Gram-negative bacterial endocarditis in adults: state-of-the-heart

Clinical characteristics and outcomes in pseudomonas endocarditis: a systematic review of individual cases : Systematic review of pseudomonas endocarditis

BACKGROUND

The landscape of Pseudomonas infective endocarditis (IE) is evolving with the widespread use of cardiac implantable devices and hospital-acquired infections. This systematic review aimed to evaluate the emerging risk factors and outcomes in Pseudomonas IE.

METHODS

A literature search was performed in major electronic databases (PubMed, Scopus, and Google Scholar) with appropriate keywords and combinations till November 2023. We recorded data for risk factors, diagnostic and treatment modalities. This study is registered with PROSPERO, CRD42023442807.

RESULTS

A total of 218 cases (131 articles) were included. Intravenous drug use (IDUs) and prosthetic valve endocarditis (PVE) were major risk factors for IE (37.6% and 22%). However, the prosthetic valve was the predominant risk factor in the last two decades (23.5%). Paravalvular complications (paravalvular leak, abscess, or pseudoaneurysm) were described in 40 cases (18%), and the vast majority belonged to the aortic valve (70%). The mean time from symptom onset to presentation was 14 days. The incidence of difficult-to-treat resistant (DTR) pseudomonas was 7.4%. Valve replacement was performed in 57.3% of cases. Combination antibiotics were used in most cases (77%), with the aminoglycosides-based combination being the most frequently used (66%). The overall mortality rate was 26.1%. The recurrence rate was 11.2%. Almost half of these patients were IDUs (47%), and most had aortic valve endocarditis (76%).

CONCLUSIONS

This review highlights the changing epidemiology of Pseudomonas endocarditis with the emergence of prosthetic valve infections. Acute presentation and associated high mortality are characteristic of Pseudomonas IE and require aggressive diagnostic and therapeutic approach.

Empirical treatment and mortality in bacteremia due to extended spectrum β-lactamase producing Enterobacterales (ESβL-E), a retrospective cross-sectional study in a tertiary referral hospital from Colombia

BACKGROUND

Infections caused by extended spectrum β-lactamase (ESβL) producing bacteria are common and problematic. When they cause bloodstream infections, they are associated with significant morbidity and mortality.

METHODS

A retrospective cross-sectional observational study was conducted in a single center in Pereira, Colombia. It included people hospitalized with bacteremia due to gram-negative bacilli with the extended-spectrum β-lactamase producing phenotype. A logistic regression analysis was constructed. Clinical characteristics and risk factors for death from sepsis were established.

RESULTS

The prevalence of bacteremia due to Enterobacterales with extended-spectrum β-lactamase producing phenotype was 17%. 110 patients were analyzed. Most patients were men (62%) with a median age of 58 years, hospital mortality was 38%. Admission to intensive care was 45%. The following risk factors for mortality were established: shock requiring vasoactive support, Pitt score > 3 points, and not having an infectious disease consultation (IDC).

CONCLUSIONS

bacteremia due to Enterobacterales with extended-spectrum β-lactamase producing phenotype have a high mortality. Early recognition of sepsis, identification of risk factors for antimicrobial resistance, and prompt initiation of appropriate empiric antibiotic treatment are important. An infectious disease consultation may help improve outcomes.

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.

Leclercia adecarboxylata infective endocarditis in a man with mitral stenosis: A case report and review of the literature

BACKGROUND

Infective endocarditis (IE) is a rare disease with a high mortality rate. Leclercia adecarboxylata (L. adecarboxylata) is a movable Gram-negative bacillus of enterobacteriaceae, and it can rarely be a pathogen which often affects immunodeficient patients. There are about three cases of immunocompetent patients with monomicrobial L. adecarboxylata infection. There are only three reported cases of IE caused by L. adecarboxylata in the world. The mitral valve is often affected in IE, and the prognosis for IE with mitral valve lesions is often poor.

