Performance of the 2023 Duke-International Society of Cardiovascular Infectious Diseases Diagnostic Criteria for Infective Endocarditis in Relation to the Modified Duke Criteria and to Clinical Management-Reanalysis of Retrospective Bacteremia Cohorts

BACKGROUND

Revised diagnostic criteria for infective endocarditis (IE), the 2023 Duke-ISCVID criteria, were recently presented and need validation. Here, we compare the 2000 modified Duke criteria for IE with Duke-ISCVID among patients with bacteremia and relate the diagnostic classification to IE treatment.

METHODS

We reanalyzed patient cohorts with Staphylococcus aureus, Staphylococcus lugdunensis, non-β-hemolytic streptococci, Streptococcus-like bacteria, Streptococcus dysgalactiae, Enterococcus faecalis, and HACEK (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) bacteremia. Episodes were classified as definite, possible, or rejected IE with the modified Duke and Duke-ISCVID criteria. Reclassification included the microbiology criteria, positron emission tomography-computed tomography, and cardiac implanted electronic devices. To calculate sensitivity, patients treated for IE were considered as having IE.

RESULTS

In 4050 episodes of bacteremia, the modified Duke criteria assigned 307 episodes (7.6%) as definite IE, 1190 (29%) as possible IE, and 2553 (63%) as rejected IE. Using the Duke-ISCVID criteria, 13 episodes (0.3%) were reclassified from possible to definite IE, and 475 episodes (12%) were reclassified from rejected to possible IE. With the modified Duke criteria, 79 episodes that were treated as IE were classified as possible IE, and 11 of these episodes were reclassified to definite IE with Duke-ISCVID. Applying the decision to treat for IE as a reference standard, the sensitivity of the Duke-ISCVID criteria was 80%. None of the 475 episodes reclassified to possible IE were treated as IE.

CONCLUSIONS

The Duke-ISCVID criteria reclassified a small proportion of episodes to definite IE at the expense of more episodes of possible IE. Future criteria should minimize the possible IE group while keeping or improving sensitivity.

Differential in vitro susceptibility to ampicillin/ceftriaxone combination therapy among Enterococcus faecalis infective endocarditis clinical isolates

OBJECTIVES

To investigate the genomic diversity and β-lactam susceptibilities of Enterococcus faecalis collected from patients with infective endocarditis (IE).

METHODS

We collected 60 contemporary E. faecalis isolates from definite or probable IE cases identified between 2018 and 2021 at the University of Pittsburgh Medical Center. We used whole-genome sequencing to study bacterial genomic diversity and employed antibiotic checkerboard assays and a one-compartment pharmacokinetic-pharmacodynamic (PK/PD) model to investigate bacterial susceptibility to ampicillin and ceftriaxone both alone and in combination.

RESULTS

Genetically diverse E. faecalis were collected, however, isolates belonging to two STs, ST6 and ST179, were collected from 21/60 (35%) IE patients. All ST6 isolates encoded a previously described mutation upstream of penicillin-binding protein 4 (pbp4) that is associated with pbp4 overexpression. ST6 isolates had higher ceftriaxone MICs and higher fractional inhibitory concentration index values for ampicillin and ceftriaxone (AC) compared to other isolates, suggesting diminished in vitro AC synergy against this lineage. Introduction of the pbp4 upstream mutation found among ST6 isolates caused increased ceftriaxone resistance in a laboratory E. faecalis isolate. PK/PD testing showed that a representative ST6 isolate exhibited attenuated efficacy of AC combination therapy at humanized antibiotic exposures.

CONCLUSIONS

We find evidence for diminished in vitro AC activity among a subset of E. faecalis IE isolates with increased pbp4 expression. These findings suggest that alternate antibiotic combinations against diverse contemporary E. faecalis IE isolates should be evaluated.

Surgical repair and replacement for native mitral valve infective endocarditis

AIMS

The clinical benefits of mitral valve repair over replacement in the setting of mitral infective endocarditis are not clearly established.

METHODS

Data of patients who underwent cardiac surgery for infective endocarditis over a 20-year period (2001-2021) at two cardiac centres were reviewed. Among them, 282 patients underwent native mitral valve surgery and were included in the study. Nearest-neighbour propensity-score matching was performed to account for differences in patients' profile between the repair and replacement subgroups.

RESULTS

Mitral valve replacement was performed in 186 patients, while in 96 cases patients underwent mitral valve repair. Propensity match analysis provided 89 well matched pairs. Mean age was 60 ± 15 years; 75% of the patients were male. Mitral valve replacement was more commonly performed in patients with involvement of both mitral leaflets, commissure(s) and mitral annulus. Patients with lesion(s) limited to P2 segment formed the majority of the cases undergoing mitral valve repair. There was no difference in terms of microbiological findings. In-hospital mortality was 7% with no difference between the repair and the replacement cohorts. Survival probabilities at 1, 5 and 10 years were 88%, 72% and 68%, respectively after mitral repair, and 88%, 78% and 63%, respectively after mitral replacement (log-rank P  = 0.94).

CONCLUSIONS

Mitral valve repair was more commonly performed in patients with isolated single leaflet involvement and provided good early and 10-year outcomes. Patients with annular disruption, lesion(s) on both leaflets and commissure(s) were successfully served on early and mid-term course by mitral valve replacement.

Sex differences in infective endocarditis: a Danish nationwide study

PURPOSE

Sex differences in infective endocarditis (IE) are reported, but patient characteristics are sparse and conflicting findings on the association between sex and short-term outcomes demand further research. We aimed to characterize sex differences in IE in terms of patient characteristics, frailty, microbiology, socioeconomic status, management and outcome on a nationwide scale.

METHODS

Between 2010 and 2020, we used Danish national registries to characterize patients with IE according to sex using ICD codes and microbiological lab reports. Frailty was assessed with the Hospital Frailty Risk Score. Mortality was reported with Kaplan-Meier estimates. Logistic regression and Cox regression were used for adjusted analyses.

RESULTS

We included 6259 patients with IE with 2047 (32.7%) female patients and 4212 (67.3%) male patients. Female patients were older (median age 75.0 years (64.3-82.2) vs. 71.7 (61.7-78.9)) and more frail (Intermediate frailty: 36.5% vs. 33.1%, High frailty: 11.4% vs. 9.2%). Staphylococcus aureus-IE were most common in both sexes (34.6% vs. 28.8%), but fewer female patients had Enterococcus-IE (10.5% vs. 18.1%). Female patients were less surgically treated (14.0% vs. 21.2%). Female sex was associated with increased in-hospital mortality (adj. OR 1.33, 95% CI 1.16-1.52), but no statistically significant difference in associated 1- and 5-year mortality from hospital discharge were identified (adj. HR 1.09, 95% CI 0.95-1.24 and 1.02, 95% CI 0.92-1.12, respectively).

CONCLUSION

Female sex is associated with increased in-hospital mortality, but not in long-term mortality as compared with male patients. Female patients have a lower prevalence of Enterococcus-IE and rates of surgery. Further research is needed to understand these differences.

Suppressive antibiotic therapy for infectious endocarditis

OBJECTIVES

Suppressive antibiotic therapy (SAT) is a long-term antibiotic strategy at times applied when an indicated surgical management of infective endocarditis (IE) is not possible. Our aim was to describe the characteristics and outcomes of patients having received SAT for IE.

METHODS

We conducted a retrospective, observational study at Strasbourg University Hospital, France between January 2020 and May 2023. We reviewed all medical files taken into consideration at weekly meetings of the local Multidisciplinary Endocarditis Team (MET) during the study period. We included patients having received SAT following the MET evaluation. The primary endpoint was all-cause mortality at most recent follow-up. Secondary endpoints included all-cause mortality at 3 and 6 months, infection relapse, and tolerance issues attributed to SAT.

RESULTS

The MET considered 251 patients during the study time, among whom 22 (9 %) had received SAT. Mean age was 77.2 ± 12.3 years. Patients were highly comorbid with a mean Charlson index score of 6.6 ± 2.5. Main indication for SAT was surgery indicated but not performed or an infected device not removed (20/22). Fourteen patients had prosthetic valve IE, including 9 TAVIs. Six patients had IE affecting cardiac implantable electronic devices. Staphylococcus aureus and enterococci were the main bacteria involved (6/22 each). Median follow-up time was 249 days (IQR 95-457 days). Mortality at most recent follow-up was 23 % (5/22). Three patients (14 %) presented tolerance issues attributed to SAT, and two patients suffered late infectious relapse.

CONCLUSION

Mortality at most recent follow-up was low and tolerance issues were rare for patients under SAT, which might be a palliative approach to consider when optimal surgery or device removal is not possible.

