Endocarditis due to rare and fastidious bacteria

Epidemiological Profile and Mortality of Infective Endocarditis Over the Past Decade: A Systematic Review and Meta-Analysis of 133 Studies

Infective endocarditis (IE) is an increasingly prevalent condition with relatively high mortality, whose epidemiology has become more complex with an aging population, an increased number of comorbidities, and an increasing incidence of health-care associated IE. Epidemiological data on the causative microorganisms of IE, prevalence of involvement of the different cardiac valves, and IE-associated mortality are clinically relevant. Eligible studies were identified through a systematic search of PubMed/MEDLINE database from 2010 to 2020, and a random effects model meta-analysis was conducted. 133 studies comprising 132,584 patients from six continents were included in this systematic review. The most common causative agents were Staphylococci species in 36% of cases, followed by Streptococci species (26%) and Enterococci species (10%). Out of studies that provided further speciation, the predominant species was Staphylococcus aureus with an incidence of 29%, followed by Viridans group Streptococcus (12%). The short-term mortality rate (defined as in-hospital or 30-day mortality) was 17%. The highest mortality was reported in studies from Latin America with a mean mortality rate of 33% and the lowest mortality was reported in studies from Oceania at 13%. The aortic valve was the most commonly affected valve (46%), followed closely by the mitral valve (43%). The prevalence of tricuspid valve IE was 7% and multivalvular IE occurred in 14% of cases. Our study highlights a shift in epidemiological profile of IE over the last decade with S. aureus identified as the most common causative microorganism of IE. PROTOCOL REGISTRATION: PROSPERO CRD42024602342.

Navigating diagnostic challenges in Bartonella-induced infective endocarditis: a case report

BACKGROUND

Blood culture-negative infective endocarditis presents a significant clinical and diagnostic challenge owing to its atypical presentation and difficulty in identifying causative pathogens. Bartonella henselae, a rare cause of blood culture-negative infective endocarditis, can further complicate its diagnosis and treatment.

CASE PRESENTATION

This case report describes the intricate diagnostic journey and therapeutic challenges encountered in a 65-year-old Tunisian female diagnosed with Bartonella henselae-induced infective endocarditis. The patient presented with symptoms of general weakness, weight loss, arthralgia, and a 2-month history of fever along with hepatic involvement characterized by cholestasis and portal hypertension. Despite initial empirical antibiotic therapy leading to temporary improvement, the patient experienced relapse, prompting further investigation. Positive serological tests for Bartonella henselae guided the initiation of targeted antibiotic therapy with rifampin and doxycycline, which resulted in significant clinical improvement. However, the subsequent acute pulmonary edema revealed severe triple-vessel coronary disease, necessitating aortic valve replacement surgery and coronary artery bypass grafting. The patient recovered well postoperatively, with cultures from the aortic valve confirming Bartonella henselae infection.

CONCLUSIONS

This report underscores the importance of heightened awareness, comprehensive diagnostic imaging, and careful consideration of treatment strategies in patients with atypical infective endocarditis. This highlights the need for the early suspicion and identification of Bartonella henselae in BCNIE cases, particularly in patients with relevant epidemiological exposure.

Advances and Challenges in Aeromonas hydrophila Vaccine Development: Immunological Insights and Future Perspectives

Aeromonas hydrophila presents a significant threat to global aquaculture due to its ability to infect freshwater and marine fish species, leading to substantial economic losses. Effective mitigation methods are essential to address these challenges. Vaccination has emerged as a promising strategy to reduce A. hydrophila infections; however, it faces several obstacles, including variability in immune responses, pathogen diversity, and environmental factors affecting vaccine efficacy. To enhance vaccine performance, researchers focus on adjuvants to boost immune responses and develop multivalent vaccines targeting multiple A. hydrophila strains. Tailoring vaccines to specific environmental conditions and optimizing vaccination schedules can further address the challenges posed by pathogen diversity and variable immune responses. This review provides an in-depth analysis of the immunological hurdles associated with A. hydrophila vaccine development. Current vaccine types-live attenuated, inactivated, subunit, recombinant, and DNA-exhibit diverse mechanisms for stimulating innate and adaptive immunity, with varying levels of success. Key focus areas include the potential of advanced adjuvants and nanoparticle delivery systems to overcome existing barriers. The review also highlights the importance of understanding host-pathogen interactions in guiding the development of more targeted and effective immune responses in fish. Complementary approaches, such as immunostimulants, probiotics, and plant-based extracts, are explored as adjuncts to vaccination in aquaculture health management. Despite notable progress, challenges remain in translating laboratory innovations into scalable, cost-effective solutions for aquaculture. Future directions emphasize the integration of advanced genomic and proteomic tools to identify novel antigen candidates and the need for industry-wide collaborations to standardize vaccine production and delivery. Addressing these challenges can unlock the potential of innovative vaccine technologies to safeguard fish health and promote sustainable aquaculture practices globally.

A case of stroke as a unique sign of subclinical infective endocarditis by Abiotrophia defectiva: a case report

PURPOSE

Here we describe a patient admitted for a stroke that was unexpectedly correlated with subclinical infective endocarditis attributable to a rarely opportunistic pathogen, Abiotrophia defectiva.

CASE REPORT

A 75-year-old man presented with a stroke. Transesophageal echocardiography suggested vegetation on all aortic valve cusps, despite the absence of clinical or laboratory signs of infection. Surprisingly, three sets of blood cultures collected without fever were positive for A. defectiva. Although the patient did not exhibit classic signs of infection during hospitalization, the severity of the valve condition necessitated replacement with a bioprosthesis.

CONCLUSIONS

This clinical case underscores the importance of investigating the infective origin of endocarditis, even in the absence of clinical or laboratory evidence. Physicians should maintain a high level of suspicion, especially in patients with highly suggestive anamnestic characteristics.

Molecular investigation of Coxiella burnetii and Bartonella in heart valve specimens of patients with endocarditis in Iran

BACKGROUND

Infective endocarditis (IE), is a medical condition that threatens human health. The aim of this study is the molecular investigation of Coxiella burnetii and Bartonella spp. in heart valves in Iran.

METHODS

In this study, 146 patients with pathological evidence of IE and underwent heart valve surgery between 2016 and 2020 were selected. Furthermore, positive samples for C. burnetii were genotyped by the Multi Spacers Typing (MST) method, and positive samples for Bartonella were sequenced on the 16SrRNA gene.

RESULTS

12 patients (8.2 %) were identified as positive cases of C. burnetii, and two novel genotypes of C. burnetii were identified using MST genotyping. Additionally, 15 patients (10.3 %) were diagnosed with Bartonella endocarditis, and all positive cases were identified as Bartonella quintana.

CONCLUSION

According to the identification of positive cases of Q fever endocarditis and Bartonella endocarditis, future studies in this field are suggested to focus on elucidating methods of prevention, diagnosis and treatment.

Oxidative Stress in Aortic Valves Associated with Infective Endocarditis: A Report on Three Cases

Background/Objectives: Infective endocarditis (IE) most commonly results from infections by Gram-positive bacteria, and, in this condition, the redox homeostasis is lost due to the overproduction of H2O2, leading to the overstimulation of the immune system and the upregulation of the production of proinflammatory cytokines. The aim of this study was to evaluate the levels of oxidative biomarkers and the enzymatic and non-enzymatic antioxidant systems in subjects with IE. Methods: The study included three cases with IE that had undergone aortic valve replacement (AVR) surgery that was complicated by IE, comparing them with subjects with AVR without IE. We determined the malondialdehyde (MDA), total antioxidant capacity (TAC), carbonyl group concentration, glutathione (GSH), thiols and the nitrate/nitrite ratio (NO3-/NO2-) in homogenized tissue from the cardiac valves. We also measured the activity of glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) and thioredoxin reductase (TrxR). The superoxide dismutase (SOD) isoforms and peroxidase activity were determined using native gels. Results: There were increases in the activity of antioxidant enzymes such as GST, SOD isoforms and peroxidases (p ≤ 0.01) and decreases in oxidative stress markers such as GSH (p = 0.05); meanwhile, MDA and carbonylation were increased (p ≤ 0.05). Conclusions: The results suggest that bacterial infections favor oxidative stress in the aortic valves, which increases the SOD isoforms and peroxidase activity. This contributes to the loss of the intricate redox homeostasis system in patients with IE, causing a positive feedback loop in the oxidative background that results in damage to the heart, likely leading to a fatal outcome.

