Infective endocarditis with negative blood cultures

Outcomes of culture-negative vs. culture-positive infective endocarditis: the ESC-EORP EURO-ENDO registry

AIM

Fatality of infective endocarditis (IE) is high worldwide, and its diagnosis remains a challenge. The objective of the present study was to compare the clinical characteristics and outcomes of patients with culture-positive (CPIE) vs. culture-negative IE (CNIE).

METHODS AND RESULTS

This was an ancillary analysis of the ESC-EORP EURO-ENDO registry. Overall, 3113 patients who were diagnosed with IE during the study period were included in the present study. Of these, 2590 (83.2%) had CPIE, whereas 523 (16.8%) had CNIE. As many as 1488 (48.1%) patients underwent cardiac surgery during the index hospitalization, 1259 (48.8%) with CPIE and 229 (44.5%) with CNIE. The CNIE was a predictor of 1-year mortality [hazard ratio (HR) 1.28, 95% confidence interval (CI) 1.04-1.56], whereas surgery was significantly associated with survival (HR 0.49, 95% CI 0.41-0.58). The 1-year mortality was significantly higher in CNIE than CPIE patients in the medical subgroup, but it was not significantly different in CNIE vs. CPIE patients who underwent surgery.

CONCLUSION

The present analysis of the EURO-ENDO registry confirms a higher long-term mortality in patients with CNIE compared with patients with CPIE. This difference was present in patients receiving medical therapy alone and not in those who underwent surgery, with surgery being associated with reduced mortality. Additional efforts are required both to improve the aetiological diagnosis of IE and identify CNIE cases early before progressive disease potentially contraindicates surgery.

Evaluation of Laboratory Predictors for In-Hospital Mortality in Infective Endocarditis and Negative Blood Culture Pattern Characteristics

Objective: This study aimed to identify possible differences between blood culture-negative and blood culture-positive groups of infective endocarditis (IE), and explore the associations between biological parameters and in-hospital mortality. Methods: This was a retrospective study of patients hospitalized for IE between 2007 and 2017. Epidemiological, clinical and paraclinical characteristics, by blood culture-negative and positive groups, were collected. The best predictors of in-hospital mortality based on the receiver-operating characteristic (ROC) analysis and AUC (area under the curve) results were identified. Results: A total of 126 IE patients were included, 54% with negative blood cultures at admission. Overall, the in-hospital mortality was 28.6%, higher in the blood culture-negative than positive group (17.5% vs. 11.1%, p = 0.207). A significant increase in the Model for End-Stage Liver Disease Excluding International Normalized Ratio (MELD-XI) score was observed in the blood culture-negative group (p = 0.004), but no baseline characteristics differed between the groups. The best laboratory predictors of in-hospital death in the total study group were the neutrophil count (AUC = 0.824), white blood cell count (AUC = 0.724) and MELD-XI score (AUC = 0.700). Conclusion: Classic laboratory parameters, such as the white blood cell count and neutrophil count, were associated with in-hospital mortality in infective endocarditis. In addition, MELD-XI was a good predictor of in-hospital death.

Prosthetic aortic valve dehiscence following infective endocarditis by a rare bacterium - Pandoraea pnomenusa

Late prosthetic valve endocarditis (PVE) is a life-threatening condition, commonly caused by bacterial organisms such as staphylococci, streptococci, or enterococci. Infrequently, it can be caused by rare organisms. We hereby report a case of late PVE of the aortic valve, due to a rare gram-negative bacterium Pandoraea pnomenusa. It is the first reported case of PVE caused by this particular organism. The patient had infective endocarditis-induced prosthetic valve dehiscence, severe aortic regurgitation, and shock, which was managed with appropriate antibiotics and supportive medical treatment. <Learning objective: Late prosthetic valve infective endocarditis should always be an important differential diagnosis in patients with artificial valve presenting with congestive cardiac failure. This case report is about aortic valve dehiscence and acute aortic regurgitation because of prosthetic valve infective endocarditis due to a rare bacterium Pandoraea pnomenusa.>.

Culture-negative infective endocarditis (CNIE): impact on postoperative mortality

Introduction

Poor postoperative outcomes have been reported after surgery for infective endocarditis (IE). Whether the absence of positive cultures impacts the prognosis remains a matter of discussion. The aim of this study was to evaluate the impact of negative cultures on the prognosis of surgically treated IE.