C-terminal deletion of RelA protein is suggested as a possible cause of infective endocarditis recurrence with Enterococcus faecium

Infective endocarditis (IE) caused by Enterococcus spp. represents the third most common cause of IE, with high rates of relapse compared with other bacteria. Interestingly, late relapses (>6 months) have only been described in Enterococcus faecalis, but here we describe the first reported IE relapse with Enterococcus faecium more than a year (17 months) after the initial endocarditis episode. Firstly, by multi locus sequence typing (MLST), we demonstrated that both isolates (EF646 and EF641) belong to the same sequence type (ST117). Considering that EF641 was able to overcome starvation and antibiotic treatment conditions surviving for a long period of time, we performed bioinformatic analysis in identifying potential genes involved in virulence and stringent response. Our results showed a 13-nucleotide duplication (positions 1638-1650) in the gene relA, resulting in a premature stop codon, with a loss of 167 amino acids from the C-terminal domains of the RelA enzyme. RelA mediates the stringent response in bacteria, modulating levels of the alarmone guanosine tetraphosphate (ppGpp). The relA mutant (EF641) was associated with lower growth capacity, the presence of small colony variants, and higher capacity to produce biofilms (compared with the strain EF646), but without differences in antimicrobial susceptibility patterns according to standard procedures during planktonic growth. Instead, EF641 demonstrated tolerance to high doses of teicoplanin when growing in a biofilm. We conclude that all these events would be closely related to the long-term survival of the E. faecium and the late relapse of the IE. These data represent the first clinical evidence of mutations in the stringent response (relA gene) related with E. faecium IE relapse.

Multimodality Imaging of Infective Endocarditis

Infective endocarditis (IE) is a complex multisystemic disease resulting from infection of the endocardium, the prosthetic valves, or an implantable cardiac electronic device. The clinical presentation of patients with IE varies, ranging from acute and rapidly progressive symptoms to a more chronic disease onset. Because of its severe morbidity and mortality rates, it is necessary for radiologists to maintain a high degree of suspicion in evaluation of patients for IE. Modified Duke criteria are used to classify cases as "definite IE," "possible IE," or "rejected IE." However, these criteria are limited in characterizing definite IE in clinical practice. The use of advanced imaging techniques such as cardiac CT and nuclear imaging has increased the accuracy of these criteria and has allowed possible IE to be reclassified as definite IE in up to 90% of cases. Cardiac CT may be the best choice when there is high clinical suspicion for IE that has not been confirmed with other imaging techniques, in cases of IE and perivalvular involvement, and for preoperative treatment planning or excluding concomitant coronary artery disease. Nuclear imaging may have a complementary role in prosthetic IE. The main imaging findings in IE are classified according to the site of involvement as valvular (eg, abnormal growths [ie, "vegetations"], leaflet perforations, or pseudoaneurysms), perivalvular (eg, pseudoaneurysms, abscesses, fistulas, or prosthetic dehiscence), or extracardiac embolic phenomena. The differential diagnosis of IE includes evaluation for thrombus, pannus, nonbacterial thrombotic endocarditis, Lambl excrescences, papillary fibroelastoma, and caseous necrosis of the mitral valve. The location of the lesion relative to the surface of the valve, the presence of a stalk, and calcification or enhancement at contrast-enhanced imaging may offer useful clues for their differentiation. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Bacteraemia with gram-positive bacteria-when and how do I need to look for endocarditis?

BACKGROUND

Patients with bacteraemia caused by gram-positive bacteria are at risk for infective endocarditis (IE). Because IE needs long antibiotic treatment and sometimes heart valve surgery, it is very important to identify patients with IE.

OBJECTIVES

In this narrative review we present and discuss how to determine which investigations to detect IE that are needed in individual patients with gram-positive bacteraemia.

SOURCES

Published original studies and previous reviews in English, within the relevant field are used.

CONTENT

First, the different qualities of the bacteraemia in relation to IE risk are discussed. The risk for IE in bacteraemia is related to the species of the bacterium but also to monomicrobial bacteraemia and the number of positive cultures. Second, patient-related factors for IE risk in bacteraemia are presented. Next, the risk stratification systems to determine the risk for IE in gram-positive bacteraemia caused by Staphylococcus aureus, viridans streptococci, and Enterococcus faecalis are presented and their use is discussed. In the last part of the review, an account for the different modalities of IE-investigations is given. The main focus is on echocardiography, which is the cornerstone of IE-investigations. Furthermore, 18F-fluorodesoxyglucose positron emission tomography/computed tomography and cardiac computed tomography are presented and their use is also discussed. A brief account for investigations used to identify embolic phenomena in IE is also given. Finally, we present a flowchart suggesting which investigations to perform in relation to IE in patients with gram-positive bacteraemia.

IMPLICATIONS

For the individual patient as well as the healthcare system, it is important both to diagnose IE and to decide when to stop looking for IE. This review might be helpful in finding that balance.

Risk factors for and consequences of positive valve cultures in patients who undergo cardiac surgery while receiving antimicrobial treatment for infective endocarditis

INTRODUCTION

Cardiac surgery is required in up to half of the patients with infective endocarditis (IE). Positive valve cultures have been associated with higher in-hospital mortality. The aims were to identify risk factors for positive valve cultures and its relation to outcome.

METHODS

Patients subjected to heart valve cultures due to surgery for IE in Skåne University Hospital, Lund, between 2012 and 2021 were identified through microbiology records. Risk factors for positive valve cultures and information on mortality and relapse were retrieved through medical records. Univariable and multivariable logistic regressions were performed.

RESULTS

A total of 345 episodes with IE in 337 patients subjected to cardiac surgery were included and valve cultures were positive in 78 (23%) episodes. In multivariable logistic regression, preoperative fever (adjusted odds ratio (AOR) 2.6, 95% confidence interval (CI) 1.2-5.6, p = 0.02), prosthetic heart valve (AOR 3.3, CI 1.4-7.9, p = 0.01), a single affected valve (AOR 4.8, CI 1.2-20, p = 0.03), blood culture findings of S. aureus, enterococci, or coagulase negative staphylococci compared to viridans streptococci (AOR 20-48, p < 0.001), and a shorter duration of antibiotic treatment (p < 0.001), were associated to positive valve culture. One-year mortality was 13% and a relapse was identified in 2.5% of episodes. No association between positive valve cultures and one-year mortality or relapse was identified.

CONCLUSIONS

Positive valve cultures were associated to short preoperative antibiotic treatment, IE caused by staphylococci, preoperative fever and prosthetic valve but not to relapse or mortality.

A cardiac intimal sarcoma mimicking infective endocarditis

Primary malignant cardiac tumors are rare and usually misdiagnosed because they can mimic more common intracardiac lesions, therefore, in clinical practice it is important to always consider even uncommon diseases in order to avoid delayed diagnosis and to plan the most appropriate therapeutic strategy in a timely fashion. We report a case of a 73-year-old man with clinical signs and imaging findings (echocardiography) suggesting infective bacterial endocarditis of the mitral valve. However, intraoperative evaluation raised suspicion that the mitral lesions had a different nature. Surgical removal of the mass was performed, and the final correct diagnosis was made through pathologic examination, revealing a mitral valve sarcoma thus allowing for the beginning of specific oncological treatment.

Burkholderia cepacia: A Rare Source of Endocarditis

A 37-year-old male with a past medical history of previous mitral valve replacement due to bacterial endocarditis and intravenous (IV) drug use was found to have Burkholderia cepacia bacteremia. Transesophageal echocardiogram revealed large mitral and tricuspid valve vegetations. Medical management was initially attempted but his bacteremia persisted, and he required urgent prosthetic mitral valve replacement and native tricuspid valve replacement. Prosthetic valve endocarditis has been associated with surgery in 48.9% of patients and a mortality of 22.8%. In patients with prosthetic valve endocarditis due to B. cepacia, valve replacement occurred in approximately 61.5% of patients and mortality is estimated to be 33.3%. To our knowledge, this is one of only a few prosthetic valve endocarditis cases caused solely by B. cepacia and our case is the first to affect multiple valves including prosthetic and native valves.

Isolated mitral valve endocarditis: Patient, disease, and surgical factors that influence outcomes

OBJECTIVE

The objectives of this study were to investigate patient characteristics, valve pathology, bacteriology, and surgical techniques related to outcome of patients who underwent surgery for isolated native (NVE) or prosthetic (PVE) mitral valve endocarditis.

METHODS

From January 2002 to January 2020, 447 isolated mitral endocarditis operations were performed, 326 for NVE and 121 for PVE. Multivariable analysis of time-related outcomes used random forest machine learning.