Microbial interactions impact stress tolerance in a model oral community

Understanding the molecular mechanisms governing microbial interactions is crucial for unraveling the complexities of microbial communities and their ecological impacts. Here, we employed a two-species model system comprising the oral bacteria Aggregatibacter actinomycetemcomitans and Streptococcus gordonii to investigate how synergistic and antagonistic interactions between microbes impact their resilience to environmental change and invasion by other microbes. We used an in vitro colony biofilm model and focused on two S. gordonii-produced extracellular molecules, L-lactate and H2O2, which are known to impact fitness of this dual-species community. While the ability of A. actinomycetemcomitans to cross-feed on S. gordonii-produced L-lactate enhanced its fitness during co-culture, this function showed little impact on the ability of co-cultures to resist environmental change. In fact, the ability of A. actinomycetemcomitans to catabolize L-lactate may be detrimental in the presence of tetracycline, highlighting the complexity of interactions under antimicrobial stress. Furthermore, H2O2, known for its antimicrobial properties, had negative impacts on both species in our model system. However, H2O2 production by S. gordonii enhanced A. actinomycetemcomitans tolerance to tetracycline, suggesting a protective role under antibiotic pressure. Finally, S. gordonii significantly inhibited the bacterium Serratia marcescens from invading in vitro biofilms, but this inhibition was lost during co-culture with A. actinomycetemcomitans and in a murine abscess model, where S. gordonii actually promoted S. marcescens invasion. These data indicate that microbial interactions can impact fitness of a bacterial community upon exposure to stresses, but these impacts are highly environment dependent.

IMPORTANCE

Microbial interactions are critical modulators of the emergence of microbial communities and their functions. However, how these interactions impact the fitness of microbes in established communities upon exposure to environmental stresses is poorly understood. Here, we utilized a two-species community consisting of Aggregatibacter actinomycetemcomitans and Streptococcus gordonii to examine the impact of synergistic and antagonistic interactions on microbial resilience to environmental fluctuations and susceptibility to microbial invasion. We focused on the S. gordonii-produced extracellular molecules, L-lactate and H2O2, which have been shown to mediate interactions between these two microbes. We discovered that seemingly beneficial functions, such as A. actinomycetemcomitans cross-feeding on S. gordonii-produced L-Lactate, can paradoxically exacerbate vulnerabilities, such as susceptibility to antibiotics. Moreover, our data highlight the context-dependent nature of microbial interactions, emphasizing that a seemingly potent antimicrobial, such as H2O2, can have both synergistic and antagonistic effects on a microbial community dependent on the environment.

Granulicatella adiacens Bacterial Infection After Pancreatectomy Whipple's Procedure

Background: Granulicatella adiacens inhabits the oral cavity, urogenital, and gastrointestinal tracts and is a typical commensal of human mucosal surfaces. It rarely causes disease. Identification of these gram-positive cocci can be challenging. Case Report: In a 58-year-old male in an oncology center, we report the first occurrence of bacterial infection caused by G. adiacens. After a precise diagnosis of the infection, the patient received effective treatment. Conclusion: Owing to a lack of sufficient diagnostic tools, G. adiacens may be a more notable pathogen than has been previously identified. Sensitivity testing standards are desperately needed.

Epidemiology, clinical characteristics, and outcome of infective endocarditis due to Abiotrophia and Granulicatella in a Tertiary Hospital in China, 2015-2023: a retrospective study

BACKGROUND

Abiotrophia (ABI) and Granulicatella (GRA) are rare causative pathogens in infective endocarditis (IE). This study aims to describe the epidemiology, clinical characteristics, and outcome of ABI/GRA-IE. The main features of ABI/GRA-IE were compared with Viridans group streptococci (VGS) IE.

METHODS

From January 2015 to December 2023, a total of 1531 definite IE in Zhongshan Hospital, Fudan University, Shanghai, China were retrospectively enrolled in this study. Clinical and laboratory data were collected.

RESULTS

Forty-five ABI/GRA-IE cases were identified, representing 2.9% of all IE cases in Zhongshan Hospital between 2015 and 2023, compared to 20.1% of VGS-IE. ABI and GRA IE shared similar clinical characteristics. Congenital valvulopathy was reported in 21 (46.7%) ABI/GRA-IE and 85 (28.8%) VGS-IE (P = 0.025). Pulmonary valve was more frequently affected in ABI/GRA-IE (6 [13.3%]) than VGS-IE (7 [2.4%]) (P = 0.002). Congestive heart failure was observed in 30 (66.7%) ABI/GRA-IE and 103 (34.9%) VGS-IE (P < 0.001). Systemic embolization excluding central nervous system (CNS) occurred in 13 (28.9%) ABI/GRA-IE and 39 (13.2%) VGS-IE (P = 0.012). In-hospital mortality was reported as 4.4% in ABI/GRA-IE and 3.7% in VGS-IE (P = 0.854).

CONCLUSION

GRA/ABI-IE was approximately one-seventh as prevalent as VGS-IE. Congestive heart failure and systemic embolization (excluding CNS) were more frequent in GRA/ABI-IE compared to VGS-IE. Mortality of ABI/GRA-IE in this study was comparable to that of VGS-IE and lower than previously reported results.

Epidemiology and treatment of invasive Bartonella spp. infections in the United States

OBJECTIVES

Bartonella spp., renowned for cat-scratch disease, has limited reports of dissemination. Tissue and blood cultures have limitations in detecting this fastidious pathogen. Molecular testing (polymerase chain reaction, PCR) and cell-free DNA have provided an avenue for diagnoses. This retrospective observational multicenter study describes the incidence of disseminated Bartonella spp. and treatment-related outcomes.

METHODS

Inclusion criteria were diagnosis of bartonellosis via diagnosis code, serology testing of blood, polymerase chain reaction (PCR) of blood, 16/18S tests of blood or tissue, cultures of blood or tissue, or cell-free DNA of blood or tissue from January 1, 2014, through September 1, 2021. Exclusions were patients who did not receive treatment, insufficient data on treatment course, absence of dissemination, or retinitis as dissemination.

RESULTS

Patients were primarily male (n = 25, 61.0%), white (n = 28, 68.3%), with mean age of 50 years (SD 14.4), and mean Charlson comorbidity index of 3.5 (SD 2.1). Diagnosis was primarily by serology (n = 34, 82.9%), with Bartonella henselae (n = 40, 97.6%) as the causative pathogen. Treatment was principally doxycycline with rifampin (n = 17, 41.5%). Treatment failure occurred in 16 (39.0%) patients, due to escalation of therapy during treatment (n = 5, 31.3%) or discontinuation of therapy due to an adverse event or tolerability (n = 5, 31.3%).

CONCLUSIONS

In conclusion, this is the largest United States-based cohort of disseminated Bartonella spp. infections to date with a reported 39% treatment failure. This adds to literature supporting obtaining multiple diagnostic tests when Bartonella is suspected and describes treatment options.

Infective endocarditis

First described more than 350 years ago, infective endocarditis represents a global health concern characterised by infections affecting the native or prosthetic heart valves, the mural endocardium, a septal defect, or an indwelling cardiac device. Over recent decades, shifts in causation and epidemiology have been observed. Echocardiography remains pivotal in the diagnosis of infective endocarditis, with alternative imaging modalities gaining significance. Multidisciplinary management requiring expertise of cardiologists, cardiovascular surgeons, infectious disease specialists, microbiologists, radiologists and neurologists, is imperative. Current recommendations for clinical management often rely on observational studies, given the limited number of well conducted randomised controlled trials studying infective endocarditis due to the rarity of the disease. In this Seminar, we provide a comprehensive overview of optimal clinical practices in infective endocarditis, highlighting key aspects of pathophysiology, pathogens, diagnosis, management, prevention, and multidisciplinary approaches, providing updates on recent research findings and addressing remaining controversies in diagnostic accuracy, prevention strategies, and optimal treatment.

