Gram stain, culture, and histopathological examination findings for heart valves removed because of infective endocarditis

Is It Useful to Repeat Blood Cultures in Endocarditis Patients? A Critical Appraisal

BACKGROUND

Previous guidelines for endocarditis have suggested repeating blood cultures until they become negative, with limited evidence.

METHODS

Literature reviews were conducted (1) on the incidence of persistent bacteremia and association with outcome and (2) on timing of valve culture negativization to examine the claim for prolongation of antibiotic therapy starting from negative blood cultures.

RESULTS

Persistent bacteremia and fever may be present in the first 3 days of endocarditis, despite treatment, and are more common in Staphylococcus (especially MRSA) and Enterococcus species. Persistent bacteremia (48-72 h), persistent infection (day 7), and new onset septic shock are related and predict in-hospital mortality. It is, however, persistent infection at day 7 and septic shock that primarily determine the infectious course of endocarditis, and not persistent bacteremia. Valve cultures at surgery become negative in most cases (>85-90%) after 14-21 days of antibiotic therapy, with no calculated benefit for prolonging therapy after 21 days.

CONCLUSIONS

Persistent infection at 7 days after appropriate antibiotic therapy is a better key event for prognosis then positive or negative blood cultures at 48-72 h. Therapy prolongation from the day of negative blood cultures is not reasonable. There is no need to survey blood cultures in endocarditis patients after starting therapy.

Novel Diagnostic Methods for Infective Endocarditis

Infective endocarditis (IE) remains a dangerous disease and continues to have a high mortality rate. Unfortunately, despite continuous improvements in diagnostic methods, in many cases, blood cultures remain negative, and the pathogen causing endocarditis is unknown. This makes targeted therapy and the selection of appropriate antibiotics impossible. Therefore, we present what methods can be used to identify the pathogen in infective endocarditis. These are mainly molecular methods, including PCR and MGS, as well as imaging methods using radiotracers, which offer more possibilities for diagnosing IE. However, they are still not widely used in the diagnosis of IE. The article summarizes in which cases we should choose them and what we are most hopeful about in further research into the diagnosis of IE. In addition, registered clinical trials that are currently underway for the diagnosis of IE are also presented.

Updates in Culture-Negative Endocarditis

Blood culture-negative infective endocarditis (BCNE) is a challenging condition associated with significant morbidity and mortality. This review discusses the epidemiology, microbiology, diagnosis, and treatment of BCNE considering advancements in molecular diagnostics and increased access to cardiac surgery. BCNE can be categorized into bacterial endocarditis with sterilized blood cultures due to previous antibiotic treatment, endocarditis caused by fastidious microorganisms, and true BCNE caused by intracellular organisms that cannot be cultured using traditional techniques. Non-infectious causes such as nonbacterial thrombotic endocarditis should also be considered. Diagnostic approaches involve thorough patient history; blood and serum testing, including appropriate handling of blood cultures; serological testing; and molecular techniques such as targeted and shotgun metagenomic sequencing. Where available, evaluation of explanted cardiac tissue through histopathology and molecular techniques is crucial. The therapy for BCNE depends on the likely causative agent and the presence of prosthetic material, with surgical intervention often required.

A retrospective analysis of blood culture-negative endocarditis at a tertiary care centre in Switzerland

AIMS OF THE STUDY

Numerous studies from different countries have contributed to an improved understanding of blood culture-negative infective endocarditis. However, little is known about its epidemiology and microbiology in Switzerland. We aimed to assess the epidemiology and microbiology of blood culture-negative endocarditis at the University Hospital Zurich, Switzerland.

METHODS

We screened all patients hospitalised between 1997 and 2020 with possible or definite endocarditis at our institution. Thereof, we identified all cases with blood culture-negative endocarditis and retrospectively retrieved patient characteristics, microbiological, histopathological, radiographic and surgical data from medical records.

RESULTS

Among 861 patients screened, 66 (7.7%) cases of blood culture-negative endocarditis were identified. Thereof, 31 cases could be microbiologically documented or not documented (n = 30), and in five cases a non-infectious aetiology was confirmed. Endocarditis predominantly affected men (77%) and the left heart (79%); predisposing factors were prosthetic valves (42%), congenital heart disease (35%) and prior endocarditis (14%). The most common reasons for negative blood cultures were antibiotic treatment prior to blood culture sampling (35%), fastidious and slow growing microorganisms (30%) and definite non-infective endocarditis (8%). Coxiella burnetii and Bartonella spp. were the most common fastidious bacteria identified. In addition to serology, identification of causative microorganisms was possible by microbiological and/or histopathological analysis of tissue samples, of which polymerase chain reaction testing (PCR) of the 16S ribosomal RNA proved to be most successful.

CONCLUSIONS

The present study provides a detailed analysis of blood culture-negative endocarditis over a time span of more than 20 years in Zurich, Switzerland. Antibiotic treatment prior to blood collection, and fastidious and slow growing organisms were identified as main reasons for sterile blood cultures. Typical culture-negative bacteria were mainly found by PCR and/or culture of tissue samples.

Infective endocarditis by HACEK: a review

Infective endocarditis (IE) is a severe disease that is still associated with high mortality despite recent advances in diagnosis and treatment. HACEK organisms (Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) are gram-negative bacteria that are part of the normal flora of the mouth and upper respiratory tract in humans. These organisms cause a wide range of infections, of which IE is one of the most notable. In order to control and prevent endocarditis caused by HACEK, measures such as oral hygiene and the use of prophylactic drugs should be used for people at risk, including people with underlying heart disease and people with artificial valves. This review is a summary of the main aspects of IE focusing on HACEK organisms.

Molecular Analysis With 16S rRNA PCR/Sanger Sequencing and Molecular Antibiogram Performed on DNA Extracted From Valve Improve Diagnosis and Targeted Therapy of Infective Endocarditis: A Prospective Study

BACKGROUND

Molecular analysis (MA) on heart valve (HV) improves the microbiologic diagnosis of infectious endocarditis (IE). The main drawback of MA is the lack of antimicrobial susceptibility information.