CASE SUMMARY

A 51-year-old man was found to have moderate to severe mitral stenosis on echocardiography. He came to our Cardiothoracic Surgery Department for surgical management. A diastolic murmur was heard on auscultation of the heart in the mitral region. On the second day of hospitalisation, he presented with slurred speech, reduced muscle strength in the left limb, and acute cerebral infarction on cranial computed tomography. Surgical treatment was decided to postpone. On the ninth day of admission, the patient developed a sudden high fever and shock and was transferred to the Cardiac Intensive Care Unit, where echocardiogram revealed an anterior mitral valve leaflet vegetation. After empirical anti-infective treatment with vancomycin (1g q12h), an emergency valve replacement was performed. Bacterial culture identified L. adecarboxylata. Anti-infective treatment with piperacillin-tazobactam (4.5g q8h) was added for 4 wk. Follow-up echocardiography showed normal bioprosthetic valve function after mitral valve replacement.

CONCLUSION

We report the first case of L. adecarboxylata IE in China, and clinicians should pay attention to this pathogen.

Importance of early diagnosis and surgical treatment of calcified amorphous tumor-related native valve endocarditis caused by Escherichia coli: a case report

BACKGROUND

Unlike Escherichia coli bacteremia, which is common, E. coli endocarditis is uncommon, particularly in patients with native valve, leading to its delayed diagnosis.

CASE PRESENTATION

We present a case of infective endocarditis caused by E. coli in a 78-year-old Japanese man with type 2 diabetes, involving persistent bacteremia and vegetation on the mitral valve (measuring 18 × 4.2 mm in diameter). He presented with recurrent fever after antimicrobial treatment for pyelonephritis. He received antibiotic therapy for 6 weeks and required surgical removal of a calcified amorphous tumor and vegetation with mitral valvuloplasty 7 days after admission. Despite an episode of multiple cerebral infarctions, he recovered fully from the infection.

CONCLUSIONS

Follow-up blood cultures should be performed for Gram-negative bacilli bacteremia among patients with unknown focus and an atypical clinical course after treatment. Early diagnosis and aggressive surgical intervention are paramount to achieving good clinical outcomes.

Gram-negative endocarditis: disease presentation, diagnosis and treatment

PURPOSE OF REVIEW

Gram-negative bacilli (GNB) cause between 1% and 10% of infective endocarditis (IE). Most episodes are caused by microorganisms of the Haemophilus spp., Aggregatibacter spp. Cardiobacterium spp., Eikenella spp., and Kingella spp (HACEK) group. The frequency of IE caused by non-HACEK (GNB-IE) has increased in recent years. Uncertainties persist regarding its best medical treatment and the appropriateness and timing of surgical treatment. In addition, there are new drugs with activity against multiresistant microorganisms, of which there is little experience in this disease. We review this topic by answering the most frequently asked questions that arise among our colleagues.

RECENT FINDINGS

HACEK microorganisms cause 1.5-2% of IE with only a 2% mortality. In contrast, non-HACEK GNB-IE accounts for 2.5-3% of all IE cases and is associated with nosocomial acquisition, advanced age, solid organ transplantation and 20-30% mortality. Drug addiction is important in areas with epidemic opioid abuse.

SUMMARY

The frequency of IE caused by GNB has been modified in recent years. HACEK episodes are no longer treated with ampicillin and aminoglycosides. In non-HACEK GNB-IE, combination therapy with a beta-lactam and a quinolone or aminoglycoside is recommended. The surgical indication and its value are evident in many patients. Management should rely on a collaborative group with experience in this disease.

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.

A relapsed Pseudomonas stutzeri prosthetic valve endocarditis: a case report and review of the literature

BACKGROUND

Pseudomonas stutzeri is a nonfluorescent denitrifying bacterium widely distributed in the environment, and it has also been isolated as an opportunistic pathogen from humans. It is a Gram-negative bacterium and a common inhabitant of soil and water.