Intraoperative Polymerase Chain Reaction from Cardiac Valve Tissue Is Beneficial for Guiding Further Therapy in Patients with Infective Endocarditis

Background: Infectious endocarditis (IE) remains a critical condition despite all the medical advances in recent decades. Reliable pathogen identification is indispensable for precise therapy. The aim of this study was to evaluate the diagnostic and therapeutic benefit of additional polymerase chain reaction (PCR) in comparison with microbiological culture alone based on intraoperative tissue sampling for patients operated on due to IE. Methods: A total of 224 patients diagnosed with acute or subacute IE were analyzed. Intraoperatively resected infectious tissue was analyzed using both PCR and microbiological culture. Subsequently, the results of the detection of bacteria obtained based on intraoperative measurements from tissue via culture and PCR were compared with preoperative blood culture results. Furthermore, we evaluated the therapeutic impact of the culture and/or PCR results obtained from cardiac tissue. Results: The 224 patients were 63 ± 17 years old, and 64 (29%) were female. In total, 149 (67%) suffered from aortic valve endocarditis, 45 (45%) had mitral valve endocarditis, and 39 (18%) were afflicted with double-valve endocarditis. Prosthetic valve endocarditis was present in 70 (31%) patients. Pathogens were detected in 70% of the cases analyzed via PCR using cardiac valve tissue and in 25% of those analyzed via a culture of cardiac valve tissue; this figure was only 64% for preoperative blood culture. Overall, a pathogen was identified in 197 patients (88%), leading to antibiotic therapy. Targeted antibiotic therapy, based on the PCR results, was carried out in 37 cases and was conducted based on a culture from cardiac valve tissue in three cases. Finally, in 12% of patients, the causative pathogen remained unclear. Conclusions: For patients suffering endocarditis, PCR analysis is indispensable and superior to preoperative blood culture and intraoperative culture in detecting bacteria. Based on PCR testing, antibiotic therapy can be individually adjusted. The high precision of pathogen identification may lead to a significant reduction in IE-associated morbidity and mortality.

Biologic and genomic characterization of a novel virulent Aeromonas hydrophila phage phiA051, with high homology to prophages

Introduction

Aeromonas hydrophila is particularly harmful to freshwater aquaculture, and the search for phage is an effective biological control method, but reports of possible temperate phages and their mutants are rare in this field. In this study, a virulent phage highly homologous to prophage in the genomes of A. hydrophila was collected and preliminary biological characterization was carried out to understand its nature.

Materials and methods

Water samples taken from eel ponds in Fujian, China were combined with the strain. Spot test method and double-layer agar plate assay was used for confirmation and purification. Phage virions were observed using transmission electron microscope. A total of 68 strains of Aeromonas spp. were used to determine the host range. MOI groups of 1,000, 100, 10, 1, 0.1, 0.01, 0.001, 0.0001, 0.00001 were prepared to detect the optimal MOI. The conditions of thermal stability assay were set as 30, 40, 50, 60, 70 and 80°C for 1 h, respectively, and conditions of acid and alkali stability assay were set as 2.0, 4.0, 6.0, 8.0, 10.0 and 12.0 of pH. MOI of 0.01 and 0.1, respectively, are set to determine the inhibitory capacity of phage.

Results

A novel virulent A. hydrophila phage designated phiA051 has been isolated from aquaculture water. Electron microscopic observation showed that the phage phiA051 was composed of an icosahedral capsid. The phage phiA051 possesses an optimal multiplicity of infection (MOI) of 0.01, and its burst size was 108 PFU/cell. The phage maintained a high viability at temperatures of 30-50°C or pH 6.0-10.0 for 1  h. Phage phiA051 has certain potentials in rapidly inhibiting the spread of pathogen early in the outbreak, and it has a linear dsDNA with GC content of 60.55% and a total length of 32,212  bp, including 46 ORFs.

Discussion

The phage phiA051 behaved as a virulent phage. However, the BLASTN result showed that 23 of the top 25 hits were genomes of Aeromonas strains. It was suggested that phiA051 was probably derived from some prophage in the chromosome of Aeromonas. Further investigation of the mechanism how phage phiA051 transforms from a temperate phage to a virulent phage will provide a unique perspective and idea to explore the potential of prophages.

Epidemiology, outcomes and prognosis of infective endocarditis in Northern Morocco

INTRODUCTION

Infective endocarditis is a rare but potentially severe disease, associated with significant morbidity and mortality. Our study aims to describe the epidemiology and management aspects of endocarditis in northern Morocco and compare it with international management guidelines.

MATERIALS AND METHODS

This is a retrospective study involving all patients hospitalized in the cardiology department of the University Hospital of Tangier for infective endocarditis over a period of 4 years and 7 months, from May 2019 to February 2024.

RESULTS

Eighty patients were hospitalized for IE during the study period. The average age of the patients was 46 years, with an even sex ratio. IE concerned native valves in 77% of cases, mechanical prostheses in 19% of cases, and on bio prostheses in 4%. The average diagnostic delay was 25 days. Blood cultures were negative in 59% of cases. The predominant infective microorganism was the bacteria Staphylococcus (65.6%). Imaging results showed vegetations in 76.3% of cases, predominantly on the mitral valve (39.3%), followed by the aortic valve (21.3%). The main complications included heart failure (51.2%), peripheral arterial embolisms (22.5%) and splenic infarction (17.5%). Management wise, the most commonly used antibiotic therapy was a combination of ceftriaxone and gentamicin. Clinical and biological improvement was observed in 70% of cases, with a mortality rate of 12.5%. Twelve patients underwent surgery (15%). Urgent surgery was indicated in 66,7% of the operated patients.

CONCLUSION

Our study highlights the challenges in managing infective endocarditis in northern Morocco. The prognosis of infective endocarditis can be improved through multidisciplinary management within the implementation of an Endocarditis Team.

Infective Endocarditis Caused by Neisseria Sicca Species 10 Years After Mechanical Aortic Valve Implantation

We report a rare case of mechanical aortic valve infective endocarditis caused by Neisseria sicca. A 44-year-old man, with a history of aortic valve replacement, presented to the hospital with a 10-day history of fever. Investigations revealed that the blood cultures grew Neisseria sicca. Although the transthoracic echocardiogram (TTE) was negative, a transesophageal echocardiogram showed a 0.5 cm × 0.3 cm piece of vegetation attached to the aortic valve. After eight weeks of therapy, according to the antibiotic susceptibility test, the patient's blood cultures were negative, and repeat TTE showed no vegetation. This report can offer valuable insights for clinical diagnosis and treatment of Neisseria sicca endocarditis, particularly when selecting sensitive antibiotics.

Novel Qnr Families as Conserved and Intrinsic Quinolone Resistance Determinants in Aeromonas spp

The environment has been identified as an origin, reservoir, and transmission route of antibiotic resistance genes (ARGs). Among diverse environments, freshwater environments have been recognized as pivotal in the transmission of ARGs between opportunistic pathogens and autochthonous bacteria such as Aeromonas spp. In this study, five environmental strains of Aeromonas spp. exhibiting multidrug resistance (MDR) were selected for whole-genome sequencing to ascertain their taxonomic assignment at the species-level and to delineate their ARG repertoires. Analyses of their genomes revealed the presence of one protein almost identical to AhQnr (A. hydrophila Qnr protein) and four novel proteins similar to AhQnr. To scrutinize the classification and taxonomic distribution of these proteins, all Aeromonas genomes deposited in the NCBI RefSeq genome database (1,222 genomes) were investigated. This revealed that these Aeromonas Qnr (AQnr) proteins are conserved intrinsic resistance determinants of the genus, exhibiting species-specific diversity. Additionally, structure prediction and analysis of contribution to quinolone resistance by AQnr proteins of the isolates, confirmed their functionality as quinolone resistance determinants. Given the origin of mobile qnr genes from aquatic bacteria and the crucial role of Aeromonas spp. in ARG dissemination in aquatic environments, a thorough understanding and strict surveillance of AQnr families prior to the clinical emergence are imperative. In this study, using comparative genome analyses and functional characterization of AQnr proteins in the genus Aeromonas, novel Aeromonas ARGs requiring surveillance has suggested.