METHODS

We conducted a prospective cohort observational study of consecutive adult patients from April 2012 to May 2021 who underwent valve surgery at our hospital. The performance of MA, blood cultures (BC) and valve cultures (VC), and the diagnostic and therapeutic impact of MA were evaluated. Molecular antibiogram results were compared to culture-based antimicrobial susceptibility testing (AST).

RESULTS

A total of 137 patients with definite IE and 52 patients with no IE were enrolled in the study. Among IE cases BC, VC, and MA were positive in 75 (55%), 30 (22%), and 120 (88%) of IE cases, respectively. Among 62 cases of BC-negative IE (BCNE), 57 achieved diagnosis with MA. MA led to a change of antimicrobial therapy in 92% of BCNE. MA was negative in 100% of patients with no IE. Molecular antibiogram performed on 17 valve specimens that resulted positive for pathogens potential carrier of genes encoding for multidrug resistant mechanisms showed 100% concordance with AST.

CONCLUSIONS

MA showed a high specificity and sensitivity in etiological diagnosis of IE. Molecular antibiogram could overcome the major limitation of MA that is the lack of susceptibility testing. We advocate for the inclusion of MA among diagnostic criteria for IE and for a more extensive use of molecular antibiogram when the culture result is negative, and MA is the only positive test.

Impact of Valve Culture Positivity on Prognosis in Patients with Infective Endocarditis Who Underwent Valve Surgery

Introduction

Infective endocarditis (IE) is a severe and fatal infection with high in-hospital and overall mortality rates of approximately up to 30%. Valve culture positivity was associated with in-hospital mortality and postoperative complications; however, few studies have analyzed the relationship between valve cultures and overall mortality over a long observation period. This study aimed to compare the association of valve culture positivity with overall mortality in patients with IE who underwent valve surgery.

Methods

A total of 416 IE patients admitted to a tertiary hospital in South Korea from November 2005 to August 2017 were retrospectively reviewed. A total of 202 IE patients who underwent valve surgery and valve culture were enrolled. The primary endpoint was long-term overall mortality. Kaplan–Meier curve and Cox proportional hazards model were used for survival analysis.

Results

The median follow-up duration was 63 (interquartile range, 38–104) months. Valve cultures were positive in 22 (10.9%) patients. The overall mortality rate was 15.8% (32/202) and was significantly higher in valve culture-positive patients (36.4%, p = 0.011). Positive valve culture [hazard ratio (HR) 3.921, p = 0.002], Charlson Comorbidity Index (HR 1.181, p = 0.004), Coagulase-negative staphylococci (HR 4.233, p = 0.001), new-onset central nervous system complications (HR 3.689, p < 0.001), and new-onset heart failure (HR 4.331, p = 0.001) were significant risk factors for overall mortality.

Conclusions

Valve culture positivity is a significant risk factor for long-term overall mortality in IE patients who underwent valve surgery. The importance of valve culture positivity needs to be re-evaluated, as the valve culture positivity rate increases with increasing early surgical intervention.

[18F]FDG-PET CT for the evaluation of native valve endocarditis

BACKGROUND

We examined the use of [18F]FDG-PET/CT for the diagnosis of native valve endocarditis (NVE).

METHODS

PET/CT images in patients with suspected NVE were retrospectively reviewed independently by two experienced physicians blinded to all clinical information. The gold standard consisted of surgical findings, when available, or the modified Duke criteria.

RESULTS

Fifty four subjects were included, 31 (57%) with a diagnosis of NVE. [18F]FDG-PET/CT correctly identified 21/31 (67.7%) subjects, yielding a sensitivity and specificity of 68% (95% CI 49-83%) and 100% (95% CI 85-100%), respectively. The sensitivity and specificity of the modified Duke criteria were 48% and 74%, respectively. Positive and negative predictive values of PET were 100% (95% CI 84-100%) and 70% (95% CI 51-84%), respectively. Modifying the Duke criteria to include [18F]FDG-PET positivity as a major criterion increased sensitivity to 77% without affecting specificity and led to the correct reclassification of 8/18 (44.4%) subjects from Possible IE to Definite IE.

CONCLUSION

The addition of a positive [18F]FDG-PET/CT as a major criterion in the modified Duke Criteria improved performance of the criteria for the diagnosis of NVE, particularly in those subjects with Possible IE.

Blood culture-negative infective endocarditis: a worse outcome? Results from a large multicentre retrospective Spanish cohort study

BACKGROUND

To assess the impact of blood cultures negative infective endocarditis (BCNIE) on in-hospital mortality.

METHODS

Prospective multicentre study with retrospective analysis of a Spanish cohort including adult patients with definite IE. Cardiac implantable devices infection were excluded. Comparisons between blood cultures positive and BCNIE groups were performed to analyse in-hospital mortality.

RESULTS

1001 cases were included of which 83 (8.3%) had BCNIE. Alternative microbiological diagnosis was achieved for 39 (47%) out 83 cases. The most frequent identifications were: Coxiella burnetii (11; 28.2%), Tropheryma whipplei (4; 10.3%), Streptococcus gallolyticus (4;10.3%) and Staphylococcus epidermidis (3; 7.7%). Surgery was performed more frequently in BCNIE group (57.8 vs. 36.9%, p < .001). All-cause in-hospital mortality rate was 26.7% without statistical difference between compared groups. BCNIE was not associated to worse mortality rate in Cox regression model (aHR = 1.37, 95% CI 0.90-2.07, p = .14). Absence of microbiological diagnosis was also not associated to worse in-hospital prognosis (aHR = 1.62, 95% CI 0.99-2.64, p = .06).

CONCLUSIONS

In our cohort, BCNIE was not associated to greater in-hospital mortality based in multivariate Cox regression models. The variables most frequently associated with mortality were indicated but not performed surgery (aHR = 2.48, 95% CI 1.73-3.56, p < .001), septic shock (aHR = 2.24, 95% CI 1.68-2.99, p < .001), age over 65 years (aHR = 1.88, 95% CI 1.40-2.52, p < .001) and complicated endocarditis (aHR = 1.79, 95% CI 1.36-2.37, p < .001).