CASE PRESENTATION

We report the case of a 51-year-old arab gentleman who has systemic lupus erythematous complicated by lupus nephritis and underwent renal transplantation twice. He underwent mitral valve replacement and 4 years later was diagnosed with prosthetic valve endocarditis caused by Pseudomonas stutzeri.

CONCLUSIONS

Literature review was conducted and revealed that this pathogen may be of a particular medical relevance in immunocompromised patients. Our case proves that early infection and relapse despite optimal antibiotics course are possible outcomes of Pseudomonas stutzeri endocarditis. To the best of our knowledge, this is the second case of fulminant early prosthetic valve endocarditis occurring only 1 month post-cardiac surgery with relapse despite a complete antibiotics course.

Non-HACEK gram negative bacilli endocarditis: Analysis of a national prospective cohort

BACKGROUND

Infective endocarditis (IE) due to non-HACEK bacilli (Haemophilus species, Actinobacillus, Cardiobacterium, Eikenella, or Kingella) is uncommon and poorly described. The objectives of this study were to describe non-HACEK Gram-Negative Bacilli (GNB) IE cases and compare characteristic of IE produced by Enterobacterales and non-fermenting (NF) GNB.

METHODS

From January 2008 to December 2018, 3910 consecutive patients with definitive IE diagnosis, defined with Modified Duke criteria, either clinical or pathological criteria (e.g. demonstration of non-HACEK GNB in valve culture)were prospectively included.

RESULTS

A total of 104 IE cases were caused by non-HACEK GNB (2.6%). Compared to IE due to other microorganisms (excluding HACEK GNB), patients with non-HACEK GNB IE presented with higher age (71 years [IQR 62-78] vs 68 years [IQR: 57-77]; p = 0.026), higher proportion of women (52% vs 31.5%, p < 0.001), higher Charlson Index (5 [IQR: 4-8] vs 4 [IQR 3-7], p = 0.003) and higher in-hospital mortality (36.5% vs 27.1%, p = 0.034). Enterobacterales cases were more frequently associated with genitourinary focus (32.8% vs 5.0%, p = 0.001). NFGNB endocarditis more frequently affected right valves (20.0% vs. 6.3%, p = 0.033), had more common healthcare-related acquisition (67.5% vs. 43.7%, p = 0.030) and venous catheter as focus (40.0% vs. 17.2%, p = 0.019). In the multivariant model, factors related with hospital mortality were: age (OR 1.05, 95%CI 1.00-1.09, p = 0.042), prosthetic valve (OR 2.31, 95%CI 0.90-5.88, p = 0.080), and not performing surgery when indicated (OR 3.60, 95%CI 1.17-11.05, p = 0.025).Patients treated with quinolone combination had lower mortality (OR 0.29; 95%CI 0.09-0.96; p = 0.043).

CONCLUSION

Non-HACEK GNB IE is a rare infection characterized by affecting elderly patients with high comorbidity, nosocomial acquisition and unfavorable outcome. Age, prosthetic valve and not performing surgery when indicated are associated with mortality.

Infective endocarditis caused by Enterobacteriaceae: phenotypic and molecular characterization of Escherichia coli and Klebsiella pneumoniae in Rio de Janeiro, Brazil

