Abstract | November 9, 2021

A Rare Case of Cutibacterium Prosthetic Valve Endocarditis

Presenting Author: Nikhilesh Srinivasan, MD, Internal Medicine Resident PGY2, Department of Internal Medicine, HCA HealthOne, Lone Tree, Colorado, Highlands Ranch, Colorado

Coauthors: Nowak, Caden, MD, Internal Medicine, PGY2, HCA HealthOne, Lone Tree, CO

Learning Objectives

  1. Recognition of less common microorganisms that cause endocarditis. 
  2. Utilization of the 16s rRNA PCR test or the use of prolonged incubation of blood cultures for up to 14 days especially in the setting of male patients who had undergone prosthetic valve replacement surgery to aid in the diagnosis of Cutibacterium endocarditis. 

Background: Infective endocarditis is mainly caused by staphylococci and streptococci, but in the absence of positive blood cultures other less common bacterial bugs such as cutibacterium must be considered. 

Methods: A 57 year old male with a past medical history of bovine aortic valve replacement and thoracic repair in 2016, HFpEF, HTN presented for worsening shortness of breath, fever, chills, and an unexplained twenty pound weight loss for the month prior to admission. Original TTE done on admission did not show any vegetations. Subsequent TEE performed later in the hospital course showed a “large, mobile vegetation on the aortic valve prosthesis that extended to the ascending aorta. Blood cultures were negative for common organisms of endocarditis and serology for bartonella/brucella/chlamydia species were also negative. 16s rRNA PCR performed was positive for DNA from cutibacterium. 

Findings: About 80% of cases of infective endocarditis are from streptococci and staphylococci. Given that the patient had met Dukes criterion for infective endocarditis yet original blood cultures did not grow the common organism’s other bugs were considered. Among the tests ordered was the 16s rRNA PCR which came back positive for cutibacterium. This type of bacterium which typically causes late-onset prosthetic valve infections has mainly been associated with aortic valves. In the most recent case series looking at cutibacterium endocarditis, it was found to have a male predominance, thought to be due to men having more sebaceous glands and hair follicles than women. 

Conclusions: This case report entails a rare type of infective endocarditis, which is a difficult one to diagnose. Given that the symptoms of Cutibacterium endocarditis are subtle due to the low virulence and slow growth our case highlights the utilization of the 16s rRNA PCR test especially in male patients with recent aortic prosthetic valve surgery in the past 4-5 years. 

Case Presentation 

Introduction: Infective endocarditis is a life-threatening bacterial infection that causes inflammation in the endocardium layer of the heart. It can affect both native and prosthetic heart valves. The most common bacterial bugs are S.aureus, coagulase-negative staph, streptococci, HACEK, candida species, and gram negative bacilli. The type of bacteria that infects the valve in hospital-acquired infective endocarditis is related to time after the valve was replaced and how it was replaced (TAVR or surgically replaced), with enterococcus more common in a TAVR. At least two sets of blood cultures should be positive with microorganisms common to endocarditis from different sites prior to the start of antibiotic therapy. In the setting of negative blood cultures with high suspicion for endocarditis, other organisms such as Bartonella and C.burnetti should be considered. In this case report, we will specifically look at cutibacterium. Typically, this is a gram-positive coccobacillus, which constitutes a part of the normal skin flora and mucosal surfaces. Although this bacterium is mainly associated with acne, there has been case reports showing that it is also associated with other pathologies, including osteomyelitis, endophthalmitis, and endocarditis. Our case explores the confirmatory diagnosis of this rare type of bacterial endocarditis, which is a difficult one that includes TEE, multiple blood cultures, and advanced PCR testing. 

Case Report: We present the case of a 57-year-old male with a past medical history of bovine aortic valve replacement and thoracic aorta repair in 2016, HFpEF, diverticulosis, and HTN, who presented to the emergency room for hypotension and epigastric abdomen pain. The patient’s main complaints were that he had been feeling nauseous and experiencing worsening shortness of breath for a month prior to admission. He also endorsed fever and chills that lasted 1 to 2 hours per day, unexplained twenty-pound weight loss, double vision, and lightheadedness. On physical exam, the patient was noted to have a new murmur best heard in the 2nd right intercostal space and poor dentition, but was otherwise unremarkable. Patient was found to have a BP of 105/58 with a WBC count of 19. Blood cultures were drawn. EKG was unremarkable. A TTE was done and showed normal parameters of heart function with mild mitral valve thickening and a normal appearing bovine aortic valve prosthesis. Due to his abdomen pain, GI was consulted and an abdomen MRI was ordered, which showed a new infarct in the spleen and kidneys. Subsequent MRI of the brain was negative. Following these new findings on imaging, the patient then underwent a TEE three days after his TTE, which showed a “large, mobile vegetation on the aortic valve prosthesis that extended into the ascending aorta.” Patient was transferred to a different hospital to undergo a sternotomy and replacement of the aortic valve. During the next several weeks, the patient’s original blood cultures and the ones drawn after transfer continued to be negative. The vegetation was also negative after testing for gram stain/culture, fungal and acid-fast organisms. The patient’s blood was also sent out for serology and was negative for bartonella, brucella, chlamydia species, and C. Burnetti. One of the last tests ordered was a 16s rRNA PCR from the vegetation, which had been ordered one month after the patient originally presented to the hospital. The PCR results found DNA from cutibacterium (formerly known propionibacterium acnes). 

