Silent Native-valve Endocarditis Caused by Propionibacterium acnes

Infective endocarditis: acne to zoonoses on the valve, an A to Z perspective

Cutibacterium acnes (C. acnes), previously known as Propionibacterium acnes, is a rare cause of infective endocarditis (IE). We provide a review of the literature and describe two recent cases from a single centre to provide insight into the various clinical presentations, progression and management of patients with this infection. The primary objective of our review is to highlight the difficulty in the initial assessment of these patients with an aim to improve the time and accuracy of diagnosis and expedite subsequent treatment. There are currently no guidelines in the literature specific to the management of IE caused by C. acnes. Our secondary objectives are to disseminate information about the indolent course of the disease and add to the growing body of evidence around this rare, yet complex, cause of IE.

Recurrent Cutibacterium acnes prosthetic valve endocarditis

A 29-year-old man with a history of congenital aortic stenosis and mechanical aortic valve replacement with previous Cutibacterium acnes prosthetic valve endocarditis (PVE) presented with a 2-week history of fevers and night sweats. Transoesophageal echocardiogram revealed a 0.6 cm×0.5 cm vegetation on the mechanical aortic valve. An anaerobic blood culture became positive for C. acnes 6 days after the blood cultures were obtained. He did not have any surgical intervention. He was successfully treated with 6 weeks of ceftriaxone, followed by chronic suppression with oral doxycycline. Despite its low virulence, a growing number of C. acnes PVE cases have been reported, owing to its biofilm production. When clinical suspicion is high, extending culture incubation duration beyond the standard 5 days might be helpful. Most cases are treated with surgical repair or replacement in conjunction with antibiotics, but medical therapy alone has been documented as being successful.

Atypical pathogens associated with cardiac implantable electronic device infections

BACKGROUND

Cardiovascular implantable electronic device (CIED) infections are associated with significant morbidity and mortality making the identification of the causative organism critical. The vast majority of CIED infections are caused by Staphylococcal species. CIED infections associated with atypical pathogens are rare and have not been systematically investigated. The objective of this study is to characterize the clinical course, management and outcome in patients with CIED infection secondary to atypical pathogens.

METHODS

Medical records of all patients who underwent CIED system extraction at the University of Chicago Medical Center between January 2010 and November 2020 were retrospectively reviewed to identify patients with CIED infection. Demographic, clinical, infection-related and outcome data were collected. CIED infections were divided into typical and atypical groups based on the pathogens isolated.

RESULTS

Among 356 CIED extraction procedures, 130 (37%) were performed for CIED infection. Atypical pathogens were found in 5.4% (n = 7) and included Pantoea species (n = 2), Kocuria species (n = 1), Cutibacterium acnes (n = 1), Corynebacterium tuberculostearicum (n = 1), Corynebacterium striatum (n = 1), Stenotrophomonas maltophilia (n = 1), and Pseudozyma ahidis (n = 1). All patients with atypical CIED infections were successfully treated with total system removal and tailored antibiotic therapy. There were no infection-related deaths.

CONCLUSIONS

CIED infections with atypical pathogens were rare and associated with good outcome if diagnosed early and treated with total system removal and tailored antimicrobial therapy. Atypical pathogens cultured from blood, tissue or hardware in patients with CIED infection should be considered pathogens and not contaminants.

Recurrent strokes in an occult case of recurrent Cutibacterium acnes prosthetic valve infective endocarditis: a case report

Background

Infective endocarditis (IE) is a known but uncommon cause of cardioembolic stroke and there are rare but recognized cases of IE without an inflammatory response. Cutibacterium acnes is an increasingly recognized source of invasive infections, including IE, but diagnosis is challenging due to its low virulence and fastidious nature.

