Diagnosis of culture negative endocarditis: novel strategies to prove the suspect guilty

Infection of Transcatheter Valvular Devices

PURPOSE OF REVIEW

This review explores the epidemiology, clinical traits, and diagnosis of Transcatheter Aortic Valve Replacement-Associated Infective Endocarditis (TAVR-IE) and mitral transcatheter edge-to-edge repair infective endocarditis (TEER-IE), focusing on a multimodal imaging approach. It addresses the rising prevalence of TAVR and TEER, emphasizing the need to understand long-term complications and clinical consequences, which poses significant challenges despite advancements in valve technology.

RECENT FINDINGS

Studies report a variable incidence of TAVR-IE and TEER-IE influenced by diverse patient risk profiles and procedural factors. Younger age, male gender, and certain comorbidities emerge as patient-related risk factors. Procedure-related factors include intervention location, valve type, and technical aspects. Microbiologically, Staphylococcus aureus, Viridans Group Streptococcus, and Enterococcus are frequently encountered pathogens. TAVR-IE and TEER-IE diagnosis involves a multimodal imaging approach due to limitations in echocardiography. Blood cultures and imaging aid identification, with Fluorescence in situ hybridization is showing promise. Treatment encompasses medical management with antibiotics and, when necessary, surgical intervention. The management approach requires a multidisciplinary "Endocarditis Team." This review underscores the need for continued research to refine risk prediction, enhance diagnostic accuracy, and optimize management strategies for TAVR-IE, considering the evolving landscape of transcatheter interventions.

Small vessel vasculitis associated with culture-negative infective endocarditis related to a cardiac device: a case report

Background

Culture-negative endocarditis is uncommon, occurring in less than a third of all cases of infective endocarditis (IE). Culture-negative IE related to a cardiac device is an even greater diagnostic challenge due to its insidious presentation, with onset of symptoms ranging between 3 and 12 months after device implantation. Sensitivity of the modified Duke’s criteria remains low in culture-negative and cardiac device-related IE (CDRIE) since classical signs and symptoms of IE are often absent. Small vessel vasculitis has been reported as an immune response to IE. Recognizing immunological phenomenon related to IE is of paramount clinical importance, prompting the search for an underlying infection and avoiding the use of immunosuppressive medications which would otherwise result in an adverse outcome.

Case summary

An 81-year-old Caucasian male presented to the ambulatory medical unit with a two-week history of a symmetrical, generalized purpuric rash. He had an indwelling permanent pacemaker following a transcatheter aortic valve implantation for severe aortic stenosis five years ago. Blood tests showed an iron deficiency anaemia, thrombocytopenia and normal renal function, both CRP and ESR were raised at 61  and 30 mm/hr, respectively. Skin biopsy demonstrated small vessel cutaneous vasculitis. Transthoracic echocardiography revealed a mobile mass measuring 0.9 × 1.7 cm, confirmed on transoesophageal echocardiogram as pacing lead endocarditis. Blood cultures were persistently negative. The patient underwent pacemaker lead extraction, following which the vasculitic rash improved.

Discussion

Blood cultures in IE are more likely to be negative if there is a prior antibiotic administration or causative micro-organisms with limited proliferation which fail to grow in conventional media conditions. Transesophageal echocardiography (TOE) offers improved sensitivity and diagnostic yield when compared to transthoracic echocardiography (TTE) in patients with a high clinical suspicion of CDRIE. The evidence in the literature describing culture-negative IE associated with small vessel vasculitis is limited. However, it is recognized that cutaneous small vessel vasculitis may be associated with an underlying bacterial infection. IE produces an inflammatory response, resulting in the deposition of circulating immune complexes and cutaneous signs which are included in the modified Duke’s criteria to aid diagnosis. Management of CDRIE requires a multi-disciplinary team approach with an ‘Endocarditis Team.’ Pacemaker lead infection requires transvenous lead extraction if it is a newly implanted lead. Locking stylets, extraction sheaths or snare retrieval are usually required in cases of older implanted leads. Surgical lead extraction remains the gold standard for larger vegetations (>20 mm) or associated valve endocarditis.