Abiotrophia defectiva Endocarditis: A Case Diagnosed Incidentally Due to Multi-organ Embolism

Abiotrophia defectiva, often referred to as nutritionally variant streptococci, is generally a benign part of human microflora, primarily found in the oral cavity, digestive tract, and genitourinary system. However, it can have a significant role in infectious endocarditis (IE). We discuss a case involving a 53-year-old male who displayed serious signs indicative of IE. The individual, who had a history of IgA nephropathy, underwent successful surgical and antibiotic intervention. Given the challenge in treating A. defectiva due to its high antibiotic resistance and the tendency for embolic events and treatment failure, a multidimensional approach involving surgical intervention and specific antibiotic therapy resulted in a successful outcome. This case underlines the need for early identification, immediate treatment, and additional research to understand better and manage A. defectiva endocarditis.

An unusual presentation of subacute Haemophilus parainfluenzae endocarditis in a low-risk woman treated by minimally invasive mitral valve repair: a case report

BACKGROUND

HACEK endocarditis is usually insidious and can often be difficult to diagnose due to the slow-growing nature of the organisms. This report presents our experience in treating a patient with Haemophilus parainfluenzae endocarditis.

CASE PRESENTATION

We describe the case of a previously fit and well 23 year-old woman who presented to her local emergency department with a four-week history of persistent febrile illness. She had associated nausea, vomiting, and lethargy. This was preceded by an episode of mucopurulent rhinorrhoea. She was treated empirically with oral amoxicillin for a putative diagnosis of rhinosinusitis. Initially, her symptoms abated, however, she was readmitted with high fevers and a new pansystolic murmur. Transthoracic echocardiography revealed a large, mobile, echogenic mass, tethered to the posterior mitral valve leaflet (PMVL) and mild mitral regurgitation (MR). On examination, she had multiple non-tender, erythematous macules on the plantar surface of her feet, consistent with Janeway lesions. Two separate blood cultures grew H. parainfluenzae. Infectious diseases recommended a four-week course of intravenous ceftriaxone. Transesophageal echocardiography demonstrated a perforation within the P3 segment of the PMVL. Subsequently, the patient underwent mitral valve repair surgery with an uneventful recovery.

CONCLUSIONS

Our case highlights the importance of promptly diagnosing HACEK endocarditis. A prolonged course of antibiotic therapy can be lifesaving, and surgery is often necessary to address complications such as perforation within the mitral valve leaflets. In our patient, we were able to perform a sliding P2 leaflet plasty for good quality repair of the mitral valve, through a minimally invasive right anterior thoracotomy.

Uncommon pathogens causing infective endocarditis

Infective endocarditis is caused by a wide range of aetiological agents. The microbiology, epidemiology, and treatment of this disease have changed considerably in the last two decades. Staphylococci and streptococci are known to be the classical causative agents; however, blood culture-negative endocarditis caused by fastidious and slow-growing organisms is now common. The list of uncommon pathogens causing endocarditis has expanded in recent years. This is a narrative literature review of the aetiological agents of endocarditis that are rarely encountered in clinical practice, their epidemiology, the characteristics of these pathogens, the clinical presentations of the cases, and their management.

Pediococcus pentosaceus Endocarditis in a Patient With Recent Transcatheter Aortic Valve Implantation and Liver Cirrhosis: A Case Report and Review of the Literature

Transcatheter aortic valve implantation (TAVI) is increasingly being used in the management of severe aortic stenosis, mainly in older and/or medically compromised patients, due to its minimally invasive nature. As in any valve replacement procedure, endocarditis is a recognized complication, more so in TAVI patients, in whom comorbidities are highly prevalent. We report the case of a 70-year-old male with a history of liver cirrhosis and a recent TAVI, who presented with recurrent fever and sustainedPediococcus pentosaceus bacteremia. The diagnosis of endocarditis was delayed, as the microorganism was initially discarded as a contaminant, given that Pediococci are rarely described as human pathogens. However, in cirrhotic patients, microbiota may cause intermittent bacteremia and thereby affect prosthetic valves. Transthoracic echocardiography was not helpful in validating the diagnosis, as is often the case in TAVI patients. Transesophageal echocardiography was deemed perilous, due to esophageal varices complicating the underlying cirrhosis. Therefore, endocarditis diagnosis was based on sustained bacteremia and Duke's criteria, including the presence of high fever, a predisposing cardiac lesion, splenic infarction, and the exclusion of an alternative diagnosis. Moreover, cirrhosis enhanced the side effects of treatment and led to the need for regimen changes and prolonged hospitalization. Given the precariousness of the situation, confirmation of treatment success by 2-deoxy-2-[fluorine-18]fluoro-D-glucose positron emission tomography-computed tomography (18F-FDG PET-CT) scan was sought. This is the first reported case of Pediococcus TAVI endocarditis in a cirrhotic patient, highlighting the unique challenges in the diagnosis and management of TAVI endocarditis in patients with co-existing conditions.

From Shadows to Spotlight: Enhancing Bacterial DNA Detection in Blood Samples through Cutting-Edge Molecular Pre-Amplification

One of the greatest challenges to the use of molecular methods for diagnostic purposes is the detection of target DNA that is present only in low concentrations. One major factor that negatively impacts accuracy, diagnostic sensitivity, and specificity is the sample matrix, which hinders the attainment of the required detection limit due to the presence of residual background DNA. To address this issue, various methods have been developed to enhance sensitivity through targeted pre-amplification of marker sequences. Diagnostic sensitivity to the single molecular level is critical, particularly when identifying bloodstream infections. In cases of clinically manifest sepsis, the concentration of bacteria in the blood may reach as low as one bacterial cell/CFU per mL of blood. Therefore, it is crucial to achieve the highest level of sensitivity for accurate detection. In the present study, we have established a method that fills the analytical gap between low concentrations of molecular markers and the minimum requirements for molecular testing. For this purpose, a sample preparation of whole blood samples with a directly downstream pre-amplification was developed, which amplifies specific species and resistance markers in a multiplex procedure. When applying pre-amplification techniques, the sensitivity of the pathogen detection in whole blood samples was up to 100 times higher than in non-pre-amplified samples. The method was tested with blood samples that were spiked with several Gram-positive and Gram-negative bacterial pathogens. By applying this method to artificial spiked blood samples, it was possible to demonstrate a sensitivity of 1 colony-forming unit (CFU) per millilitre of blood for S. aureus and E. faecium. A detection limit of 28 and 383 CFU per ml of blood was achieved for E. coli and K. pneumoniae, respectively. If the sensitivity is also confirmed for real clinical blood samples from septic patients, the novel technique can be used for pathogen detection without cultivation, which might help to accelerate diagnostics and, thus, to decrease sepsis mortality rates.

Culture-negative endocarditis with multifocal spread and flail mitral valve leaflet: a case report

Introduction

Blood culture-negative infective endocarditis is the condition in which a causative organism cannot be identified after inoculation of at least three samples using standard blood-culture systems for 7 days. It has a low reported incidence of about 2.5-31%. Causes may be infectious or non-infectious; use of prior antibiotic therapy is usually the leading factor.

Case presentation

The authors present a case of true culture-negative endocarditis involving the mitral valve, with multiple foci of spread including brain, spleen, liver, and Intervertebral disc, which remained persistent despite treatment with intravenous broad-spectrum antibiotics on an inpatient and outpatient basis but eventually improved after upgrading alternative broad-spectrum antibiotic for an extended duration. The patient had complications in the form of a flail mitral valve with persistent mitral regurgitation, requiring mitra-clip placement.