Methods

This was a single-center, retrospective study. From January 2000 to June 2019, all patients who underwent valvular surgery for IE were included in the study. The primary endpoint was early postoperative mortality. A covariate balancing propensity score was developed to minimize the differences between the culture-positive IE (CPIE) and culture-negative IE (CNIE) cohorts. Using the estimated propensity scores as weights, an inverse probability treatment weighting (IPTW) model was built to generate a weighted cohort. Then, to adjust for confounding related to CPIE and CNIE, a doubly robust method that combines regression model with IPTW by propensity score was adopted to estimate the causal effect of the exposure on the outcome.

Results

During the study period, 327 consecutive patients underwent valvular repair/replacement with the use of cardiopulmonary bypass and cardioplegic cardiac arrest for IE. Their mean age was 61.4 ± 15.4 years, and 246 were males (75.2%). Native valve IE and prosthetic valve IE accounted for 87.5% and 12.5% of cases, respectively. Aortic (182/327, 55.7%) and mitral valves (166/327, 50.8%) were mostly involved; 20.5% of isolated mitral valve diseases were repaired (22/107 patients). The tricuspid valve was involved in 10 patients (3.3%), and the pulmonary valve in 1 patient (<1%). Fifty-nine patients had multiple-valve disease (18.0%). Blood cultures were negative in 136/327 (41.6 %). A higher postoperative mortality was registered in CNIE than in CPIE patients (19% vs 9%, respectively, p = 0.01). The doubly robust analysis after IPTW by propensity score showed CNIE to be associated with early postoperative mortality (odds ratio 2.10; 95% CI, 1.04–4.26, p = 0.04).

Conclusions

In our cohort, CNIE was associated with a higher early postoperative mortality in surgically treated IE patients after dedicated adjustment for confounding. In this perspective, any effort to improve preoperative microbiological diagnosis, thus allowing targeted therapeutic initiatives, might lead to overall better postoperative outcomes in surgically treated IE.

Fluorescence in situ hybridization for identification and visualization of microorganisms in infected heart valve tissue as addition to standard diagnostic tests improves diagnosis of endocarditis

OBJECTIVES

In infective endocarditis (IE), identification of the causative organism and consecutive treatment are crucial for patient survival. Although the macroscopic aspect resembles infected tissue, standard diagnostic tests often fail to allow one to identify bacteria. Fluorescence in situ hybridization (FISH) is a molecular, culture-independent technique that allows one to identify and visualize microorganisms within tissue and to recognize their morphology, number and activity. We analysed the diagnostic benefit of FISH/polymerase chain reaction (PCR) by comparing its results to those of standard diagnostic tests.

METHODS

From September 2015 to April 2018, 128 patients underwent first-time or redo valve surgery to treat IE. Patients were designated according to the modified Duke criteria as definite (n = 61), possible (n = 34) or rejected (n = 33) IE. Tissue specimens obtained intraoperatively were analysed using FISH/PCR in addition to undergoing standard diagnostic testing and PCR alone.

RESULTS

We used blood cultures to detect microorganisms in 67/128 patients; valve cultures, in 34/128; PCR, in 67/128; histopathological diagnosis showed IE in 72/128 cases. We were able to detect microorganisms in 103/128 cases using FISH/PCR, with 55/61 in definite IE. Furthermore, we were able to identify 26 cases of bacterial biofilm using FISH/PCR, despite antibiotic treatment of 61 in the definite, 13 in the possible and 1 in the rejected group, including 8/33 patients in the rejected group with active bacteria. In all cases, the patient's therapy was altered.

CONCLUSIONS

FISH/PCR was used to identify microorganisms in cases in which standard diagnostic tests failed to provide sufficient results for various reasons. Furthermore, FISH/PCR enabled us to identify bacterial biofilms and to differentiate between active versus degraded bacteria, thus indicating the impact of treatment. Therefore, we suggest FISH/PCR as an additional diagnostic tool in IE alongside standard diagnostic tests.

Clinical features and outcomes of infective endocarditis in Egypt: an 11-year experience at a tertiary care facility

BACKGROUND

Few data are available on the characteristics of infective endocarditis (IE) cases in Egypt. The aim of this work is to describe the characteristics and outcomes of IE patients and evaluate the temporal changes in IE diagnostic and therapeutic aspects over 11 years.