Antibacterial and Antifungal Management in Relation to the Clinical Characteristics of Elderly Patients with Infective Endocarditis: A Retrospective Analysis

Infective endocarditis (IE) is increasingly prevalent in the elderly, particularly due to the rising frequency of invasive procedures and intracardiac devices placed on these individuals. Several investigations have highlighted the unique clinical and echocardiographic characteristics, the microorganisms implicated, and the prognosis of IE in the elderly. In addition, the old population seems to be fairly diverse, ranging from healthy individuals with no medical history to patients with many ailments and those who are immobile. Furthermore, the therapy of IE in this group has not been well investigated, and worldwide recommendations do not propose tailoring the treatment approach to the patient’s functional state and comorbid conditions. A multicenter research study was designed as a retrospective study of hospitalized patients with infective endocarditis, aiming to examine the characteristics of elderly patients over 65 years old with infective endocarditis in relation to the antibiotic and antifungal treatments administered, as well as to quantify the incidence of treatment resistance, adverse effects, and mortality in comparison to patients younger than 65. Based on a convenience sampling method, we included in the analysis a total of 78 patients younger than 65 and 131 patients older than 65 years. A total of 140 patients had endocarditis on native valves and 69 patients had endocarditis on prosthetic valves. A significantly higher proportion of elderly patients had signs of heart failure on admission, and the mortality rate was significantly higher in the elderly population. A majority of infections had a vascular cause, followed by dental, maxillo-facial, and ENT interventions. The most common complications of IE were systemic sepsis (48.1% of patients older than 65 years vs. 30.8% in the younger group). The most frequent bacterium involved was Staphylococcus aureus, followed by Streptococcus spp. in a total of more than 50% of all patients. The most commonly used antibiotics were cephalosporins in 33.5% of cases, followed by penicillin in 31.2% and glycopeptides in 28.7%, while Fluconazole was the initial option of treatment for fungal endocarditis in 24.9% of cases. Heart failure at admission (OR = 4.07), the development of septic shock (OR = 6.19), treatment nephrotoxicity (OR = 3.14), severe treatment complications (OR = 4.65), and antibiotic resistance (OR = 3.24) were significant independent risk factors for mortality in the elderly patients. Even though therapeutic management was initiated sooner in the older patients, the associated complications and mortality rate remained significantly greater than those in the patients under 65 years old.

First Case of Infective Endocarditis With Streptococcus equinus in an Immunocompetent Patient in North America: A Case Report and Review of Literature

Infective endocarditis (IE) can be caused by bacterial or fungal infections invading the endocardial surface of the heart, such as its valves and chambers. Staphylococcus and Streptococcus species are mainly responsible for IE. Streptococcus equinus (S. equinus) has been rarely noted to cause IE. We present a case of a 69-year-old white male with a past medical history of severe aortic regurgitation, who during an elective aortic heart valve replacement surgery was noted to have multiple plaque-like vegetations at the base of the mitral valve that were positive for S. equinus. To date, there are only four cases of S. equinus endocarditis reported worldwide, with a high possibility of our case being the first reported in North America.

Culture-negative endocarditis with neurologic presentations and dramatic response to heparin: a case report

Background

Blood culture-negative endocarditis (BCNE) is diagnosed in 2–7% of patients with infective endocarditis (IE) and recent antibiotic use is a known risk factor. Altered mental status may be a presenting symptom. Besides empiric antibiotics, intravenous anticoagulation using heparin may have a role in the management of such patients.

