Haemophilus aphrophilus and Eikenella corrodens Coinfection of Brain: An Unusual Case from China

Background

The HACEK group comprises Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae, are Gram-negative bacteria that are slow-growing and fastidious. These organisms are common causes of culture-negative endocarditis. However, brain abscesses caused by Haemophilus aphrophilus and E. corrodens have been rarely reported. The case we describe, which was promptly identified and successfully treated, will be meaningful for the diagnosis and treatment of such infectious diseases.

Case Presentation

Herein, we report a case of brain abscess in a young man who was infected with Haemophilus aphrophilus and E. corrodens. The patient was admitted to the hospital with sudden onset of vomiting, coma, and fever. Magnetic resonance imaging (MRI) of the brain and cerebrospinal fluid cell counts suggested cerebral abscess, he underwent drainage of the abscess and empirical antimicrobial therapy of meropenem (2 g every 8 hours) and linezolid (0.6 g every 12 hours) for more than 10 days without significant improvement. Metagenomic next-generation sequencing (mNGS) of drainage fluid and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) detection for isolated bacteria from samples suggested the presence of H. aphrophilus and E. corrodens. After 7 weeks of ceftriaxone (2 g every 12 hours) and meropenem (2 g every 8 hours) intravenously, the patient was discharged with a normal temperature and brain MRI showed improvement of the lesion.

Conclusion

Similar cases reported in previous studies were always associated with bacterial blood dissemination after dental surgery or myocarditis; however, the patient in our case had no any associated risk factors. As far as we know, this is the only case of central nervous system infection caused by H. aphrophilus and E. corrodens that has utilized combined mNGS and MALDI-TOF MS in the diagnosis.

Haemophilus influenzae endocarditis: a case report and literature review

INTRODUCTION

Haemophilus influenzae (HI) is an exceedingly rare cause of infective endocarditis (IE).

CASE PRESENTATION/METHODS

We present a case of a 90-year-old female diagnosed with HI-IE involving the native tricuspid valve in the absence of traditional risk factors for right-sided endocarditis. She was treated with a 5-week course of IV Ampicillin from negative cultures and suffered no complications. We also conducted a thorough literature review through PubMed and Google Scholar, which yielded a mere 15 reported cases of HI-IE.

RESULTS

Fourteen of the reported HI-IE cases included epidemiological data, showing no gender predominance. The mean age of the subjects was 39.5, with the mitral valve being the most implicated (64%) and tricuspid valve involvement being rare (21%).

CONCLUSION

Native tricuspid valve IE is an uncommon entity, especially in the absence of IV drug use. Haemophilus influenzae is an extremely rare cause of IE, with a literature review showing merely 15 reported cases. This article cites the 16th case of HI-IE published in the literature.

[Brain abscess due to Aggregatibacter aphrophilus]

Brain abscess is a focal suppurative process produced in most cases by bacterial agents. Aggregatibacter aphrophilus is a gram-negative bacteria belonging to the HACEK group, which causes infective endocarditis, liver abscesses, among others. Brain abscesses secondary to this germ are rare and, in most cases, it is associated with contact with pets, poor dental hygiene or dental procedures. Treatment consists of drainage of the abscess (greater than 2.5 cm) combined with antibiotic therapy, ideally beta-lactams. The case of a 64-year-old male patient with no relevant history is here presented. He was admitted to the emergency service due to headache, hemianopsia of a week's duration and later tonic-clonic seizures, in whom imaging studies and culture of a brain lesion subsequently revealed a brain abscess due to A. aphrophilus. This case aims to illustrate about the rarity of this infection, because A. aphrophilus is a normal part of the oropharyngeal flora and respiratory tract, in which it rarely causes invasive bacteremia.

An insidious Aggregatibacter actinomycetemcomitans infection of an ascending aortic endovascular graft

While HACEK group organisms cause only 1-3% of infective endocarditis (IE) cases, their insidious and varied clinical presentations make for difficult and often delayed diagnoses. We present a 65-year-old male with persistent exertional dyspnea, hemoptysis, and weight loss who was diagnosed with a HACEK aortic graft infection and IE.

Endocarditis due to Aggregatibacter Segnis: a rare case report

BACKGROUND

As a member of the HACEK group, Aggregatibacter segnis (A. segnis) is a fastidious Gram-negative coccobacillus that resides in the human oropharyngeal flora. Infective endocarditis caused by A. segnis is rarely reported.

CASE PRESENTATION

A 31-year-old male was admitted to our hospital for a 3-month history of intermittent high fever, chills, and chest distress. On presentation, he was febrile and tachycardic but otherwise with stable vital signs. Physical examination revealed systolic murmurs in the aortic and mitral valve areas. Pitting edema was evident in the lower extremities. Transthoracic echocardiography demonstrated multiple vegetations in the mitral and aortic valves. Severe regurgitation of the aortic valve and left heart dysfunction were also detected. With the suspicion of infective endocarditis and heart failure, we immediately performed microbiological tests and arranged the cardiac replacement surgery. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and metagenomic next-generation sequencing (mNGS) identified A. segnis from the bloodstream. While the surgical specimen culture was negative, the mNGS was positive for A. segnis. The patient was treated with ceftriaxone for four weeks and discharged. He remained clinically well, with laboratory results restored.

CONCLUSION

This is the first report of A. segnis infective endocarditis that combined MALDI-TOF and metagenomic next-generation sequencing in the diagnosis. The hypothesis-independent molecular techniques can outperform conventional tools to prevent diagnostic delay.

