Graphical Abstract
Key words: Doppler ultrasound, echocardiography, endocarditis
Abstract
Background
Triple-valve endocarditis is a very rare entity and even more so in the absence of prosthetic valves.
Case Summary
We describe the doubly unusual occurrence of native triple-valve endocarditis caused by Corynebacterium striatum in an otherwise immunocompetent 72-year-old woman in an urban hospital in New Zealand. She presented with colitis initially and was treated empirically, and a positive blood culture with C striatum was disregarded as being a contaminant. Upon another presentation with recrudescent fevers, investigations revealed endocarditis requiring urgent valve surgery. Intraoperatively, the rare finding of triple-valve endocarditis was made necessitating prosthetic replacement.
Discussion
C striatum has been reported to cause only 0.2% to 0.4% of cases of native valve endocarditis.
Take-Home Message
Often dismissed as a contaminant in blood cultures, C striatum can cause native valve endocarditis and should be regarded with caution in the context of the clinical presentation.
History of Presentation
A 72-year-old woman presented to the hospital with a 2-day history of fevers that followed a diarrheal illness of 3 weeks’ duration with accompanying malaise and weight loss.
Past Medical History
Her past medical history included a moderate abdominal aortic aneurysm of 37 mm that was under surveillance, chronic obstructive pulmonary disease resulting from 30 pack-years of smoking, hypertension, and a recent diagnosis of COVID-19 from which she had made a complete recovery. There was no history of structural heart disease or rheumatic fever. She had never used intravenous drugs.
Differential Diagnosis
The differential diagnosis included infectious causes, including a post–COVID-19 syndromic manifestation; gastroenteritis; and noninfectious causes of colitis including inflammatory bowel disease, malignancy, or ischemic etiologies. Further investigations were needed to ascertain the cause of her presentation.
Investigations
She was found to be hypovolemic in the emergency department at presentation and had raised inflammatory markers with a C-reactive protein of 367 mg/L, and a white blood cell count of 14.1 × 109/L. Fluid resuscitation was given, with ceftriaxone 2 g and metronidazole 500 mg intravenously. A portal venous phase computed tomography scan of the abdomen showed right-sided colitis with mucosal enhancement of the cecum and ascending colon. A single blood culture set (aerobic and anaerobic bottle) was taken and grew Corynebacterium striatum, which was thought to be a contaminant.
Management
The patient improved on antibiotics and was discharged with oral amoxicillin/clavulanic acid therapy for treatment of colitis. Eleven days later, she presented again with fevers and rigors and recurrence of diarrhea. A repeat abdominal scan showed improvement of colitis. A stable abdominal aortic aneurysm with an intramural thrombus was noted. She was empirically restarted on ceftriaxone and metronidazole, and her fevers resolved and inflammatory markers improved over the following 2 days. Fecal polymerase chain reaction did not detect any enteric pathogens, and a Clostridioides difficile toxin test was negative. Repeat blood cultures were taken at presentation and after 2 days had growth of C striatum, resistant to penicillin and clindamycin and susceptible to tetracycline and vancomycin. A treatment course of intravenous vancomycin was therefore initiated. A cardiovascular examination revealed a loud pansystolic murmur, and echocardiography was performed. This showed an eccentric mitral valve regurgitation jet, with a mobile echo density associated with the tip of the posterior leaflet, and possible ruptured chordae. There was also aortic regurgitation with thickened aortic cusps, and some suggestion of an irregular appearance on the tricuspid valve.
This warranted a transesophageal echocardiographic study, which showed large vegetations on the right coronary cusp (Videos 1 and 2) of the aortic valve (largest 5 mm × 9 mm) in addition to the previously described posterior mitral vegetation (Video 3) as well as thickening of the anterior mitral valve leaflet. There was significant thickening of the interatrial septum, but no obvious features of an abscess. The tricuspid valve was not clearly visualized during this scan but appeared irregular.