Change of the Pattern of the Demographic Characteristics of the Patients with Endocarditis: Clinical Case of Infectious Endocarditis in Man with Injectible Drug Dependence, Complicated with Pneumonia and Peripheral Necroses of Feet, Arms, Nose (Own Clinical Observations and Experience of Education in State and English Language)

Infectious endocarditis is multisystem disease, which is the result of the infection (usually bacterial) of endocardial heart surface. Despite of the latest medical achievements in diagnostics and treatment, infectious endocarditis is still a disease with high mortality rate and severe complications. During last decades in developed countries there are obvious changes of demographic characteristics of the patients with infectious endocarditis, namely increasing of aged patients with degenerative valvular diseases, of patients with anamnesis of invasive manipulations and procedures. Beside with well known risk factors (artificial valves and implanted heart devices), there are increasing roles of injectible drug-dependence, human immunodeficiency virus and wide contact with health protection system as predisposing factors for infectious endocarditis. The article contains literature data of the main populational risk groups of infectious endocarditis. Clinical case of severe (fatal) infectious endocarditis in patient with injectible drug dependence is submitted. Special features of the case are peripheral dry necroses of feet, arms, nose, which are very close to the description of symmetrical peripheral gangrene. This rare disorder was first described by Hutchinson in 1891 in 37-year old man, who had gangrene of fingers, hands and ears after shock. Symmetrical peripheral gangrene can be induced by different infection and non-inflection causes. The majority of these cases are connected to the treatment of cardiogenic shock with disseminated intravascular coagulation. Submitted description of the case of symmetrical peripheral gangrene in patient with infectious endocarditis will be useful for different medical care specialists as a reminder of the necessity of constant monitoring of the skin color of the distal parts of the limbs in severe sick patients.

Anti-biofilm Approach in Infective Endocarditis Exposes New Treatment Strategies for Improved Outcome

Infective endocarditis (IE) is a life-threatening infective disease with increasing incidence worldwide. From early on, in the antibiotic era, it was recognized that high-dose and long-term antibiotic therapy was correlated to improved outcome. In addition, for several of the common microbial IE etiologies, the use of combination antibiotic therapy further improves outcome. IE vegetations on affected heart valves from patients and experimental animal models resemble biofilm infections. Besides the recalcitrant nature of IE, the microorganisms often present in an aggregated form, and gradients of bacterial activity in the vegetations can be observed. Even after appropriate antibiotic therapy, such microbial formations can often be identified in surgically removed, infected heart valves. Therefore, persistent or recurrent cases of IE, after apparent initial infection control, can be related to biofilm formation in the heart valve vegetations. On this background, the present review will describe potentially novel non-antibiotic, antimicrobial approaches in IE, with special focus on anti-thrombotic strategies and hyperbaric oxygen therapy targeting the biofilm formation of the infected heart valves caused by Staphylococcus aureus. The format is translational from preclinical models to actual clinical treatment strategies.

Modern trends in identification of causative agents in infective endocarditis

Advances in the diagnosis and treatment of patients with infectious endocarditis are limited by the high frequency of cases with an unknown etiology and imperfection of microbiological (cultural) methods. To overcome these problems new approaches to the identification of infectious endocarditis pathogens were introduced, which allowed achieving certain positive results. However, it should be noted that despite the wide variety of diagnostic tools currently used, there is no ideal method for etiological laboratory diagnosis of infectious endocarditis. The article discusses the features and place of immunochemical, molecular biological (MALDI-TOF MS, real-time PCR, sequencing, in situ fluorescence hybridization, metagenomic methods, etc.), immunohistochemical methods, and their advantages and limitations.

[Infective Endocarditis with Unknown Etiology: Possibilities of Conquering and Role of Microbiologistics]

Current infectious endocarditis (IE) is characterized by changes in its etiological and epidemiological profiles associated with increased incidence of IE of undetermined etiology. This requires a search for ways to enhance the effectivity of diagnosis. Microbiologistics along with high-tech methods becomes decisively important for identifying the pathogen by studying cultures of blood and tissues from the affected heart valve. This determines timely diagnosis and treatment to be introduced to medical practice as a component of personalized medicine. The article focuses on the validity and features of microbiological (cultural), immunochemical, and molecular biological [MALDI-TOF MS (matrix-activated laser desorption/ionization with time-of-flight mass spectrometry), polymerase chain reaction, sequencing] studies.

Corynebacterium jeikeium native valve infective endocarditis case report: a confirmed microbiological and pathological diagnosis from heart valvular tissue

Background

The Modified Duke criteria is an important structured schematic for the diagnosis of infective endocarditis (IE). Corynebacterium jeikeium is a rare cause of IE that is often resistant to standard IE anti-microbials. We present a case of C. jeikeium IE, fulfilling the Modified Duke pathological criteria.

Case summary

A 50-year-old male presented with left leg peripheral vascular disease with septic changes requiring amputation. Routine echocardiography post-amputation demonstrated severe aortic valve regurgitation with vegetations that required valve replacement. Two initial blood cultures from a single venepuncture showed Streptococcus mitis which was treated with penicillin G prior to surgery. Subsequent aortic valve tissue cultured C. jeikeium with suggestive IE histological valvular changes and was successfully treated on a prolonged course of vancomycin.

Discussion

This is the first C. jeikeium IE case diagnosed on heart valvular tissue culture and highlights the importance for the fulfilment of the Modified Duke criteria in diagnosing left-sided IE. Mixed infection IE is rare, and this case possibly represents an unmasking of resistant C. jeikeium IE following initial treatment of penicillin G.

Detection of Native and Prosthetic Valve Endocarditis: Incremental Attributes of Functional FDG PET/CT over Morphologic Imaging

PURPOSE OF REVIEW

The clinical and incremental value of functional imaging with ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG PET/CT) for the diagnosis and management of patients with suspected native and prosthetic valve infective endocarditis (IE).