The etiological agent for infective endocarditis (IE), a life-threatening disease, is usually gram-positive bacteria. However, gram-negative bacteria can rarely cause IE and 4% of cases are associated with morbidity and mortality. This study aimed to characterize Escherichia coli and Klebsiella pneumoniae isolates from the blood of patients with IE. The characteristics of blood isolates were compared with those of urinary isolates from patients with urinary tract infections (UTIs). The results of this study revealed that K. pneumoniae isolates from patients with IE were phylogenetically related to those from patients with UTI. Additionally, the resistance phenotype, resistance gene, virulence gene, and plasmid profiles were similar between the blood and urinary isolates. The isolates belonging to the sequence types (STs) 76, 36, 101 (K. pneumoniae), and 69 (E. coli) are reported to be associated with drug resistance. The Enterobacteriaceae isolates from patients with IE did not produce extended-spectrum β-lactamase or carbapenemase. Additionally, this study investigated the virulence phenotype, biofilm formation ability, and the ability to adhere to the epithelial cells in vitro of the isolates. The isolates from patients with IE exhibited weaker biofilm formation ability than the urinary isolates. All isolates from patients with IE could adhere to the renal epithelial cells. However, three isolates from patients with UTIs could not adhere to the epithelial cells. The closely related K. pneumoniae isolates (648, KP1, KP2, KP3, and KP4) could not form biofilms or adhere to the epithelial cells. In summary, the molecular analysis revealed that the genetic characteristics of IE-causing K. pneumoniae and E. coli were similar to those of UTI-causing isolates. These isolates belonged to the STs that are considered treatable. Genetically similar isolates did not exhibit the same virulence phenotype. Thus, these non-hypervirulent clones must be monitored as they can cause complex infections in susceptible hosts.

Triggers of Inflammatory Heart Disease

Inflammatory heart disease (IHD) is a group of diseases that includes pericarditis, myocarditis, and endocarditis. Although males appear to be more commonly affected than females, IHD can be seen in any age group. While the disease can be self-limiting leading to full recovery, affected individuals can develop chronic disease, suggesting that identification of primary triggers is critical for successful therapies. Adding to this complexity, however, is the fact that IHD can be triggered by a variety of infectious and non-infectious causes that can also occur as secondary events to primary insults. In this review, we discuss the immunological insights into the development of IHD as well as a mechanistic understanding of the disease process in animal models.

Native valve infective endocarditis due to ampicillin-resistant Escherichia coli in the postoperative period of a right radical nephrectomy due to xanthogranulomatous pyelonephritis

Infective endocarditis (IE) due to Escherichia coli is a rare disease, although increasingly frequent. Persistent fever in septic patients despite adequate treatment raises the need to consider IE as a differential diagnosis. We present the case of a 36-year-old male patient who underwent a radical right nephrectomy as a result of diagnosis of xanthogranulomatous pyelonephritis, presenting in the postoperative period a state of septic shock with persistent fever of 41°C. Given the finding of a new-onset murmur, he was diagnosed with a mitroaortic IE by means of a transesophageal echocardiogram (TEE), having to undergo cardiac surgery for valve replacement. After multiple postoperative complications, he is successfully discharged.

Best Practices of Blood Cultures in Low- and Middle-Income Countries

Bloodstream infections (BSI) have a substantial impact on morbidity and mortality worldwide. Despite scarcity of data from many low- and middle-income countries (LMICs), there is increasing awareness of the importance of BSI in these countries. For example, it is estimated that the global mortality of non-typhoidal Salmonella bloodstream infection in children under 5 already exceeds that of malaria. Reliable and accurate diagnosis of these infections is therefore of utmost importance. Blood cultures are the reference method for diagnosis of BSI. LMICs face many challenges when implementing blood cultures, due to financial, logistical, and infrastructure-related constraints. This review aims to provide an overview of the state-of-the-art of sampling and processing of blood cultures, with emphasis on its use in LMICs. Laboratory processing of blood cultures is relatively straightforward and can be done without the need for expensive and complicated equipment. Automates for incubation and growth monitoring have become the standard in high-income countries (HICs), but they are still too expensive and not sufficiently robust for imminent implementation in most LMICs. Therefore, this review focuses on "manual" methods of blood culture, not involving automated equipment. In manual blood cultures, a bottle consisting of a broth medium supporting bacterial growth is incubated in a normal incubator and inspected daily for signs of growth. The collection of blood for blood culture is a crucial step in the process, as the sensitivity of blood cultures depends on the volume sampled; furthermore, contamination of the blood culture (accidental inoculation of environmental and skin bacteria) can be avoided by appropriate antisepsis. In this review, we give recommendations regarding appropriate blood culture sampling and processing in LMICs. We present feasible methods to detect and speed up growth and discuss some challenges in implementing blood cultures in LMICs, such as the biosafety aspects, supply chain and waste management.

