Lactococcus garvieae: An Uncommon Human Pathogen Causing Infective Endocarditis in a Valve-in-Valve Transcatheter Aortic Valve Replacement

Abstract

Lactococcus garvieae is a fish pathogen and an uncommon cause of human infections. There is a growing body of evidence showing its potential for causing endocarditis especially in those with prior valve surgery. In this case report, we present what we believe is the first case of endocarditis by L. garvieae affecting a valve-in-valve transcatheter aortic valve replacement that was successfully treated. Specific guidelines for the management of these patients are lacking. Our experience can contribute to the current knowledge regarding this life-threatening infection as well as to the future care of these patients. We aim to emphasize that despite not being recognized as a typical endocarditis microorganism by the Duke Criteria, the possibility of endocarditis needs to be highly entertained in patients with L. garvieae bacteremia, especially when prosthetic valves are present. Consequently, clinicians should pursue further this diagnosis with transesophageal echocardiogram and/or alternative imaging modalities (e.g., PET-CT scan and MRI) regardless of an initial negative transthoracic echocardiogram. Reaching a diagnosis of L. garvieae endocarditis led us to the decision of prolonging the antibiotic course for 6 weeks with successful results. Ultimately, surgery was not required owing to the absence of prosthetic aortic valve dysfunction and paravalvular extension of the infection.

Figure 1

Microscopy. Gram-stain smear (1000× magnification) showing gram-positive (violet) cocci in chains consistent with Lactococcus garvieae.

Figure 2

Electrocardiogram. Initial electrocardiogram revealing atrial fibrillation with fast ventricular response (126 bpm). There were no new ST-segment changes suggestive of acute ischemia.

Figure 3

Chest X-ray (CXR): there are mildly increased interstitial markings (chronic in character), cardiomegaly, and no evidence of consolidation or pleural effusion. Loop monitor can be visualized in the CXR at the left lower chest wall as well as a valve-in-valve TAVR (red arrow).

Figure 4

Transthoracic echocardiogram parasternal long-axis view. (a) Valve-in-valve TAVR (red arrow) with some artifacts causing suboptimal resolution and visualization of the bioprosthesis, yet no overt large vegetations were detected. No pericardial effusion present and systolic function was preserved (55%). (b) Diastolic frame showing no evidence of significant regurgitation by color Doppler. RV: right ventricle; LV: left ventricle; LA: left atrium.

Figure 5

Transesophageal echocardiogram (TEE) midesophageal views (Video 1). Various frames of TEE images showing an elongated and oscillating echogenic structure (red arrow) attached to the right coronary cusp leaflet of the valve-in-valve TAVR (blue arrow) consistent with an infective endocarditis vegetation (measuring 0.7 cm). No significant insufficiency or paravalvular extension of infection was detected. No evidence in favor of valvular thrombosis. The other native valves (especially the mitral valve) had no vegetations. LA: left atrium; Ao: ascending aorta.

Figure 6

Lactococcus garvieae antimicrobial sensitivities.