RECENT FINDINGS

The diagnosis of IE is challenging because of the highly variable clinical presentations, especially in the case of prosthetic valve endocarditis (PVE). FDG PET/CT has been shown to play an important role for the diagnosis of PVE as a major Duke criterion. Whether FDG PET/CT could play a similar role in patients with suspected native valve endocarditis (NVE) is less well established. It is increasingly recognized that IE is a multisystem disorder, and identification of extra-cardiac manifestations on whole-body FDG PET/CT impacts management and prognosis of patients with IE. Finally, FDG PET/CT provides incremental prognostic value over other clinical and para-clinical parameters, enabling prediction of in-hospital mortality, IE recurrence, hospitalization, and new onset heart failure and embolic events. FDG PET/CT plays a key role in the investigation of patients with suspected IE, enabling detection of valvular infection and extra-cardiac manifestations of the infection which has important prognostic implications.

Determinants and consequences of positive valve culture when cardiac surgery is performed during the acute phase of infective endocarditis

The optimal timing of cardiac surgery in infective endocarditis (IE) remains debated: Early surgery decreases the risk of embolism, and heart failure, but is associated with an increased rate of positive valve culture. To determine the determinants, and the consequences, of positive valve culture when cardiac surgery is performed during the acute phase of IE, we performed a retrospective study of adult patients who underwent cardiac surgery for definite left-sided IE (Duke Criteria), in two referral centres. During the study period (2002-2016), 148 patients fulfilled inclusion criteria. Median age was 65 years [interquartile range, 53-73], male-to-female ratio was 2.9 (110/38). Cardiac surgery was performed after 14 days [5-26] of appropriate antibiotics. Valve cultures returned positive in 46 cases (31.1%). Factors independently associated with positive valve culture were vegetation size ≥ 10 mm (OR 2.83 [1.16-6.89], P = 0.022) and < 14 days of appropriate antibacterial treatment before surgery (OR 4.68 [2.04-10.7], P < 0.001). Positive valve culture was associated with increased risk of postoperative acute respiratory distress syndrome (37.0% vs. 15.7%, P = 0.008) but was associated neither with an increased risk of postoperative relapse nor with the need for additional cardiac surgery. Duration of appropriate antibacterial treatment and vegetation size are independently predictive of positive valve culture in patients operated during the acute phase of IE. Positive valve culture is associated with increased risk of postoperative acute respiratory distress syndrome.

Acute Mitral Regurgitation of Unknown Etiology Associated with Disseminated Intravascular Coagulation Eventually Diagnosed as Enterococcus Faecalis Infective Endocarditis by Mitral Valve Surgery

Patient: Female, 70

Final Diagnosis: Infective endocarditis

Symptoms: Dyspnea

Medication: —

Clinical Procedure: —

Specialty: Cradiology

The "3M" Approach to Cardiovascular Infections: Multimodality, Multitracers, and Multidisciplinary

Cardiovascular infections are associated with high morbidity and mortality. Early diagnosis is crucial for adequate patient management, as early treatment improves the prognosis. The diagnosis cannot be made on the basis of a single symptom, sign, or diagnostic test. Rather, the diagnosis requires a multidisciplinary discussion in addition to the integration of clinical signs, microbiology data, and imaging data. The application of multimodality imaging, including molecular imaging techniques, has improved the sensitivity to detect infections involving heart valves and vessels and implanted cardiovascular devices while also allowing for early detection of septic emboli and metastatic infections before these become clinically apparent. In this review, we describe data supporting the use of a Multimodality, Multitracer, and Multidisciplinary approach (the 3M approach) to cardiovascular infections. In particular, the role of white blood cell SPECT/CT and [¹⁸F]FDG PET/CT in most prevalent and clinically relevant cardiovascular infections will be discussed. In addition, the needs of advanced hybrid equipment, dedicated imaging acquisition protocols, specific expertise for image reading, and interpretation in this field are discussed, emphasizing the need for a specific reference framework within a Cardiovascular Multidisciplinary Team Approach to select the best test or combination of tests for each specific clinical situation.

Laboratory Diagnosis of Infective Endocarditis

Infective endocarditis is life-threatening; identification of the underlying etiology informs optimized individual patient management. Changing epidemiology, advances in blood culture techniques, and new diagnostics guide the application of laboratory testing for diagnosis of endocarditis. Blood cultures remain the standard test for microbial diagnosis, with directed serological testing (i.e., Q fever serology, Bartonella serology) in culture-negative cases. Histopathology and molecular diagnostics (e.g., 16S rRNA gene PCR/sequencing, Tropheryma whipplei PCR) may be applied to resected valves to aid in diagnosis. Herein, we summarize recent knowledge in this area and propose a microbiologic and pathological algorithm for endocarditis diagnosis.

Histopathology of valves in infective endocarditis, diagnostic criteria and treatment considerations

BACKGROUND

Infective endocarditis (IE) is a severe disease. Pathogen isolation is fundamental so as to treat effectively and reduce morbidity and mortality. Blood and valve culture and histopathology (HP) are routinely employed for this purpose. Valve HP is the gold standard for diagnosis.

OBJECTIVES

To determine the sensitivity and specificity of clinical criteria for IE (the modified Duke and the St Thomas' minor modifications, STH) of blood and valve culture compared to valve HP, and to evaluate antibiotic treatment duration.

METHODS

Prospective case series of patients, from 2006 to 2014 with surgically treated IE. Statistical analysis was done by the R software.

RESULTS

There were 136 clinically definite episodes of IE in 133 patients. Mean age ± SD was 43 ± 15.6 years and IE was left sided in 81.6 %. HP was definite in 96 valves examined, which were used as gold standard. Sensitivity of blood culture was 61 % (CI 0.51, 0.71) and of valve culture 15 % (CI 0.07, 0.26). The modified Duke criteria were 65 % (CI 0.55, 0.75) sensitive and 33 % specific, while the STH's sensitivity was 72 % (CI 0.61, 0.80) with similar specificity. In multivariate analysis and logistic regression, the only variable with statistical significance was duration of antibiotic therapy postoperatively.

CONCLUSIONS

Valve HP had high sensitivity and valve culture low sensitivity in the diagnosis of IE. The STH's criteria were more sensitive than the modified Duke criteria. Valve HP should guide duration of postoperative antibiotic treatment.