Infective endocarditis and brain abscess secondary to Aggregatibacter aphrophilus

Aggregatibacter aphrophilus is a rare cause of infective endocarditis that was first described in 1940 by Khairat et al. and is now classified under the HACEK group of bacteria (Haemophilus spp., Aggregatibacter spp., Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae). There is limited literature describing the extracardiac complications of infective endocarditis caused by this organism. We report a case of a 53-year-old male with no significant past medical history who developed acute infective endocarditis complicated by a brain abscess caused by A. aphrophilus. The patient underwent aspiration of the abscess and treated with a long course of intravenous antimicrobials. This case represents a rare complication of infective endocarditis caused by A. aphrophilus and to the best of our knowledge, is the second reported case in the literature describing such a complication in a previously healthy patient. Although neurological sequela is associated with higher mortality and may be the presenting symptom of infective endocarditis, it may also be clinically silent - only detected upon imaging.

Escherichia coli endocarditis of a native mitral valve

Escherichia coli (E.coli) is a rare cause of endocarditis, although is a common causative agent of bacteremia. An 89-year-old woman presented with recurrent episodes of fever and persistent E. coli bacteremia with 3-month duration, despite antimicrobial therapy. At first, a urinary tract infection was diagnosed and later a mycotic aneurysm of the abdominal aorta was found and required an endovascular repair. The persistence of fever and the evidence of a systolic murmur at the mitral focus raised the suspicion of endocarditis. A transesophageal echocardiogram and a cardiac Magnetic Resonance Imaging (MRI) confirmed the presence of a vegetation at the mitral valve and the patient was treated with ceftriaxone. The presence of comorbid conditions and certain bacterial virulence factors predispose to this rare condition. A high level of suspicion is important to early diagnosis and prompt therapy.

Native valve endocarditis due to Escherichia coli infection: a case report and review of the literature

Background

Infective endocarditis due to Escherichia coli is a rare disease but is increasing in frequency, especially among older women. In addition, its mortality rate is higher than that of endocarditis due to the HACEK-group gram-negative bacteria (Haemophilus spp., Aggregatibacter spp., Cardiobacterium hominis, Eikenella corrodens, and Kingela spp.).

Case presentation

A 58-year-old Japanese woman with a history of alcohol abuse was admitted to our hospital because of a fever. She was diagnosed with infective endocarditis due to E. coli based on repeated blood cultures and transthoracic echocardiography, which revealed vegetations attached to the anterior leaflet and chordae tendineae of the mitral valve. Despite administration of sulbactam/ampicillin and gentamycin, she developed purulent spondylitis during hospitalization and required treatment with meropenem administration for 6 weeks, leading to resolution of the endocarditis. She took oral levofloxacin for 2 months, and the spondylitis was completely cured 7 months after discharge.

Conclusion

Escherichia coli affects native valves without degenerative valvulopathy rather than prosthetic valves, especially in patients with risk factors such as an immunosuppressive status, excessive alcohol consumption, or treatment with hemodialysis. Peripheral embolization, congestive heart failure, and valve-ring abscesses are major complications of E. coli endocarditis; notably, infective myocarditis can also occur. The mortality and surgical intervention rates are 21% and 42%, respectively. Physicians should be cognizant of the necessity of surgical intervention when E. coli endocarditis is resistant to antibiotic therapy.

[Infective endocarditis in the elderly: The current view of the problem]

The review gives the current views of the etiology and risk factors of infective endocarditis (IE) in the elderly. It reports the specific clinical picture of the disease at this age, including clinically apparent syndromes, comorbidity, and various clinical signs and peculiarities of IE. Particular emphasis is placed on the diagnosis of an endocardial infectious lesion, which is based on the use of the modified Duke criteria. The methods of IE diagnosis, particularly microbiological examination, imaging techniques, among which echocardiography in different modes plays a particular role, are listed. The treatment of the disease is based on the latest recommendations for antibiotic therapy with and without regard to a specific etiological factor. The issues of surgical intervention, as well as approaches to preventing IE in elderly people are discussed.

