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ORIGINAL ARTICLE
Year : 2022 | Volume
: 11
| Issue : 3 | Page : 71-75
Demographic characteristics, predisposing factors, clinical presentations, echocardiographic findings, complications, and outcomes of patients with viridans streptococcal endocarditis
Pardis Moradnejad1, Shabnam Boudagh2
1 Rajaei Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
2 Echocardiography Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran
Correspondence Address:
Dr. Shabnam Boudagh
Echocardiography Research Center, Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran
Iran
Source of Support: None, Conflict of Interest: None
DOI: 10.4103/rcm.rcm_23_22
Background: Several microorganisms are associated with infective endocarditis (IE), but the most common IE causes are staphylococci and streptococci. Among streptococci, the viridans group streptococci are responsible for a considerable percentage of all IE cases. Methods: Since 2006, the Iranian Registry of Infective Endocarditis has recorded information regarding all adult patients with a definite or possible IE diagnosis according to the modified Duke criteria. Patients with viridans streptococcal endocarditis were detected through three blood culture sets. The patients' demographic characteristics, predisposing factors, clinical presentations, and echocardiographic findings were recorded. Results: Of 731 patients diagnosed with endocarditis, viridans streptococci were found in 46 (6.3%) patients, consisting of 28 (60.9%) men and 18 (39.1%) women at a mean age of 42.56 ± 15.46 years, who were subsequently included in the study. Among the 46 patients with viridans streptococcal endocarditis, 26 had a subacute course, whereas 20 had an acute course. Vegetation was detected in 35 patients. All the patients were treated with the standard antibiotic regimen for viridans streptococcal endocarditis, and cardiac surgery was performed on 16 patients. Conclusions: Clinicians should pay sufficient heed to the following points in all cases of viridans streptococcal endocarditis: firstly, an appropriate antibiotic regimen must be based on a precise minimal inhibitory concentration determination for the usual antibiotics. Secondly, since prolonged antibiotic therapy is crucial to the eradication of microorganisms within vegetation, all patients with viridans streptococcal endocarditis must receive an adequate therapy course.
Keywords: Endocarditis, Enterococcus, viridans Streptococcus
Several microorganisms are associated with infective endocarditis (IE), but the most common IE causes are staphylococci and streptococci.[1] While streptococci were once the most frequent cause of IE,[2],[3] they seem to have been superseded by staphylococci in recent years.
Among streptococci, the viridans group streptococci (VGS) are responsible for a considerable percentage of all IE cases.[4] The VGS encompasses various groups of microorganisms comprising the main microbiota in the oropharynx and the gastrointestinal tract. At least 30 known species of VGS have been identified to date, and they are known as opportunistic pathogens usually involving damaged tissues such as cardiac valves. During bacteremia, viridans streptococci adhere to impaired cardiac valves and trigger the vegetation process.[5]
Viridans streptococci constitute one of the most frequent etiologic agents in subacute bacterial native valve endocarditis (NVE) and late prosthetic valve endocarditis (PVE).[4]
MethodsSince 2006, the Iranian Registry of IE (IRIE) at Rajaie Cardiovascular Medical and Research Center has recorded information regarding all adult patients with a definite (2 major, 1 major plus 3 minor, or 5 minor criteria) or possible (1 major plus 1 minor or 3 minor criteria) IE diagnosis according to the modified Duke criteria. In 2016, the IRIE joined the European International Registry (Euro-Endo) with a view to conducting more in-depth research on IE.[6],[7]
The current study was approved by the Institutional Ethics Committee (IR.RHC.REC.1400.049) and performed following the Helsinki Declaration of the World Medical Association (2000). Informed written consent was obtained from all the study participants.
Patients with viridans streptococcal endocarditis were detected through three blood culture sets processed under sterile conditions using BACTEC™ blood culture media (Becton, Dickinson and Company, Franklin Lakes, NJ, USA). The patients' demographic characteristics, predisposing factors, clinical presentations, echocardiographic findings, laboratory data, surgical treatments, antibiotic therapies, and cardiac and extracardiac complications were recorded.
The collected data were transferred to a data registry coordinating center through a secure, electronic web-based system called the “Regitory.” The system is safeguarded by password-protected logins, accessible only to authorized personnel at the data registry coordinating center. The information fed into the Regitory is rechecked by an experienced infectious disease specialist and an expert cardiologist. Throughout the present investigation, the patients' records and their system entry process were checked by random audit.
The mean ± standard deviation and frequencies (percentages) were used for descriptive analysis. The statistical analysis was performed with the SPSS software, version 18, for Windows (SPSS Inc., Chicago, Illinois, USA).
ResultsDemographic characteristics
Of 731 patients diagnosed with endocarditis according to the modified Duke criteria, 372 (50.9%) had culture-positive IE. The most frequent causative microorganisms were aureus staphylococci (n = 82, 11.2%), enterococci (n = 60, 8.2%), and coagulase-negative staphylococci (n = 55, 7.5%). In addition, viridans streptococci were found in 46 (6.3%) patients, consisting of 28 (60.9%) men and 18 (39.1%) women at a mean age of 42.56 ± 15.46 years, who were subsequently included in the study. Based on the modified Duke criteria, definite IE was diagnosed in 39 (84.8%) patients and possible IE in 7 (15.2%) [Table 1] and [Table 2].