Diagnostic value of imaging in infective endocarditis: a systematic review

Sensitivity and specificity of the modified Duke criteria for native valve endocarditis are both suboptimal, at approximately 80%. Diagnostic accuracy for intracardiac prosthetic material-related infection is even lower. Non-invasive imaging modalities could potentially improve diagnosis of infective endocarditis; however, their diagnostic value is unclear. We did a systematic literature review to critically appraise the evidence for the diagnostic performance of these imaging modalities, according to PRISMA and GRADE criteria. We searched PubMed, Embase, and Cochrane databases. 31 studies were included that presented original data on the performance of electrocardiogram (ECG)-gated multidetector CT angiography (MDCTA), ECG-gated MRI, ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT, and leucocyte scintigraphy in diagnosis of native valve endocarditis, intracardiac prosthetic material-related infection, and extracardiac foci in adults. We consistently found positive albeit weak evidence for the diagnostic benefit of ¹⁸F-FDG PET/CT and MDCTA. We conclude that additional imaging techniques should be considered if infective endocarditis is suspected. We propose an evidence-based diagnostic work-up for infective endocarditis including these non-invasive techniques.

Infective endocarditis

Infective endocarditis (IE) is a rare, life-threatening disease that has long-lasting effects even among patients who survive and are cured. IE disproportionately affects those with underlying structural heart disease and is increasingly associated with health care contact, particularly in patients who have intravascular prosthetic material. In the setting of bacteraemia with a pathogenic organism, an infected vegetation may form as the end result of complex interactions between invading microorganisms and the host immune system. Once established, IE can involve almost any organ system in the body. The diagnosis of IE may be difficult to establish and a strategy that combines clinical, microbiological and echocardiography results has been codified in the modified Duke criteria. In cases of blood culture-negative IE, the diagnosis may be especially challenging, and novel microbiological and imaging techniques have been developed to establish its presence. Once diagnosed, IE is best managed by a multidisciplinary team with expertise in infectious diseases, cardiology and cardiac surgery. Antibiotic prophylaxis for the prevention of IE remains controversial. Efforts to develop a vaccine that targets common bacterial causes of IE are ongoing, but have not yet yielded a commercially available product.

Diagnosis of blood culture-negative endocarditis and clinical comparison between blood culture-negative and blood culture-positive cases

PURPOSE

To analyze the clinical characteristics of blood culture-negative endocarditis (BCNE) and how it compares to those of blood culture-positive endocarditis (BCPE) cases and show how molecular tools helped establish the etiology in BCNE.

METHODS

Adult patients with definite infective endocarditis (IE) and having valve surgery were included. Valves were studied by polymerase chain reaction (PCR). Statistical analysis compared BCNE and BCPE.

RESULTS

One hundred and thirty-one patients were included; 53 (40 %) had BCNE. The mean age was 45 ± 16 years; 33 (62 %) were male. BCNE was community-acquired in 41 (79 %). Most patients were referred from other hospitals (38, 73 %). Presentation was subacute in 34 (65 %), with fever in 47/53 (90 %) and a new regurgitant murmur in 34/42 (81 %). Native valves were affected in 74 %, mostly left-sided. All echocardiograms showed major criteria for IE. Antibiotics were used prior to BC collection in 31/42 (74 %). Definite histological diagnosis was established for 35/50 (70 %) valves. PCR showed oralis group streptococci in 21 (54 %), S. aureus in 3 (7.7 %), gallolyticus group streptococci in 2 (5.1 %), Coxiella burnetii in 1 (2.5 %) and Rhizobium sp. in 1 (2.5 %). In-hospital mortality was 9/53 (17 %). Fever (p = 0.06, OR 4.7, CI 0.91-24.38) and embolic complications (p = 0.003, OR 3.3, CI 1.55-6.82) were more frequent in BCPE cases, while new acute regurgitation (p = 0.05, OR 0.3, CI 0.098-0.996) and heart failure (p = 0.02, OR 0.3, CI 0.13-0.79) were less so.

CONCLUSIONS

BCNE resulted mostly from prior antibiotics and was associated with severe hemodynamic compromise. Valve histopathology and PCR were useful in confirming the diagnosis and pointing to the etiology of BCNE.

Twenty-Year Experience in the Diagnosis and Treatment of Infective Endocarditis

Aims

The aim of this study was to compare the etiology, clinical course, selected diagnostic methods and efficacy of the treatment used in patients with infective endocarditis (IE) in the nineteen eighties and nineties.

Material and Methods

The study group comprised 300 patients with infective endocarditis hospitalized in the Institute of Cardiology in Warsaw in the following years: from 1982 to 1987 (150 patients: 75 successive patients with IE on the prosthetic valve and 75 successive patients with IE on the native valve), as well as from 1990 to 2003 (150 patients: 75 successive patients with IE on the prosthetic valve and 75 successive patients with IE on the native valve).

Results

In the nineties, immunological symptoms, embolism formation and progressive heart failure were diagnosed decidedly more frequently. Early prosthetic valve endocarditis (PVE) (up to 60 days after operation) occurred significantly more frequently in the eighties. The quantity of negative blood cultures in PVE has not decreased, it is still observed in over 20% of cases. For 20 years the etiology of PVE has remained the same, the dominant pathogen remains Staphylococcus. The frequency of PVE caused by Streptococci has markedly reduced. In both the decades analyzed the etiology of native valve endocarditis (NVE) was similar. In the eighties Streptococcus was predominant. In successive years the number of infections caused by Staphylococci was the same as that caused by Streptococci.

Conclusions

The incidence of early PVE decreased in the nineties. More patients were treated surgically with lesser peri-operative mortality. A lower incidence of infective endocarditis on prosthetic valves caused by streptococci may signify better prophylaxis against infective endocarditis. Infective endocarditis with sterile blood cultures continues to occur frequently.