Aggregatibacter actinomycetemcomitans infection in a 15-year-old boy with pulmonary empyema: a case report and review of literature

BACKGROUND

Aggregatibacter actinomycetemcomitans (Aa), previously known as Actinobacillus actinomycetemcomitans, is a slow-growing Gram-negative coccobacillus, member of the HACEK group of bacteria colonizing oral flora. Besides causing infectious diseases in the oral cavity such as dental caries and periodontitis, it is responsible for severe extra-oral infections secondary to hematogenous spread or aspiration, such as endocarditis, soft tissue abscesses and osteomyelitis. The diagnosis depends on prolonged bacterial culture of biological material obtained through biopsy. Aa is susceptible to most antibiotics but complete eradication often requires a long term treatment.

CASE PRESENTATION

We report the case of a 15-year-old previously healthy boy diagnosed with both pulmonary empyema and subphrenic chest wall abscess caused by Aa. He was admitted to our Pediatric Emergency department for evaluation of a right mass associated with marked asthenia and dry cough. After radiological findings etiological diagnosis was made by culture of fluid drainage of pleural empyema. He started empirical antibiotic therapy with intravenous piperacillin/tazobactam, whose sensibility was confirmed by the antibiogram, then, for occurrance of hepatopathy it was switched to ciprofloxacin: the patient almost completely recovered after 6-month therapy.

CONCLUSIONS

Extra-oral infections caused by Aa are extremely rare, especially in children, and not well described yet. To our knowledge, there is only another similar case described in literature. However, the case described in our manuscript represents the only one presenting with pulmonary empyema without involvement of lung parenchyma in children. We also conducted a brief review of published cases of Aa infection in the pediatric population. This case report reminds us the importance of an accurate inspection of the oral cavity during the examination of pediatric patients.

Cardiobacterium hominis infective endocarditis: A literature review

Background

Cardiobacterium hominis is a member of the HACEK group, which causes infective endocarditis (IE) but is rarely associated with other infections. It is difficult to biologically identify C. hominis because of its slow growth in culture. However, the clinical features of C. hominis IE remain unclear.

Method

We searched the PubMed database for all articles of C. hominis IE published between January 2000 and July 2022.

Results

The major clinical features of 44 previously reported cases of C. hominis IE were as follows: the median age was 59 years, of which 36 were men; the initial presenting symptoms were chest discomfort (30 %), followed by fever (27 %), night sweats (20 %), fatigability (18 %), weight loss (16 %), and dyspnea (16 %). Almost half of the patients were febrile upon admission. The major predisposing factors were postsurgical valve treatment (57 %), dental treatment or caries (20 %), and congenital valve abnormality (5 %). The median time to identify C. hominis in the blood culture was 4 days, but the longest time was 42 days. The most commonly infected valve was the aortic valve, and the most common complication was systemic embolism. Surgical treatment was performed in 23 (52 %) patients. The most frequent initial treatment regimen was cephem antibiotics, with a median treatment duration of 6 weeks. The overall mortality and recovery rates of C. hominis IE were 9 % and 91 %, respectively.

Conclusion

If C. hominis infection is confirmed, physicians should check for the presence of vegetations of the heart valves and understand these characteristics.

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.

Bacterial endocarditis with AACEK (HACEK) organisms

INTRODUCTION

Gram-negative organisms of the AACEK group, formerly known as HACEK, rarely cause endocarditis.

CASE SERIES

We present three cases of bacterial endocarditis, involving native and prosthetic valves, caused by AACEK organisms. In two patients, Cardiobacterium hominis was the responsible organism, and in a third, Aggregatibacter aphrophilus was implicated. A dental source of infection was identified in two patients, and in all three patients, the presentation of endocarditis was subacute.

DISCUSSION

This case series highlights the indolent nature of infection with the AACEK organisms. It also demonstrates the crucial role of multimodality imaging, especially transesophageal echocardiography, in the diagnosis of AACEk endocarditis of both native and prosthetic valves, and in delineating the extent of abscess in those with prosthetic valve infection.

The first case of cholecytitis caused by Aggregatibacter kilianii in Korea

BACKGROUND

The bacterial genus Aggregatibacter was categorized in 2006 to accommodate the former Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and H. segnis species. Aggregatibacter kilianii is a normal resident of the human upper respiratory tract but can also cause serious infections. A. kilianii is relatively newly identified and has been isolated from conjunctivitis, wounds, abdominal abscesses, and blood.

CASE PRESENTATION

An 80-year-old female patient with distal common bile duct cancer was admitted to our hospital with sudden loss of consciousness and general weakness, fever, and abdominal pain for 3 days. Two colonial morphologies were isolated from both the blood and bile cultures; one was identified as Streptococcus constellatus subsp. pharyngis, but the other was not recognized by Vitek2 and MALDI-TOF. The 16 S rRNA sequences showed 99.73% similarity with the sequence of A. kilianii strains.

CONCLUSION AND DISCUSSION

This article presents the first case of a clinical isolate of A. kilianii outside Europe. This case is also the first of the antimicrobial profile of this strain. This report highlights the importance of proper molecular identification for timely diagnosis and treatment of disease.

Analysis of the fecal and oral microbiota in chronic recurrent multifocal osteomyelitis

BACKGROUND

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory bone disease for which a lack of bacterial involvement is a key diagnostic feature to distinguish it from other symptomatically related diseases. However, the growing evidence suggesting an involvement of the host-associated microbiota in rheumatic disorders together with the now wide accessibility of modern culture-independent methods warrant a closer examination of CRMO.