Table 1: Demographic data, clinical features, and clinical courses in 46 episodes of viridans streptococcal infective endocarditis
Table 2: Predisposing factors, laboratory data, diagnoses, and therapeutic protocols in 46 episodes of viridans streptococcal infective endocarditisThe most common predisposing factor was congenital heart disease (n = 11, 23.9%), followed by prosthetic valves (n = 9, 19.56%) and recent dental procedures (n = 5, 10.86%). Concerning the history of the frequent predisposing factors, ventricular septal defects were reported in four patients, bicuspid aortic valves in four, the patent ductus arteriosus in one, both pulmonary valve stenosis and the ventricular septal defect in one, and both pulmonary stenosis and the atrial septal defect in one. The predisposing factors with lower prevalence rates were chronic kidney disease, diabetes mellitus, IE history, intravenous drug use, immune deficiency, and implantable cardioverter-defibrillator use.
The study population's demographic characteristics, clinical features, and predisposing factors are presented in [Table 1] and [Table 2].
Clinical features and laboratory data
Among the 46 patients with viridans streptococcal endocarditis, 26 (56.52%) had a subacute course (>6 weeks), whereas 20 (43.48%) had an acute course (<6 weeks).
Fever (n = 40, 87%), loss of appetite (n = 16, 34.8%), sweating (n = 13, 28.3%), and splenomegaly (n = 12, 26%) comprised the most frequent symptoms, respectively. The most common clinical features are presented in [Table 1].
The results of the patients' laboratory tests are shown in [Table 2], according to which, 40 (86.9%) patients suffered from anemia, 38 (82.6%) had elevated erythrocyte sedimentation rates (ESRs), 15 (32.6%) exhibited leukocytosis, and 6 (13%) had thrombocytopenia.
Echocardiographic findings
The entire study population underwent echocardiography. The results regarding the 46 patients with viridans streptococcal endocarditis demonstrated native valve IE in 37 (80.4%), PVE in 9 (19.6%: 6 late-onset and 3 early-onset PVE cases), and implantable cardioverter-defibrillator-related IE in 1. Furthermore, left-sided IE was more frequent than right-sided IE.
Vegetation was detected in 35 (76%) patients, with the most common locations of vegetation being the mitral valve (n = 18) and the aortic valve (n = 9). Multivalvular involvement was detected in five patients: four with aortic and mitral valve involvement and one with aortic, mitral, and tricuspid valve involvement. In two patients, vegetation was detected on the ventricular septal defect.
Pseudoaneurysms were observed in 7 (15.2%) patients, dehiscence of prosthetic valves in 4 (8.7%), leaflet perforation in 3 (6.5%), abscess formation in 2 (4.3%), and fistula formation in 1 (2.17%).
The echocardiographic findings are illustrated in [Table 3].
Table 3: Echocardiographic findings in 46 episodes of viridans streptococcal infective endocarditisComplications and outcomes
Central nervous system emboli, heart failure, intracranial mycotic aneurysms, and renal complications (i.e., acute kidney injury and glomerulonephritis) were reported in 6 (13%), 5 (10.9%), 4 (8.7%), and 4 (8.7%) patients, respectively. Further, splenic abscesses were detected in 2 (4.34%) patients and splenic infarction in 1 (2.17%). In addition, septic pulmonary embolism was observed in 1 (2.17%).
The studied patients' complications are shown in [Table 4].
Table 4: Complications in 46 episodes of viridans streptococcal infective endocarditisAll the patients were treated with the standard antibiotic regimen for viridans streptococcal endocarditis, and cardiac surgery was performed on 16 (34.8%) patients [Table 2].
Four patients were discharged with personal consent before treatment completion. No mortality was observed among the other patients.
DiscussionBefore the advent of antibiotics, viridans streptococci were accountable for approximately three-quarters of all IE cases, whereas the antibiotic era has witnessed a substantial decline to 20% in the incidence of streptococcal endocarditis.[3],[4],[8],[9] What is also intriguing in this regard is that although streptococci were once the most common cause of IE,[2],[3] recent evidence indicates their replacement by staphylococci.[10],[11],[12] The noted shift in the epidemiologic paradigm could be a consequence of the increasing use of intracardiac devices, intravascular prostheses, intravenous catheters, and hemodialysis.[1]
Streptococcal endocarditis usually has a subacute course, with low-grade fever and no chills. The fever has no particular pattern but is usually prolonged. Night sweats and weight loss may occur.
In the present study, we evaluated 46 patients with viridans streptococcal endocarditis, of whom 26 (56.52%) had a subacute course (>6 weeks) and 20 (43.48%) an acute course (<6 weeks). Moreover, fever, loss of appetite, and sweating were the most frequent symptoms.