RESULTS

Staphylococcus aureus was the most common causative organism. Of 326 patients with NVE, 88 (27%) underwent standard mitral valve repair, 43 (13%) extended repair, and 195 (60%) valve replacement. Compared with NVE with standard repair, patients who underwent all other operations were older, had more comorbidities, worse cardiac function, and more invasive disease. Hospital mortality was 3.8% (n = 17); 0 (0%) after standard valve repair, 3 (7.0%) after extended repair, 8 (4.1%) after NVE replacement, and 6 (5.0%) after PVE re-replacement. Survival at 1, 5, and 10 years was 91%, 75%, and 62% after any repair and 86%, 62%, and 44% after replacement, respectively. The most important risk factor for mortality was renal failure. Risk-adjusted outcomes, including survival, were similar in all groups. Unadjusted extended repair outcomes, particularly early, were similar or worse than replacement in terms of reinfection, reintervention, regurgitation, gradient, and survival.

CONCLUSIONS

A patient- and pathology-tailored approach to surgery for isolated mitral valve endocarditis has low mortality and excellent results. Apparent superiority of standard valve repair is related to patient characteristics and pathology. Renal failure is the most powerful risk factor. In case of extensive destruction, extended repair shows no benefit over replacement.

A Case of Infective Endocarditis Caused by Citrobacter koseri: Unraveling a Rare Pathogen and Dire Outcome

Citrobacter koseri (formerly classified as Citrobacter diversus) is a gram-negative bacillus (GNB) that occurs as an opportunistic pathogen in neonates and immunocompromised patients. Citrobacter species have been implicated in nosocomial settings leading to infections involving the urinary tract, respiratory tract, liver, biliary tract, meninges, and even in rarer conditions-blood stream infection and infective endocarditis (IE). Gram-negative bacilli are responsible for 3% to 4% of all IE cases and have been traditionally associated with intravenous drug users. Patients with non-HACEK (species other than Haemophilus species, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, or Kinglella species) GNB IE have poor clinical outcomes with higher rates of in-hospital mortality and complications. The American Heart Association (AHA) and Infectious Diseases Society of America (IDSA) both recommend the use of combination antibiotic therapy with a beta-lactam (penicillins, cephalosporins, or carbapenems) and either an aminoglycoside or fluoroquinolones for 6 weeks (about 1 and a half months) to treat IE due to non-HACEK GNB. Citrobacter koseri is becoming more recognized due to its inherent resistance to ampicillin and emerging drug resistance to beta lactams and aminoglycosides requiring carbapenem therapy. Our case is of a 75-year-old male with no previously reported history of primary or secondary immunodeficiency disorders who developed C koseri blood stream infection. His infectious work-up revealed mitral valve IE and septic cerebral emboli resulting in ischemic infarcts. This case illustrates the importance of recognizing GNB organisms as rising human pathogens in IE cases even without active injection drug use or nosocomial exposure.

Prognosis of prosthetic valve infective endocarditis due to Streptococcus spp., a retrospective multi-site study to assess the impact of antibiotic treatment duration

PURPOSE

The duration of antibiotic treatment for prosthetic valve endocarditis caused by Streptococcus spp. is largely based on clinical observations and expert opinion rather than empirical studies. Here we assess the impact of a shorter antibiotic duration.

OBJECTIVES

To assess the impact of antibiotic treatment duration for streptococcal prosthetic valve endocarditis on 12-month mortality as well as subsequent morbidity resulting in additional cardiac surgical interventions, and rates of relapse and reinfection.

METHODS

This retrospective multisite (N= 3) study examines two decades of data on patients with streptococcal prosthetic valve endocarditis receiving either 4 or 6 weeks of antibiotics. Overall mortality, relapse, and reinfection rates were also assessed for the entire available follow-up period.

RESULTS

The sample includes 121 patients (median age 72 years, IQR [53; 81]). The majority (74%, 89/121) received a ß-lactam antibiotic combined with aminoglycoside in 74% (89/121, median bi-therapy 5 days [1; 14]). Twenty-eight patients underwent surgery guided by ESC-guidelines (23%). The 12-month mortality rate was not significantly affected by antibiotic duration (4/40, 10% in the 4-week group vs 3/81, 3.7% in the 6-week group, p=0.34) or aminoglycoside usage (p=0.1). Similarly, there were no significant differences between the 2 treatment groups for secondary surgical procedures (7/40 vs 21/81, p=0.42), relapse or reinfection (1/40 vs 2/81 and 2/40 vs 5/81 respectively).

CONCLUSIONS

Our study found no increased adverse outcomes associated with a 4-week antibiotic duration compared to the recommended 6-week regimen. Further randomized trials are needed to ascertain the optimal duration of treatment for streptococcal endocarditis.

A high throughput microphysiological model of prosthetic valve endocarditis for investigating factors that influence bacterial adhesion under fluid shear stress

Prosthetic heart valves are associated with almost one quarter of cases of infective endocarditis, a rare but serious condition with a staggering 25 % mortality rate. Without the endothelium of native valves, the risk of infection is exacerbated for implanted devices exposed to blood. There are currently no physiologically relevant in vitro or animal models of prosthetic valve endocarditis (PVE). Of particular importance, Staphylococcus aureus, a common agent of PVE, has demonstrated enhanced binding to blood plasma proteins (e.g., fibrinogen) and exposed matrix under fluid shear stress (FSS). An in vitro platform that mimics the multiple physiological determinants for S. aureus adhesion to prosthetic valve materials would facilitate the discovery of new treatments to minimize PVE. To this end, we developed a first-of-its-kind microphysiological model of PVE to study the effects of several key variables (endothelial cell coverage, fibrinogen deposition, surface treatments, and FSS) on S. aureus adhesion to bioprosthetic material surfaces. Our model demonstrated that viable endothelial monolayers diminished the deposition of fibrinogen and that fibrinogen was required for the subsequent adhesion of S. aureus to the bioprosthetic surface model. Next, we examined factors that affected endothelial cell coverage, such as FSS and glutaraldehyde, a common chemical treatment for bioprosthetic materials. In particular, glutaraldehyde treatment obstructed endothelialization of otherwise biocompatible collagen-coated surfaces, further enabling fibrinogen and S. aureus deposition. In future work, this model could impact multiple research areas, such as screening candidate bioprosthetic valve materials and new surface treatments to prevent PVE and further understanding host-pathogen interactions.

The Silent Threat: Bartonella quintana Endocarditis Unveiling Heart Failure and Severe Pulmonary Hypertension

BACKGROUND Bartonella quintana is a slow-growing gram-negative bacterium that can cause severe culture-negative endocarditis. In many cases, its insidious onset can be difficult to diagnose given the variable symptoms in the early phases of the disease. This delay in detection and thus treatment can cause advanced consequences of the disease, including heart failure and severe pulmonary hypertension. CASE REPORT A 51-year-old man presented to the Emergency Department with signs and symptoms indicating an acute stroke. Further investigation showed that the source was cardioembolic, and despite negative blood cultures, endocarditis was suspected due to echocardiogram findings. Bartonella endocarditis was diagnosed based on serology results. Further testing indicated severe pulmonary hypertension, a sequelae of chronic heart failure in the setting of endocarditis. This caused a significant delay in valvular repair surgery. This case illustrates the progression from acute to chronic infection, the sequelae of this disease process, and the considerations involved in management. CONCLUSIONS Bartonella is an under-appreciated cause of endocarditis and can evolve into chronic disease with clinical consequences requiring nuanced management. We described a case of chronic culture-negative endocarditis that presented with acute embolic stroke and the sequelae of severe multi-valvular disease in a patient with recent incarceration and unstable housing. This case provides clinicians with valuable insight into the recognition of Bartonella endocarditis, the variable clinical presentations of this pathology, the nuanced and multifactorial approaches to medical management, and the indications for surgery.

Evaluating the heart valve tissue diffusion of amoxicillin in infective endocarditis: a pilot prospective observational non-comparative study

OBJECTIVES

Treating patients with infective endocarditis (IE) due to streptococci and enterococci currently involves high-dosage antibiotics. Recent literature suggests a 30%-70% diffusion rate could be extrapolated to human heart valve tissue. The objective of this study was to evaluate the diffusion coefficient of amoxicillin in heart valve tissue of patients operated for IE.

METHODS

Adult patients were prospectively included that underwent surgery at the European Hospital Georges Pompidou for IE due to streptococci and enterococci and had previous IV amoxicillin treatment. Plasma (taken 48 h preoperatively) and heart valve tissue amoxicillin concentrations were measured with a validated LC-MS/MS method. The MIC values of amoxicillin were measured for all available isolates.