Case presentation

A 23-year-old male patient was referred to our center with fever, altered mental status and abnormal gait. Neurologic examination revealed Wernicke’s aphasia. Cardiac auscultation revealed systolic murmur at the left sternal border. ECG (electrocardiogram) was unremarkable. Brain MRI showed multiple cerebellar lesions. Transthoracic echocardiography (TTE) demonstrated three large masses on the right ventricle (RV), tricuspid valve (TV), and anterior mitral valve (MV) leaflet. Blood cultures (three sets) were negative. Intravenous heparin therapy was administered. After 48 h, the second TTE demonstrated that one valvular lesion disappeared and the other two lesions showed a significant decrease in size. The patient’s neurological symptoms resolved gradually. Further workup for collagen vascular disorders did not show any abnormality.

Conclusion

BCNE should be considered in patients with fever and neurologic manifestations. TTE should be performed to detect valvular abnormalities. Intravenous heparin could be used in such patients when TTE demonstrate valvular vegetations.

Baseline C-reactive protein levels and prognosis in patients with infective endocarditis: A prospective cohort study

Background

Early diagnosis and risk-stratification among infective endocarditis (IE) patients are limited by poor microbiological yield and inadequate characterization of vegetations. A simple tool that can predict adverse outcomes in the early phase of management is required.

Aim

To study the prognostic value of C-reactive protein (CRP) levels at admission and its role in predicting various clinical outcomes.

Methods

In a prospective study of consecutive IE patients diagnosed by modified Duke’s criteria, we measured the peak levels of CRP and erythrocyte sedimentation rate (ESR) in the first 3 days of admission and correlated it with in-hospital mortality, six-month mortality, embolic phenomena and the need for urgent surgery. Predefined laboratory-microbiological sampling protocols and antibiotic-initiation protocols were followed. Receiver-operating-characteristics curves were generated to identify a reliable cut-off for CRP in predicting various outcomes.

Results

Out of 101 patients who were treated, 85 patients had ‘definite’ IE. Blood cultures were positive in 55% (n = 39); and Staphylococcus species was the most common organism. Major complications occurred in 74.1% (n = 63) and in-hospital mortality was 32.9% (n = 28). Mean ESR and CRP levels were 102 ± 31 mm/h and 51 ± 20 mg/l, respectively. In multivariable analysis, high CRP levels were independently predictive of mortality, major complications, embolic events and need for urgent surgery. A CRP >40 mg/l predicted adverse outcomes with a sensitivity of 73% and specificity of 99%.

Conclusion

The study shows that baseline CRP level in the first 3 days of admission is a strong predictor of short term adverse outcomes in IE patients, and a useful marker for early risk stratification.

Profile of infective endocarditis observed from 2003 - 2010 in a single center in Italy

Background

This study aimed to provide a contemporary picture of the epidemiologic, clinical, microbiologic characteristics and in-hospital outcome of infective endocarditis (IE) observed in a single center in Italy.

Methods

We performed a retrospective study of patients with definite or probable IE observed at the “L. Sacco” Hospital in Milan, Italy, from January 1, 2003 through December 31, 2010.

Results

189 episodes of IE in 166 patients were included. The mean number of incident IE in the study period was of 1.27 (range 0.59-1.76) cases per 1000 patients admitted. The median age of the cohort was 57 (interquartile range, 43-72) years, 63% were male and 62.5% had native valve IE. Twenty-six percent were active intravenous drug users (IVDU), 29% had a health care-associated IE and 5% chronic rheumatic disease. Twenty-nine percent of the cases occurred in patients affected by chronic liver disease and 19% in HIV positive subjects. Staphylococcus aureus was the most common pathogen (30%), followed by streptococci. The mitral (34%) and aortic (31%) valves were involved most frequently. The following complications were common: stroke (19%), non-stroke embolizations (25%), heart failure (26%) and intracardiac abscess (9%). Surgical treatment was frequently employed (52%) but in hospital mortality remained high (17%). Health care-associated IE and complications were independently associated with an increased risk of in-hospital death, while surgery was associated with decreased mortality.

Conclusion

S. aureus emerged as the leading causative organism of IE in a University hospital in northern Italy. Our study confirmed the high in-hospital mortality of IE, particularly if health care associated, and the protective role of surgery.