Evaluation of antibiotic therapy following valve replacement for native valve endocarditis

We retrospectively evaluated 105 patients at the Mayo Clinic between 1970 and 2006 with native valve endocarditis who underwent acute valve surgery. The objective was to determine if outcomes differed based on whether they had received an antibiotic regimen recommended for native valve endocarditis or one for prosthetic valve endocarditis. Fifty-two patients had streptococcal and 53 had staphylococcal infections. Patients with each type of infection were divided into two groups: the first received postoperative monotherapy (with a beta-lactam or vancomycin), and the second received combination therapy (with an aminoglycoside for streptococcal infection, and gentamicin and/or rifampin for staphylococcal infection). The duration and types of antibiotics given pre- and postoperatively, valve cultures results, antibiotic-related adverse events, relapses, and mortality rates within 6 months of surgery were analyzed. Cure rates were similar regardless of the regimen administered. With the small number of patients in each group, a multicenter study with a larger cohort of patients is needed to better define optimal postoperative treatment regimens in this population.

Heart valves should not be routinely cultured

Heart valve (HV) culture is one of the major Duke criteria for the diagnosis of definite infectious endocarditis (IE). However, previous series suggest that heart valve culture does not have good sensitivity (7.8 to 17.6%) and may be contaminated during manipulation. Our goal was to establish the value of routine cultures of heart valves in patients with and without IE. From 2004 to 2006, resected heart valves were systematically cultured according to standard procedures. The definition and etiology of IE were based on the Duke criteria and on valve PCR of specimens from blood culture-negative patients. Bacterial and fungal broad-range PCR was performed. A total of 1,101 heart valves were studied: 1,030 (93.6%) from patients without IE and 71 (6.4%) from patients with IE (42 patients). Overall, 321 (29.2%) cultures were positive (28/71 [39.4%] IE cases and 293/1,030 [28.4%] non-IE). All IE patients with negative heart valve cultures had received antimicrobial therapy. The yield of culture of heart valves for IE diagnosis was as follows: sensitivity, 25.4%; specificity, 71.6%; positive predictive value (PPV), 5.8%; and negative predictive value, 93.3%. Because of its poor sensitivity and PPV, valve cultures should not be performed for patients without a clinical suspicion of IE. For patients with confirmed IE, heart valve cultures should be interpreted with caution.

Swedish guidelines for diagnosis and treatment of infective endocarditis

Swedish guidelines for diagnosis and treatment of infective endocarditis (IE) by consensus of experts are based on clinical experience and reports from the literature. Recommendations are evidence based. For diagnosis 3 blood cultures should be drawn; chest X-ray, electrocardiogram, and echocardiography preferably transoesophageal should be carried out. Blood cultures should be kept for 5 d and precede intravenous antibiotic therapy. In patients with native valves and suspicion of staphylococcal aetiology, cloxacillin and gentamicin should be given as empirical treatment. If non-staphylococcal etiology is most probable, penicillin G and gentamicin treatment should be started. In patients with prosthetic valves treatment with vancomycin, gentamicin and rifampicin is recommended. Patients with blood culture negative IE are recommended penicillin G (changed to cefuroxime in treatment failure) and gentamicin for native valve IE and vancomycin, gentamicin and rifampicin for prosthetic valve IE, respectively. Isolates of viridans group streptococci and enterococci should be subtyped and MIC should be determined for penicillin G and aminoglycosides. Antibiotic treatment should be chosen according to sensitivity pattern given 2-6 weeks intravenously. Cardiac valve surgery should be considered early, especially in patients with left-sided IE and/or prosthetic heart valves. Absolute indications for surgery are severe heart failure, paravalvular abscess, lack of response to antibiotic therapy, unstable prosthesis and multiple embolies. Follow-up echocardiography should be performed on clinical indications.

Surgery for infective endocarditis

Infective endocarditis (IE) is estimated to have an incidence of five to seven cases per 100,000 person-years. Although not a common clinical entity, IE is associated with substantial morbidity and risk of mortality. IE, especially infections due to Staphylococcus aureus, are increasingly healthcare-associated infections. Despite significant advances in diagnosis and management, mortality from IE has changed little since the availability of penicillin; however, this lack of improvement in mortality is likely due to an increasing number of infections from more virulent and drug-resistant pathogens coupled with infections that occur in patients with other comorbidities and those associated with prosthetic valves. Surgery is an important part of therapy for many patients, but surprisingly, little evidence is available to help clinicians determine which patients will benefit most from surgical therapy for the management of IE.

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.

Successful ceftriaxone therapy of endocarditis due to penicillin non-susceptible viridans streptococci

Viridans streptococci are a major cause of infective endocarditis, and penicillin non-susceptibility is increasing in these organisms. We present the initial reported case of infective endocarditis due to penicillin non-susceptible viridans streptococci successfully treated with ceftriaxone monotherapy. The lack of evidence supporting the recommendations for treatment of endocarditis due to penicillin non-susceptible viridans streptococci is discussed.

Quantitative Histological Examination of Bioprosthetic Heart Valves

BACKGROUND

The histological features that characterize infective endocarditis in bioprosthetic valves are not accurately defined. Moreover, bioprosthetic valves may have a noninfective, degenerative evolution associated with calcifications, vegetation-like lesions, and inflammatory infiltrates. Such histological findings may be misdiagnosed as infective endocarditis.

METHODS

Pathologic analysis of inflamed bioprosthetic valve tissues was conducted retrospectively for 21 patients who underwent surgical removal of a bioprosthetic valve because of suspected infective endocarditis and for 67 patients who underwent surgical removal of a bioprosthetic valve because of noninfective dysfunction. To better define the histological criteria for infective endocarditis, we used quantitative image analysis to compare these 2 groups of patients with respect to vegetations, calcifications, and patterns of inflammation.

RESULTS

Histologically, infective endocarditis in patients with bioprostheses was characterized by demonstration of microorganisms, vegetations, and neutrophil-rich, inflammatory infiltrates. Valve tissue specimens from patients whose bioprosthetic valves were removed because of noninfective complications showed, in 30% of cases, inflammatory infiltrates mainly composed of macrophages and lymphocytes. Inflammatory adherent thrombi that can occur to the surface of noninfective degenerative bioprostheses are differentiated because their vegetations have macrophage-rich content. A neutrophil surface area with a cutoff value of > or =1.5% of the total valve tissue surface area is highly specific (94%) for infective endocarditis.