RESULTS

Seventeen patients were included. Eleven (64.7%) patients had native valve IE and six (35.3%) had prosthetic valve IE. Fourteen IE cases (82.4%) were due to streptococci, one (5.9%) was due to enterococci and two (11.8%) were Haemophilus spp, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae group infections. Median (IQR) amoxicillin dose administered was 10.5 (8.0-12.0) g/day corresponding to 138.2 (112.5-160.0) mg/kg/day. The median amoxicillin plasma concentrations pre-surgery and intra-tissular weighted concentrations were 31.9 (25.9-51.9) mg/L and 19.0 (7.9-31.4) µg/g, respectively. Median tissue/plasma concentration ratio was 0.47 (0.24-0.67), with a median amoxicillin plasma/MIC ratio of 487 (179-745), and median amoxicillin tissue/MIC ratio of 42 (14-116).

CONCLUSIONS

With a significant diffusion coefficient, amoxicillin dosage in heart valve tissues showed a concentration/MIC ratio well above current recommendations for bactericidal activity. Our study suggests that lower doses can be considered for susceptible bacteria.

Recurrence of bacteremia and infective endocarditis according to bacterial species of index endocarditis episode

PURPOSE

In patients surviving infective endocarditis (IE) recurrence of bacteremia or IE is feared. However, knowledge is sparse on the incidence and risk factors for the recurrence of bacteremia or IE.

METHODS

Using Danish nationwide registries (2010-2020), we identified patients with first-time IE which were categorized by bacterial species (Staphylococcus aureus, Enterococcus spp., Streptococcus spp., coagulase-negative staphylococci [CoNS], 'Other' microbiological etiology). Recurrence of bacteremia (including IE episodes) or IE with the same bacterial species was estimated at 12 months and 5 years, considering death as a competing risk. Cox regression models were used to compute adjusted hazard ratios of the recurrence of bacteremia or IE.

RESULTS

We identified 4086 patients with IE; 1374 (33.6%) with S. aureus, 813 (19.9%) with Enterococcus spp., 1366 (33.4%) with Streptococcus spp., 284 (7.0%) with CoNS, and 249 (6.1%) with 'Other'. The overall 12-month incidence of recurrent bacteremia with the same bacterial species was 4.8% and 2.6% with an accompanying IE diagnosis, while this was 7.7% and 4.0%, respectively, with 5 years of follow-up. S. aureus, Enterococcus spp., CoNS, chronic renal failure, and liver disease were associated with an increased rate of recurrent bacteremia or IE with the same bacterial species.

CONCLUSION

Recurrent bacteremia with the same bacterial species within 12 months, occurred in almost 5% and 2.6% for recurrent IE. S. aureus, Enterococcus spp., and CoNS were associated with recurrent infections with the same bacterial species.

Trueperella pyogenes endocarditis in a Swiss farmer: a case report and review of the literature

BACKGROUND

Trueperella pyogenes (T. pyogenes) is a bacterium that colonizes the skin and mucosal surfaces of various domestic and wild animals. It rarely leads to infections in humans, with only a few descriptions available in the literature.

CASE PRESENTATION

A 71-year-old Swiss farmer with a history of recurring basal cell carcinoma and metastasized pancreatic neuroendocrine tumor presented with signs of sepsis after a three-day history of general weakness, malaise and fever. Clinical and echocardiographic findings, as well as persistent bacteremia were consistent with mitral valve endocarditis caused by T. pyogenes. The patient's condition gradually improved under antibiotic treatment with piperacillin/tazobactam (empiric therapy of sepsis), and later penicillin G based on resistance testing. He was discharged after 13 days and continued outpatient antibiotic therapy with ceftriaxone, resulting in a total antibiotic treatment duration of six weeks. This is the first literature review of T. pyogenes endocarditis in humans. Among nine cases of T. pyogenes endocarditis, three patients had documented contact with farm animals and five had an underlying condition that compromised the immune system. While antibiotic resistance of T. pyogenes is an emerging concern, susceptibility to beta-lactam antibiotics seems to persist. The mortality of T. pyogenes endocarditis described in the literature was high, with 66% of patients not surviving the disease.

CONCLUSIONS

T. pyogenes is a rare causative organism of infectious endocarditis in humans and descriptions are mainly restricted to case reports. In our review of the literature, we found that both an impaired immune system and contact with farm animals might be risk factors. Growth of T. pyogenes in blood cultures is unlikely to be missed during routine analysis, as it shows marked beta-hemolysis on blood agar culture plates, which generally leads to further characterization of the bacteria. Susceptibility to penicillin, ceftriaxone, and macrolides seems to be retained and the reported mortality in the few patients with T. pyogenes endocarditis is high.

Microbiologic diagnostics and pathogen spectrum in infective endocarditis of surgically treated patients: a five-year, retrospective, monocentric study

PURPOSE

The spectrum of causative organisms in infective endocarditis (IE) has changed significantly in the last decades. Reliable pathogen detection is crucial for appropriate antimicrobial therapy for IE. The aim of the study was to evaluate the diagnostic value of microbiological methods for detecting the causative microorganism of IE and to analyze the spectrum of pathogens.

METHODS

A total of 224 cases (211 unique patients, some with multiple surgeries) were included into this retrospective study. Patients were diagnosed with IE according to the modified Duke criteria from January 2016 to July 2021 and underwent heart valve surgery in a tertiary hospital. Pathogen detection was performed by blood culture, microbiological culture and 16S rDNA PCR of explanted heart valve material.

RESULTS

A causative pathogen of IE was detected in 95.5% (n = 214) of cases. Blood cultures were positive in 83.3%, while a pathogen in the examined heart valve samples was identified in 32.6% by culture and in 88.2% by 16S rDNA PCR. A microorganism was identified by 16S rDNA PCR in 61.1% of blood culture negative cases but only in 19.4% by heart valve culture. The most common pathogens were Staphylococcus aureus (27%), viridans group streptococci (20%), enterococci (19%) and coagulase-negative staphylococci (CoNS 8%). Cutibacterium acnes (7%) was detected in prosthetic valve IE cases only.

CONCLUSION

Blood culture as a comparatively non-invasive and straightforward technique remains an important and reliable method for initial detection of the causative organism in IE. Diagnostic stewardship programs should broadly emphasize proper collection of blood cultures, particularly sampling prior to any antibiotic treatment. Additionally, molecular testing using 16S rDNA tissue PCR can be used with culture techniques to increase the diagnostic yield, especially in the case of a negative blood culture.

16S rRNA Gene PCR/Sequencing of Heart Valves for Diagnosis of Infective Endocarditis in Routine Clinical Practice

Sequencing is increasingly used for infective endocarditis (IE) diagnosis. Here, the performance of 16S rRNA gene PCR/sequencing of heart valves utilized in routine clinical practice was compared with conventional IE diagnostics. Subjects whose heart valves were sent to the clinical microbiology laboratory for 16S rRNA gene PCR/sequencing from August 2020 through February 2022 were studied. A PCR assay targeting V1 to V3 regions of the 16S rRNA gene was performed, followed by Sanger and/or next-generation sequencing (NGS) (using an Illumina MiSeq), or reported as negative, depending on an algorithm that included the PCR cycle threshold value. Fifty-four subjects, including 40 with IE, three with cured IE, and 11 with noninfective valvular disease, were studied. Thirty-one positive results, 11 from NGS and 20 from Sanger sequencing, were generated from analysis of 16S rRNA gene sequence(s). Positivity rates of blood cultures and 16S rRNA gene PCR/sequencing of valves were 55% and 75%, respectively (P = 0.06). In those with prior antibiotic exposure, positivity rates of blood cultures and 16S rRNA gene PCR/sequencing of valves were 11% and 76%, respectively (P < 0.001). Overall, 61% of blood culture-negative IE subjects had positive valve 16S rRNA gene PCR/sequencing results. 16S rRNA gene-based PCR/sequencing of heart valves is a useful diagnostic tool for pathogen identification in patients with blood culture-negative IE undergoing valve surgery in routine clinical practice.

The 2023 Duke-International Society for Cardiovascular Infectious Diseases Criteria for Infective Endocarditis: Updating the Modified Duke Criteria

The microbiology, epidemiology, diagnostics, and treatment of infective endocarditis (IE) have changed significantly since the Duke Criteria were published in 1994 and modified in 2000. The International Society for Cardiovascular Infectious Diseases (ISCVID) convened a multidisciplinary Working Group to update the diagnostic criteria for IE. The resulting 2023 Duke-ISCVID IE Criteria propose significant changes, including new microbiology diagnostics (enzyme immunoassay for Bartonella species, polymerase chain reaction, amplicon/metagenomic sequencing, in situ hybridization), imaging (positron emission computed tomography with 18F-fluorodeoxyglucose, cardiac computed tomography), and inclusion of intraoperative inspection as a new Major Clinical Criterion. The list of "typical" microorganisms causing IE was expanded and includes pathogens to be considered as typical only in the presence of intracardiac prostheses. The requirements for timing and separate venipunctures for blood cultures were removed. Last, additional predisposing conditions (transcatheter valve implants, endovascular cardiac implantable electronic devices, prior IE) were clarified. These diagnostic criteria should be updated periodically by making the Duke-ISCVID Criteria available online as a "Living Document."

