A rare case of isolated mitral valve endocarditis by Gemella sanguinis: Case report and review of the literature

Highlights • Gemella sanguinis is a very rare cause of infective endocarditis.• Only 12 cases previously reported in the literature, only two of which involved exclusively the mitral valve.• Usually associated with preexisting cardiac condition or oral infection/instrumentation.• Valve replacement along with prolonged antibiotic course resulted in successful outcomes in the majority of cases.


Introduction
Infective endocarditis (IE) remains a potentially lethal condition with significant clinical impact. Gram positive cocci, including Staphylococcus aureus, viridans streptococci and Enterococcus spp. are the most common causative pathogens identified, followed by fungal and HACEK organisms [1]. Gemella spp. has been implicated as a rare IE pathogen. Here, we describe the third known case of isolated Gemella sanguinis mitral valve involvement. The patient was successfully treated with surgical valve replacement along with extended course of antibiotics. This work has been reported in accordance to the Surgical CAse REport (SCARE) guidelines [2].

Presentation of case
A 53-year-old male with known murmur for approximately 2 years presented to the emergency department of communitybased tertiary care center with complaints of acute onset of right medial thigh pain associated with left toe and right fourth finger pain and swelling for 3 days that led to inability to move his leg. He denied any trauma to the area, fever, chills, chest pain or shortness of breath. He reported associated malaise, chills and anorexia for 4 months and 22 lbs. weight loss over 3 months for which he underwent a colonoscopy, CT scan of the chest, abdomen and pelvis and transthoracic echocardiogram which were reportedly unremarkable. He was diagnosed with mitral valve prolapse in Colombia about 3 months prior to presentation and one month later he underwent a root canal procedure for which he did not receive prophylactic antibiotics.
On physical exam, he was afebrile without conduction abnormalities, tachycardia or hypotension. A pansystolic murmur in the precordial area and tenderness in the right groin, right index finger and left big toe without evidence of acute limb or digit ischemia were present.
Laboratory workup revealed anemia with hemoglobin of 9.1 g/dL, leukocyte count 13,800 cells/mL with 82% neutrophils), normal platelet count (210,000 ells/mL), creatinine 1 mg/mL, CRP 14.5 mg/dL with ESR 98 mm/hr. CT of the abdomen and pelvis revealed hypodensity of the right medial hip and thigh corresponding to the area of patient's right hip pain.
A transthoracic echocardiogram showed normal left ventricular function, however the posterior mitral valve leaflet was flail with resulting eccentric, anteriorly directed severe mitral regurgitation. An echodensity on the posterior leaflet measuring 1.4 × 2.3 cm concerning for vegetation was appreciated. Three sets of blood cultures were obtained, and the patient was started empirically on vancomycin 1000 mg IV twice daily and ceftriaxone 2 g IV daily.
A subsequent transesophageal echocardiogram confirmed the presence of severe MR with preserved LVEF and a large echodensity on the posterior leaflet measuring 1.3 × 0.7 cm, consistent with a vegetation (Fig. 1). Cardiac catheterization was negative for coronary artery disease. On right thigh MRI, prominent intramuscular  edema throughout the right adductor muscles with a subtle focus of signal abnormality distally suspicious for a collection versus hematoma was found and was managed nonoperatively. Per the European Society of Cardiology (ESC) guidelines, the presence of subacute mitral regurgitation with unfavorable hemodynamic performance prompted us to offer the patient surgical intervention [3]. After discussing the risks and benefits of mechanical versus bioprosthetic device types, we followed the patient's His postoperative course was complicated by complete heart block, for which he underwent successful permanent pacemaker placement. His admission blood cultures grew Gemella sanguinis by VITEK 2 System (bioMérieux, Durham, NC), which was pansensitive on antibiogram. Vancomycin was switched to penicillin G 4,000,000 units every 6 h which was changed to daptomycin 8 mg/kg IV and ceftriaxone 2 g IV daily on discharge for a total of 6 weeks since valve replacement. The patient was seen in the office one month after his mitral valve replacement and he was making appropriate recovery.

Discussion and conclusion
Gemella sanguinisis a Gram-positive, non-spore forming, catalase-negative, oxidase-negative facultative anaerobe [4]. It is part of the normal oral, genitourinary and gastrointestinal flora and can be distinguished from the other Gemella spp. using biochemical tests and electrophoretic analysis of whole-cell protein [4,5].
A very small number of case reports of G. sanguinis IE have been published since its first isolation in 1998 [4,[6][7][8][9][10][11][12][13][14][15][16]. Unlike most reported cases that involve the aortic valve, with or without additional native valve involvement, this is only the third reported case of isolated mitral valve involvement. Two prosthetic valve infections and an isolated tricuspid valve infection have been published. Preexisting cardiac and/or recent dental abnormalities were present in the majority of IE cases secondary to Gemella spp. (Table 1). Per ESC guidelines, antibiotic prophylaxis should be considered for dental procedures requiring manipulation of the gingival region, including such procedures as root canal as in the case of the current patient presentation (Class IIa, Level C evidence) [3].
IE due to G. sanguinis appears to be relatively indolent and responds well to broad-spectrum antibiotics, including betalactams, vancomycin and/or aminoglycosides. Although successful non-operative management has been previously described [15], valve replacement has been required in the majority of cases. Sur-gical repair in conjunction with a prolonged course of IV antibiotics resulted in a good outcome, even in complicated cases.
Surgical replacement of the mitral valve was warranted for our patient secondary to the presence of severe mitral regurgitation with features of poor hemodynamic performance on presentation. Given the lack of robust data owing to the rarity of the infection, we would recommend that clinicians follow the current established recommendations for prophylaxis and surgical management of bacterial IE [3,17].

Conflicts of interest
The authors report no conflicts of interest

Ethical approval
The New York Presbyterian -Queens IRB conducted a review of the submission and concluded that activities described in this study do not constitute human subjects research as the project does not involve identifiable private information from the patient and the subject has consented to the publication of their case. As a result, 455 CFR part 46 does not apply. A letter by Dr. Phyllis August, MD, MPH, Administrative Director of the New York Presbyterian -Queens IRB was provided and is available upon request.

Consent
Written consent was obtained from the patient to publish a case report regarding his disease. It is available upon request.

Registration of research studies
N/A.

Guarantor
The first and last author (ACS, DVA) accept full responsibility for the study and guarantee its accuracy.

Provenance and peer review
Not commissioned, externally peer-reviewed.