Aortic vascular graft infection caused by Cardiobacterium valvarum: a case report

An unusual case of Cardiobacterium valvarum causing aortic endograft infection and osteomyelitis

BACKGROUND

HACEK (Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella corrodens, and Kingella spp.) group organisms are responsible for 0.8% to 6% of all infective endocarditis cases, with Cardiobacterium spp. being the third most commonly implicated HACEK microorganism. Within this genus is Cardiobacterium valvarum (C. valvarum), a novel organism described in 2004. To date, only 15 cases of C. valvarum infection have been reported in the English-language literature, and have primarily been cases of infective endocarditis in patients with valvular disease. C. valvarum has not been reported to cause infections spreading to the surrounding bone.

CASE PRESENTATION

We present a case of a 57-year-old man with a history of aortic dissection followed by aortic endograft replacement who presented with back pain. He was found to have radiographic evidence of an infected aortic endograft, along with vertebral osteomyelitis, discitis, and epidural phlegmon. Blood cultures identified C. valvarum as the causative organism. The patient was treated with ceftriaxone and surgical intervention was deferred due to the patient's complex anatomy. His course was complicated by septic cerebral emboli resulting in cerebrovascular accident.

CONCLUSIONS

This case report highlights C. valvarum, a rare and emerging HACEK group microorganism that warrants consideration in high-risk patients with evidence of subacute infection and disseminated disease. While C. valvarum classically presents as infective endocarditis, extra-cardiac manifestations have also been described. As demonstrated in this case, endograft involvement and osteomyelitis may occur in rare circumstances.

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.

Conventional culture diagnostics vs. multiplex PCR for the detection of causative agents of vascular graft infections - results of a single centre observational pilot study

Background: Timely diagnosis of vascular graft infections is of major importance in vascular surgery. The detection of causative microorganisms is needed for specific medical treatment, but conventional culture is often slow, insensitive and inconclusive due to antibiotic pre-treatment. Detection of bacterial DNA by polymerase chain reaction (PCR) might bypass these problems. We hypothesised that multiplex PCR (mPCR) is feasible, fast and sensitive to detect causative microorganisms in vascular graft infections. Patients and methods: We performed a pilot observational prospective study comparing conventional culture and a commercial mPCR. Inclusion criteria were: confirmed graft infection, suspicious imaging, clinical suspicion, anastomotic aneurysm and repeated graft occlusion. Diagnostic methods were performed using identical samples. Time to result, microorganisms and antibiotic resistance in both groups were compared using Student's t-test or nonparametric tests. Results: 22 samples from 13 patients were assessed and 11 samples were negative for bacteria. Some showed multiple germs. In total, we found 15 different organisms. 13 samples matched, 9 had non-concordant results. Out of the mismatches 3 microorganisms identified in PCR were not detected by culture. Time to result with PCR was shorter (median 5 h vs. 72 h, p < 0.001) than with culture. No resistance genes were detected by mPCR, but conventional culture allowed susceptibility testing and revealed resistance in 5 samples. Conclusions: mPCR seems to be a feasible and quick tool to detect causes of vascular graft infections within 24 h and might be helpful in antibiotic pre-treated patients. The detection of antibiotic resistance with mPCR needs improvement for clinical practice.

Infective endocarditis caused by Cardiobacterium valvarum

We report a case with infective endocarditis (IE) due to Cardiobacterium valvarum. The patient was a 57-year-old male, who was referred to our hospital based on suspected IE detected by transthoracic echocardiography at a neighbourhood clinic. Three sets of blood cultures obtained on admission yielded positive results, and revealed rather slender and linear Gram-negative bacilli with a rosette formation that dyed minimally, with a pale white appearance. Although no isolates were identified by conventional methods, C. valvarum was ultimately identified by 16 S ribosomal RNA genotyping. HACEK group strains are difficult to identify by conventional methods. Therefore, if Gram-negative bacilli are isolated from IE patients, 16 S ribosomal RNA genotyping will be necessary. Furthermore, IE due to C. valvarum is very rare. We thus discuss our case in comparison with previous reports.

A case of Cardiobacterium valvarum endocarditis with cerebral hemorrhage after MVR, TVP and vegetation removal operation

Background

Cardiobacterium is a fastidious Gram-negative bacillus, and is a rare human pathogen in clinical settings. Herein, we describe a case of Cardiobacterium valvarum (C. valvarum) endocarditis with a rare complication of cerebral hemorrhage after mitral valve replacement (MVR), tricuspid valve prosthesis (TVP) and vegetation removal operation.

Case presentation

A 41-year-old woman who had a history of gingivitis developed into infective endocarditis due to the infection of C. valvarum. Then, she was hospitalized to receive MVR, TVP and vegetation removal operation. The indicators of patient tended to be normal until the abrupt cerebral hemorrhage occurred on day 15 after operation. This is the first well-described case of C. valvarum infection in China, and the first report of C. valvarum endocarditis with cerebral hemorrhage after MVR, TVP and vegetation removal operation worldwide.

Conclusions

We reported the first case of C. valvarum infection in China clinically, with a rare complication of cerebral hemorrhage after MVR, TVP and vegetation removal operation.

Bacterial Diversity and Community Structure of Supragingival Plaques in Adults with Dental Health or Caries Revealed by 16S Pyrosequencing

Dental caries has a polymicrobial etiology within the complex oral microbial ecosystem. However, the overall diversity and structure of supragingival plaque microbiota in adult dental health and caries are not well understood. Here, 160 supragingival plaque samples from patients with dental health and different severities of dental caries were collected for bacterial genomic DNA extraction, pyrosequencing by amplification of the 16S rDNA V1–V3 hypervariable regions, and bioinformatic analysis. High-quality sequences (2,261,700) clustered into 10,365 operational taxonomic units (OTUs; 97% identity), representing 453 independent species belonging to 122 genera, 66 families, 34 orders, 21 classes, and 12 phyla. All groups shared 7522 OTUs, indicating the presence of a core plaque microbiome. α diversity analysis showed that the microbial diversity in healthy plaques exceeded that of dental caries, with the diversity decreasing gradually with the severity of caries. The dominant phyla of plaque microbiota included Bacteroidetes, Actinobacteria, Proteobacteria, Firmicutes, Fusobacteria, and TM7. The dominant genera included Capnocytophaga, Prevotella, Actinomyces, Corynebacterium, Neisseria, Streptococcus, Rothia, and Leptotrichia. β diversity analysis showed that the plaque microbial community structure was similar in all groups. Using LEfSe analysis, 25 differentially abundant taxa were identified as potential biomarkers. Key genera (27) that potentially contributed to the differential distributions of plaque microbiota between groups were identified by PLS-DA analysis. Finally, co-occurrence network analysis and function predictions were performed. Treatment strategies directed toward modulating microbial interactions and their functional output should be further developed.