METHODS

In this study, we show through bacterial 16S rRNA gene profiling that numerous features of the oral- and fecal microbial communities differentiate children with and without CRMO.

RESULTS

Notably, communities in diseased children are characterized by a lack of potential probiotic bacteria in the fecal community and an overabundance of known pathobionts in the oral microbial communities. Of special interest is the HACEK group, a set of commonly known oral pathogens that are implicated in the development of several acute and chronic diseases such as osteitis and rheumatoid arthritis. Furthermore, we observe that gut bacterial communities in the diseased children appear to reflect an altered host physiology more strongly than the oral community, which could suggest an oral disease origin followed by propagation and/or responses beyond the oral cavity.

CONCLUSIONS

Bacterial communities, in particular the oral microbiota, may serve as an indicator of underlying susceptibility to CRMO, or play a yet undefined role in its development.

Quantitative sequencing clarifies the role of disruptor taxa, oral microbiota, and strict anaerobes in the human small-intestine microbiome

BACKGROUND

Upper gastrointestinal (GI) disorders and abdominal pain afflict between 12 and 30% of the worldwide population and research suggests these conditions are linked to the gut microbiome. Although large-intestine microbiota have been linked to several GI diseases, the microbiota of the human small intestine and its relation to human disease has been understudied. The small intestine is the major site for immune surveillance in the gut, and compared with the large intestine, it has greater than 100 times the surface area and a thinner and more permeable mucus layer.

RESULTS

Using quantitative sequencing, we evaluated total and taxon-specific absolute microbial loads from 250 duodenal-aspirate samples and 21 paired duodenum-saliva samples from participants in the REIMAGINE study. Log-transformed total microbial loads spanned 5 logs and were normally distributed. Paired saliva-duodenum samples suggested potential transmission of oral microbes to the duodenum, including organisms from the HACEK group. Several taxa, including Klebsiella, Escherichia, Enterococcus, and Clostridium, seemed to displace strict anaerobes common in the duodenum, so we refer to these taxa as disruptors. Disruptor taxa were enriched in samples with high total microbial loads and in individuals with small intestinal bacterial overgrowth (SIBO). Absolute loads of disruptors were associated with more severe GI symptoms, highlighting the value of absolute taxon quantification when studying small-intestine health and function.

CONCLUSION

This study provides the largest dataset of the absolute abundance of microbiota from the human duodenum to date. The results reveal a clear relationship between the oral microbiota and the duodenal microbiota and suggest an association between the absolute abundance of disruptor taxa, SIBO, and the prevalence of severe GI symptoms. Video Abstract.

Haemophilus parainfluenzae endocarditis in a low-risk woman: a case report

Haemophilus parainfluenzae endocarditis is a rare but dangerous disease. With this work, we intend to show the importance of early diagnosis and appropriate treatment in order to avoid complications. We also highlight the importance of local epidemiology to choose antibiotic prophylaxis for high-risk procedures in selected predisposed patients.

Eikenella glucosivorans sp. nov., isolated from a human throat swab, and emendation of the genus Eikenella to include saccharolytic species

A novel species within the genus Eikenella is described, based on the phenotypical, biochemical and genetic characterization of a strain of a facultatively anaerobic, Gram-negative rod-shaped bacterium. Strain S3360^T was isolated from the throat swab of a patient sampled during routine care at a hospital. Phylogenetic analyses (full-length 16S rRNA gene and whole-genome sequences) placed the strain in the genus Eikenella, separate from all recognized species but with the closest relationship to Eikenella longinqua (NML 02-A-017^T). Eikenella is one of the genera in the HACEK group known to be responsible for rare cases of endocarditis in humans. Until the recent descriptions of Eikenella exigua, Eikenella halliae and Eikenella longinqua, Eikenella corrodens had been the only validly published species in this genus since its description as Bacteroides corrodens in 1958. Unlike these species, strain S3360^T is able to metabolize carbohydrates (glucose). The average nucleotide identities of strain S3360^T with E. longinqua (NML 02-A-017^T) and E. corrodens (NCTC 10596^T), the type species of the genus, were 90.5 and 84.7 %, respectively, and the corresponding genome-to-genome distance values were 41.3 and 29.0 %, respectively. The DNA G+C content of strain S3360^T was 58.4 mol%. Based on the phenotypical, biochemical and genetic findings, strain S3360^T is considered to represent a novel species within the genus Eikenella, for which the name Eikenella glucosivorans sp. nov. is proposed. The type strain is S3360^T (DSM 110714^T=CCOS 1935^T=CCUG 74293^T). In addition, an emendation of the genus Eikenella is proposed to include species which are saccharolytic.