Carbonic Anhydrase Inhibition as a Target for Antibiotic Synergy in Enterococci

Enterococcus faecalis is a hospital-associated opportunistic pathogen that can cause infections with high mortality, such as infective endocarditis. With an increasing occurrence of multidrug-resistant enterococci, there is a need for alternative strategies to treat enterococcal infections. We isolated a gentamicin-hypersusceptible E. faecalis strain from a patient with infective endocarditis that carried a mutation in the alpha-carbonic anhydrase (α-CA) and investigated how disruption of α-CA sensitized E. faecalis to killing with gentamicin. The gentamicin-hypersusceptible α-CA mutant strain showed increased intracellular gentamicin uptake in comparison to an isogenic strain encoding full-length, wild-type α-CA. We hypothesized that increased gentamicin uptake could be due to increased proton motive force (PMF), increased membrane permeability, or both. We observed increased intracellular ATP production in the α-CA mutant strain, suggesting increased PMF-driven gentamicin uptake contributed to the strain's gentamicin susceptibility. We also analyzed the membrane permeability and fatty acid composition of isogenic wild-type and α-CA mutant strains and found that the mutant displayed a membrane composition that was consistent with increased membrane permeability. Finally, we observed that exposure to the FDA-approved α-CA inhibitor acetazolamide lowered the gentamicin MIC of eight genetically diverse E. faecalis strains with intact α-CA but did not change the MIC of the α-CA mutant strain. These results suggest that α-CA mutation or inhibition increases PMF and alters membrane permeability, leading to increased uptake of gentamicin into E. faecalis. This connection could be exploited clinically to provide new combination therapies for patients with enterococcal infections. IMPORTANCE Enterococcal infections can be difficult to treat, and new therapeutic approaches are needed. In studying an E. faecalis clinical strain from an infected patient, we found that the bacteria were rendered hypersusceptible to aminoglycoside antibiotics through a mutation that disrupted the α-CA. Our follow-on work suggested two different ways that α-CA disruption causes increased gentamicin accumulation in E. faecalis: increased proton motive force-powered uptake and increased membrane permeability. We also found that a mammalian CA inhibitor could sensitize a variety of E. faecalis strains to killing with gentamicin. Given that mammalian CA inhibitors are frequently used to treat conditions such as glaucoma, hypertension, and epilepsy, our findings suggest that these "off-the-shelf" inhibitors could also be useful partner antibiotics for the treatment of E. faecalis infections.

The three-noes right-sided infective endocarditis: An unrecognized type of right-sided endocarditis

The "3 noes right-sided infective endocarditis" (3no-RSIE: no left-sided, no drug users, no cardiac devices) was first described more than a decade ago. We describe the largest series to date to characterize its clinical, microbiological, echocardiographic and prognostic profile. Eight tertiary centers with surgical facilities participated in the study. Patients with right-sided endocarditis without left sided involvement, absence of drug use history and no intracardiac electronic devices were retrospectively included in a multipurpose database. A total of 53 variables were analyzed in every patient. We performed a univariate analysis of in-hospital mortality to determine variables associated with worse prognosis. the study was comprised of 100 patients (mean age 54.1 ± 20 years, 65% male) with definite 3no-RSIE were included (selected from a total of 598 patients with RSIE of all the series, which entails a 16.7% of 3no-RSIE). Most of the episodes were community-acquired (72%), congenital cardiopathies were frequent (32% of the group of patients with previous known predisposing heart disease) and fever was the main manifestation at admission (85%). The microbiological profile was led by Staphylococci spp (52%). Vegetations were detected in 94% of the patients. Global in-hospital mortality was 19% (5.7% in patients operated and 26% in patients who received only medical treatment, P < .001). Non-community acquired infection, diabetes mellitus, right heart failure, septic shock and acute renal failure were more common in patients who died. the clinical profile of 3no-RSIE is closer to other types of RSIE than to LSIE, but mortality is higher than that reported on for other types of RSIE. Surgery may play an important role in improving outcome.

Clinical Significance of a 16S-rDNA Analysis of Heart Valves in Patients with Infective Endocarditis: a Retrospective Study

A substantial proportion of patients with infective endocarditis (IE) are subjected to heart valve surgery. Microbiological findings on valves are important both for diagnostics and for tailored antibiotic therapy, post-operatively. The aims of this study were to describe microbiological findings on surgically removed valves and to examine the diagnostic benefits of 16S-rDNA PCR and sequencing (16S-analysis). Adult patients who were subjected to heart valve surgery for IE between 2012 and 2021 at Skåne University Hospital, Lund, where a 16S-analysis had been performed on the valve, constituted the study population. Data were gathered from medical records, and the results from blood cultures, valve cultures, and 16S-analyses of valves were compared. A diagnostic benefit was defined as providing an agent in blood culture negative endocarditis, providing a new agent in episodes with positive blood cultures, or confirming one of the findings in episodes with a discrepancy between blood and valve cultures. 279 episodes in 272 patients were included in the final analysis. Blood cultures were positive in 259 episodes (94%), valve cultures in 60 episodes (22%), and 16S-analyses in 227 episodes (81%). Concordance between the blood cultures and the 16S-analysis was found in 214 episodes (77%). The 16S-analyses provided a diagnostic benefit in 25 (9.0%) of the episodes. In blood culture negative endocarditis, the 16S-analyses had a diagnostic benefit in 15 (75%) of the episodes. A 16S-analysis should be routinely performed on surgically removed valves in blood culture negative endocarditis. In patients with positive blood cultures, 16S-analysis may also be considered, as a diagnostic benefit was provided in some patients. IMPORTANCE This work demonstrates that it can be of importance to perform both cultures and analysis using 16S-rDNA PCR and sequencing of valves excised from patients undergoing surgery for infective endocarditis. 16S-analysis may help both to establish a microbiological etiology in cases of blood culture negative endocarditis and to provide help in situations where there are discrepancies between valve and blood cultures. In addition, our results show a high degree of concordance between blood cultures and 16S-analyses, indicating that the latter has a high sensitivity and specificity for the etiological diagnosis of endocarditis in patients who were subjected to heart valve surgery.

Virulence of Staphylococcus Infection in Surgically Treated Patients With Endocarditis : A Multicenter Analysis

OBJECTIVE

Infective endocarditis (IE) caused by Staphylococcus species (spp.) is believed to be associated with higher morbidity and mortality rates. We hypothesize that Staphylococcus spp. are more virulent compared with other commonly causative bacteria of IE with regard to short-term and long-term mortality.

BACKGROUND

It remains unclear if patients suffering from IE due to Staphylococcus spp. should be referred for surgical treatment earlier than other IE patients to avoid septic embolism and to optimize perioperative outcomes.

MATERIALS AND METHODS

The database of the CAMPAIGN registry, comprising 4917 consecutive patients undergoing heart valve surgery, was retrospectively analyzed. Patients were divided into 2 groups with regard to the identified microorganisms: Staphylococcus group and the non- Staphylococcus group. The non- Staphylococcus group was subdivided for further analyses: Streptococcus group, Enterococcus group, and all other bacteria groups.

RESULTS

The respective mortality rates at 30 days (18.7% vs 11.8%; P <0.001), 1 year (24.7% vs 17.7%; P <0.001), and 5 years (32.2% vs 24.5%; P <0.001) were significantly higher in Staphylococcus patients (n=1260) compared with the non- Staphylococcus group (n=1787). Multivariate regression identified left ventricular ejection fraction <30% ( P <0.001), chronic obstructive pulmonary disease ( P =0.045), renal insufficiency ( P =0.002), Staphylococcus spp. ( P =0.032), and Streptococcus spp. ( P =0.013) as independent risk factors for 30-day mortality. Independent risk factors for 1-year mortality were identified as: age ( P <0.001), female sex ( P =0.018), diabetes ( P =0.018), preoperative stroke ( P =0.039), chronic obstructive pulmonary disease ( P =0.001), preoperative dialysis ( P <0.001), and valve vegetations ( P =0.004).

CONCLUSIONS

Staphylococcus endocarditis is associated with an almost twice as high 30-day mortality and significantly inferior long-term outcome compared with IE by other commonly causative bacteria. Patients with Staphylococcus infection are more often female and critically ill, with >50% of these patients suffering from clinically relevant septic embolism. Early diagnosis and referral to a specialized center for surgical treatment are strongly recommended to reduce the incidence of preoperative deterioration and stroke due to septic embolism.

