Streptococcus Pluranimalium Infective Endocarditis Complicated by New Onset Heart Failure

Infective Complicated by New Onset Bacterial or infectious endocarditis (IE) is a relatively rare infection, but is associated with significant incidence of mortality. While IE most often results from infection of one or more heart valves by Staphylococcus or Streptococcus spp ., other less virulent bacteria can be the etiologic agent and generally produce more indolent disease. Here we report the occurrence of native valve endocarditis due to infection with the emerging bacterium Streptococcus pluranimalium . Review of available literature indicates this is the fifth reported case globally of endocarditis following pluranimalium bacteremia and the first case associated with the complication of new onset heart failure.


Introduction
Infectious endocarditis (IE) is an infection of the interior lining of the heart, most often on one or more heart valves, and presents most commonly with fever and a new or worsened heart murmur. However, IE is associated with many other symptoms such as anorexia, weight loss, malaise, myalgias, arthralgias, dyspnea, splenomegaly, petechiae, Janeway lesions, Osler nodes, and splinter hemorrhages [1]. Complications that may occur with IE include valvular insufficiency which can lead to heart failure, septic emboli which can lead to organ infarction and pulmonary embolism, intracerebral hemorrhage, metastatic infection, and systemic immune reactions such as glomerulonephritis. Notably, heart failure is a relatively common complication of infective endocarditis [2] and is associated with increased morbidity and mortality [2,3]. Diagnosis of endocarditis is usually straightforward.
However, the modified Duke criteria can be used as a guideline for diagnostic assessment if the presentation is unusual or complicated by confounding signs or symptoms [4].
IE is a diagnosis that needs to be made rather quickly due to the severity of the disease and its associated mortality, especially when heart failure develops. Heart failure is the most common cause of death in native valve infective endocarditis [3]. As such, its rapid diagnosis and treatment are essential for patient care.
The incidence of endocarditis has begun to increase over the past two decades, and this is attributed in large part to increased use of intracardiac procedures and cardiac implantable electronic devices or CIED [1]. In contrast, the prevalence of infective endocarditis associated heart failure seems to be declining in recent years [2]. Treatment includes antibiotic therapy and addressing any valvular damage and resulting complications. This can include medical treatment for congestive heart failure and valvular replacement surgery. Early surgery in this context is clinically important since it reduces mortality and improves patient outcomes [1,[3][4][5].
viridians Streptococcus causes 76% of these infections, while pyogenic streptococci account for 17% of the cases with S. agalactiae associated with 78% of the pyogenic streptococcal infections [7].
Other bacteria involved in IE include S. epidermidis, Enterococcispp, S. gallolyticus group members, and the HACEK group (comprised of Haemophilus spp.,Aggregatibacterspp.,Cardiobacteriumhominis, Eikenellacorrodens, and Kingellaspp. [6]. Several risk factors have been clearly associated with the development of IE and, in some cases, with specific etiologic agents [6]. Intravenous injection drug use is a major risk factor for developing endocarditis and is most associated with S. aureus infections. Another risk factor traditionally associated with endocarditis is poor dentition, allowing a pathway for oral flora such as viridans streptococci to invade the bloodstream. Additional conditions that may predispose for development of IE include underlying rheumatic heart disease or congenital heart disease, intravascular cardiac procedures, use of CIED, prosthetic valve replacement, hemodialysis, intravenous catheters, and immune suppression [6].
In the past five years, a new bacterium has been implicated in at least four cases of IE [8][9][10][11]. This bacterium, Streptococcus pluranimalium, was first isolated in 1999 from a case of bovine mastitis, but has been isolated from a number of other agricultural and domesticated animals including chickens, goats, cats, canaries, sheep, Nile tilapia, a pheasant, and an alpaca [12][13][14].
S. pluranimalium can be isolated from various mucosal surfaces (e.g. cervix, vagina, lung, tonsils), avian crop, and from milk of infected dairy animals [12,15]. In addition to IE, S. pluranimalium has been reported as the causal agent in three cases of a brain abscess including one patient whose primary presentation was IE [11,16,17], one case of subdural empyema [18], and five cases of sepsis [19][20][21][22][23] with one case including septic arthritis [21], one case developing sepsis following a dental procedure [22], and a third case initially presenting as pneumonia with S. pluranimalium isolated from blood cultures [23]. This report now describes a fifth case of IE with S. pluranimalium associated bacteremia and is the first report of new onset heart failure as a complication of this infection. generally distinguish these bacteria [15]. Full protein analyses can conclusively identify S. pluranimalium, but this level of testing cannot be routinely performed in a clinical diagnostic laboratory.

Case Presentation
In case descriptions reporting the identification method for S. pluranimalium, most relied solely upon bacterial identification by Vitek instrumentation with a single report confirming Vitek identification with 16SrRNA sequencing [19]. Primary use of Vitekbased assays for identification has been called into question by a report from Pongratz, et. al. that showed an inability of molecular techniques such as MALDI-TOF or 16S rRNA sequencing to confirm S. pluranimalium as the identity of clinical bacterial isolates identified as such by Vitek [25]. Thus, given the apparent high degree of variability among clinical isolates, it may be necessary to re-evaluate the validity or standardization of S. pluranimalium identification techniques if conclusive identification is deemed necessary for effective treatment.
A second potential challenge is effective treatment of S.
pluranimalium. Resistance to multiple antibiotics has been reported in some isolates of S. pluranimalium, and it is likely that the different strains of S. pluranimalium have differing levels of antibiotic resistance. Antimicrobial susceptibility testing of S. pluranimalium seems to indicate that at least one strain has developed resistance to erythromycin and lincomycin [26].
However, as evidenced in this case report, some S. pluranimalium strains are still susceptible to more commonly used antibiotics such as penicillin. Thus, it may be advisable to urge antibiotic sensitivity testing with a diagnosis of S. pluranimalium infection in order to appropriately treat the patient while avoiding unwarranted use of antibiotics such as vancomycin to minimize acquisition of drug resistance against our "last line" antibiotics.
The third challenge in considering S. pluranimalium associated disease is fully understanding the epidemiology of this organism.
As it was initially isolated from cattle with bovine mastitis and shown to be present in a number of agricultural animals including  [27] and the onset of S.
pluranimalium-associated disease following dental procedures [22] and in patients with evidence of poor dental hygiene in this report and others [11,22,18]. With a high incidence of viridans streptococci causing endocarditis and a degree of morphological and biochemical similarity between viridans streptococci and S. pluranimalium, it is intriguing to consider whether some cases of endocarditis attributed to viridans streptococci may in fact be due to S. pluranimalium. Furthermore, with the occurrence of five cases of S. pluranimalium associated endocarditis and eight additional cases of septicemia, brain abscess or subdural empyema, septic arthritis, or pneumonia caused by S. pluranimalium in the past six years, one might speculate whether this may be related to the policy change of antibiotic prophylaxis prior to dental procedures in some previously designated at-risk populations.
This paper describes the development of endocarditis following S. pluranimalium bacteremia with the first description of the complication of new onset heart failure. The report adds to the growing body of literature that demonstrates S. pluranimalium is an emerging pathogen associated with endocarditis, septicemia, and brain infections. With consideration of the additional twelve cases globally, questions regarding the accurate identification of S. pluranimalium, its treatment, and understanding of the epidemiology and transmission for human infection have been raised.