Discussion

Positive blood culture is one of the major diagnostic criteria to establish infective endocarditis. Patients may have persistent negative cultures due to previous antibiotic use, the presence of fastidious organisms, or the use of inappropriate techniques or media. Involvement of a multidisciplinary team, use of multimodal investigations, and appropriate antibiotic stewardship are crucial. Extended duration of treatment and upgrading antibiotics can be helpful next steps in highly suspicious cases. With multifocal spread as in our case, it further becomes challenging to control and treat the infection as it is frequently connected with higher morbidity and mortality.

Conclusion

Blood culture-negative endocarditis is an entity that can present with early complications. It is diagnostically and therapeutically challenging to treat such patients. Multimodal approaches for early diagnosis and appropriate treatment are crucial owing to its high morbidity and mortality.

Infective endocarditis caused by Gemella haemolysans in a patient with bicuspid aortic valve: A case report

Gemella haemolysans is a gram-positive coccus, and commensal of the upper respiratory tract and oral mucosa. In rare cases, it has been identified as an opportunistic pathogen in the development of endocarditis. Here, we describe a case of Gemella haemolysans endocarditis in a patient with bicuspid aortic valve. A 14-year-old male presented to our hospital with a 1-month history of intermittent fever. Gemella haemolysans was isolated from the patient's blood cultures. Transesophageal echocardiography revealed severe aortic stenosis and a pseudoaneurysm of the mitral-aortic intervalvular fibrosa. The patient underwent aortic valve replacement with pseudoaneurysm of the mitral-aortic intervalvular fibrosa repair and remained symptom-free during follow-up. This case highlights the importance of considering atypical pathogens as causative agents of infective endocarditis.

A Dual-Pathogen Mitral Valve Endocarditis Caused by Coxiella burnetii and Streptococcus gordonii-Which Came First?

Infective endocarditis (IE) is still a life-threatening disease with high morbidity and mortality. While usually caused by a single bacterium, poly-microbial infective endocarditis (IE) is rare. Here, we report a (blood-culture-negative) dual pathogen mitral valve IE caused by Coxiella burnetii and Streptococcus gordonii: A 53-year-old woman was presented to an internal medicine department with abdominal pain for further evaluation. Within the diagnostic work up, transthoracic echocardiography (TTE) revealed an irregularly shaped echogenic mass (5 × 13 mm) adherent to the edge of the posterior mitral valve leaflet and protruding into the left atrium. As infected endocarditis was suspected, blood cultures were initially obtained, but they remained negative. Chronic Q fever infection was diagnosed using serologic testing. After the occurrence of cerebral thromboembolic events, the patient was admitted for mitral valve surgery. Intraoperatively, a massively destructed mitral valve with adhering vegetations was noted. Examination of the mitral valve by broad-range bacterial polymerase chain reaction (PCR) and amplicon sequencing confirmed Coxiella burnetii infection and yielded Streptococcus gordonii as the second pathogen. Based on the detailed diagnosis, appropriate antibiotic therapy of both pathogens was initiated, and the patient could be discharged uneventfully on the 11th postoperative day after a successful minimal-invasive mitral valve replacement.

Case series of 12 Bartonella quintana endocarditis from the Southwest Indian Ocean

BACKGROUND

Bartonella spp. are fastidious bacteria frequently identified as the cause of blood culture-negative (BCN) endocarditis. However, Bartonella infections are difficult to diagnose in routine laboratory testing and their incidence is probably underestimated. We investigated the epidemiological and clinical features of Bartonella endocarditis cases diagnosed between 2009 and 2021 on Reunion Island (Southwest Indian Ocean).

METHOD

We retrospectively included all patients diagnosed with Bartonella endocarditis at Reunion Island University Hospital during this period. Endocarditis was diagnosed on the basis of microbiological findings, including serological tests (IFA) and PCR on cardiac valves, and the modified Duke criteria. We used then the multispacer typing (MST) method to genotype the available Bartonella strains.

FINDINGS

We report 12 cases of B. quintana endocarditis on Reunion Island (83.3% in men, median patient age: 32 years). All the patients originated from the Comoros archipelago. The traditional risk factors for B. quintana infection (homelessness, alcoholism, exposure to body lice) were absent in all but two of the patients, who reported head louse infestations in childhood. Previous heart disease leading to valve dysfunction was recorded in 50% of patients. All patients underwent cardiac valve surgery and antimicrobial therapy with a regimen including doxycycline. All patients presented high C-reactive protein concentrations, anemia and negative blood cultures. The titer of IgG antibodies against Bartonella sp. exceeded 1:800 in 42% of patients. Specific PCR on cardiac valves confirmed the diagnosis of B. quintana endocarditis in all patients. Genotyping by the MST method was performed on four strains detected in preserved excised valves and was contributive for three, which displayed the MST6 genotype.

CONCLUSIONS

Bartonella quintana is an important cause of infective endocarditis in the Comoros archipelago and should be suspected in patients with mitral valve dysfunction and BCN from this area.

Occult deterioration of an aortic annular abscess: how do we diagnose a pseudoaneurysm periaortic valve? A case report

BACKGROUND

Infectious endocarditis (IE) is a disease caused by the colonization of toxic microorganisms on the endocardium of heart valves [1]. Although much progress has been made in the diagnosis and treatment of IE, its complications, such as annular abscesses [2], still have a high mortality rate. In this case, we describe a patient with infective endocarditis complicated by occult deteriorated aortic annular abscess.

CASE PRESENTATION

A 44-year-old man was admitted due to weakness of his right limbs and unclear speech for 10 h. He had recurrent fevers for 1 month before admission. Transthoracic echocardiography showed a mix-echoic vegetation attached to the bicuspid aortic valve, moderate aortic regurgitation and a possible aortic annular abscess. Blood cultures were negative and empiric antibiotic therapy was begun. The patient did not have fever again and seem to be clinically improved. However, follow-up transesophageal echocardiography revealed a large periaortic abscess led to aortic sinus pseudoaneurysm. The patient underwent mechanical prosthetic valve replacement and annulus reconstruction successfully. Perivalvular abscess may be insidious deterioration in patients who seem to be clinically improved, which requires us to pay more attention.

DISCUSSION

Occult deterioration of an aortic annular abscess is rare and more attention should be paid. Re-evaluation of echocardiography is required even if the patient's symptoms improve.

Updates in Culture-Negative Endocarditis

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

Contribution of Positron Emission Tomography-Computed Tomography (PET/CT) to the Diagnosis of Endocarditis Due to an Infected Pacemaker Associated With Spondylodiscitis

The incidence of cardiac device-related endocarditis (CDRIE) is increasing, and its diagnosis and treatment may occasionally be problematic. Echocardiography is important for its diagnosis, and 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET/CT) may also be useful as a diagnostic procedure. A case of CDRIE due to an infected pacemaker is presented. In this case, blood cultures were repeatedly negative, and transesophageal ultrasound examination did not reveal signs of the disease. However, PET/CT revealed the infection. The causative organism was Corynebacterium spp, and this was finally identified by polymerase chain reaction of a sample of the device material. Eight weeks before the development of CDRIE symptoms, the patient had been empirically treated for spondylodiscitis caused by a non-identified organism. CDRIE and spondylodiscitis are closely associated infections. The present case of CDRIE was treated successfully with six weeks of combination antimicrobial treatment. PET/CT may contribute to CDRIE diagnosis by locating the site(s) of the infection, especially in cases that are ultrasound and culture negative.

A Comprehensive Review on Cardiovascular Complications of COVID-19: Unraveling the Link to Bacterial Endocarditis

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has ushered in a new era of understanding the multifaceted nature of infectious diseases. Beyond its well-documented respiratory impact, COVID-19 has unveiled intricate interactions with the cardiovascular system, with potential implications that extend to bacterial endocarditis. This review explores the complex interplay between COVID-19 and bacterial endocarditis, elucidating shared risk factors, theoretical mechanisms, and clinical implications. We examine the diverse cardiovascular manifestations of COVID-19, ranging from myocarditis and thromboembolic events to arrhythmias, and delve into the pathogenesis, clinical features, and diagnostic challenges of bacterial endocarditis. By analyzing potential connections, such as viral-induced endothelial disruption and immune modulation, we shed light on the plausible relationship between COVID-19 and bacterial endocarditis. Our synthesis highlights the significance of accurate diagnosis, optimal management, and interdisciplinary collaboration in addressing the challenges posed by these intricate interactions. In addition, we underscore the importance of future research, emphasizing prospective studies on bacterial endocarditis incidence and investigations into the long-term cardiovascular effects of COVID-19. As the boundaries of infectious diseases and cardiovascular complications converge, this review calls for continued research, vigilance, and coordinated efforts to enhance patient care and public health strategies in a rapidly evolving landscape.