Case summary

A 47-year-old man presented with a multi-focal stroke suggestive of a cardioembolic source. Outpatient transoesophageal echocardiography (TOE) was concerning for vegetation or thrombus associated with his previous mitral valve repair. He remained clinically well, with no evidence of an inflammatory response and sterile blood cultures. Computed tomography–positron emission tomography (CT-PET) corroborated the TOE findings, however, given the atypical presentation, he was treated for valvular thrombus. Following discharge, he quickly re-presented with further embolic phenomena and underwent emergency mitral valve replacement. Intraoperative findings were consistent with prosthetic valve IE (PVE) and a 6-week course of antibiotics commenced. C. acnes was identified on molecular testing. Eighteen months later, he re-presented with further neurological symptoms. Early TOE and CT–PET were consistent with IE. Blood cultures grew C. acnes after prolonged incubation. Given the absence of surgical indications, he was managed medically, and the vegetation resolved without valvular dysfunction. He continues to be followed up in an outpatient setting.

Discussion

In patients presenting with multi-territory stroke, IE should be considered despite sterile blood cultures and absent inflammatory response. C. acnes is an increasingly recognized cause of PVE in this context, often requiring surgical intervention. A high index of suspicion and collaboration with an Endocarditis Team is therefore essential to diagnose and treat.

Bacterial pericarditis and empyema caused by Cutibacterium acnes in a patient with metastatic lung cancer

Bacterial pericarditis and empyema due to Cutibacterium acnes has rarely been reported. C.acnes, a normal component of human skin flora, is often considered a contaminant when isolated from body fluids and thus cases may be underreported. We report the first case of concurrent purulent pericarditis and empyema caused by C. acnes in a patient with newly diagnosed metastatic lung cancer. Our patient underwent pericardial window creation and placement of pericardial and bilateral chest tubes and was successfully treated with culture directed antibiotic therapy.

Clinical impact of extended blood culture examination: Too much of a good thing

Blood culture is the most critical examination for diagnosing bacterial infections. The longer the blood culture incubation period, the higher the chances of identifying bacterial strains. However, unnecessary extension of the incubation period can burden the capacity of the instrument and merely result in the detection of contaminant bacteria having no clinical significance. This study aimed to optimize the blood culture incubation period using the currently available continuous-monitoring automated blood culture instrument. This was a 2-year retrospective study performed at Osaka University Hospital (January 1, 2016 to December 31, 2017). The BD BACTEC™ FX blood culture system (Becton Dickinson, Sparks, MD, USA) and BD BACTEC™ Plus series blood culture bottles were used. All blood cultures were incubated for more than 12 consecutive days. We reviewed the clinical data of cases that tested positive between 6 and 12 days of incubation. During the study period, 14,822 sets of blood culture were drawn. Of 1751 sets testing positive, 95.7% (1665 sets) became positive within 5 days of incubation. The overall contamination rate (false positives) after 6 days of incubation was 80.2% (69/86 sets). Based on the positive blood culture results, antimicrobials were changed in 7.0% (6/86) of the sets, and a diagnosis of infectious disease was made in only one case. There was no death associated with the extended blood culture results. In conclusion, the clinical impact of extended blood culture incubation for 6 days or more was limited, and a routine extension of the incubation period might be unnecessary.

Recent advances in understanding Propionibacterium acnes ( Cutibacterium acnes) in acne

The skin commensal Propionibacterium acnes, recently renamed Cutibacterium acnes, along with the other major pathophysiological factors of increased seborrhea, hyperkeratinization of the pilosebaceous unit, and inflammation, has long been implicated in the pathogenesis of acne. Recent advances have contributed to our understanding of the role of P. acnes in acne. Although there are no quantitative differences in P. acnes of the skin of patients with acne compared with controls, the P. acnes phylogenic groups display distinct genetic and phenotypic characteristics, P. acnes biofilms are more frequent in acne, and different phylotypes may induce distinct immune responses in acne. P. acnes plays a further important role in the homeostasis of the skin’s microbiome, interacting with other cutaneous commensal or pathogenic microorganisms such as Staphylococcus epidermidis, Streptococcus pyogenes, and Pseudomonas species. In the era of increasing antimicrobial resistance, the selection of acne treatment targeting P. acnes and the prevention of antibiotic resistance play a key role in improving outcomes in acne patients and public health.