[Infective endocarditis due to non-HACEK gram-negative bacilli in a Level III cardiovascular center in Argentina (1998-2016)]

Non-HACEK Gram-negative bacilli are a rare cause of infective endocarditis. Epidemiological, diagnostic and prognostic aspects of this entity are little known, and there is limited experience. The aim of this study was to analyze the clinical, microbiological and in-hospital outcomes of non-HACEK Gram negative bacilli endocarditis and to compare them with those due to other microorganisms.

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.

Risk Factors and Outcomes of Endocarditis Due to Non-HACEK Gram-Negative Bacilli: Data from the Prospective Multicenter Italian Endocarditis Study Cohort

The objective of this study was to investigate predisposing factors and outcomes of infective endocarditis (IE) caused by non-HACEK Gram-negative bacilli (GNB) in a contemporary multicenter cohort. Patients with IE due to GNB, prospectively observed in 26 Italian centers from 2004 to 2011, were analyzed. Using a case-control design, each case was compared to three age- and sex-matched controls with IE due to other etiologies. Logistic regression was performed to identify risk factors for IE due to GNB. Factors associated with early and late mortality were assessed by Cox regression analysis. The study group comprised 58 patients with IE due to GNB. We found that Escherichia coli was the most common pathogen, followed by Pseudomonas aeruginosa and Klebsiella pneumoniae The genitourinary tract as a source of infection (odds ratio [OR], 13.59; 95% confidence interval [CI], 4.63 to 39.93; P < 0.001), immunosuppression (OR, 5.16; 95% CI, 1.60 to 16.24; P = 0.006), and the presence of a cardiac implantable electronic device (CIED) (OR, 3.57; 95% CI, 1.55 to 8.20; P = 0.003) were factors independently associated with IE due to GNB. In-hospital mortality was 13.8%, and mortality rose to 30.6% at 1 year. A multidrug-resistant (MDR) etiology was associated with in-hospital mortality (hazard ratio [HR], 21.849; 95% CI, 2.672 to 178.683; P = 0.004) and 1-year mortality (HR, 4.408; 95% CI, 1.581 to 12.287; P = 0.005). We conclude that the presence of a genitourinary focus, immunosuppressive therapy, and an indwelling CIED are factors associated with IE due to GNB. MDR etiology is the major determinant of in-hospital and long-term mortality.

Effect of Histophilus somni on Heart and Brain Microvascular Endothelial Cells

Histophilus somni is a pathogenic gram-negative bacterium responsible for pneumonia and septicemia in cattle. Sequelae include infectious thrombotic meningoencephalitis (ITME), myocarditis, arthritis, and abortion. These syndromes are associated with widespread vasculitis and thrombosis, implicating a role for endothelium in pathogenesis. Histopathologic and immunohistochemical investigation of 10 natural cases of bovine H. somni myocarditis and 1 case of ITME revealed intravascular H. somni in large biofilm-like aggregates adherent to the luminal surface of microvascular endothelium. Ultrastructurally, bacterial communities were extracellular and closely associated with degenerating or contracted endothelial cells. Histophilus somni was identified by bacterial culture and/or immunohistochemistry. Western blots of the bacterial isolates revealed that they expressed the immunodominant protective 40 kDa OMP and immunoglobulin-binding protein A (IbpA) antigens. The latter is a large surface antigen and shed fibrillar antigen with multiple domains. The cytotoxic DR2Fic domain of IbpA was conserved as demonstrated by polymerase chain reaction. Treatment of endothelial cells in vitro with IbpA in crude culture supernatants or purified recombinant GST-IbpA DR2Fic (rDR2) cytotoxin induced retraction of cultured bovine brain microvascular endothelial cells. By contrast, no retraction of bovine endothelium was induced by mutant rDR2H/A with an inactive Fic motif or by a GST control, indicating that the cytotoxic DR2Fic motif plays an important role in endothelial cell retraction in vasculitis. The formation of biofilm-like aggregates by H. somni on bovine microvascular endothelium may be fundamental to its pathogenesis in heart and brain.