Infective Endocarditis among Pediatric Patients with Prosthetic Valves and Cardiac Devices: A Review and Update of Recent Emerging Diagnostic and Management Strategies

Infective endocarditis (IE) is a disease of the endocardium, which leads to the appearance of vegetation on the valves, cardiac structures, or, potentially, vascular endothelium of the heart. The risk of IE can be increased more than 140 times by congenital heart disease (50-59% of all IE), particularly if cyanotic. An increase in mortality may result from IE in patients with a complex cardiac pathology or patients with an implanted prosthetic material, most frequently conduits in a pulmonary position. Cardiac implantable electronic devices (CIED) infective endocarditis is a life-threatening complication representing 10% of all cases of endocarditis. Common signs of presentation are often fever and chills; redness and swelling at the pocket of the pacemaker, including the erosion and exteriorization of the device; and life-threatening sepsis. The use of intracardiac echocardiography for the diagnosis of IE is an innovative method. This may be needed, especially in older children undergoing complex cardiac surgery, when transthoracic echocardiography (TTE) and transesophageal echocardiography (TOE) failed to provide a reliable diagnosis. The 2018 European Heart Rhythm Association (EHRA) experts' consensus statement on transvenous lead extraction recommends complete device removal and antimicrobial therapy for any device-related infection, including CIED-IE. The most detected microorganism was Staphylococcus Aureus. In addition, cardiac surgery and interventional cardiology associated with the placement of prostheses or conduits may increase the risk of IE up to 1.6% for Melody valve implantation. Our manuscript presents a comprehensive review of infective endocarditis associated with cardiac devices and prostheses in the pediatric population, including recent advances in diagnosis and management.

Host-Bacterium Interaction Mechanisms in Staphylococcus aureus Endocarditis: A Systematic Review

Staphylococci sp. are the most commonly associated pathogens in infective endocarditis, especially within high-income nations. This along with the increasing burden of healthcare, aging populations, and the protracted infection courses, contribute to a significant challenge for healthcare systems. A systematic review was conducted using relevant search criteria from PubMed, Ovid's version of MEDLINE, and EMBASE, and data were tabulated from randomized controlled trials (RCT), observational cohort studies, meta-analysis, and basic research articles. The review was registered with the OSF register of systematic reviews and followed the PRISMA reporting guidelines. Thirty-five studies met the inclusion criteria and were included in the final systematic review. The role of Staphylococcus aureus and its interaction with the protective shield and host protection functions was identified and highlighted in several studies. The interaction between infective endocarditis pathogens, vascular endothelium, and blood constituents was also explored, giving rise to the potential use of antiplatelets as preventative and/or curative agents. Several factors allow Staphylococcus aureus infections to proliferate within the host with numerous promoting and perpetuating agents. The complex interaction with the hosts' innate immunity also potentiates its virulence. The goal of this study is to attain a better understanding on the molecular pathways involved in infective endocarditis supported by S. aureus and whether therapeutic avenues for the prevention and treatment of IE can be obtained. The use of antibiotic-treated allogeneic tissues have marked antibacterial action, thereby becoming the ideal substitute in native and prosthetic valvular infections. However, the development of effective vaccines against S. aureus still requires in-depth studies.

A Rare Case of Bartonella henselae Infective Endocarditis Causing an Embolic Cerebrovascular Accident

Bartonella is a facultative intracellular Gram-negative aerobic rod that is an important cause of culture-negative endocarditis that only accounts for 3% of all infective endocarditis (IE) cases. Throughout the literature, there have been very few documented cases of an embolic stroke caused by Bartonella henselae (B. henselae) IE. Following a comprehensive review of the literature, it appears that only a small number of articles have reported on the correlation between cerebrovascular accidents (CVAs) and Bartonella IE. Here, we present a case of a 42-year-old male with a cerebral embolic event as a complication of B. henselae IE.

Case report of culture-negative endocarditis in lupus nephritis

Background

Cardiovascular involvement is frequent in systemic lupus erythematosus (SLE). Valvular abnormalities are increasingly being recognized with the advent of echocardiography.

Case summary

We present a case of a 46-year-old lady who presented to the emergency department with upper limb ischaemia. On examination, she had poor dentition and a short systolic murmur on auscultation. A blood workup revealed a diagnosis of SLE. Further investigations showed vegetations on the mitral valve. Initially, an infective endocarditis (IE) diagnosis was made, which was treated with antibiotics. High-dose steroids and immunosuppressants were initiated due to her clinical deterioration and biopsy-proven lupus nephritis. She improved clinically before being discharged home.

Discussion

It can be difficult to distinguish between IE and Libman-Sacks endocarditis (LSE), especially in the setting of risk factors for both. Antibiotics and immunosuppressants might be started simultaneously in these cases. A multidisciplinary team is required to manage challenging cases of culture-negative endocarditis. Procalcitonin may have a role in differentiating bacterial endocarditis and LSE.

Development of a surface plasmon resonance (SPR) assay for rapid detection of Aeromonas hydrophila

Aquaculture plays an increasingly important if not critical role in the current and future world food supply. Aeromonas hydrophila, a heterotrophic, Gram-negative, bacterium found in fresh or brackish water in warm climates poses a serious threat to the aquaculture industry in many areas, causing significant economic losses. Rapid, portable detection methods of A. hydrophila are needed for its effective control and mitigation. We have developed a surface plasmon resonance (SPR) technique to detect PCR (polymerase chain reaction) products that can replace agarose gel electrophoresis, or otherwise provide an alternative to costlier and more complicated real-time, fluorescence-based detection. The SPR method provides sensitivity comparable to gel electrophoresis, while reducing labor, cross-contamination, and test time, and employs simpler instrumentation with lower cost than real-time PCR.

New Perspectives for Prosthetic Valve Endocarditis: Impact of Molecular Imaging by FISHseq Diagnostics

BACKGROUND

The microbial etiology of prosthetic valve infective endocarditis (PVE) can be difficult to identify. Our aim was to investigate the benefit of molecular imaging technique fluorescence in situ hybridization (FISH) combined with 16S rRNA-gene polymerase chain reaction (PCR) and sequencing (FISHseq) for the analysis of infected prosthetic heart valves.

METHODS

We retrospectively evaluated the diagnostic outcome of 113 prosthetic valves from 105 patients with suspected PVE, treated in 2003-2013 in the Department of Cardiac Surgery, Charité University Medicine Berlin. Each prosthetic valve underwent cultural diagnostics and was routinely examined by FISH combined with 16S rRNA gene PCR and sequencing. We compared classical microbiological culture outcomes (blood and valve cultures) with FISHseq results and evaluated the diagnostic impact of the molecular imaging technique.

RESULTS

Conventional microbiological diagnostic alone turned out to be insufficient, as 67% of preoperative blood cultures were noninformative (negative, inconclusive, or not obtained) and 67% of valve cultures remained negative. FISHseq improved the conventional cultural diagnostic methods in PVE in 30% of the cases and increased diagnostic accuracy. Of the valve culture-negative PVE cases, FISHseq succeeded in identifying the causative pathogen in 35%.

CONCLUSIONS

FISHseq improves PVE diagnostics, complementing conventional cultural methods. In addition to species identification, FISH provides information about the severity of PVE and state of the pathogens (eg, stage of biofilm formation, activity, and localization on and within the prosthetic material). As a molecular imaging technique, FISHseq enables the unambiguous discrimination of skin flora as contaminant or infectious agent.