The patient had developed severe mitral regurgitation and moderate aortic regurgitation (Video 4, Video 5, Video 6) and therefore was accepted for inpatient valve replacement. Computed tomography angiography of the heart showed no coronary disease. She was taken to the operating room for surgery. Intraoperatively, it was found that she had vegetations on the trileaflet aortic valve, chordal rupture, and vegetations on the mitral valve that extended up to the annulus but not involving it. In addition, there was an area of supra-annular vegetation on the septal leaflet of the tricuspid valve, which necessitated the replacement of all 3 valves with bioprostheses (19-mm Inspiris [Edwards Lifesciences Inc] bovine aortic valve; 27-mm Trifecta [St Jude Medical Inc] porcine mitral valve; and 27 mm Mosaic [Medtronic Inc] porcine tricuspid valve]). The operation was otherwise uncomplicated. Tissue cultures from all 3 valves did not grow any bacteria, although gram-positive bacilli were seen on Gram stain from the aortic valve.
Outcome and Follow-Up
The postoperative course was uneventful, with the patient initially dependent on backup pacing, but able to regain sinus rhythm. She remained on intravenous vancomycin but was changed to oral linezolid for outpatient therapy and subsequently to oral doxycycline. The abdominal aortic aneurysm and thrombus was imaged again and not found to have any features suggestive of mycotic aneurysm or septic emboli. It remains under surveillance. The patient completed 6 weeks of antibiotic therapy and recovered well. An echocardiogram at 2 months showed well-seated valves with a mildly dyskinetic septum and a mildly reduced ejection fraction of 45%. Two years after the operation, she remains well, her left ventricular function has normalized with acceptable transvalvular gradients across the prosthetic valves, and she remains symptom-free.
Discussion
Triple-valve endocarditis is a very rare entity, causing only 0.2% to 0.4% of cases of native valve endocarditis.1,2 We believe this case is significant not only for the rarity of triple-valve disease, but also because the offending organism is a rare cause of endocarditis, especially of native valves.
Infective endocarditis remains a life-threatening condition with a global annual incidence estimated to be between 3 and 10 per 100,000 people and with an overall mortality approaching 25% to 30% at 1 year. Corynebacterium species are gram-positive aerobes that mostly are rod shaped except during certain phases of their life cycle in which they are club shaped, conferring their name “coryne” (clublike). They are often regarded as contaminants in blood cultures.3,4 In a Swedish study of more than 4,000 cases of infectious endocarditis, only 30 were caused by corynebacteria, of which only 10 patients had native valve disease. Half of those cases required surgery, and, of note, the mortality rate of Corynebacterium endocarditis was 13%; which is comparable to Staphylococcus aureus (15%), well known to be a virulent organism.5
The rapid identification and treatment of infective endocarditis is crucial to be able to change the prognosis of the disease, especially in high-risk population subgroups. Given that in the first presentation our patient's positive blood culture was regarded as a contaminant, it is imperative that the clinician consider the risk profile and the possibility of systemic infection due to Corynebacterium species. Most cases in the Swedish study occurred in elderly adults with a mean age of 71 years and in immunocompromised patients. Our subject was in this age group but was not known to have immune deficiency and did not have any other predisposing factors. For both presentations, our patient presented acutely unwell and responded to antibiotics, which would not have treated C striatum. The cause of colitis for the initial presentation was never determined but possibly could have been related to emboli from endocarditis causing ischemia.
Multivalvular endocarditis carries a greater chance of mortality and morbidity, so in addition, to antibiotic treatment, surgical interventions are often warranted.6, 7, 8 Acute indications for surgery include mitral or aortic valvular compromise, left ventricular impairment, rupture, fistula, perivalvular extension, or perforation. Other indications include abscess, failure to respond to antimicrobial therapy, persistent large vegetations (especially >1 cm), ongoing bacteremia, or septic embolization.6,7 Our patient had perivalvular extension and severe mitral regurgitation and moderate aortic regurgitation that fulfilled criteria for prompt surgical management.
