Evaluation of 16S rDNA Heart Tissue PCR as a Complement to Blood Cultures for the Routine Etiological Diagnosis of Infective Endocarditis

Novel Diagnostic Methods for Infective Endocarditis

Infective endocarditis (IE) remains a dangerous disease and continues to have a high mortality rate. Unfortunately, despite continuous improvements in diagnostic methods, in many cases, blood cultures remain negative, and the pathogen causing endocarditis is unknown. This makes targeted therapy and the selection of appropriate antibiotics impossible. Therefore, we present what methods can be used to identify the pathogen in infective endocarditis. These are mainly molecular methods, including PCR and MGS, as well as imaging methods using radiotracers, which offer more possibilities for diagnosing IE. However, they are still not widely used in the diagnosis of IE. The article summarizes in which cases we should choose them and what we are most hopeful about in further research into the diagnosis of IE. In addition, registered clinical trials that are currently underway for the diagnosis of IE are also presented.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

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

Ureaplasma parvum Septic Arthritis, a Clinic Challenge

Ureaplasma parvum is usually part of the normal genital microbiota. Rarely, it can cause invasive infections such as septic arthritis or meningitis. A case of a 74-year-old woman with follicular lymphoma who developed cellulitis followed by elbow arthritis with negative routine bacterial cultures is described. U. parvum was identified in the synovial fluid using a broad-range 16S ribosomal RNA gene polymerase chain reaction (PCR) and also in vaginal fluid by a targeted PCR (Anyplex™ II STI-7). Multilocus Sequence Typing (MLST) revealed that isolates from both sources belonged to ST4, a worldwide distributed clone. Treatment consisted of surgery and targeted antibiotic therapy with doxycycline and azithromycin. Evolution showed initial clinical improvement in arthritis despite functional sequelae. Ureaplasma arthritis should be considered as a rare cause of arthritis in negative culture, especially in immunosuppressed patients. In these cases, the treatment is not well established, but according to this and previous works, patients could improve with doxycycline, azithromycin or fluoroquinolone therapy on a prolonged basis.

Endocarditis in the intensive care unit: an update

PURPOSE OF REVIEW

The incidence of infective endocarditis (IE) is increasing worldwide, resulting in a higher number of patients with IE being admitted to intensive care units (ICU). Nearly half of patients with IE develop a complication during their clinical course. However, few well conducted studies or reviews are devoted to critically ill IE patients. This review discusses the contemporary perioperative and intensive care literature.

RECENT FINDINGS

IE epidemiology is changing towards elderly and frail patients. ICU patients are at risk of risk of developing IE because they are often in a pro-inflammatory state and many also have several indwelling catheters, which favors infection. Increased performance and recent advances in cardiac imaging allow for easier diagnosis of EI, but the applicability of these techniques to ICU patients is still relatively limited. New developments in antibiotic treatment and adjunctive therapies are explored further in this review.

SUMMARY

The lack of evidence on ICU patients with IE highlights the critical importance of multidisciplinary decision-making and the need for further research.

Guanxin Xiaoban capsules could treat atherosclerosis by affecting the gut microbiome and inhibiting the AGE-RAGE signalling pathway

Introduction. Atherosclerosis is a chronic disorder in which plaque builds up in the arteries and is associated with several cardiovascular and cerebrovascular diseases such as coronary artery disease, cerebral infarction and cerebral haemorrhage. Therefore, there is an urgent need to discover new medications to treat or prevent atherosclerosis.Hypothesis/Gap Statement. The active components of Guanxin Xiaoban capsules may have an effect on the gut microbiome of patients with atherosclerosis and have a role in their therapeutic targets.Aim. The aim of this study was to identify genes and pathways targeted by active ingredients in Guanxin Xiaoban capsules for the treatment of atherosclerosis based on network pharmacology and analysis of changes to the gut microbiome.Methods. Mice were treated with Guanxin Xiaoban capsules. The 16S rDNA genome sequence of all microorganisms from each group of faecal samples was used to evaluate potential structural changes in the gut microbiota after treatment with Guanxin Xiaoban capsules. Western blotting and real-time quantitative PCR were used to detect gene targets in aortic and liver tissues. Haematoxylin and eosin staining was used to observe improvements in mouse arterial plaques.Results. The gut microbiota of atherosclerotic mice is disturbed. After Guanxin Xiaoban treatment, the abundance of bacteria in the mice improved, with an increase in the proportion of Akkermansia and a significant decrease in the proportion of Faecalibaculum. The main ingredients of Guanxin Xiaoban capsules are calycosin, liquiritin, ferulic acid, ammonium glycyrrhizate, aloe emodin, rhein and emodin. The core genes of this network were determined to be glutathione S-transferase mu 1 (GSTM1), vascular endothelial growth factor A (VEGFA) and cyclin-dependent kinase inhibitor 1A (CDKN1A). The compound-target gene network revealed an interaction between multiple components and targets and contributed to a better understanding of the potential therapeutic effects of the capsules on atherosclerosis. In addition, expression of the AGE-receptor for the AGE (RAGE) pathway was significantly inhibited and the mice showed signs of arterial plaque reduction. Guanxin Xiaoban capsules may improve atherosclerosis and reduce the plaque area by inhibiting the AGE-RAGE signalling pathway to delay the development of atherosclerosis. This mechanism appears to involve changes in the gut microbiota. Therefore, Guanxin Xiaoban capsules have potential value as a treatment for atherosclerosis.

Oral bacteria in infective endocarditis requiring surgery: a retrospective analysis of 134 patients

Objectives

It has been reported that bacteria associated with infective endocarditis originate from the oral cavity in 26–45% of cases. However, little is known on the counts and species of periodontal microbiota in infected heart valves. The aim of this study was to identify these aspects of periodontal microbiota in infective endocarditis and to potentially initiate a dental extraction concept for periodontally compromised teeth concerning patients requiring heart valve surgery.

Materials and methods

The retrospective study group consisted of tissue samples from infected heart valves of 683 patients who had undergone heart valve surgery. Before patients had undergone cardiac surgery, the following laboratory tests confirmed the occurrence of endocarditis in all patients: blood cultures, echocardiography, electrocardiography, chest X-ray, and electrophoresis of the serum proteins. The specimens were aseptically obtained and deep frozen immediately following surgery. Microbiological diagnosis included proof of germs (dichotomous), species of germs, and source of germs (oral versus other).

Results

Microbiota was detected in 134 (31.2%) out of 430 enrolled patients. Oral cavity was supposed to be the source in 10.4% of cases, whereas microbiota of the skin (57.5%) and gastrointestinal tract (GIT, 24.6%) were detected considerably more frequently. Moreover, periodontal bacteria belonged mostly to the Streptococci species and the yellow complex. None of the detected bacteria belonged to the red complex.

Conclusion

Most frequently, the skin and GIT represented the site of origin of the microbiota. Nevertheless, the oral cavity represented the source of IE in up to 10%.

Consequently, it needs to be emphasized that a good level of oral hygiene is strongly recommended in all patients undergoing heart valve surgery in order to reduce the bacterial load in the oral cavity, thereby minimizing the hematogenous spread of oral microbiota. The prerequisites for conservative dental treatment versus radical tooth extraction must always be based on the patient’s cooperation, and the clinical intraoral status on a sense of proportion in view of the overall clinical situation due to the underlying cardiac disease.

Clinical relevance

The oral cavity is a source of oral microbiota on infected heart valves. Patients requiring heart valve surgery should always undergo a critical evaluation of dental treatment affecting periodontally compromised teeth, favoring a systematic, conservative-leaning recall.