Infectious endocarditis caused by Bartonella henselae associated with infected pets: two case reports

BACKGROUND

Blood culture-negative infective endocarditis is a potentially severe disease that can be associated with infectious agents such as Bartonella spp., Coxiella burnetti, Tropheryma whipplei, and some fungi.

CASE PRESENTATION

Reported here are two cases of blood culture-negative infective endocarditis in patients with severe aortic and mitral regurgitation in Brazil; the first case is a 47-year-old white man and the second is a 62-year-old white woman. Bartonella henselae deoxyribonucleic acid was detectable in the blood samples and cardiac valve with vegetation paraffin-fixed tissue samples. Additionally, an investigation was carried out on patients' pets, within the context of One Health, and serum samples collected from cats and dogs were reactive by indirect immunofluorescence assay.

CONCLUSIONS

Even though the frequency of bartonellosis in Brazil is unknown, physicians should be aware of the possibility of blood culture-negative infective endocarditis caused by Bartonella, particularly in patients with weight loss, kidney changes, and epidemiological history for domestic animals.

Infective Endocarditis After Transcatheter Aortic Valve Implantation: A Systematic Review

Infective endocarditis (IE) after transcatheter aortic valve implantation (TAVI) is a rare but potentially fatal event. In this systematic review, we searched PubMed and Embase for large TAVI studies and registries to identify the incidence, presentation, microbiology, risk factors, and outcomes of IE in this population. After application of the selection criteria and quality assessment, 8 studies representing 255,310 TAVR cases and 4218 cases of IE qualified for this review. IE following TAVI is uncommon with an incidence of 0.87 to 1.7 events per 100 person-years. Most events occur in the first year following valve implantation. Staphylococcus , Enterococcus , and Streptococcus species are the most common pathogens. Risk factors include age, sex, concomitant comorbidities, and procedural factors. Outcomes are dismal, and surgical intervention is rare in this population.

[Infective endocarditis with bivalvular involvement due to Erysipelothrix rhusiopathiae. Report of one case]

The microbiology of infective endocarditis (IE) varies in different populations and depends on public health conditions and socioeconomic status. In low-income countries, oral Streptococci affect hearts with rheumatic valve disease in patients with poor dentition. In high-income countries, Staphylococci are the most common cause, affecting elderly and immunocompromised patients, or those with invasive devices. Gram - positive bacili as IE pathogens are unusual. Erysipelothrix rhusiopathiae is a Gram positive bacili. It causes skin diseases in domestic and farm animals, but in humans, is a very unusual pathogen. This infection is considered a zoonosis, since most cases are linked to direct contact with vector animals. We report a 62 year-old male patient with a history of exposure to animals, who developed an infective endocarditis with severe bivalve regurgitation and septic shock, requiring antimicrobials and surgical resolution. Erysipelothrix rhusiopathiae was isolated from blood and valve vegetation cultures. The patient had a successful evolution and was discharged from the hospital.

All Staphylococcus aureus bacteraemia-inducing strains can cause infective endocarditis: Results of GWAS and experimental animal studies

OBJECTIVES

We aimed at determining whether specific S. aureus strains cause infective endocarditis (IE) in the course of Staphylococcus aureus bacteraemia (SAB).

METHODS

A genome-wide association study (GWAS) including 924 S. aureus genomes from IE (274) and non-IE (650) SAB patients from international cohorts was conducted, and a subset of strains was tested with two experimental animal models of IE, one investigating the early step of bacterial adhesion to inflamed mice valves, the second evaluating the local and systemic developmental process of IE on mechanically-damaged rabbit valves.

RESULTS

The genetic profile of S. aureus IE and non-IE SAB strains did not differ when considering single nucleotide polymorphisms, coding sequences, and k-mers analysed in GWAS. In the murine inflammation-induced IE model, no difference was observed between IE and non-IE SAB strains both in terms of adhesion to the cardiac valves and in the propensity to cause IE; in the mechanical IE-induced rabbit model, there was no difference between IE and non-IE SAB strains regarding the vegetation size and CFU.

CONCLUSION

All strains of S. aureus isolated from SAB patients must be considered as capable of causing this common and lethal infection once they have accessed the bloodstream.

Incidence and mortality of infective endocarditis in the last decade: a single center study

BACKGROUND

Infective endocarditis (IE) is a significant disease characterized by high mortality and complications. The aim of this study was to evaluate the incidence/100 000 inhabitants and the in-hospital mortality/100 000 inhabitants of IE during the last 10 years in the province of Ravenna.

METHODS AND RESULTS

We reviewed the public hospitals discharge database from January 2010 to December 2020 using the international classification of disease codification (ICD-9) for IE. We used the Italian national statistical institute (ISTAT) archive to estimate the number of Ravenna inhabitants/year. In 10 years, we identified a total of 407 patients with diagnosis of IE.The incidence of IE increased significantly from 6.29 cases/100 000 inhabitants in 2010 to 19.58 cases/100 000 inhabitants in 2020 ( P  < 0.001). Also, the in-hospital mortality from IE increased over the same number of years, from 1.8 deaths/100 000 inhabitants in 2010 to 4.4 deaths/100 000 inhabitants in 2020 ( P  < 0.001). The mortality rate (%) of IE over the years did not increase ( P = 0.565). Also, over the years there was no difference in the site of infection ( P  = 0.372), irrespective of the valve localization or type, native valve ( P  = 0.347) or prosthetic valve ( P  = 0.145). On logistic regression analysis, age was the only predictor of in-hospital mortality (odds ratio 1.045, 95% confidence interval: 1.015; 1.075, P  = 0.003).

CONCLUSIONS

Ravenna-based data on IE showed increased disease incidence but unchanged mortality rate over 10 years of follow-up. Age remains the sole predictor of population-based mortality, irrespective of the nature of the valve, native or substitute, and the organism detected on microbiology.

Increasing clinical impact and microbiological difficulties in diagnosing coagulase-negative staphylococci in infective endocarditis - a review starting from a series of cases

Coagulase-negative staphylococci (CoNS) are an emergent aetiology of infective endocarditis (IE) on native valves in previously healthy individuals, its presence is associated with prosthetic valves or with other cardiac implants. The identification of CoNS in cultures was customarily seen as contamination, but more recent epidemiological studies have revealed an increasing number of causative and virulent new CoNS species. Starting from two clinical cases of community-acquired CoNS IE on native valves, the review debates the difficulties in identifying CoNS as the causal pathogens, comprising differentiation of contamination from infection in IE, alongside the challenges raised by antibiotic resistance. Even if the risk of CoNS IE is more increased in subjects with prosthetic materials or other foreign devices and immunodeficiencies, native valve infections with these staphylococci are increasing and should be considered important pathogens in IE. Despite the lack of sensitive and specific tools to correctly differentiate contamination from infection in CoNS endocarditis, a comprehensive evaluation with clinical and paraclinical data accurately succeeds in establishing the diagnosis. The genetic profile of CoNS predisposes to antibiotic multi-resistance, making the treatment of IE challenging; the rapid identification of antibiotic susceptibility is essential to prescribe the appropriate therapy and improve outcomes.

[Better Late than Never - Fever of Unknown Origin in a Patient with a Prosthetic Valve]

Better Late than Never - Fever of Unknown Origin in a Patient with a Prosthetic Valve Abstract. A patient presents with worsening of his general condition, chills and dyspnoea on exertion. With a history of aortic valve replacement, infective endocarditis is suspected, but due to negative imaging by transesophageal echocardiography and negative blood cultures cannot be confirmed. Finally, Cutibacterium acnes prosthetic valve endocarditis is diagnosed after culture of C. acnes during an extended incubation period of blood cultures, the presence of embolic complications and a characteristic finding on PET-CT scan.