A Widespread Bacterial Secretion System with Diverse Substrates

In host-associated bacteria, surface and secreted proteins mediate acquisition of nutrients, interactions with host cells, and specificity of tissue localization. In Gram-negative bacteria, the mechanism by which many proteins cross and/or become tethered to the outer membrane remains unclear. The domain of unknown function 560 (DUF560) occurs in outer membrane proteins throughout Proteobacteria and has been implicated in host-bacterium interactions and lipoprotein surface exposure. We used sequence similarity networking to reveal three subfamilies of DUF560 homologs. One subfamily includes those DUF560 proteins experimentally characterized thus far: NilB, a host range determinant of the nematode-mutualist Xenorhabdus nematophila, and the surface lipoprotein assembly modulators Slam1 and Slam2, which facilitate lipoprotein surface exposure in Neisseria meningitidis (Y. Hooda, C. C. Lai, A. Judd, C. M. Buckwalter, et al., Nat Microbiol 1:16009, 2016, https://doi.org/10.1038/nmicrobiol.2016.9; Y. Hooda, C. C. L. Lai, T. F. Moraes, Front Cell Infect Microbiol 7:207, 2017, https://doi.org/10.3389/fcimb.2017.00207). We show that DUF560 proteins from a second subfamily facilitate secretion of soluble, nonlipidated proteins across the outer membrane. Using in silico analysis, we demonstrate that DUF560 gene complement correlates with bacterial environment at a macro level and host association at a species level. The DUF560 protein superfamily represents a newly characterized Gram-negative secretion system capable of lipoprotein surface exposure and soluble protein secretion with conserved roles in facilitating symbiosis. In light of these data, we propose that it be titled the type 11 secretion system (TXISS). IMPORTANCE The microbial constituency of a host-associated microbiome emerges from a complex physical and chemical interplay of microbial colonization factors, host surface conditions, and host immunological responses. To fill unique niches within a host, bacteria encode surface and secreted proteins that enable interactions with and responses to the host and co-occurring microbes. Bioinformatic predictions of putative bacterial colonization factor localization and function facilitate hypotheses about the potential of bacteria to engage in pathogenic, mutualistic, or commensal activities. This study uses publicly available genome sequence data alongside experimental results from Xenorhabdus nematophila to demonstrate a role for DUF560 family proteins in secretion of bacterial effectors of host interactions. Our research delineates a broadly distributed family of proteins and enables more accurate predictions of the localization of colonization factors throughout Proteobacteria.

HACEK Infective Endocarditis at a Tertiary Children's Hospital

HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella species) are rare causes of endocarditis. HACEK organisms are fastidious and may escape detection by culture techniques, but the use of molecular studies may aid diagnosis. A 10-year review of pediatric HACEK endocarditis cases at Texas Children's Hospital identified 10 patients, with 2 cases recognized by next-generation sequencing, highlighting potential benefits of these assays.

Infective endocarditis caused by HACEK group bacteria-a registry-based comparative study

Infective endocarditis (IE) caused by bacteria within Haemophilus (excluding Haemophilus influenzae), Aggregatibacter, Cardiobacterium, Eikenella and Kingella (HACEK) is rare. This study aimed to describe clinical features of IE caused by HACEK genera in comparison with IE due to other pathogens. Cases of IE due to HACEK were identified through the Swedish Registry of Infective Endocarditis (SRIE). Clinical characteristics of IE cases caused by HACEK were compared with cases of IE due to other pathogens reported to the same registry. Ninety-six patients with IE caused by HACEK were identified, and this corresponds to 1.8% of all IE cases. Eighty-three cases were definite endocarditis, and the mortality rate was 2%. The median age was 63 years, which was lower compared to patients with IE caused by other pathogens (66, 70 and 73 years respectively, p ≤ 0.01). Patients with IE caused by Haemophilus were younger compared to patients with IE due to Aggregatibacter (47 vs 67 years, p ≤ 0.001). Patients with IE due to HACEK exhibited longer duration from onset of symptoms to hospitalization and had more prosthetic valve endocarditis compared to patients with IE due to Staphylococcus aureus (10 vs 2 days, p ≤ 0.001, and 35 vs 14%, p ≤ 0.001). This is, to date, the largest study on IE due to HACEK. Aggregatibacter was the most common cause of IE within the group. The condition has a subacute onset and often strikes in patients with prosthetic valves, and the mortality rate is relatively low.

A rare case of voluminous brain abscess due to Actinomyces meyeri and Aggregatibacter aphrophilus: is there any evidence for a prolonged antibiotic oral relay?

We present the case of a patient with a voluminous cerebral abscess caused by Aggregatibacter aphrophilus and Actinomyces meyeri occurring a week post dental scaling. Both these bacteria are rarely involved in brain abscesses, and so far, cases of cerebral actinomyces have mostly been treated surgically and with intravenous (IV) antibiotics for 3-4 months, then put on oral antibiotic therapy with penicillin or amoxicillin for a further 3-12 months. Our patient underwent drainage through craniotomy and was subsequently put on intravenous ceftriaxone for 3 months accompanied by brain imaging control at the end of this period which showed complete regression of the abscess. Following parenteral treatment, no oral antibiotics were given since pharmacokinetic properties do not allow to attain high tissue concentration in the brain. This treatment gave excellent results.

An unexpected case of Cardiobacterium valvarum prosthetic arthritis without cardiac lesions: Case report and literature review

We report a case of prosthetic arthritis caused by Cardiobacterium valvarum, which has been exclusively reported to cause intravascular infections. A 81-year-old Japanese female complained prosthetic knee joint pain. Arthrocentesis cultured no pathogen, and surgical replacement of the implant surface was performed. Modified Levinthal medium culture and 16S rRNA sequencing has finally led to diagnosis of C. valvarum prosthetic knee arthritis without cardiac lesions. Fastidious bacteria such as C. valvarum can be candidate pathogens of orthopedic infections whose causative agents are sometimes unidentified. Further development of molecular diagnostics is expected, but also the importance of conventional methods should be noted.