RESULTS

The IE registry included 398 patients referred to the Endocarditis Unit of a tertiary care facility with the diagnosis of possible or definite IE. Patients were recruited over two periods; period 1 (n = 237, 59.5%) from February 2005 to December 2011 and period 2 (n = 161, 40.5%) from January 2012 to September 2016. An electronic database was constructed to include information on patients' clinical and microbiological characteristics as well as complications and mortality. The median age was 30 years and rheumatic valvular heart disease was the commonest underlying cardiac disease (34.7%). Healthcare-associated IE affected 185 patients (46.5%) and 275 patients (69.1%) had negative blood cultures. The most common complications were heart failure (n = 148, 37.2%), peripheral embolization (n = 133, 33.4%), and severe sepsis (n = 100, 25.1%). In-hospital mortality occurred in 108 patients (27.1%). Period 2 was characterized by a higher prevalence of injection drug use-associated IE (15.5% vs. 7.2%, p = 0.008), a higher staphylococcal IE (50.0% vs. 35.7%, p = 0.038), lower complications (31.1% vs. 45.1%, p = 0.005), and a lower in-hospital mortality (19.9% vs. 32.1%, p = 0.007).

CONCLUSION

This Egyptian registry showed high rates of culture-negative IE, complications, and in-hospital mortality in a largely young population of patients. Improvements were noted in the rates of complications and mortality in the second half of the reporting period.

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

Microbiological and clinical profile of infective endocarditis patients: an observational study experience from tertiary care center Karachi Pakistan

Background

The study analyzed microbiological and antimicrobial susceptibility profile of organisms isolated from patients with infective endocarditis (2015–17) and compared disease outcomes in cohorts of endocarditis patient with history of prior invasive vascular intervention (high risk group) vs those without (native valve group). We hypothesized that high risk group would be more likely to have severe disease outcomes.

Methods

This was a prospective cohort study (2015–17). All blood and cardiac tissue samples of enrolled patients suspected of endocarditis according to modified Duke’s criteria were followed for microbiological and antimicrobial susceptibility profile. The high risk group was compared with the native valve group with 90 day follow up to determine difference in clinical course and outcome in terms of disease severity (defined as any patient with endocarditis undergoing surgical management, readmission or dying). The data was analyzed using SPSS 21.0 software and chi-square test. 90 day mortality was calculated using Kaplan Meier survival curves.

Results

Total 104 patients with endocarditis were enrolled. Overall culture positivity rate was 71.2%. Streptococcus species were the most common isolate (36.7%), followed by S. aureus (17.3%) cases. In Streptococcus species, 14.2% showed intermediate susceptibility to penicillin. Thirty six patients were included in the cohort analysis. A poor outcome was seen in 85.7% high risk group as compared to 50% of native valve group. The overall mortality rate was 19.4%.

Conclusions

We found Streptococcus species to be the predominant pathogen for endocarditis overall. However Staphylococcus aureus predominated native valve group. High risk group showed more complicated clinical course.

Electronic supplementary material

The online version of this article (10.1186/s13019-018-0781-y) contains supplementary material, which is available to authorized users.

Combined efficacy of C-reactive protein and red blood cell distribution width in prognosis of patients with culture-negative infective endocarditis

Objective

To evaluate the combined effect of C-reactive protein (CRP) and red blood cell distribution width (RDW) on the prediction of in-hospital and long-term poor outcomes in patients with blood culture-negative infective endocarditis (BCNE).

Results

Patients with high CRP and high RDW has the highest incidence of in-hospital death (2.3% vs. 7.8% vs. 5.6% vs. 17.5%, P < 0.001). CRP > 17.8 mg/L (odds ratio [OR]=2.41, 95% confidence interval [CI], 1.06–5.51, P = 0.037), RDW >16.3 (OR = 2.29, 95% CI, 1.10–4.77, P = 0.027), and these two values in combination (OR = 3.15, 95% CI, 1.46–6.78, P=0.003) were independently associated with in-hospital death. Patients with RDW > 16.3 had higher long-term mortality (P = 0.003), while no significant correlation was observed for CRP (P = 0.151).

Materials and Methods

In total, 572 participants with BCNE were consecutively enrolled. They were classified into four groups based on the optimal CRP and RDW cut-off values (which were determined using a receiver operating characteristic analysis): low CRP and low RDW (n = 216), high CRP and low RDW (n = 129), low CRP and high RDW (n = 107), and high CRP and high RDW (n = 120).

Conclusions

Increased CRP and RDW, especially in combination, are independently associated with in-hospital death in BCNE. RDW, but not CRP, has long-term prognostic value.