A High Daptomycin Dose Is Associated with Better Bacterial Clearance in Infections Caused by Vancomycin-Resistant Enterococcus faecium Regardless of Daptomycin Minimum Inhibitory Concentration in a Rat Infective Endocarditis Model

A high daptomycin dose has been suggested for treating vancomycin-resistant Enterococcus faecium (VREf) infections. However, even a 12 mg/kg daptomycin dose might be insufficient for treating VREf with high daptomycin minimum inhibitory concentrations (MICs). Additionally, animal pharmacodynamic and infection models to confirm the efficacy of 12 mg/kg daptomycin are lacking. Male Wistar rats were used for pharmacokinetic profiling and for the development of an infective endocarditis (IE) model. Daptomycin-susceptible dose-dependent VREf (DSE) (MIC of 0.5 mg/L) and daptomycin nonsusceptible VREf (DNSE) (MIC of 8 mg/L) were used for the IE models. The bacterial load of vegetation was the primary outcome and was evaluated after 3 days of daptomycin treatment. Daptomycin administered subcutaneously (s.c.) at 45 and 90 mg/kg, which corresponded to maximum serum concentrations (Cmax) of 122.6 mg/L and 178.5 mg/L, respectively, was equivalent to doses of 8 mg/kg and 12 mg/kg, respectively, in humans. The Cmax/MIC value was correlated with the bacterial load of vegetation after treatment (r = -0.88, P < 0.001). The 90 mg/kg s.c. group showed a significantly lower bacterial load of vegetation (log10 CFU/g) than the 45 mg/kg s.c. group against DSE (0 versus 4.75, P < 0.001) and DNSE (5.12 versus 6.98, P = 0.002). The 90 mg/kg s.c. group did not sterilize the vegetation against DNSE. Although the human equivalent dose of 12 mg/kg daptomycin was more effective than the smaller dose in reducing the bacterial load in DSE and DNSE IE, the dose could not sterilize the vegetation during a DNSE treatment. Further treatment strategies by which to manage severe VREf infections, especially at high daptomycin MICs, are urgently needed. IMPORTANCE Using a rat IE model with pharmacokinetic analysis, the treatment response of VREf IE was found to be daptomycin dose-dependent, presented as Cmax/MIC or as the 24 h area under the concentration-time curve (AUC0-24)/MIC. Daptomycin 90 mg/kg s.c. significantly reduced the bacterial load against DSE and DNSE. It also showed significant activity against DSE and DNSE, compared to 45 mg/kg s.c. Although daptomycin 90 mg/kg can eradicate the bacterial load after 3 days of treatment against DSE, eradication cannot be achieved with 90 mg/kg daptomycin against DNSE.

Epidemiologic and clinical characteristics of infective endocarditis: a single-center retrospective study in the Bronx, New York

OBJECTIVE

There is paucity of data on the epidemiological, microbiological, and clinical characteristics of patients admitted with infective endocarditis (IE) in the Bronx, New York.

PATIENT AND METHODS

We conducted a retrospective study at Jacobi Medical Center, a tertiary care hospital in the Bronx. All adult patients who were hospitalized with a primary diagnosis of new-onset IE between January 1st, 2010 and September 30th, 2020 were included. The primary outcome was in-hospital mortality. A logistic regression model was used to identify baseline variables associated with in-hospital mortality.

RESULTS

182 patients were included in this analysis (female sex: 38.5%, median age: 54 years). 46 patients (25.3%) reported intravenous drug use. 153 patients (84.1%) had positive blood cultures. Staphylococcus aureus (S. aureus) was the most common isolated pathogen (45.1% of monomicrobial IE). Nearly half of the cases secondary to S. aureus were methicillin resistant Staphylococcus aureus (MRSA) (34/69). 164 patients (90.1%) were diagnosed with native valve IE. The mitral valve was involved in 32.4% of patients followed by the aortic valve (19.8%). The in-hospital mortality was 18.1%. The mortality was higher in the cohort 2010-2015 compared to the cohort 2016-2020 (22.1% vs 14.6%). Increasing age, MRSA IE, and active malignancy were the only variables found to have significant association with in-hospital death.

CONCLUSION

S. aureus was the most common causative agent and MRSA accounted for about half of the S. aureus IE cases. The incidence of IE in patients with intravenous drug use increased over time, while the median age decreased. The in-hospital death rate was higher in 2010-2015 compared to 2016-2020.

Sign of the Times: Updating Infective Endocarditis Diagnostic Criteria to Recognize Enterococcus faecalis as a Typical Endocarditis Bacterium

The modified Duke criteria requires that Enterococcus faecalis bacteremia must be both community-acquired and without known focus in order to be considered a microbiological "Major" diagnostic criterion in the diagnosis of infective endocarditis. We believe that the microbiological diagnostic criteria should be updated to regard E. faecalis as a "typical" endocarditis bacterium as is currently the case, for example, viridans group streptococci and Staphylococcus aureus. Using data from a prospective study of 344 patients with E. faecalis bacteremia evaluated with echocardiography, we demonstrate that designating E. faecalis as a "typical" endocarditis pathogen, regardless the place of acquisition or the portal of entry, improved the sensitivity to correctly identify definite endocarditis from 70% (modified Duke criteria) to 96% (enterococcal adjusted Duke criteria).

Pathogen Detection in Infective Endocarditis Using Targeted Metagenomics on Whole Blood and Plasma: a Prospective Pilot Study

Initial microbiologic diagnosis of infective endocarditis (IE) relies on blood cultures and Bartonella and Coxiella burnetii serology. Small case series and one prospective study have preliminarily reported application of metagenomic sequencing on blood or plasma for IE diagnosis. Here, results of a prospective pilot study evaluating targeted metagenomic sequencing (tMGS) for blood-based early pathogen detection and identification in IE are reported. Subjects diagnosed with possible or definite IE at a single institution were prospectively enrolled with informed consent from October 2020 to July 2021. Blood was drawn and separated into whole blood and plasma. Both specimen types were subjected to nucleic acid extraction and PCR targeting the V1-V3 region of the 16S ribosomal RNA gene, followed by next-generation sequencing on an Illumina MiSeqTM platform. 35 subjects, 28 (80%) with definite and 7 (20%) with possible IE were enrolled, including 6 (17%) with blood culture-negative endocarditis (BCNE). Overall, 20 whole blood (59%) and 16 plasma (47%) samples tested positive (P = 0.47). When results of whole blood and plasma testing were combined, a positive tMGS result was found in 23 subjects (66%). tMGS identified a potential pathogen in 5 of 6 culture-negative IE cases. Although further study is needed, the results of this pilot study suggest that blood-based tMGS may provide pathogen identification in subjects with IE, including in culture-negative cases.

Subtherapeutic Doses of Vancomycin Synergize with Bacteriophages for Treatment of Experimental Methicillin-Resistant Staphylococcus aureus Infective Endocarditis

Background. Recurrent therapeutic failures reported for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE) with vancomycin may be due to poor bactericidal activity. Alternative antibacterial approaches using bacteriophages may overcome this limitation. Objectives. An experimental rat model of MRSA IE (EE) was used to examine the efficacy of vancomycin combined with a 1:1 bacteriophage (phage) cocktail composed of Herelleviridae vB_SauH_2002 and Routreeviridae 66. Methods. Six hours after inoculation with ca. 5 log10 colony forming units (CFU) of MRSA strain AW7, animals were treated with either: (i) saline, (ii) an equimolar two-phage cocktail (bolus of 1 mL followed by a 0.3 mL/h continuous infusion of 10 log10 plaque forming units (PFU)/mL phage suspension), (iii) vancomycin (at a dose mimicking the kinetics in humans of 0.5 g b.i.d.), or (iv) a combination of both. Bacterial loads in vegetations, and phage loads in vegetations, liver, kidney, spleen, and blood, were measured outcomes. Results. Phage cocktail alone was unable to control the growth of strain AW7 in cardiac vegetations. However, when combined with subtherapeutic doses of vancomycin, a statistically significant decrease of ∆4.05 ± 0.94 log10 CFU/g at 24 h compared to placebo was detected (p < 0.001). The administration of vancomycin was found to significantly impact on the local concentrations of phages in the vegetations and in the organs examined. Conclusions. Lytic bacteriophages as an adjunct treatment to the standard of care antibiotics could potentially improve the management of MRSA IE. Further studies are needed to investigate the impact of antibiotics on phage replication in vivo.

A Massive Number of Extracellular Tropheryma whipplei in Infective Endocarditis: A Case Report and Literature Review

Whipple’s disease (WD) is a chronic multisystemic infection caused by Tropheryma whipplei. If this bacterium presents an intracellular localization, associated with rare diseases and without pathognomonic signs, it is often subject to a misunderstanding of its physiopathology, often a misdiagnosis or simply an oversight. Here, we report the case of a patient treated for presumed rheumatoid arthritis. Recently, this patient presented to the hospital with infectious endocarditis. After surgery and histological analysis, we discovered the presence of T. whipplei. Electron microscopy allowed us to discover an atypical bacterial organization with a very large number of bacteria present in the extracellular medium in vegetation and valvular tissue. This atypical presentation we report here might be explained by the anti-inflammatory treatment administrated for our patient’s initial diagnosis of rheumatoid arthritis.