Epidemiology, bacteriology, and clinical characteristics of HACEK bacteremia and endocarditis: a population-based retrospective study

The objective was to describe the epidemiology, bacteriology, clinical presentation, risk factors for endocarditis (IE), diagnostic workup, and outcome of patients with bacteremia caused by the non-influenzae Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella genera (HACEK). A retrospective population-based cohort of patients with bacteremia collected from 2012 to 2017 was identified. Clinical data from identified patients were collected from medical records to classify patients, calculate incidences, analyze risk factors of IE, and describe the management and outcome of the cohort. A total of 118 episodes of HACEK bacteremia were identified, of which 27 were definite IE. The incidence of HACEK bacteremia was 5.2 and of HACEK IE 1.2 episodes per 1,000,000 inhabitants per year. Other focal infections were identified in 55 of 118 of the episodes, most commonly within the abdomen (26 episodes). The propensity to cause IE ranged from 62 in Aggregatibacter actinomycetemcomitans to 6% in Eikenella. Risk factors for IE were cardiac implantable electronical device, predisposing cardiac conditions, community acquisition, long duration of symptoms, multiple positive blood cultures, fever, heart murmur, embolization, and unknown origin of infection. The scoring system DENOVA developed to predict IE in bacteremia with Enterococcus faecalis also had a high sensitivity and specificity for predicting IE in HACEK bacteremia. The 30-day mortality was 4% in IE and 15% in non-IE bacteremia, and only one case of relapse was found. IE is common in bacteremia with Aggregatibacter, Cardiobacterium, and Kingella but relatively rare in Haemophilus and Eikenella. Treatment failures are very rare, and DENOVA can be used to evaluate the need for transesophageal echocardiography.

A review of current treatment strategies for infective endocarditis

INTRODUCTION

Infective endocarditis is one of the most difficult-to-treat infectious diseases.

AREAS COVERED

We restricted this review to the anti-infective treatment of the main bacteria responsible for infective endocarditis, i.e. staphylococci, streptococci, enterococci, and Gram-negative bacilli, including HACEK. Specific topics of major interest in treatment strategy are covered as well, including empirical treatment, oral switch, and treatment duration. We searched in the MEDLINE database to identify relevant studies, trials, reviews, or meta-analyses until May 2020.

EXPERT OPINION

The use of aminoglycosides for the treatment of endocarditis has been dramatically reduced over the last 20 years. It should be administered once daily, and no longer than 2 weeks. For staphylococcal endocarditis, recent data reinforced the role of anti-staphylococcal penicillins, for methicillin-susceptible isolates (alternative, cefazolin), and vancomycin for methicillin-resistant isolates (alternative, daptomycin). For staphylococcal prosthetic-valve endocarditis, these treatments will be reinforced by the addition of gentamicin during the first 2 weeks, and rifampin throughout the whole treatment duration, i.e. 6 weeks. The optimal duration of antibacterial treatment is 4 weeks for most native valve endocarditis, and 6 weeks for prosthetic-valve endocarditis. The oral switch is safe in patients stabilized after the initial intravenous course.

Description of Eikenella halliae sp. nov. and Eikenella longinqua sp. nov., derived from human clinical materials, emendation of Eikenella exigua Stormo et al. 2019 and emendation of the genus Eikenella to include species which are strict anaerobes

The Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella (HACEK) group genus Eikenella contained a single species, Eikenella corrodens, for many years. In November 2019, Eikenella exigua was described after recovery from a brain abscess and blood culture in Norway. Coincidentally, characterization of 22 Gram-negative bacteria resembling Eikenella from 17 Canadian patients had been underway. Seven isolates from five patients were conclusively identifiable as E. corrodens. One (NML 120819) was deemed to represent a species of the genus Eikenella most closely related to E. corrodens. Fourteen isolates had 97.6 to 98.8% similarities to E. corrodens by 16S rRNA gene sequencing, forming three distinct groups by genome analyses. The largest contained ten anaerobic isolates from eight patients recovered from blood, brain, bone and other abscesses; upon re-evaluation, this group was found to be most consistent with E. exigua. A second facultatively anaerobic clade consisted of two ocular isolates from one patient and a sinus isolate from a second patient. The third taxon consisted of a single strictly anaerobic blood culture isolate. The novel taxa, like E. corrodens, were poorly reactive biochemically and difficult to discern from each other phenotypically and chemotaxonomically, including by cellular fatty acids. MALDI-TOF (Bruker) and whole-genome sequencing were used to further characterize isolates. Draft genomes for the strains had similar DNA G+C contents (55.38-58.53 mol%) while sizes varied from 1.82 Mb to 2.54 Mb. We propose here emendations of the genus Eikenella and the species Eikenella exigua, as well as describing Eikenella halliae sp. nov. NML 130454^T (=LMG 30894^T=NCTC 14180^T) and Eikenella longinqua sp. nov. NML 02-A-017^T (=LMG 30896^T=NCTC 14179^T), on the basis of these findings.

Infective Endocarditis Related to Unusual Microorganisms: A Prospective Population-Based Study

Background

Increased access to heart valves through early surgery and progress in molecular microbiology have reduced the proportion of infective endocarditis (IE) with no microbiological documentation and increased the proportion of IE associated with unusual microorganisms.

Methods

We performed an ancillary study of a large prospective population-based survey on IE. Unusual-microorganism IE was defined as definite IE (Duke-Li criteria) due to microorganisms other than streptococci, staphylococci, or enterococci.