Evaluation of Infective Endocarditis in Children: A 19-Year Retrospective Study in Taiwan

Background: Infective endocarditis (IE) is an important cause of morbidity and mortality in pediatric patients with heart disease. Little literature has explored differences in the presentation of endocarditis in children with and without heart disease. This study aimed to compare the clinical outcomes and determine the risk of in-hospital death in the study population. Methods: Data were retrospectively collected from 2001 to 2019 from the Chang Gung Research Database (CGRD), which is the largest collection of multi-institutional electronic medical records in Taiwan. Children aged 0–20 years with IE were enrolled. We extracted and analyzed the demographic and clinical features, complications, microbiological information, and outcomes of each patient. Results: Of the 208 patients with IE, 114 had heart disease and 94 did not. Compared to those without heart disease, more streptococcal infections (19.3% vs. 2.1%, p < 0.001) and cardiac complications (29.8% vs. 6.4%, p < 0.001) were observed in patients with heart disease. Although patients with heart disease underwent valve surgery more frequently (43.9% vs. 8.5%, p < 0.001) and had longer hospital stays (28.5 vs. 12.5, p = 0.021), their mortality was lower than that of those without heart disease (3.5% vs. 10.6%, p = 0.041). Thrombocytopenia was independent risk factor for in-hospital mortality in pediatric patients with IE (OR = 6.56, 95% CI: 1.43–40.37). Conclusion: Among pediatric patients diagnosed with IE, microbiological and clinical features differed between those with and without heart disease. Platelet counts can be used as a risk factor for in-hospital mortality in pediatric patients with IE.

Native Valve Endocarditis Caused by Nocardia asteroides in an Immunocompetent Host: A Case Report and a Review of the Literature

Nocardia species are a rare cause of infective endocarditis (IE). We describe a case of native valve endocarditis caused by Nocardia asteroides in a 38-year-old Hispanic male with no apparent environmental exposures or risk factors for IE. Transesophageal echocardiography revealed severe mitral regurgitation, prompting emergent replacement of the valve. Nocardia asteroides were isolated from the tissue culture of the mitral valve. MRI of the brain also demonstrated innumerable micronodular intra-axial lesions throughout the brain, consistent with disseminated nocardiosis. The patient was treated with intravenous trimethoprim/sulfamethoxazole, meropenem, and amikacin for a six-week course, followed by oral trimethoprim/sulfamethoxazole and minocycline for 12 months. Follow-up after 18 months revealed no evidence of relapse. Although several cases of endocarditis due to Nocardia asteroides have been reported in immunocompromised hosts, to the best of our knowledge we believe the present case is the first to describe native valve endocarditis by Nocardia asteroides in an immunocompetent host with no apparent risk factors for IE.

Clinical and biological diagnosis and follow-up of patients treated for endovascular infections due to Coxiellaburnetii

The objective of this study was to evaluate the effectiveness of the recommended treatment for endovascular infections due to Coxiella burnetii. This single-center retrospective study was conducted in 13 patients with endovascular infection due to C. burnetii between January 2001 and December 2020 for a definite or possible endovascular infection due to C. burnetii with a minimum follow-up of 18 months post-infection. Clinical and biological data, including serology, blood and tissue PCR results, doxycycline and hydroxychloroquine assays were collected. Among the 13 patients, 11 had endocarditis (8 definite and 3 possible) and 2 had a vascular infection. At the time of diagnosis, fever was present in only 46% of cases. In case of endocarditis, 73% of patients had a pathological echocardiography. Biologically, the CRP level was low (52 mg/l ± 44). Autoimmune antibodies (antinuclear factor, neutrophil anticytoplasm) were present in 23% of patients. At the time of diagnosis, tissue PCR was very sensitive (100%) unlike blood or serum (29%). Blood levels of doxycycline and hydroxychloroquine were within expected values. Only one patient experienced treatment failure at two years, requiring surgery. For the 7 patients whose phase I IgG titres fell below 1/800, a minimum of 18 months of treatment was necessary. In the long term, the clinical and biological cure was 100% and 92% respectively, underlining the importance of monitoring the serum dosages of doxycycline and hydroxychloroquine. Given its sensitivity, tissue PCR could be added to the major Duke criteria.

Culture-negative tricuspid valve endocarditis in an intravenous drug abuser masquerading as pulmonary tuberculosis in Nepal: a case report

Infective endocarditis is an infection of the heart valves or endocardium caused by bacterial, viral, or fungal microorganisms. Blood cultures are used to detect the bacteria causing infective endocarditis, and echocardiography is performed to find the damaged heart valves. In blood culture-negative endocarditis, no endocarditis-causing organisms can be found in blood cultures, and blood cultures using usual laboratory methods remain sterile after inoculation of at least three independent blood samples.

Case presentation

A 24-year-old male with a history of polysubstance abuse presented with complaints of fever, cough, and shortness of breath. He had a past history of pulmonary tuberculosis 4 years ago, for which he was treated with antitubercular therapy. High-resolution computed tomography of the chest revealed multiple cavitary lesions and consolidative areas in the bilateral lungs. Based on these findings, a provisional diagnosis of reactivation of pulmonary tuberculosis was considered, and antitubercular therapy was started. Due to his deteriorating condition, he was readmitted and evaluated. Bronchoalveolar lavage was done and sent for culture and sensitivity testing, which showed the presence of Staphylococcus aureus, and treatment was started accordingly. Despite continuing intravenous antibiotics for 5 days, the patient was not improving. Three sets of samples were withdrawn for blood culture and sensitivity testing, which came out to be negative. Transthoracic echocardiography was done, which revealed vegetation in the tricuspid valve. The patient was diagnosed with culture-negative tricuspid valve endocarditis based on the clinical criteria.

Discussion

Blood culture-negative endocarditis is difficult to diagnose and presents challenges. When faced with a diagnosis like culture-negative endocarditis in the context of a condition that can appear very similar, like tuberculosis, a broad differential diagnostic approach is important.

Conclusion

Intravenous drug use is the main cause of right-sided valvular infective endocarditis. Endocarditis should be considered in intravenous drug users even in the absence of positive blood cultures. An appropriate antibiotic regimen and long-term follow-up with a multidisciplinary team are necessary for a good outcome.

Bartonella henselae Infective Endocarditis: A Rare Cause of Pauci-Immune Necrotizing Glomerulonephritis-A Case Report

Rationale

Bartonella sp. are the most common causes of culture-negative infective endocarditis (IE) cases in the United States. Although, infection-related glomerulonephritis can frequently mimic primary vasculitis due to pauci-immune pattern, majority of previously reported cases of Bartonella henselae-associated glomerulonephritis have immune-complex deposits on immunofluorescence. We present a rare case of B henselae IE-related pauci-immune necrotizing glomerulonephritis. Timely recognition of this atypical presentation led to appropriately directed medical therapy.

Presenting concerns of the patient

A 33-year-old Caucasian male with a history of human immunodeficiency virus (HIV) on highly active antiretroviral therapy (HAART), alcohol abuse, previous subarachnoid hemorrhage (SAH), and recent wisdom tooth extraction (on amoxicillin) was transferred from an outside hospital for further evaluation of severe headache. He was diagnosed with an SAH and right anterior cerebral artery mycotic aneurysm. The serum creatinine at the outside hospital was 292 umol/L (3.3 mg/dL) with a previously normal baseline around 2 years ago. The serum creatinine at our institution was 256 umol/L (3.0 mg/dL). The urinalysis demonstrated +100 protein, +3 blood and 29 red blood cells/high power field. The urine protein creatinine ratio (UPC) was 1.7 g/g. Serologic evaluation was positive for a low C4 10.2 mg/dL, elevated rheumatoid factor 40 IU/mL and an elevated proteinase 3 (PR-3) antineutrophilic cytoplasmic antibodies (ANCA Ab) 4.0 U/mL. A transesophageal echocardiogram (TEE) showed echo densities on both mitral and aortic valve. Blood cultures were negative. Further serologic evaluation was positive for B henselae IgG titer of 1:2560 (normal <1:320) with a negative IgM titer.