CONCLUSIONS

When no microorganisms are detected and vegetations are not found in bioprosthetic valve tissues during the histological examination, a neutrophil-rich inflammation might better define the term "active endocarditis" in the Duke criteria and would allow differentiation between infective endocarditis and inflammatory, noninfective valve processes in patients with bioprosthetic valves.

Evolving trends in infective endocarditis

Infective endocarditis is a microbial infection of the endocardial surface and, despite improvements in diagnostic accuracy, medical therapy and surgical techniques, mortality remains high. This review focuses on changes in epidemiology, microbiology and diagnosis, as well as changes in medical and surgical management of infective endocarditis affecting native and prosthetic valves in adults, that have evolved during the past two decades. Significant changes have included an increasing involvement of prosthetic valves and nosocomially-acquired disease, an increased involvement of staphylococci as the causative agents, and a recognition that elderly individuals with degenerative valvular disease are the most vulnerable population. Topics still requiring study include whether and when valve replacement should be performed, and how to predict perivalvular complications or embolisation based on echocardiography findings. Optimisation of antimicrobial treatment schemes (choice of the antibiotic, dose and duration) also requires further investigation.

Bacteriological Outcome after Valve Surgery for Active Infective Endocarditis: Implications for Duration of Treatment after Surgery

BACKGROUND

There has been no systematic evaluation of outcome after surgery for infective endocarditis with respect to duration of antibiotic treatment.

METHODS

We performed a retrospective chart review of episodes of valve surgery for active infective endocarditis at Green Lane Hospital (Auckland, New Zealand) for 1963-1999. We recorded the duration of antibiotic treatment before and after valve surgery; the extent of infection at operation; Gram stain, culture, and histopathological testing results for valve samples; and the bacteriological outcome after surgery. The primary outcome measure was relapse, defined as endocarditis due to the same species within 1 year after surgery.

RESULTS

For the 358 patients in our study, the median duration of follow-up was 4.8 years. Thirty-two patients (9%) had 36 subsequent episodes of endocarditis. Relapse occurred after 3 (0.8%) of the operations (95% CI, 0.2%-2.0%). Relapse of infection was unrelated to the duration of antibiotic treatment before or after surgery, positive valve culture results, positive Gram stain results, or perivalvular infection. Since 1994, we have reduced the duration of antibiotic treatment by approximately 7 days for those with positive valve culture results and by approximately 14 days for those with negative valve culture results, without any increase in the number of relapses.

CONCLUSIONS

Relapse is an uncommon event following surgery for endocarditis. Commonly suggested indications for prolonging postoperative treatment are not associated with higher relapse rates, and their relevance is debatable. We conclude that it is unnecessary to continue treatment for patients with negative valve culture results for an arbitrary 4-6-week period after surgery. Two weeks of treatment appears to be sufficient, and, for those operated on near the end of the standard period of treatment, simply completing the planned course should suffice.

Infective endocarditis: a review of the best treatment options

Despite significant advances in antimicrobial therapy and an enhanced ability to diagnose and treat complications, infective endocarditis is still associated with substantial morbidity and mortality today, and its incidence has not decreased over the past decades. This apparent paradox may be explained by a progressive change in risk factors, leading to an evolution in its epidemiological and clinical features. In fact, new risk factors for endocarditis have emerged, such as intravenous drug abuse, diffusion of heart surgery procedures and prosthetic valve implantation, atherosclerotic valve disease in elderly patients, and nosocomial disease. Recently identified microorganisms (including Bartonella spp., Abiotrophia defectiva, and the HACEK group of bacteria [including Haemophilus spp., Actinobacillus spp., Cardiobacterium hominis, Eikenella corrodens and Kingella kingae]) are sometimes the cause of culture-negative endocarditis, and emerging resistant bacteria (such as methicillin- or vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci) are becoming a new challenge for conventional antibiotic therapy. New therapeutic approaches need to be developed for the treatment of infective endocarditis caused by drug-resistant Gram-positive cocci, and some antimicrobial compounds recently introduced in clinical practice (such as streptogramins and oxazolidinones) may be an effective alternative, but further clinical studies are needed in order to confirm their effectiveness and safety. This review should help redefine the best therapeutic and preventive strategies against infective endocarditis.

Diagnosis of infectious endocarditis in patients undergoing valve surgery

PURPOSE

Histologic examination of valve samples is considered as the gold standard for the diagnosis of infectious endocarditis. Molecular tools are also very promising for patients with negative-culture endocarditis. Thus, we studied the contribution of valvular histology, culture, and 16S rRNA PCR amplification plus sequencing to the diagnosis of infectious endocarditis in patients undergoing valve surgery.

SUBJECTS AND METHODS

We performed culture, histological examination, and broad-range PCR amplification plus sequencing on valve samples taken from 127 patients with infectious endocarditis and from 118 patients without endocarditis. The sensitivity and specificity of these tests for the diagnosis of endocarditis in patients undergoing valve surgery were studied.

RESULTS

The sensitivity of PCR was of 61% (64/105) whereas that of histological examination was of 63% (62/98) and that of valve culture was of only 13% (14/105). All 68 positive PCR results considered reliable according to an interpretation scheme were from patients with infectious endocarditis, resulting in a 100% (118/118) specificity of the interpreted molecular approach. The specificity of histology was also of 100% (118/118) when using stringent criteria (ie, presence of vegetation, microorganisms, and/or valvular inflammation with mainly polymorphonuclear cells). PCR identified an etiological agent in 38% (5/13) of definite blood culture-negative infectious endocarditis.

CONCLUSION

We show that valvular histology with stringent criteria is the gold standard for the diagnosis of infectious endocarditis. Broad-range amplification of 16S rRNA gene is indicated for infectious endocarditis of unknown etiology, whereas valve culture is of limited sensitivity.