Differentiation of Staphylococcus spp. by high-resolution melting analysis

High-resolution melting analysis (HRMA) is a fast (post-PCR) high-throughput method to scan for sequence variations in a target gene. The aim of this study was to test the potential of HRMA to distinguish particular bacterial species of the Staphylococcus genus even when using a broad-range PCR within the 16S rRNA gene where sequence differences are minimal. Genomic DNA samples isolated from 12 reference staphylococcal strains ( Staphylococcus aureus , Staphylococcus capitis , Staphylococcus caprae , Staphylococcus epidermidis , Staphylococcus haemolyticus , Staphylococcus hominis , Staphylococcus intermedius , Staphylococcus saprophyticus , Staphylococcus sciuri , Staphylococcus simulans , Staphylococcus warneri , and Staphylococcus xylosus ) were subjected to a real-time PCR amplification of the 16S rRNA gene in the presence of fluorescent dye EvaGreen™, followed by HRMA. Melting profiles were used as molecular fingerprints for bacterial species differentiation. HRMA of S. saprophyticus and S. xylosus resulted in undistinguishable profiles because of their identical sequences in the analyzed 16S rRNA region. The remaining reference strains were fully differentiated either directly or via high-resolution plots obtained by heteroduplex formation between coamplified PCR products of the tested staphylococcal strain and phylogenetically unrelated strain.

Excellent Prognosis of Culture Negative Endocarditis in Hemodialysis Patients: A Case Series

Despite improved diagnostic methods, antimicrobial agents and more sophisticated echocardiographic studies, the incidence of infective endocarditis remains high, especially in a uremic and end stage renal disease (ESRD) population. Culture negative endocarditis (CNE) patients with normal renal function have increased morbidity and mortality, but clinical features and outcome in hemodialysis patients remains unclear. This study reported five survival cases of CNE in hemodialysis patients. The prognosis of all dialysis-related CNE patients enrolled in this study was excellent.

Cerebral hemorrhage, splenic and renal embolisms due to infective endocarditis

Infective endocarditis is occurring more and more frequently in elderly persons and it has been associated with various clinical, bacteriological, and prognostic features. We present a 63-year-old woman with infective endocarditis which is the first reported case with cerebral hemorrhage, splenic and renal embolisms.

[Therapy and prophylaxis of infective endocarditis]

Infective endocarditis is an infection of cardiovascular structures which is typically caused by bacteria. Despite recent medical advances mortality ranges from 20 to 25%. Without treatment, IE is a lethal disease. The mortality rate depends on several clinical factors including the causative microorganism, the time of diagnosis, and the initiation of an adequate therapeutic regimen. The diagnosis is based on positive blood culture results with identical microorganisms and the demonstration of endocardial involvement. Negative blood cultures represent a diagnostic challenge which may increase the importance of diagnostic tools such as serology and PCR. An early and targeted initiation of an antibiotic therapy after microbiologic testing is crucial for therapeutic success. The immediate cooperation of Cardiologists, Microbiologists, Infectious Disease Specialists and Cardiac Surgeons is highly recommended to allow an adequate medical and surgical treatment in complex cases.Prophylaxis appears reasonable due to the inherent high mortality. The efficacy of an antibiotic prophylaxis is, nevertheless, not rigorously proven. Even if a high efficacy is assumed, the number needed to treat is extremely high due to the low individual risk. Thus, current guidelines recommend an antibiotic prophylaxis only in patients with a high risk for an adverse outcome.