Diagnoses

A percutaneous kidney biopsy revealed pauci-immune necrotizing glomerulonephritis, with 14/16 glomeruli globally sclerotic, and 2 glomeruli with active segmental necrotizing lesions. There was no evidence of immune-complex deposition on immunofluorescence or electron microscopy. Clinical findings were consistent with B henselae IE associated mycotic aneurysm and necrotizing glomerulonephritis.

Intervention

Empiric treatment for an active glomerulonephritis with immunosuppressive agents was deferred on admission, given concern for an underlying infectious process and mycotic aneurysms in an HIV-positive patient. He received antibiotic treatment with doxycycline and ceftriaxone with gentamicin for synergy. Despite this, the mitral and aortic valve regurgitation worsened, and he developed congestive heart failure requiring aortic valve replacement and mitral valve repair. The explanted aortic valve was positive for B henselae by polymerase chain reaction (PCR) confirming the diagnosis of B henselae IE.

Outcomes

Immunosuppression was deferred due to timely identification of an atypical presentation of B henselae-associated ANCA antibodies-positive, pauci-immune necrotizing glomerulonephritis. A course of antibiotic treatment resulted in improved renal functions along with undetectable B henselae and PR3 Ab titers. The serum creatinine decreased to 176 umol/L (2 mg/dL) and remained stable 12 months after discharge.

Teaching points

B henselae IE should be suspected in patients with pauci-immune necrotizing glomerulonephritis and culture-negative IE. This is imperative for optimal decision making in the management of such patients. Having high clinical suspicion can avoid unnecessary and potentially deleterious use of immunosuppressive agents.

Changes in the oral and nasal microbiota in pediatric obstructive sleep apnea

Background

Several clinical studies have demonstrated that pediatric obstructive sleep apnea (OSA) is associated with dysbiosis of airway mucosal microbiota. However, how oral and nasal microbial diversity, composition, and structure are altered in pediatric OSA has not been systemically explored.

Methods

30 polysomnography-confirmed OSA patients with adenoid hypertrophy, and 30 controls who did not have adenoid hypertrophy, were enrolled. Swabs from four surface oral tissue sites (tongue base, soft palate, both palatine tonsils, and adenoid) and one nasal swab from both anterior nares were collected. The 16S ribosomal RNA (rRNA) V3-V4 region was sequenced to identify the microbial communities.

Results

The beta diversity and microbial profiles were significantly different between pediatric OSA patients and controls at the five upper airway sites. The abundances of Haemophilus, Fusobacterium, and Porphyromonas were higher at adenoid and tonsils sites of pediatric patients with OSA. Functional analysis revealed that the differential pathway between the pediatric OSA patients and controls involved glycerophospholipids and amino acid metabolism.

Conclusions

In this study, the oral and nasal microbiome of pediatric OSA patients exhibited certain differences in composition compared with the controls. However, the microbiota data could be useful as a reference for studies on the upper airway microbiome.

Infective endocarditis due to Haemophilus sputorum

Introduction

Haemophilus species are gram-negative, non-motile, facultative anaerobic coccobacilli in the larger family of Pasteurellaceae . Implicated in a variety of human diseases, Haemophilus species are also included in the 'HACEK' group of organisms, which are fastidious gram-negative bacteria, a well-described but uncommon cause of endocarditis. Among the Haemophilus species responsible for endocarditis, Haemophilus parainfluenzae is the most frequently isolated. However, novel species of Haemophilus have recently been described, and their clinical significance remains uncertain.

Case presentation

A 35-year-old man was admitted to the hospital after presenting with a 3 month history of nightly fevers, night sweats and unintentional weight loss, with a new murmur detected on cardiac auscultation. Blood cultures returned positive for Haemophilus sputorum identified by matrix assisted laser desorption ionization - time of flight MS, and confirmed with whole genome sequencing. Echocardiography revealed the presence of an aortic valve vegetation, with aortic and mitral valve leaflet perforations. He was successfully treated with surgical bioprosthetic valve replacements and pathogen-directed antibiotics without complications.

Conclusion

We describe a case of infective endocarditis due to H. sputorum , a newly identified Haemophilus species, which to the best of our knowledge has yet to be reported, and discuss the available literature regarding this organism.

Granulicatella spp., a Causative Agent of Infective Endocarditis in Children

Granulicatella spp. are non-motile, non-sporulating, facultatively anaerobic Gram-positive cocci. Throughout the literature, these organisms have been referred to by several names, such as “nutritionally deficient streptococci”, “vitamin-B dependent streptococci” and “pyridoxal-dependent streptococci”, because of their fastidious nutritional requirements, which can often make culture isolation challenging. Known to be a member of the normal microbiota of the human oral cavity and urogenital and intestinal tracts, similar to other streptococci, Granulicatella spp. can cause bacteremia, sepsis and infective endocarditis. Considering the difficulty in growing this organism on culture medium, the fact that it is now included among the bacteria known to be responsible for culture-negative infective endocarditis suggests that its pathogenic role could be highly underestimated. Moreover, being considered such a rare causative agent, it is not a target of standard antibiotic empiric treatment. We present a rare case of G. elegans endocarditis in a young child and review the medical literature on Granulicatella endocarditis in the pediatric population, with the aim of sharing knowledge about this microorganism, which can be challenging for a clinician who is not familiar with it.

Case report: A prosthetic valve endocarditis caused by Legionella bozemanae in an immunocompetent patient

Extrapulmonary infections with Legionella species are rare, but important to acknowledge. We report a case of infective endocarditis (IE) with Legionella bozemanae in a 66-year-old immunocompetent man with an aortic homograft. The diagnosis was made by direct 16S rRNA gene amplification from valve material, confirmed by a targeted Legionella-PCR in serum and the detection of L. bozemanae specific antibodies. To our knowledge, this is the first confirmed case of IE with L. bozemanae as causative pathogen. The infected aortic prosthesis was replaced by a homograft, and the patient was successfully treated with levofloxacin and azithromycin for 6 weeks.

Molecular and Serological Diagnostic Approach to Define the Microbiological Origin of Blood Culture-Negative Infective Endocarditis

Blood culture-negative infective endocarditis (BCNIE) poses a significant challenge in determining the best antibiotic regimen for this life-threatening infection, which should be treated with as specific and effective a regimen as feasible. The goal of this study was to determine the prevalence of BCNIE among definite infective endocarditis (IE) cases and to study the impact of a molecular and serological diagnostic approach in defining the microbiological origin of BCNIE. This study included 94 definite IE cases. Serum and blood samples from BCNIE patients were tested using serological, broad-range PCR, and sequencing assays. Valve tissue sections obtained from 42 operated patients were subjected to culture and molecular studies. BCNIE accounted for 63 (67%) of the cases. Of these cases, blood PCR followed by sequencing could diagnose 11 cases. Zoonotic infective endocarditis was detected in 7 (11%) patients by serology and PCR (four Brucella, two Bartonella, and one Coxiella). Sequencing of valve PCR bands revealed 30 positive cases. Therefore, the percentage of BCNIE with unidentified etiology was reduced from 67% to 27.7% through a combination of all diagnostic procedures utilized in our study. Blood and valve PCR and sequencing assays are valuable techniques for the etiological diagnosis of BCNIE, especially in cases with previous antibiotic therapy. However, these tests should be used as part of a larger diagnostic strategy that includes serology, microscopy, and valve culture. The use of an automated blood culture system, and proper blood culture collection before ordering antibiotics, will guide IE etiological diagnosis.

Native valve, prosthetic valve, and cardiac device-related infective endocarditis: A review and update on current innovative diagnostic and therapeutic strategies

Infective endocarditis (IE) is a life-threatening microbial infection of native and prosthetic heart valves, endocardial surface, and/or indwelling cardiac device. Prevalence of IE is increasing and mortality has not significantly improved despite technological advances. This review provides an updated overview using recent literature on the clinical presentation, diagnosis, imaging, causative pathogens, treatment, and outcomes in native valve, prosthetic valve, and cardiac device-related IE. In addition, the experimental approaches used in IE research to improve the understanding of disease mechanisms and the current diagnostic pipelines are discussed, as well as potential innovative diagnostic and therapeutic strategies. This will ultimately help towards deriving better diagnostic tools and treatments to improve IE patient outcomes.