Results

Of 471 cases of documented IE, 46 (9.8%) were due to unusal microorganisms; the following were involved in >1 case: Candida albicans (n = 4), Cutibacterium acnes (n = 4), Pseudomonas aeruginosa (n = 3), Cardiobacterium hominis (n = 3), and Coxiella burnetii (n = 2). Cases were documented with blood cultures (n = 37, 80.4%), heart valve polymerase chain reaction (PCR; n = 5), heart valve culture (n = 2), PCR on vertebral biopsy (n = 1), or serology (n = 1). As compared with IE due to staphylococci, streptococci, or enterococci (n = 420), IE due to unusual microorganisms occurred more frequently in patients with previously known heart disease (69.0% vs 44.3%; P = .002), prosthetic valve (40.5% vs 18.1%; P = .0006), longer duration of fever (mean, 35.1 ± 46.8 days vs 12.5 ± 17.8; P = .003), and who were more often nosocomial (38.1% vs 20.2%; P = .02).

Conclusions

In this population-based study, 9.8% of IE cases were due to unusual microorganisms, with a predominance of anaerobes, yeast, and gram-negative bacilli. As compared with IE related to staphylococci, streptococci, or enterococci, IE cases related to unusual microorganisms were associated with previously known heart disease, prosthetic valve, longer duration of fever, and nosocomial acquisition.

Trial registration

ORCID 0000-0003-3617-5411

Pediatric acute dacryocystitis due to Eikenella corrodens: A case report

Eikenella corrodens is a facultatively anaerobic gram-negative rod bacterium in the oropharynx and respiratory tract. It is a member of HACEK (Haemophilus spp., Aggregatibacter spp., Cardiobacterium hominis, E. corrodens, and Kingella kingae) group commonly associated with endocarditis and craniofacial infections. It is usually susceptible to penicillin, second and third-generation cephalosporins, and carbapenem, but has variable susceptibility to first-generation cephalosporin. We herein provide a description of the first case of pediatric acute dacryocystitis caused by E. corrodens. The patient did not respond to oral cephalexin and required surgical drainage followed by intravenous cefotaxime. Also provided is a brief review of the current literature.

Intracranial Hemorrhaging Following Cardiobacterium hominis Endocarditis

Acute infectious endocarditis (IE) is a complex disease that presents as a serious clinical condition associated with a high mortality rate, especially due to intracranial hemorrhaging (ICH). The most common causative organism is Staphylococcus aureus. We herein report a patient with ICH following subacute IE with a positive blood culture for Cardiobacterium hominis. A review of the existing literature revealed that acute IE associated with Cardiobacterium has been reported to cause ICH in only seven previous cases. Prolonged culture-specific antibiotic therapy along with extended surveillance of blood culture is therefore essential for timely intervention.

Infective endocarditis caused by Cardiobacterium hominis endocarditis: A case report and review of the literature

BACKGROUND

While it has been increasing cases of C. hominis endocarditis in the past decades due to advances of diagnostic methods, the epidemiology and clinical manifestations of IE caused by C. hominis is still unknown.

CASE PRESENTATION

A 62-year old man was admitted to our institute with fever, anorexia and general fatigue for the preceding one month. He had a past medical history of both aortic and mitral valves replacement due to cardiac diseases. He was diagnosed as IE caused by C. hominis according to the modified duke criteria. The patient received 2 weeks of combination therapy of intravenous ceftriaxone (CTRX) 2g and gentamycin 180mg daily followed by 4 weeks CTRX 2g daily alone. Oral moxifloxacin 400mg once daily was given for an additional 4 weeks. After the antibiotic therapy was discontinued, disease recurrence was not observed. We reviewed previously reported C. hominis IE cases in 60 publications including ours. Of 73 patients enrolled, 53 were male, the mean age was 52 years. The most common risk factor of IE was past history of cardiac diseases in 44/73 (60%). As for antibiotics initially prescribed, third-generation cephalosporins was most frequently used in 28/69 (41%). While the cure rate was 67/73 (93%), 31/73 patients (43%) received a surgical intervention. Embolic lesions to the central nervous system and vertebrae were seen in 16/72 (22%) and 5/72 (7%).

CONCLUSION

IE caused by C. hominis has a favorable prognosis, showing the cure rate of 93%. Physicians should recognize the possible occurrence of emboli among IE patients.

HACEK infective endocarditis: Epidemiology, clinical features, and outcome: A case-control study

OBJECTIVES

The study aimed to describe the epidemiological, microbiological, and clinical features of a population sample of 17 patients with HACEK infective endocarditis (HACEK-IE) and to compare them with matched control patients with IE caused by viridans group streptococci (VGS-IE).

METHODS

Cases of definite (n=14, 82.2%) and possible (n=3, 17.6%) HACEK-IE included in the Infective Endocarditis Hospital Clinic of Barcelona (IE-HCB) database between 1979 and 2016 were identified and described. Furthermore, a retrospective case-control analysis was performed, matching each case to three control subjects with VGS-IE registered in the same database during the same time period.

RESULTS

Seventeen out of 1209 IE cases (1.3%, 95% confidence interval 0.69-1.91%) were due to HACEK group organisms. The most frequently isolated HACEK species were Aggregatibacter spp (n=11, 64.7%). Intracardiac vegetations were present in 70.6% of cases. Left heart failure (LHF) was present in 29.4% of cases. Ten patients (58.8%) required in-hospital surgery and none died during hospitalization. In the case-control analysis, there was a trend towards larger vegetations in the HACEK-IE group (median (interquartile range) size 11.5 (10.0-20.0) mm vs. 9.0 (7.0-13.0) mm; p=0.068). Clinical manifestations, echocardiographic findings, LHF rate, systemic emboli, and other complications were all comparable (p>0.05). In-hospital surgery and mortality were similar in the two groups. One-year mortality was lower for HACEK-IE (1/17 vs. to 6/48; p=0.006).