Lessons of the month 1: Mesenteric ischaemia secondary to infective endocarditis

A 60-year-old woman presented with sudden-onset epigastric pain, vomiting and small volume rectal bleeding. She had a history of mechanical mitral valve replacement, for which she was on warfarin. Computed tomography (CT) angiography of the abdomen showed gallstones, a fluid-filled stomach and faecal loading. She subsequently deteriorated with worsening abdominal pain and haemodynamic instability. Non-contrast CT showed small bowel ischaemia and infarction. She rapidly deteriorated and a decision was made that surgery was likely to be futile. She died soon afterwards. On review of the initial CT angiography, an occlusion within the superior mesenteric artery (SMA) was visualised. The post mortem showed small bowel infarction due to embolic occlusion of the SMA secondary to bacterial endocarditis of the prosthetic mitral valve. This case should prompt awareness among clinicians that acute mesenteric ischaemia secondary to septic embolisation should be considered in patients with risk factors for infective endocarditis presenting with acute abdominal pain.

Endocarditis-TR: Diagnosis, treatment, and prognosis of the infective endocarditis patients admitting tertiary centres of Turkey

BACKGROUND

Infective endocarditis (IE) is still a significant cause of morbidity and mortality among cardiovascular diseases. ENDOCARDITIS-TR study aims to evaluate the compliance of the diagnostic and therapeutic methods being used in Turkey with current guidelines.

METHODS

The ENDOCARDITIS-TR trial is a multicentre, prospective, observational study consisting of patients admitted to tertiary centres with a definite diagnose of IE. In addition to the demographic, clinical, microbiological, and echocardiographic findings of the patients, adverse events, indications for surgery, and in-hospital mortality were recorded during a 2-year time interval.

RESULTS

A total of 208 IE patients from 7 tertiary centres in Turkey were enrolled in the study. The study population included 125 (60.1%) native valve IE (NVE), 65 (31.3%) prosthetic IE (PVIE), and 18 (8.7%) intracardiac device-related IE (CDRIE). One hundred thirty-five patients (64.9%) were culture positive, and the most frequent pathogenic agent was methicillin-susceptible Staphylococcus aureus (MSSA) (18.3%). Among 155 (74.5%) patients with an indication for surgery, only 87 (56.1%) patients underwent surgery. The all-cause mortality rate was 29.3% in-hospital follow-up. Multivariable Cox regression analysis revealed that absence of surgery when indicated (HR: 3.29 95% CI: 0.93-11.64 p = 0.05), albumin level at admission (HR: 0.46 95% CI: 0.29-0.73 P < 0.01), abscess formation (HR: 2.11 95% CI: 1.01-4.38 p = 0.04) and systemic embolism (HR: 1.78 95% CI: 1.05-3.02 p = 0.03) were ascertained independent predictors of in-hospital all-cause mortality.

DISCUSSION

The short-term results of the ENDOCARDITIS-TR trial showed the high frequency of staphylococcal IE, relatively high in-hospital mortality rates, shortage of surgical treatment despite guideline-based surgical indications and low usage of novel imaging techniques. The results of this study will provide a better insight to physicians in respect to their adherence to clinical practice guidelines.

Serologic testing for Bartonella in Manitoba, Canada, 2010-2020: a retrospective case series

BACKGROUND

Bartonella are gram-negative bacilli not identified by routine bacterial culture. The objectives of this study were to review the results of all serologic testing for Bartonella ordered in Manitoba, Canada, and to review cases with positive test results among adults to assess species identification, risk factors, clinical manifestations and outcomes.

METHODS

This retrospective study included all Bartonella serologic tests ordered in Manitoba and performed at the National Microbiology Laboratory, Winnipeg, from Jan. 1, 2010, until Dec. 31, 2020. We analyzed the aggregate data for all serologic tests for Bartonella for patients of all ages. We reviewed the charts of adult (age ≥ 18 yr) patients with serologic positivity for Bartonella who had a medical chart at 1 of Winnipeg's 2 largest hospitals (Health Sciences Centre and St. Boniface Hospital) to extract clinical and demographic data and create a case series. Descriptive statistics were performed.

RESULTS

During the study period, 1014 Bartonella serologic tests were ordered in adult and pediatric patients, of which 24 (2.4%) gave a positive result. Sixteen adults (12 men and 4 women; mean age 48 yr) seen at a participating hospital had a positive result. Molecular species-level identification occurred on explanted cardiac valves in 5 (31%) of the 16 cases; B. quintana was identified in all 5. Six patients (38%) were diagnosed with probable B. quintana infection, for a total of 11 B. quintana cases (69%); 8 (73%) of the 11 had endocarditis. Four cases of B. quintana infection (36%) were associated with rural residence. Four cases (25%) of probable B. henselae were identified; 2 patients had fever and lymphadenopathy, and 2 had endocarditis. The remaining patient was deemed to have a false-positive result as his B. henselae titre was at the threshold for positivity, his B. quintana serologic test gave a negative result, and his clinical syndrome was not suggestive of Bartonella infection. Two patients died; both had multivalvular B. quintana endocarditis with ruptured intracranial mycotic aneurysms.

INTERPRETATION

Bartonella quintana was a common cause of Bartonella serologic positivity among adults in Manitoba in 2010-2020 and was associated with endocarditis and systemic embolization. As B. quintana is transmitted by body lice, active case finding for people who lack suitable housing, both in urban and rural settings, should prioritize those with elevated Bartonella titres to receive echocardiography and detect endocarditis before systemic embolization occurs.

Legionella endocarditis: A case report and review

BACKGROUND

Legionella is a well known but infrequent cause of bacterial endocarditis.

METHODS

We report a case of endocarditis caused by Legionella spp. We reviewed previously reported cases in PubMed, Google Scholar and in references included in previous reports, and summarized relevant clinical data.

RESULTS

A 63-year-old man with a history of aortic valve replacement developed persistent fever and monoarthritis. Transesophageal echocardiography showed perivalvular abscess. He died during surgery. Blood and valve cultures were negative. Legionella spp. was demonstrated with 16S-rRNA PCR from the resected material. Twenty cases of Legionella endocarditis have been reported. Harboring a prosthetic valve was the main risk factor. Prognosis was favorable, both for patients treated with or without surgical valve replacement. Overall mortality was <10%.

CONCLUSIONS

Legionella is an infrequent cause of endocarditis. It frequently requires surgical treatment. Prognosis is good. Molecular techniques are likely to become the gold standard for diagnosis.

Infective endocarditis in patients with rheumatic heart disease: a single-centre retrospective comparative study

AIMS

We reviewed the baseline characteristics and outcomes of patients with infective endocarditis (IE) and compared those with and without rheumatic heart disease (RHD).

METHODS

We retrospectively reviewed patients ≥15 years with IE treated at Auckland City Hospital between January 2016 and December 2018 and excluded device-related IE and complex congenital heart disease. RHD status was based on echocardiographic features or previous history of rheumatic fever with valvular disease. Microbiologic and echocardiographic results, treatment modalities and complications were recorded. Demographics and outcomes were compared based on RHD status.

RESULTS

There were 155 patients with IE. Twenty-two had RHD. The mean age at admission was 45 years for RHD patients, which was 19 years younger than for non-RHD patients. There were significantly more Pacific patients with RHD (55% vs 14%). Previous IE and prosthetic valve endocarditis (PVE) were more common in RHD patients (27% vs 5%, and 77% vs 29%, respectively). After a median follow-up of 29 months, there was no significant difference in all-cause mortality between the two groups. However, 25/155 patients (16%) had died from IE-related causes (septic or cardiogenic shock post cardiac surgery, or embolic complications), with a significantly higher mortality in patients with RHD (7/22 (32%) patients, HR: 2.5) on univariate analysis. On multivariable analysis, PVE, heart failure, Staphylococcus aureus infection, diabetes, stroke and cardiac abscess were all associated with increased mortality, whereas RHD was not independently associated with increased mortality.

CONCLUSIONS

In this retrospective single-centre audit, patients with RHD experienced IE at a younger age, had a higher incidence of prosthetic valve endocarditis and a prior history of IE. Although there was no difference in all-cause mortality, mortality in patients with RHD was almost exclusively secondary to complications of IE. This highlights the need for prevention strategies against endocarditis in the RHD population, including use of antibiotic prophylaxis¬, accessible dental health care and a high clinical suspicion for IE in RHD by healthcare providers.

[How to diagnose infective endocarditis?]

We report on three patients with infective endocarditis, which differ greatly in clinical manifestations. Infective endocarditis (IE) is defined by, a mostly bacterial, infection of a native or prosthetic heart valve, the endocardial surface or a cardiac device. It is a rare condition, but it's incidence is increasing because of an increased incidence of elderly patients with chronic disease and cardiac devices. IE is heterogeneous in aetiology, clinical manifestations, and course. It can involve almost any organ system. The presentation often remains subtle and varies with nonspecific symptoms ranging from a mild infection to septic shock and multiorgan failure. IE remains a highly mortal disease, since the diagnosis is missed often. A thorough anamnesis and physical examination can be helpful. Blood cultures prior to antibiotics and echocardiography are key diagnostic steps if there's a clinical suspicion of IE.