Mild splenomegaly is a common feature of IE. Nonetheless, hepatomegaly and peripheral adenopathy are not characteristics of viridans streptococcal endocarditis, and their presence suggests another diagnosis.[4] Our findings demonstrated splenomegaly in 12 (26%) patients but no hepatomegaly or adenopathy.
More than 80% of patients with viridans streptococcal endocarditis have underlying heart diseases. In the present study, a history of congenital heart disease was reported in 11 (23.9%) patients, prosthetic valve use in 9 (19.56%), mitral valve prolapse in 2 (4.34%), and implantable cardioverter-defibrillator use in 1 (2.17%). Notably, IE in young women with isolated mitral valve involvement is often caused by Streptococcus viridans.[4] Based on our results, 19.56% of the studied patients (n = 9) with mitral valve involvement were young women.
Viridans streptococci are also important etiologic agents in late-onset PVE. In this investigation, 9 (19.6%) patients suffered from PVE, with late-onset PVE detected in 6 (13%).
Intracardiac abscesses or heart blocks are not associated with subacute viridans streptococcal endocarditis.[4] We found paravalvular abscesses in only 2 (4.34%) patients.
The diagnosis of subacute viridans streptococcal endocarditis requires the presence of high-grade continuous bacteremia. In the case of only 1–2 positive blood cultures for viridans streptococci, the clinician should consider skin contamination in the blood culture samples. Accordingly, streptococcal bacteremia, fever, murmurs, vegetation, and the peripheral manifestation of endocarditis without high-grade continuous bacteremia suggest other diagnoses such as marantic endocarditis.[4]
Laboratory abnormalities related to subacute viridans streptococcal endocarditis include elevated ESRs, mild leukocytosis, mild anemia, and sometimes thrombocytosis. We detected anemia in 40 (86.9%) patients, elevated ESRs in 38 (82.6%), leukocytosis in 15 (32.6%), thrombocytopenia in 6 (13%), and thrombocytosis in 2 (4.34%).
Glomerulonephritis is the most common renal manifestation of subacute bacterial endocarditis and microscopic hematuria due to glomerulonephritis.[4] Our results revealed 2 (4.34%) patients with glomerulonephritis.
Symptomatic central nervous system complications arise in between 15% and 30% of patients with IE, with cerebral embolism as the most common manifestation.[4],[13],[14],[15] In the present study, central nervous system embolism was observed in 6 (13%) patients.
Mycotic aneurysms usually occur during the active phase and sometimes months or years after the successful treatment of IE. They are more common in viridans streptococcal endocarditis and are most frequently found in the intracranial vessels.[4],[14] According to our findings, intracranial mycotic aneurysms were present in 4 (8.7%) patients.
The optimal antibiotic regimen for viridans streptococcal endocarditis is based on a high degree of antibiotic activity against the pathogen and an effective antibiotic concentration in the blood and vegetation. Appropriate antimicrobial therapy for viridans streptococcal endocarditis can confer the rapid resolution of bacteremia and usually the complete resolution of cardiac vegetation. Relapses are infrequent provided that the antibiotic therapy course is adequate.[4]
Most VGS strains are highly penicillin-susceptible (minimal inhibitory concentrations [MICs] <0.12 μg/mL). The preferred regimen consists of 4 weeks of penicillin G or ceftriaxone for highly penicillin-susceptible streptococcal NVE and 6 weeks of penicillin G or ceftriaxone with or without 2 weeks of gentamicin for highly penicillin-susceptible streptococcal PVE.
While a few VGS strains are relatively resistant to penicillin (MICs >0.12 μg/mL and <0.5 μg/mL), a tiny percentage of VGS strains are fully resistant to penicillin (MIC ≥0.5 μg/mL). The preferred regimen consists of 4 weeks of penicillin G or ceftriaxone combined with 2 weeks of gentamicin for relatively penicillin-resistant streptococcal NVE and 6 weeks of penicillin G or ceftriaxone combined with gentamicin for relatively penicillin-resistant streptococcal PVE.
For the treatment of patients with fully penicillin-resistant streptococcal endocarditis, the American Heart Association recommends treatment with regimens used for enterococcal endocarditis.[14],[16],[17] Our entire study population received treatment with a standard antibiotic regimen.
Among our study population, four patients were discharged with personal consent before treatment completion. No mortality was observed among the other patients, which is consistent with other studies that have reported a low mortality rate for patients suffering from endocarditis caused by viridans streptococci compared with those suffering from endocarditis caused by other microorganisms.[18]
ConclusionsAlthough antibiotic therapy for viridans streptococcal endocarditis can confer good outcomes and high cure rates, clinicians should pay sufficient heed to the following points in all cases of viridans streptococcal endocarditis:
Firstly, an appropriate antibiotic regimen must be based on a precise MIC determination for the usual antibiotics. Secondly, since prolonged antibiotic therapy is crucial to the eradication of microorganisms within vegetation, all patients with viridans streptococcal endocarditis must receive an adequate therapy course.
Ethical clearance
The current study was approved by the Institutional Ethics Committee (IR.RHC.REC.1400.049) and performed following the Helsinki Declaration of the World Medical Association (2000).
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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