CONCLUSIONS

HACEK-IE represented 1.3% of all IE cases. Clinical features and outcomes were comparable to those of the VGS-IE control group. Despite the trend towards a larger vegetation size, the embolic event rate was not higher and the 1-year mortality was significantly lower for HACEK-IE.

Whole-Genome Sequencing of Aggregatibacter Species Isolated from Human Clinical Specimens and Description of Aggregatibacter kilianii sp. nov

Aggregatibacter species are commensal bacteria of human mucosal surfaces that are sometimes involved in serious invasive infections. During the investigation of strains cultured from various clinical specimens, we encountered a coherent group of 10 isolates that could not be allocated to any validly named species by phenotype, mass spectrometry, or partial 16S rRNA gene sequencing. Whole-genome sequencing revealed a phylogenetic cluster related to but separate from Aggregatibacter aphrophilus The mean in silico DNA hybridization value for strains of the new cluster versus A. aphrophilus was 56% (range, 53.7 to 58.0%), whereas the average nucleotide identity was 94.4% (range, 93.9 to 94.8%). The new cluster exhibited aggregative properties typical of the genus Aggregatibacter Key phenotypic tests for discrimination of the new cluster from validly named Aggregatibacter species are alanine-phenylalanine-proline arylamidase, N-acetylglucosamine, and β-galactosidase. The name Aggregatibacter kilianii is proposed, with PN_528 (CCUG 70536^T or DSM 105094^T) as the type strain.

Eikenella corrodens endocarditis and liver abscess in a previously healthy male, a case report

Background

Eikenella corrodens is one of the HACEK bacteria constituting part of the normal flora of the oropharynx, however, still an uncommon pathogen. We report a case of a large Eikenella corrodens liver abscess with simultaneously endocarditis in a previously healthy male.

Case presentation

A 49-year-old Danish man was admitted because of one-month malaise, fever, cough and unintentional weight loss. On admission there was elevated white blood cell count and C-reactive protein, as well as affected liver function tests. Initially pneumonia was suspected, but due to lack of improvement on pneumonia treatment, a PET-CT scan was performed, which showed a large multiloculated abscess in the liver. The abscess was drained using ultrasound guidance. Culture demonstrated Eikenella corrodens. Transesophageal echocardiography revealed aortic endocarditis. The patient was treated with antibiotics and abscess drainage, on which he slowly improved. He was discharged after 1.5 months of hospitalisation. On follow-up 2 months later, the patient was asymptomatic with normalized biochemistry and ultrasound showed complete regression of the abscess.

Conclusions

This is the first case of documented Eikenella corrodens concurrent liver abscess and endocarditis. The case report highlights that Eikenella corrodens should be considered as a cause of liver abscess. Empirical treatment of pyogenic liver abscess will most often cover Eikenella corrodens, but the recommended treatment is a third generation cephalosporin or a fluoroquinolon. A multiloculated liver abscess may require drainage several times during treatment. The finding of Eikenella corrodens should elicit an echocardiography to diagnose endocarditis even in patients without clinical signs of endocarditis.

Prosthetic Valve Endocarditis caused by HACEK Organisms: a Case Reports and Systematic Review of the Literature

HACEK is a rare cause of prosthetic valve endocarditis (PVE). We describe 42-year-old male patient who presented with Aggregatibacter aphrophilus PVE and cerebral infarct. A. aphrophilus was isolated from his blood cultures as the sole pathogen, which was confirmed by subsequent 16S rRNA sequencing. He was treated with valve replacement surgery and an 8 week course of pathogen-directed antibiotic therapy and followed for 20 months without recurrence.

Atypical presentation of infective endocarditis

The HACEK group of organisms are one of the infrequent causes of infective endocarditis. Infective endocarditis should be recognized and treated promptly to prevent excessive morbidity and mortality associated with the disease. Sometimes the diagnosis is delayed due to vague and subtle presentation. Through this case report, risk factors of Cardiobacterium hominis endocarditis and its atypical presentation is illustrated to increase the recognition of infective endocarditis as one of the differential diagnosis. [Full article available at http://rimed.org/rimedicaljournal-2016-07.asp, free with no login].

Aggregatibacter aphrophilus ventriculitis following C1-C2 transarticular screw fixation

OBJECTIVE

Central nervous system (CNS) infections after cervical spine surgery are a rare but serious complication and may be caused by uncommon pathogens. We report the case of a 57-year-old male who developed slowly progressive mental confusion with headaches, increased daytime sleepiness and mild gait disturbance within the last 3 weeks. Six weeks prior to admission to our department, he underwent an atlantoaxial fusion by C1-C2 transarticular screw fixation for rheumatoid arthritis related C1-C2 multidirectional instability.

METHODS

We analyzed clinical and neuroradiological findings.

RESULTS

The findings were consistent with communicating hydrocephalus secondary to ventriculitis and the left C1-C2 screw was found to be misplaced with perforation of the dura. The situation was interpreted as implant related surgical site infection of the cerebrospinal fluid followed by ventriculitis and hydrocephalus. Bacterial broad range 16S rRNA gene PCR from the cerebrospinal fluid (CSF) followed by sequencing identified Aggregatibacter aphrophilus as the causative agent, while conventional cultures remained negative due to its fastidious growth. The patient was successfully treated with a lumbar drain and intravenous ceftriaxone.