Conclusions
Our case is a reminder for clinicians to have a low threshold for repeating blood cultures when a bacterium that is usually considered to be a contaminant is isolated from a patient with an unexplained presentation or diagnostic uncertainty, as consequences can be life threatening as demonstrated in this situation.
Visual Summary.
Timeline of the Case
| Timeline | Events |
|---|---|
| Day 1 | A 72-y-old woman presents with 2-d history of fevers and rigors, with preceding 3 wk of diarrheal illness with malaise. Raised inflammatory markers and single blood culture positive for commensal skin organism Corynebacterium striatum. Note made of colitis on abdominal computed tomography scan. Patient treated empirically and discharged after clinical improvement. |
| Day 11 | Patient presented again with recurrence of symptoms. Abdominal computed tomography scan showed improvement of colitis. Blood cultures continued to grow C. striatum raising clinical suspicion for occult infection. Clinical examination revealed new pansystolic murmur. Echocardiogram requested. |
| Day 12 | Transthoracic echocardiography showed large vegetation on aortic valve and mitral valve with associated regurgitation. |
| Day 12 | Transesophageal echocardiography showed significant aortic regurgitation with large vegetation, mitral regurgitation with prolapse and possibility of tricuspid valve involvement. Surgical team contacted for consideration of inpatient surgery. |
| Day 14 | Patient was taken to operating room and underwent triple-valve replacement. Uneventful recovery and discharge following operation. |
| Day 60 | Transthoracic echocardiography showed well-seated valves with acceptable transvalvular gradients and mildly reduced ejection fraction and mildly dyskinetic septum. |
| 2 y postoperative | Patient had a normal examination and was symptom-free. Normalization of left ventricular function, well-seated and functional prosthetic valves. |
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Take-Home Messages
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•
This is a very rare case of native triple-valve endocarditis caused by an atypical organism, Corynebacterium striatum, a skin commensal that rarely causes disease and is often dismissed as a contaminant in blood cultures.
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•
Given the relatively low virulence of C striatum, infections can be advanced by the time of diagnosis, as described here in the form of triple-valve endocarditis necessitating urgent surgery and debridement, and associated with increased risks of morbidity and mortality especially in higher-risk populations, so clinicians should maintain suspicion in unexplained presentations in diagnostically uncertain situations.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
Appendix
For supplemental videos, please see the online version of this paper.
Appendix
Transesophageal Echocardiography Clip of Aortic Valve Showing Large Vegetation on the Right Coronary Cusp
Transesophageal Echocardiography Clip of the Aortic and Tricuspid Valves Showing Vegetation and Irregularity
Transesophageal Echocardiography Clip of the Mitral Valve Showing Posterior Valve Vegetation and Thickened Surfaces of the Anterior Leaflet
Transesophageal Echocardiography Clip of Color Flow Demonstrating Significant Aortic and Mitral Valve Regurgitation Due to Endocarditis
Transesophageal echocardiography Clip of Color Doppler Showing En Face View of Regurgitant Flow From Aortic Valve With Eccentric Mitral Regurgitation Jet
Transesophageal Echocardiography Clip of Severe Mitral Regurgitation With Flow Reversal Seen in the Pulmonary Vein
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Transesophageal Echocardiography Clip of Aortic Valve Showing Large Vegetation on the Right Coronary Cusp
Transesophageal Echocardiography Clip of the Aortic and Tricuspid Valves Showing Vegetation and Irregularity
Transesophageal Echocardiography Clip of the Mitral Valve Showing Posterior Valve Vegetation and Thickened Surfaces of the Anterior Leaflet
Transesophageal Echocardiography Clip of Color Flow Demonstrating Significant Aortic and Mitral Valve Regurgitation Due to Endocarditis
Transesophageal echocardiography Clip of Color Doppler Showing En Face View of Regurgitant Flow From Aortic Valve With Eccentric Mitral Regurgitation Jet
Transesophageal Echocardiography Clip of Severe Mitral Regurgitation With Flow Reversal Seen in the Pulmonary Vein