German guidelines for the diagnosis and management of infective endocarditis

This Gudelines are the translation of the German Guidelines for the Diagnosis and Management of Infective Endocarditis, which were prepared by the Working Group on Infective Endocarditis of the Paul-Ehrlich-Society and the German Society for Cardiology, Heart, and Circulatory Research in cooperation with the Deutsche Gesellschaft für Thorax-, Herz und Gefässchirurgie (DGTHG; German Society for Thorax-, Cardiac-, and Vascular Surgery), the Deutsche Gesellschaft für Infektiologie (DGI; German Society for Infectious Diseases), the Deutsche Gesellschaft für Internistische Intensivmedizin und Notfallmedizin (DGIIN; German Society for Internal Intensive Care Medicin and Emergency Medicine), the Deutsche Gesellschaft für Hygiene und Mikrobiologie (DGHM; German Society for Hygiene and Microbiology) and the Deutsche Gesellschaft für Innere Medizin (DGIM; German Society for Internal Medicine) (Naber CK et al. [S2 Guideline for diagnosis and therapy of infectious endocarditis] Z Kardiol. 2004;93:1005-21). The Guidelines provide recommendations for the diagnosis and management of infective endocarditis.

DNA sequence-based detection of group B Streptococcus directly from heart valve tissue in a patient with culture-negative endocarditis

A human case of culture-negative bacterial endocarditis is presented where conventional methods failed to determine a microbial aetiology. DNA sequencing performed directly on autopsy heart valve tissue revealed Streptococcus agalactiae (group B streptococcus). To our knowledge, this is the first report of DNA sequence-based detection of this organism directly from a heart valve.

Clinical features remain important for the diagnosis of infective endocarditis in the modern era

BACKGROUND

Infective endocarditis (IE) can be difficult to diagnose, due to multiple (often non-specific) presenting features.

AIM

To assess the predictive accuracy of classical clinical features and blood investigations readily available at the time of presentation.

DESIGN

Cross-sectional analysis.

METHODS

We studied 29 IE cases and 79 controls (clinically suspicious contemporaneous cases where IE was subsequently excluded) from a hospital-based group of patients referred to a cardiac department with possible infective endocarditis. Patients were identified from the echocardiography database. Cases were defined by final diagnosis. Symptoms, signs, risk factors for IE and blood investigations were recorded from case notes and examined by univariate and multivariate analyses.

RESULTS

The sensitivity, specificity, and positive and negative predictive values of transthoracic echocardiography (TTE) for detection of IE in clinically suspected cases were 71%, 98%, 57% and 99%, respectively. Univariate analyses revealed a significant association between IE and several clinical features. Under multivariate analysis, previous heart valve surgery (OR 13.3, 90%CI 3.2-55.6), positive blood cultures (OR 17.2, 90%CI 4.9-58.8), signs of embolism (OR 11.4, 90%CI 3.0-43.5), a new, altered or changing murmur (OR 10.3, 90%CI 2.8-38.5) and splenomegaly (OR 18.2, 90%CI 3.6-90.9) were independent predictors for IE.

DISCUSSION

Clinical features at presentation continue to be important for the diagnosis of IE. Features such as positive blood cultures, signs of embolism and a changing heart murmur should be used to guide investigation and treatment of IE prior to echocardiography, or when TTE is negative.

Results of surgical treatment for infective endocarditis in children

OBJECTIVE

Infective endocarditis is uncommon condition, with a high degree of morbidity and mortality. It is less common in children, albeit tending to be associated with congenital cardiac malformations. We describe our experience of the need for surgical treatment in children with infective endocarditis.

PATIENTS AND METHODS

We analyzed retrospectively the records of 9 children aged below 16 years seen between May 2003 and March 2005 with infective endocarditis, reviewing the demographic details, clinical presentation, microbiological and echocardiographic data, operative findings, and outcome.

RESULTS

Apart from pre-existing renal insufficiency in 1 patient, congenital cardiac malformations were the predisposing factors. Blood cultures were positive in 3, but remained negative in the other 6 patients. The indications for surgical treatment included uncontrolled sepsis, congestive heart failure, recurrent endocarditis, patch or graft dehiscence, and pseudoaneursymal formation. Death due to uncontrolled sepsis resulting in multiorgan failure occurred in 1 patient, who had tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral arteries. Another patient died late postoperatively due to cardiac failure after relapse of the endocarditis in the setting of negative blood cultures.