Klebsiella oxytoca Endocarditis With Complete Heart Block

Gram-negative bacterial endocarditis causes 5% of all bacterial endocarditis. Among gram-negative bacteria, Klebsiella species are rare causes of native valve endocarditis. Klebsiella oxytoca is an extremely rare subspecies that can infrequently cause endocarditis and is associated with poor outcome. We report a case of Klebsiella oxytoca endocarditis in an elderly man who initially presented with stroke but later developed sepsis and heart block secondary to endocarditis.

HACEK endocarditis: a review

INTRODUCTION

The HACEK group, referring to Haemophilus spp., Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae, is a rare cause of infective endocarditis (IE). It causes the majority of Gram-negative endocarditis cases and has an excellent prognosis and simple management if properly identified. However, delay in diagnosis and associated complications can render the infection fatal.

AREAS COVERED

Over the past few decades, there have been tremendous advancements in understanding the manifestations and progression of HACEK endocarditis (HE). This review tackles the epidemiology of HE, the microbiological characteristics of each organism in the HACEK group, the methods used to diagnose HE, the clinical manifestations, complications, and mortality of patients with HE, as well as the recommended treatment and preventive methods. Expert Commentary: The lack of robust randomized controlled trials in diagnosis and treatment of HE makes it difficult to determine the optimal management of such infections. Nevertheless, advancements in culturing methods have shown progress in isolating and identifying these fastidious organisms. Positive blood cultures for any of the HACEK organisms in the setting of no definite focus of infection is highly suggestive of HE. In such cases, treatment with ceftriaxone or a fluoroquinolone, even without obtaining antibiotic susceptibilities, should be initiated. Moreover, the decision to proceed with surgical intervention should be individualized. As is the case for other IE, HE requires the collaboration of a multidisciplinary team consisting of the infectious disease specialist, cardiologist, cardiothoracic surgeon, and the microbiologist.

A comparison of different antibiotic regimens for the treatment of infective endocarditis

BACKGROUND

Infective endocarditis is a microbial infection of the endocardial surface of the heart. Antibiotics are the cornerstone of treatment, but their use is not standardised, due to the differences in presentation, populations affected and the wide variety of micro-organisms that can be responsible.

OBJECTIVES

To assess the existing evidence about the clinical benefits and harms of different antibiotics regimens used to treat people with infective endocarditis.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE Classic and EMBASE, LILACS, CINAHL and the Conference Proceedings Citation Index on 30 April 2015. We also searched three trials registers and handsearched the reference lists of included papers. We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled trials assessing the effects of antibiotic regimens for treating possible infective endocarditis diagnosed according to modified Duke's criteria. We considered all-cause mortality, cure rates and adverse events as the primary outcomes. We excluded people with possible infective endocarditis and pregnant women.

DATA COLLECTION AND ANALYSIS

Three review authors independently performed study selection, 'Risk of bias' assessment and data extraction in duplicate. We constructed 'Summary of findings' tables and used GRADE methodology to assess the quality of studies. We described the included studies narratively.