PCR detection of bacteria on cardiac valves of patients with treated bacterial endocarditis

We used broad-range PCR amplification and sequencing to detect and identify bacterial DNA in 156 valves of patients treated for infective endocarditis (IE). Bacterial DNA was found more frequently in patients who underwent valve replacement while on antibiotic treatment for IE (60%) than in patients who had completed antibiotic treatment for IE (37%; P = 0.02). We found specific bacterial DNA in valves removed from 11 of 30 patients who had completed antibiotic treatment for IE. Six had no histological evidence of IE. The presence of DNA was significantly correlated with the presence of histologic lesions (P = 0.001) and with the presence of bacteria detected by Gram staining (P < 0.001). Bartonella and streptococci were detected for much longer after antibiotic treatment by PCR than other species (P = 0.047 and 0.04, respectively), and coagulase-negative staphylococci were detected for much shorter periods (P = 0.02). The finding that bacterial DNA was more likely to be detected in valves of patients with active IE than in patients who had completed antibiotic treatment for IE shows that bacterial DNA is cleared slowly. There was no significant correlation between the duration of antibiotic therapy and the presence of bacterial DNA in valves. Since the persistence of bacterial DNA in valves does not necessarily indicate the persistence of viable bacteria, the detection of bacterial DNA in valves from IE patients should be interpreted with caution, in particular in those patients with a past history of treated IE.

Quantitative Histological Examination of Mechanical Heart Valves

BACKGROUND

Histological demonstration of microorganisms, vegetations, or active endocarditis in cardiac valve tissue is included in the Duke criteria and is considered to be a criterion of confirmed infective endocarditis. However, the histological features that characterize infective endocarditis are not accurately defined at the qualitative and quantitative levels.

METHODS

Pathologic analysis of tissue adjoining mechanical cardiac valves was undertaken retrospectively for 21 patients who underwent surgical removal of a mechanical valve because of suspected infective endocarditis and 69 patients who underwent surgical removal of a mechanical valve because of noninfectious dysfunction. To better define the histological criteria for infective endocarditis, we used quantitative image analysis to compare these 2 groups of patients with respect to valvular fibrosis, calcifications, vegetations, patterns of inflammation, and vascularization.

RESULTS

Histologically, infective endocarditis in patients with mechanical valves was characterized by the demonstration of microorganisms, vegetations, and significant neutrophil-rich inflammatory infiltrates with extensive neovascularization. In contrast, valve tissue specimens from patients with mechanical valves that were removed because of noninfectious complications showed significant rates of extensive fibrosis and, when present, inflammatory infiltrates that were mainly composed of macrophages and lymphocytes. A neutrophil surface area with a cutoff value of > or =2% of the total valve tissue surface is highly predictive of (90%) and specific for (98%) infective endocarditis.

CONCLUSIONS

When no microorganisms are detected and vegetations are lacking in tissue adjacent to a mechanical valve, neutrophil-rich inflammation and extensive neovascularization might better histologically define the term "active endocarditis" in the Duke criteria. This definition would allow differentiation between infective endocarditis and inflammatory noninfectious valve processes in patients with mechanical cardiac valves.

Latent infective endocarditis: epidemiology and clinical characteristics of patients with unsuspected endocarditis detected after elective valve replacement

BACKGROUND

The diagnosis of infective endocarditis is usually made on the basis of clinical and laboratory criteria and may be confirmed by histologic examination or culture of excised valves. We tried to determine the incidence and significance of inflammatory changes in valves excised during operations for reasons other than infective endocarditis.

METHODS

The charts and histopathology of all patients undergoing valve replacement during a 10-year period (1993-2002) were reviewed. A total of 868 patients underwent a total of 970 valve replacements during this period, of whom 11 patients (1.3%) were for endocarditis, with the remaining 857 (98.7%) for other indications. All excised valves were cultured and examined histologically for the presence of inflammatory infiltrates, vegetations, and microorganisms.

RESULTS

In 8 of 857 patients (0.9%), the histologic examination unexpectedly demonstrated an infiltrate suggestive of endocarditis. Blood and valve cultures, and serologic tests for Mycoplasma, Chlamydia, Legionella, Q fever, Brucella, Rickettsiae, VDRL, and Bartonella were negative in all but 1 patient, who was found to have Q fever. All received a prolonged course of antibiotics. Six patients had an uneventful recovery; 1 had intramyocardial abscesses and expired during cardiac reoperation; and 1 had recurrent fever and dehiscence of the aortic and mitral valve prostheses and after two cardiac reoperations remains in severe heart failure.

CONCLUSIONS

The presence of an unexpected inflammatory infiltrate in heart valves excised for reasons other than endocarditis may occur in 0.9% of such operations; these infiltrates could indicate presence of endocarditis. A microbial origin should be sought, and patients should receive empiric antibiotic treatment for endocarditis.

Culture results of heart valves resected because of streptococcal endocarditis: insights into duration of treatment to achieve valve sterilization

OBJECTIVES

To analyse the culture results of heart valves removed following streptococcal endocarditis in order to gain insight into the duration of treatment required for valve sterilization.

PATIENTS AND METHODS

Retrospective review of 131 episodes of streptococcal endocarditis: 94 due to alpha-haemolytic streptococci; 15 due to beta-haemolytic streptococci; 10 due to nutritionally deficient streptococci; eight due to the Streptococcus anginosus group and four due to Streptococcus pneumoniae. Patients had their valves removed during antimicrobial treatment. Culture results were analysed with respect to duration of treatment before surgery.

RESULTS

For alpha-haemolytic streptococci, 17 (18%) valves were culture-positive and 77 (82%) culture-negative after a median (range) of 4 (1-20) and 16 (4-58) days of treatment, respectively, P < 0.001. For beta-haemolytic streptococci, two valves (13%) were culture-positive; both patients had received < or = 4 days of treatment. Four patients (40%) with nutritionally deficient streptococci were culture-positive, and had received < or = 8 days of treatment. For the S. anginosus group, two valves (25%) were culture-positive; both patients had received < or = 4 days of treatment before operation. Overall, only one of 131 (0.8%) valves was culture-positive after 14 days of treatment. All valves infected with beta-haemolytic streptococci, nutritionally deficient streptococci and the S. anginosus group, who were treated for more than 8 days before surgery, were culture-negative.

CONCLUSIONS

Our findings support current treatment guidelines for endocarditis caused by alpha-haemolytic streptococci. We suggest that the recommended duration of treatment for endocarditis resulting from other streptococci may be excessive and treatment trials evaluating 2 and 4 week regimens are justified.