CONCLUSION

Despite advances in antimicrobial therapy, diagnosis, and measures of treatment for infective endocarditis, complications continue to be responsible for substantial morbidity and mortality. Since blood cultures are frequently negative, clinical and echocardiographic findings should be the major determinants of strategies used for treatment. We believe that our small series of patients seen over the past two years in which surgical treatment was performed will be helpful in guiding the clinical perspectives for children with infective endocarditis.

Albendazole as an alternative therapeutic agent for childhood giardiasis in Turkey

The efficacy of albendazole for the treatment of giardiasis has been indicated by previous in-vitro and in-vivo studies. In order to compare the therapeutic efficacy of albendazole and metronidazole, 107 Giardia-positive children (aged 3-15 years), diagnosed by three consecutive positive stool examinations, were enrolled in the study. Of these children, 52 were given a single daily dose of albendazole 10 mg/kg for 5 days, and 55 were given metronidazole 20 mg/kg daily in three doses for 7 days. Parasite eradication was achieved in 47 (90.4%) of 52 children treated with albendazole and 49 (89.1%) of 55 children treated with metronidazole (p > 0.05). These results suggest that albendazole is an effective treatment option for childhood giardiasis.

Emerging issues in infective endocarditis

Infective endocarditis, a serious infection of the endocardium of the heart, particularly the heart valves, is associated with a high degree of illness and death. It generally occurs in patients with altered and abnormal heart architecture, in combination with exposure to bacteria through trauma and other potentially high-risk activities involving transient bacteremia. Knowledge about the origins of endocarditis stems from the work of Fernel in the early 1500s, and yet this infection still presents physicians with major diagnostic and management dilemmas. Endocarditis is caused by a variety of bacteria and fungi, as well as emerging infectious agents, including Tropheryma whiplei, Bartonella spp., and Rickettsia spp. We review the evolution of endocarditis and compare its progression with discoveries in microbiology, science, and medicine.

Detection of bacterial DNA in cardiac vegetations by PCR after the completion of antimicrobial treatment for endocarditis

PCR with broad-range primers for prokaryotic 16S rRNA genes was used to identify bacterial DNA in tissue from patients undergoing valve replacements following a previous episode of infective endocarditis (IE). Of eight valves investigated, bacterial DNA was detected in three from patients for whom IE had been treated by antibiotic therapy 5, 12 and 18 months previously. The demonstration of bacterial DNA within resected heart valves suggests either recurrence of infection, treatment failure or the persistence of bacterial debris within the cardiac vegetation. There may also be implications for routine use of PCR in the diagnosis of infection.

Recent trends in infective endocarditis: influence of case definitions

PURPOSE OF REVIEW

Infective endocarditis continues to pose major challenges in diagnosis and management despite advances in understanding the epidemiology, microbiology, and pathology of the disease. The purpose of this article is to provide a review of diagnosis, microbiology, and treatment of infective endocarditis, particularly as they are influenced by case definitions.

RECENT FINDINGS

Case definitions have a critical effect on the interpretation of trends in infective endocarditis, and recent studies have proposed more specific criteria. Studies have also addressed the appropriate use of echocardiography to assist in the diagnosis and management of infective endocarditis. Staphylococcus aureus has become an increasingly common cause of infective endocarditis, and the microbiology of nosocomial infective endocarditis is changing. Newer techniques are being used to aid in the identification of causal agents in blood culture-negative infective endocarditis. Antimicrobial guidelines for the treatment of infective endocarditis are readily available, including a proposal to avoid premature discharge of patients on outpatient antibiotic therapy. Additional studies have been conducted on combination antibiotic therapy, duration of treatment, dosing of aminoglycosides, alternative agents for gram-positive organisms, aspirin therapy, and surgical interventions.

SUMMARY

Recent trends in diagnosis, microbiology, and treatment of infective endocarditis are described, and case definitions play a critical role in their interpretation.