CONCLUSIONS

To our knowledge, this is the first report of Aggregatibacter aphrophilus ventriculitis following C1-C2 transarticular screw fixation.

Endocarditis due to gram-negative bacilli at a French teaching hospital over a 6-year period: clinical characteristics and outcome

BACKGROUND

Infective endocarditis (IE) due to gram-negative bacilli (GNB) is rare. However, several studies described a change in the epidemiological profile of patients within the past few years.

METHODS

We reviewed all cases diagnosed and followed in the infectious diseases ward of a French teaching hospital in Paris between 2009 and 2014, inclusive.

RESULTS

Among the 17 patients with definite GNB-IE (11 male, mean age 54 years), 12 (70%) were due to non-HACEK GNB and 5 (30%) to HACEK group GNB. A prosthetic valve was involved in 10 cases (8 in non-HACEK and 2 in HACEK group). Escherichia coli (4/12 patients) and Pseudomonas aeruginosa (3/12 patients) were the most common pathogens in the first group; all the pathogens in the second group were Haemophilus spp. One-third of the patients with non-HACEK GNB had nosocomial IE, whereas injection drug use-related infections were rare (2/12). All patients with HACEK infection had at least one complication (intracardiac abscess, stroke or other systemic embolization). All patients were treated by antibiotic combination therapy during a median time of 42 days (interquartile range (IQR) = 42-42) and 10 (59%) underwent cardiac surgery. One death at 9 months was observed in the non-HACEK group.

CONCLUSIONS

Regarding HACEK IE, this report supports the frequent association with vascular complications. Regarding non-HACEK GNB IE, this report supports the increasing proportion of nosocomial infections. We reported a high proportion of surgery in the therapeutic management of both HACEK and non-HACEK groups associated with no in-hospital mortality.

A Case of Aggregatibacter aphrophilus Multiple Abscess

We report a case of brain and lung abscesses caused by Agreggatibacter aphrophilus in a 43-YEAR-OLD man with past history of splenectomy and drug addiction, in the absence of endocarditis. Microbiological samples remain negatives and diagnosis was made by 16S rDNA PCR performance on abscess fluid for this coccobacillus that belongs to the HACEK group. The patient’s clinical symptoms resolved within 6 weeks of treatment with cefotaxim.

Permanent pacemaker-associated actinomycetemcomitans endocarditis: A case report

Aggregatibacter actinomycetemcomitans is a Gram-negative bacillus, member of the HACEK group of bacteria, and it is a very rare cause of endocarditis. It is also an extremely rare cause of device-associated infection of the heart. We describe the case of a 25 year-old man who presented with pacemaker-associated endocarditis due to Aggregatibacter actinomycetemcomitans and also discuss the implications and treatment of this organism.

A pediatric case of cardiobacterium hominis endocarditis

Gram negative endocarditis is relatively rare in pediatrics but when they occur they are most frequently caused by one of the HACEK (Haemophilus species, Actinobacillus actinomycetemcomitans, C. hominis, Eikenella corrodens and Kingella kingae) group of microorganisms. Within the HACEK group of microorganisms there have been approximately 100 cases of Cardiobacterium hominis endocarditis reported in the literature, but only 2 previous cases of endocarditis and one case of pericarditis have been reported in children. In this report, we present a case of a 12-year-old boy with a right ventricle to pulmonary artery conduit for Tetralogy of Fallot with pulmonary atresia who presented at an annual cardiology examination with a 3 week history of fatigue and was found to have a vegetation on routine echocardiogram. Subsequent blood cultures grew Cardiobacterium hominis and the patient was treated successfully with 6 weeks of appropriate antibiotic therapy. We present this case and a review of the literature of the HACEK group of microorganisms in pediatrics.

Haemophilus aphrophilus associated spleen abscess: an unusual presentation of subacute endocarditis

The HACEK group of bacteria (Haemophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella spp.), is uncommon pathogens of infective endocarditis, but can cause life-threatening events such as heart failure or formation of lethal emboli. Here we report a 58-year-old Asian man with a past history of congenital valvular heart disease who presented with sudden onset of left flank pain followed by fever with chills for 2 weeks. Abdominal computed tomography (CT) indicated a 1.6 cm abscess in the spleen. Culturing indicated the presence of Haemophilus aphrophilus. We diagnosed the patient with subacute endocarditis complicated with spleen abscess. The patient recovered fully after two weeks antibiotic (Ceftriaxone) treatment. Clinicians should give further attention to infective endocarditis caused by bacteria in the HACEK group in patients with metastatic infection such as spleen abscess with suspected valvular heart disease.

Pyogenic ventriculitis complicating Aggregatibacter aphrophilus infective endocarditis: A case report and literature review

Pyogenic ventriculitis (PV) is an uncommon, but frequently fatal infection that results from inflammation of the ventricular ependymal lining associated with a purulent ventricular system. PV has been rarely reported as a secondary complication of infective endocarditis. Prompt diagnosis and treatment with appropriate culture-directed antibiotics with adequate central nervous system penetration is crucial when managing patients who are suspected of having PV. The present study reports on a fatal case of a previously well 42-year-old alcoholic woman with infective endocarditis caused by Aggregatibacter aphrophilus, with secondary brain abscess and spontaneous rupture into the ventricles causing PV.