Final/Working Diagnosis: In order to make the definitive diagnosis of infective endocarditis, the patient must meet either 2 major clinical criteria, 1 major and any 3 minor, or 5 minor clinical criteria outlined by the Duke criterion. The major criteria include: positive blood cultures from two separate sites for typical microorganisms of endocarditis, echocardiogram support, and new valvular regurgitation. The minor criteria include: predisposing heart condition or intravenous drug use, fever >38 C, vascular phenomena, immunologic phenomena, and positive blood cultures not meeting major criterion. In our case report, the patient had high suspicion for infective endocarditis given the new murmur noted on physical examination and the patient’s pre-existing heart condition requiring an aortic bovine valve replacement. Typically, the first diagnostic test that patients with suspicion for infective endocarditis undergo in the hospital setting is a TTE, although TEE is the imaging modality of choice as it has greater sensitivity. A TEE allows the valve to be more accurately assessed for fistula, abscess, or leaflet perforation. In the case of diagnosing cutibacterium endocarditis, additional confirmatory tests are necessary. 

In general, cutibacterium prosthetic valve endocarditis affects 1-6% of patients with a cardiac valve prosthesis. Cutibacterium may cause infections of endovascular devices such as prosthetic valves, pacemakers, and defibrillators. Infection can be divided into local infection (pocket infection) and device-related bloodstream infections, including device-related endocarditis. Endocarditis caused by cutibacterium has been associated with both native and prosthetic valves but more often develops on valve prostheses, most commonly the aortic valve. Symptoms of endocarditis are often subtle due to the low virulence and slow growth of C. acnes. The mortality rate is 15 to 27 percent due to valvular and perivalvular destruction associated with delayed diagnosis of infection. 

When looking at one case series of 15 cases of Cutibacterium endocarditis, 13 patients had a prosthetic valve. The mean onset of infection was four years following surgery as was similar in our case report. Late-onset prosthetic valve infections due to Cutibacterium may be difficult to diagnose, as clinical manifestations may be limited to valve dysfunction with few symptoms suggestive of infection. Central nervous system emboli, congestive heart failure, cardiac abscess, and valve dehiscence may complicate such infections. Furthermore, histological examination of excised paravalvular tissues in such cases may demonstrate minimal evidence of acute inflammation. In our case report and many other prior cases reports the utilization of the 16S ribosomal RNA testing on tissue samples aided in the eventual diagnosis. 

When looking at demographics of cutibacterium it has been shown to have a male predominance with 100% of cases reported in males in the most recent case series conducted to date. Although no definitive link has been found, it is thought that males have a higher predilection to cutibacterium endocarditis due to men having more sebaceous glands and hair follicles than women. In our case report, it was hypothesized that our patient had this bacterium introduced to their bloodstream 5 years ago during their aortic valve replacement from skin flora. 

Management/Outcome: A recent clinical study done on fifty-one patients in Sweden who tested positive for Cutibacterium endocarditis showed promising results of the two definitive treatments for this condition. All patients in this study were given antibiotics. Nineteen of the fifty-one patients were treated conservatively solely with antibiotics. Of the nineteen treated solely with antibiotics, sixteen were declared cured by eradication of the microorganism, while three had relapses. The most frequently used combination of antibiotics in this study population was a beta-lactam and an aminoglycoside for a mean of forty-two days. The most frequently used beta-lactam in this study was benzyl-penicillin. The other definitive treatment of this rare type of endocarditis was cardiac surgery in combination with antibiotics. Of the fifty-one patients in this study, 63% of them underwent this treatment modality. The median time to surgery was five days after commencing antibiotic treatment. This treatment modality appeared to be superior to the use of antibiotics solely with a cure rate of 97%. 

The mainstay of treatment of the patient presented in our case was the use of antibiotics. The patient received treatment with a beta-lactam (benzyl-penicillin) in combination with an aminoglycoside for a total of forty days with complete resolution of symptoms. 

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