Evaluation of empirical treatment for blood culture-negative endocarditis

OBJECTIVES

Much progress has been made in understanding the main causes of blood culture-negative endocarditis (BCNE). Few studies concerning BCNE treatment (due to previous antibiotics used or fastidious pathogens) are available. We performed this study to evaluate the effectiveness of our therapeutic protocol in BCNE, based on compliance with the protocol, outcome and 1 year mortality.

PATIENTS AND METHODS

We collected prospectively and analysed retrospectively cases of BCNE between 2002 and 2014, using a simplified and standardized protocol developed by our multidisciplinary team. We apply two kinds of protocols to treat BCNE, which include only four intravenous antimicrobial agents: amoxicillin, vancomycin, gentamicin and amphotericin B.

RESULTS

We had 177 patients with definite BCNE. There were 154 (87.0%) patients treated with both appropriate antimicrobial agents and appropriate duration of treatment. We analysed the causes of inappropriate treatment in 13 (7.3%) cases and inappropriate duration in 10 (5.6%) cases. The treatment changes were justified in all cases except one of discharge against medical advice. The fatality rate was 5.1% (nine cases) and all deaths occurred in the group of patients who were treated with appropriate treatment; however, four deaths were not attributable to empirical treatment failure. Concerning the other deaths, the lack of surgical management, in association with empirical treatment, could explain our protocol's failure, such as poorly tolerated surgery.

CONCLUSIONS

Our protocol is efficient and our mortality rate was low, compared with the literature review. This may result from a strategy that uses a sampling procedure and a standardized protocol at the same time.

Bugs, hosts and ICU environment: countering pan-resistance in nosocomial microbiota and treating bacterial infections in the critical care setting

ICUs are areas where resistance problems are the largest, and these constitute a major problem for the intensivist's clinical practice. Main resistance phenotypes among nosocomial microbiota are (i) vancomycin-resistance/heteroresistance and tolerance in grampositives (MRSA, enterococci) and (ii) efflux pumps/enzymatic resistance mechanisms (ESBLs, AmpC, metallo-betalactamases) in gramnegatives. These phenotypes are found at different rates in pathogens causing respiratory (nosocomial pneumonia/ventilator-associated pneumonia), bloodstream (primary bacteremia/catheter-associated bacteremia), urinary, intraabdominal and surgical wound infections and endocarditis in the ICU. New antibiotics are available to overcome non-susceptibility in grampositives; however, accumulation of resistance traits in gramnegatives has led to multidrug resistance, a worrisome problem nowadays. This article reviews microorganism/infection risk factors for multidrug resistance, suggesting adequate empirical treatments. Drugs, patient and environmental factors all play a role in the decision to prescribe/recommend antibiotic regimens in the specific ICU patient, implying that intensivists should be familiar with available drugs, environmental epidemiology and patient factors.

Tropheryma whipplei aortic valve endocarditis without systemic Whipple's disease

Culture-negative endocarditis is most often the result of prior antimicrobial therapy. Tropheryma whipplei is the etiologic agent of Whipple's disease, which is typically characterized by diarrhea, weight loss, and intra-abdominal lymphadenopathy. We present the case of a 48-year-old male with Whipple's endocarditis of the aortic valve who did not develop signs of systemic Whipple's disease. Our patient was treated with a regimen that included ceftriaxone for 6 weeks prior to his cardiac surgery, yet valve pathology demonstrated abundant T. whipplei, suggesting that a prolonged antibiotic course is necessary for the treatment of Whipple's endocarditis.

Molecular methods for diagnosis of infective endocarditis

Infective endocarditis (IE) is a life-threatening disease associated with high mortality. Conventional microbiologic diagnosis is based mainly on culture-dependent methods that often fail because of previous antibiotic therapy or the involvement of fastidious or slowly growing microorganisms. In recent years, molecular techniques entered the field of routine diagnostics. Amplification-based methods proved useful for detection of microorganisms in heart valve tissue. More recently, they were applied to blood samples from patients with IE. Direct detection of microorganisms in valve specimens by fluorescence in situ hybridization allowed identification of the causative agent and simultaneous visualization of complex microbial communities. These techniques will gain more importance in the near future, provided that procedures are standardized and results are interpreted with caution. With this review, we intend to give an overview of the impact and limitations of molecular techniques for the diagnosis of IE, including a focus on recent developments.

