Aerococcus viridans native valve endocarditis

Aerococcus viridans is an infrequent human pathogen and few cases of infective endocarditis have been reported. A case involving a 69-yearold man with colon cancer and hemicolectomy 14 years previously, without recurrence, is reported. A diagnosis of native mitral valve endocarditis was established on the basis of clinical presentation, characteristic echocardiographic findings and pathological specimen examination after urgent valve replacement. A viridans endocarditis appears to be particularly virulent, requiring a surgical approach in four of 10 cases reported and death in one of nine. Given the aggressive nature of A viridans endocarditis and the variable time to diagnosis (a few days to seven months), prompt recognition of symptoms and echocardiography, in addition to blood cultures, should be performed when symptoms persist.

The present article describes a case of A viridans endocarditis in a patient with no obvious risk factor for immunosuppression or previous valvular abnormality.

CAse PreseNtAtIoN
The patient was a 69-year-old man with colon cancer and hemicolectomy 14 years previously, without recurrence.He was admitted to hospital after five weeks of general deterioration, fatigue, weight loss, chills and sweats.He reported undergoing a dental cleaning one month before admission.Physical examination revealed a man with a heart rate of 82 beats/min, blood pressure of 122/86 mmHg, a respiratory rate of 22 breaths/min and a temperature of 37.2°C.His lungs were clear and cardiac sounds revealed a grade III/VI pansystolic blowing murmur at the apex radiating to the axilla with a laterally displaced apex.There were no heaves or thrills.The jugular venous pulse was noted at 2 cm above the sternal angle, at 30°.Abdominal examination revealed no hepatomegaly or splenomegaly.No peripheral stigmata of embolic phenomena were identified in the extremities, skin or retina.The neurological examination was unremarkable.
Blood work revealed a hemoglobin level of 126 g/L, a white blood cell count of 13.45×10 9 /L , an absolute neutrophil count of 10.96×10 9 /L and a platelet count of 243×10 9 /L.Serum electrolytes and creatinine levels were normal, as were liver enzyme levels and coagulation profile.An electrocardiogram showed normal sinus rhythm with a normal QRS interval.Chest radiography showed no cardiomegaly or pulmonary edema.Transesophageal echocardiography demonstrated two large mitral valve vegetations; the first identified was a multilobulated vegetation on the anterior leaflet 2.4 cm ×1.4 cm with perforation of the leaflet, and another vegetation measuring 1.7 cm ×1.0 cm was identified on the posterior leaflet.Doppler interrogation confirmed moderate to severe mitral regurgitation.No abscesses were identified.The other valves were case report otherwise normal on echocardiography.Two different sets of blood cultures grew A viridans, with sensitivities to ceftriaxone (0.25 µg/mL) and penicillin (0.03 µg/mL).
Surgery was performed six days after admission because of general deterioration, evidence of moderate to severe mitral regurgitation and fenestration of the anterior mitral valve leaflet.Blood-based cardioplegia was administered for myocardial protection.Through a left atriotomy, direct visualization of the mitral valve revealed large vegetations on the anterior and posterior leaflets with marked anatomical destruction of the valve (Figure 1A).Closer examination showed marked distortion of the valve apparatus, with a fenestration of the anterior leaflet (Figure 1B and 1C).The annulus was preserved.Mitral valve replacement using a bioprosthetic valve was performed.Care was taken to preserve the papillary-annular continuity to maintain ventricular function by saving as much of the mitral subvalvular apparatus as possible.Both the surgery and the postoperative course were uneventful.On postoperative day 7, he was discharged home without complications.A six-week treatment of penicillin was provided via pump through an indwelling intravenous line.Repeat postoperative blood cultures were negative for any growth.
Gross pathological examination (Figure 1) of the mitral valve revealed a firm thrombus, 2.0 cm in its greatest dimension, attached  to the ventricular aspect of a somewhat thickened valve.The thrombotic lesion appeared to have eroded into the valve, creating fullthickness valvular perforations measuring 1.0 cm and 0.7 cm in its greatest dimension (Figures 1B and 1C).Histological assessment of the valve revealed a prominent fibrinous exudate with neutrophils and tissue destruction, as well as areas of organization and fibrosis (Figures 2A to 2D).Furthermore, microscopy revealed a prominent population of Gram-positive cocci in clusters (Figure 2E), consistent with the A viridans found in the patient's blood.Nectrotic debris and fibrotic destruction of the valve are shown in Figure 2F.

DIsCUssIoN
We identified 10 previously reported cases of A viridans endocarditis (Table 1).In all reported cases, vegetations were identified on the mitral or aortic valves.One case resulted in congestive heart failure and death after discharge.In three cases, the isolated strain of A viridans was resistant to penicillin or quinolones.The laboratory findings were often nonspecific, with elevation in markers of inflammation (C-reactive protein, erythrocyte sedimentation rate and a mild leukocytosis).Blood cultures and echocardiography provided the diagnosis in all instances reported.As in the present case, the symptoms of endocarditis are often nonspecific.From the onset of symptoms to first medical contact, a delay of at least five weeks was reported.This delay likely contributed to the destruction and perforation of the mitral valve leaflet.

CoNClUsIoN
A viridans endocarditis appears to be particularly virulent, despite its often long latency period (subacute 73% [eight of 11 cases] and acute 23% [three of 11 cases]) and comparably lower mortality rates (9% [one of 11 cases]) as opposed to left-sided, native valve Staphylococcus aureus infective endocarditis (30% to 40%).It nonetheless required a surgical approach in 45% (five of 11) of the cases reported.Given the aggressive nature of A viridans endocarditis and the variable time to diagnosis (a few days to seven months), prompt recognition of symptoms, blood cultures and echocardiography, including transesophageal echocardiography, should be performed when blood cultures are positive and suspicion index is high.

Figure 1 )Figure 2 )
Figure 1) A Intraoperative view of the mitral valve through a left atreiotomy.Vegetations (arrows are seen on the anterior and posterior valve leaflets).BResected specimen.The anterior valve leaflet is perforated (arrow).Large vegetations are seen on the anterior valve leaflet and the Pi segment of the posterior leaflet.Note the intense inflammation and fibrotic reaction contributing to the distorsion of the valve apparatus.C Ventricular aspect of the resected mitral valve showing the perforation of the anterior leaflet (arrow)