MAIN RESULTS

Four small randomised controlled trials involving 728 allocated/224 analysed participants met our inclusion criteria. These trials had a high risk of bias. Drug companies sponsored two of the trials. We were unable to pool the data due to the heterogeneity in outcome definitions and the different antibiotics used.The included trials compared the following antibiotic schedules. The first trial compared quinolone (levofloxacin) plus standard treatment (anti-staphylococcal penicillin (cloxacillin or dicloxacillin), aminoglycoside (tobramycin or netilmicin) and rifampicin) versus standard treatment alone reporting uncertain effects on all-cause mortality (8/31 (26%) with levofloxacin plus standard treatment versus 9/39 (23%) with standard treatment alone; RR 1.12, 95% CI 0.49 to 2.56, very low quality evidence). The second trial compared daptomycin versus low-dose gentamicin plus an anti-staphylococcal penicillin (nafcillin, oxacillin or flucloxacillin) or vancomycin. This showed uncertain effects in terms of cure rates (9/28 (32.1%) with daptomycin versus 9/25 (36%) with low-dose gentamicin plus anti-staphylococcal penicillin or vancomycin, RR 0.89 95% CI 0.42 to 1.89; very low quality evidence). The third trial compared cloxacillin plus gentamicin with a glycopeptide (vancomycin or teicoplanin) plus gentamicin. In participants receiving gentamycin plus glycopeptide only 13/23 (56%) were cured versus 11/11 (100%) receiving cloxacillin plus gentamicin (RR 0.59, 95% CI 0.40 to 0.85; very low quality evidence). The fourth trial compared ceftriaxone plus gentamicin versus ceftriaxone alone and found no conclusive differences in terms of cure (15/34 (44%) with ceftriaxone plus gentamicin versus 21/33 (64%) with ceftriaxone alone, RR 0.69, 95% CI 0.44 to 1.10; very low quality evidence).The trials reported adverse events, need for cardiac surgical interventions, uncontrolled infection and relapse of endocarditis and found no conclusive differences between comparison groups (very low quality evidence). No trials assessed septic emboli or quality of life.

AUTHORS' CONCLUSIONS

Limited and very low quality evidence suggested that there were no conclusive differences between antibiotic regimens in terms of cure rates or other relevant clinical outcomes. However, because of the very low quality evidence, this needs confirmation. The conclusion of this Cochrane review was based on randomised controlled trials with high risk of bias. Accordingly, current evidence does not support or reject any regimen of antibiotic therapy for treatment of infective endocarditis.

HACEK endocarditis: state-of-the-art

The HACEK group of bacteria - Haemophilus parainfluenzae, Aggregatibacter spp. (A. actinomycetemcomitans, A. aphrophilus, A. paraphrophilus, and A. segnis), Cardiobacterium spp. (C. hominis, C. valvarum), Eikenella corrodens, and Kingella spp. (K. kingae, K. denitrificans) - are fastidious gram-negative bacteria, part of the normal microbiota of oral and upper respiratory tract in humans. Although their pathogenicity is limited, they are responsible for 1-3% of all infective endocarditis. HACEK endocarditis mostly affect patients with underlying heart disease or prosthetic valves, and are characterized by an insidious course, with a mean diagnosis delay of 1 month (Haemophilus spp.) to 3 months (Aggregatibacter and Cardiobacterium spp.). The advent of continuously monitored blood culture systems with enriched media has erased the need for extended incubation for the diagnosis of HACEK endocarditis. Medical treatment relies on third-generation cephalosporin, with a favorable outcome in 80-90% of cases, with or without cardiac surgery.

The need for a specific risk prediction system in native valve infective endocarditis surgery

The need for a specific risk score system for infective endocarditis (IE) surgery has been previously claimed. In a single-center pilot study, preliminary to future multicentric development and validation, bivariate and multivariate (logistic regression) analysis of early postoperative mortality predictors in 440 native valve IE patients were performed. Mathematical procedures assigned scores to the independent predictors emerged (AUC of the ROC curve: 0.88). Overall mortality was 9.1%. Six predictors were identified and assigned scores, including age (5–13 points), renal failure (5), NYHA class IV (9), critical preoperative state (11), lack of preoperative attainment of blood culture negativity (5), perivalvular involvement (5). Four risk classes were drawn ranging from “very low risk” (≤5 points, mean predicted mortality 1%), and to “very high risk” (≥20 points, 43% mortality). IE-specific risk stratification models are both needed, as disease-specific factors (e.g., cultures, abscess), beside the generic ones (e.g., age, renal impairment) affect mortality, and feasible.