[Diagnosis and treatment of infective endocarditis. Current ESC guidelines]

To account for the current evidence in the field of infective endocarditis and to harmonize deviant national guidelines, in 2009 the European Society of Cardiology published novel recommendations on the prevention, diagnosis and treatment of infective endocarditis.The most important changes can be found concerning antimicrobial prophylaxis for endocarditis, the antimicrobial treatment of endocarditis caused by S. aureus and the indications for surgical treatment.Due to the weak evidence about prophylactic administration of antibiotics before procedures at risk for bacteraemia to prevent infective endocarditis, the novel guidelines recommend prophylaxis only in patients with the highest risk for infection and lethal course of endocarditis. These are patients with prosthetic valves or prosthetic material used for cardiac repair, patients with previous endocarditis and patients with congenital heart disease. A narrow definition of procedures at risk was proposed only including dental procedures requiring manipulation of the gingival or periapical region of teeth.For endocarditis caused by S. aureus an additional gentamicin administration was previously recommended but this is now seen only as optional due to its nephrotoxicity. In methicillin-resistant strains daptomycin is a possible alternative to vancomycin. In strains susceptible to methicillin, beta-lactamic antibiotics were definitively preferred than the usage of vancomycin due to better outcome. The current guidelines recommend definitive timing and risk constellations for surgical treatment of infective endocarditis. For example, cardiac shock due to valvular lesions refractory to medical treatment should give rise to an emergency intervention within 24 h. Other indication groups contain uncontrolled infection and prevention of embolism and indications were defined as urgent or elective depending on the clinical situation.

"Grey zone" patterns of unexplained endocarditis: still a challenge for clinical decision making

The authors report two cases of unexplained active inflammatory endocarditis with totally different clinical presentations. The patients had undergone previous mitral repair surgery and were referred for multiple soft mobile masses on the mitral ring without clinical or laboratory signs of endocarditis. Serologic screening and blood culture results were negative, including those for specific fastidious bacteria, as well as immunologic tests to rule out "nonbacterial thrombotic endocarditis." Before new surgery, both patients were treated with long-term antibiotic and anticoagulant therapy, with no significant changes in clinical setting and echocardiographic patterns. In neither case was it possible to characterize a specific microorganism: the intraoperative findings were highly evocative of active endocarditis with a macroscopic infiltration of the mitral ring, and culture results from surgical material and valvular tissue were negative.

Getting to the heart of the problem: serological and molecular techniques in the diagnosis of infective endocarditis

Infective endocarditis is diagnosed using the Duke criteria, which rely predominantly on cardiac imaging and recovery of a causative organism from the bloodstream. These criteria can be inconclusive, particularly when blood cultures remain sterile either due to the fastidious nature of the infecting organism or prior antibiotic therapy. Serology and, more recently, molecular techniques have been investigated as a solution to the problematic negative blood culture. The detection of elevated antibody levels has proved particularly useful in the diagnosis of those patients infected with organisms that cannot be cultured using standard laboratory methods, whilst molecular methods have been successfully used in the detection of both fastidious pathogens and those inhibited by prior antibiotic therapy. In view of recent and ongoing developments in the field of molecular diagnostics, these techniques will become increasingly important not only in the routine investigation of infectious disease, but specifically the diagnosis of endocarditis.

Aldose reductase structures: implications for mechanism and inhibition

During chronic hyperglycaemia, elevated vascular glucose level causes increased flux through the polyol pathway, which induces functional and morphological changes associated with secondary diabetic complications. Inhibitors of aldose reductase (ARIs) have been widely investigated as potential therapeutic agents, but to date only epalrestat is successfully marketed for treatment of diabetic neuropathy, in Japan. Promising compounds during in vitro studies or in trials with animal models have failed to proceed beyond clinical trials and to everyday use, due to a lack of efficacy or adverse side effects attributed to lack of inhibitor specificity and likely inhibition of the related aldehyde reductase (ALR1). Knowledge of the catalytic mechanism and structures of the current inhibitors complexed with ALR2 are means by which more specific and tightly bound inhibitors can be discovered. This review will provide an overview of the proposed catalytic mechanism and the current state of structure-based drug design.

Molecular methods for diagnosis of infective endocarditis

The culture of viable microorganisms from the blood or from cardiac tissue is currently the most important test for diagnosis of IE. This is followed by phenotypic identification methods used for taxonomic positioning of isolates. However, in those cases where the invading microorganism is difficult or impossible to culture (including instances of prior antimicrobial treatment), molecular methods provide the best means for detection. Molecular identification methods, either nucleic acid target or signal amplification alone or in combination with sequence analysis can offer a more specific and in some cases a more rapid alternative to the phenotypic methods. We propose revised Duke criteria of IE, including positive identification of an organism by molecular biology methods.