ECG: sinus rhythm, 80/min, QRS axis at 60 degrees, with no ST-T changes.
Infectious endocarditis was the most likely diagnosis considering the fever, the inflammatory syndrome and the presence of the mechanical aortic valve. Subsequently an echocardiography was performed that showed preserved LVEF, a mitral valve with degenerative changes, a mild mitral regurgitation, a functional mechanical aortic valve, mild aortic regurgitation due to prosthetic leaks, with no pericardial effusion or signs of endocarditis (with the reserve of a difficult imaging window). The TEE revealed a pulsating hypoechoic mass with internal septation and systolic-diastolic flow on the aortic annulus, a mobile mass of 14 mm attached to the prosthetic aortic disc and a 19 mm, hypoechoic mass that seems to be attached to the aortic conduit at approximately 25 mm from the aortic root.
An abdominal computer tomography and a colono-scopy revealed spleen infarctions and colonic diverticulosis.
The abscess, the multiple vegetations and systemic embolism put the patient in a high-risk mortality group and represent a surgical emergency, but the surgical team recommended to delay the procedure due to the altered general status of the patient. He was admitted to the Cardiology Unit and started on antibiotics. The patient is to be transferred to the Cardiovascular Surgical Unit for surgery.
Case particularities: Infectious endocarditis of the aortic conduit is not as commonly described and im-plies a higher surgical risk. A Spanish study published in 2016 enrolled 3200 patients from GAMES (Spanish Collaboration on Endocarditis), 27 of whom had a history of surgical repair of an aortic root aneurysm- 9 had exclusive involvement of the prosthetic valve and 18 had both components affected. The median time from surgery to the infectious process was 24 months and in most cases the pathogens involved were part of the Staphylococcus Spp. There were no cases of infectious endocarditis of the aortic conduit caused by Enterococccus Spp.
On the other hand, the ESC guidelines for the management of infectious endocarditis mentions a possible link between some species of bacteria and colorectal cancer. The relationship between S. bovis and colorectal cancer has been well established, but the link between E. bovis and colonic disease needs to be further studied. The preliminary results of a study published in 2017 that enrolled 154 patients showed that colorectal cancer was diagnosed in 50% of the patients with infectious endocarditis caused by Enterococccus Spp and recommended screening the patients with no obvious source of infection with a colonoscopy. In this case, we had a very high suspicion of cancer recurrence, but the diverticulosis was the source of infection.
The studies that prove a link between colonic disease and Enterococcus bacteremia are retrospective and involve a small numer of patients. A study that enrolled 202 patients who underwent a colonoscopy maximum a year after the infectious episode revealed that 70% had a colonic disease, 35% had diverticulosis- but no link between the gastrointestinal pathology and endo-carditis could be proven.
There is at least one case of a patient with infectious endocarditis with Enterococcus faecalis and a history of Bentall procedure and diverticulosis described by the literature, but in that case only the aortic valve was affected.
Conclusion: Our knowledge about infectious endocar-ditis is constantly evolving. In underdeveloped countries the rheumatic heart disease remains the main predisposing factor, but in Western states 10-30% of cases involve a prosthetic valve. Also, the number of cases linked to colorectal pathology rises, bringing to our attention the need for further investigations- colonoscopy, PET-CT and for the inclusion of other specialists in the “Endocarditis Team”.

ISSN – online: 2734 – 6382
ISSN-L 1220-658X
ISSN – print: 1220-658X
The Romanian Journal of Cardiology is indexed by:
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CODE: 379
CME Credits: 10 (Romanian College of Physicians)