Native Valve Endocarditis with Aorta-to-Left Atrial Fistula Due to Corynebacterium amycolatum

Current diagnosis and treatment of infective endocarditis

The incidence of infective endocarditis continues to rise with a yearly incidence of around 15,000 to 20,000 new cases in the USA. As a result, rapid diagnosis, effective treatment and prompt recognition of complications are essential to desirable clinical outcomes. Recent guidelines such as the Duke criteria have incorporated echocardiography for diagnosis of infective endocarditis, making this diagnostic test mandatory for patients with suspected infective endocarditis. The diversity of pathogens that can cause infective endocarditis, some of which cannot be cultured easily, makes diagnosis even more difficult. Coagulase-negative staphylococci and viridans streptococci groups continue to be the major causative microorganisms of infective endocarditis. In the case of culture-negative endocarditis or infective endocarditis caused by fastidious microorganisms, the polymerase chain reaction and probe-based diagnostic methods are available to clinical reference laboratories.

Endocarditis due to Corynebacterium amycolatum

Corynebacterium amycolatum, a normal inhabitant of human skin, is a Gram-positive, non-spore-forming, mycolic acid-free, aerobic or facultative anaerobic bacillus. Since its description in 1988, it has only rarely been associated with infective endocarditis. This paper describes a case of infective endocarditis successfully treated by combination therapy with daptomycin and rifampicin. To the best of our knowledge, this is the first case report of C. amycolatum endocarditis from the USA successfully treated with these agents.

Corynebacterium endocarditis species-specific risk factors and outcomes

Background

Corynebacterium species are recognized as uncommon agents of endocarditis, but little is known regarding species-specific risk factors and outcomes in Corynebacterium endocarditis.

Methods

Case report and Medline search of English language journals for cases of Corynebacterium endocarditis. Inclusion criteria required that cases be identified as endocarditis, having persistent Corynebacterium bacteremia, murmurs described by the authors as identifying the affected valve, or vegetations found by echocardiography or in surgical or autopsy specimens. Cases also required patient-specific information on risk factors and outcomes (age, gender, prior prosthetic valve, other prior nosocomial risk factors (infected valve, involvement of native versus prosthetic valve, need for valve replacement, and death) to be included in the analysis. Publications of Corynebacterium endocarditis which reported aggregate data were excluded. Univariate analysis was conducted with chi-square and t-tests, as appropriate, with p = 0.05 considered significant.

Results

129 cases of Corynebacterium endocarditis involving nine species met inclusion criteria. Corynebacterium endocarditis typically infects the left heart of adult males and nearly one third of patients have underlying valvular disease. One quarter of patients required valve replacement and one half of patients died. Toxigenic C. diphtheriae is associated with pediatric infections (p < 0.001). Only C. amycolatum has a predilection for women (p = 0.024), while C. pseudodiphtheriticum infections are most frequent in men (p = 0.023). C. striatum, C. jeikeium and C. hemolyticum are associated with nosocomial risk factors (p < 0.001, 0.028, and 0.024, respectively). No species was found to have a predilection for any particular heart valve. C. pseudodiphtheriticum is associated with a previous prosthetic valve replacement (p = 0.004). C. jeikeium infections are more likely to require valve replacement (p = 0.026). Infections involving toxigenic C. diphtheriae and C. pseudodiphtheriticum are associated with decreased survival (p = 0.001 and 0.032, respectively).

Conclusion

We report the first analysis of species-specific risk factors and outcomes in Corynebacterium endocarditis. In addition to species-specific associations with age, gender, prior valvular diseases, and other nosocomial risk factors, we found differences in rates of need for valve replacement and death. This review highlights the seriousness of these infections, as up to 28% of patients required valve replacement and 43.5% died.

Mycotic Aneurysms of Aortic Root and Aorta-to-Left Atrial Fistula Complicating Bicuspid Aortic Valve Endocarditis

Unlike root abscess, fistula formation is quite uncommon in aortic valve endocarditis. In this report, we describe a patient with subacute bicuspid aortic valve endocarditis complicated by aortic insufficiency, mycotic aneurysms of the aortic root and fistulous communication between the aorta and the left atrium and his recovery upon surgical treatment.

Fatal ascending aorta-to-right ventricle fistula formation after Staphylococcus aureus endocarditis of bicuspid aortic valve

We present a case of a 46-year-old man with advanced acquired immunodeficiency syndrome and congenitally bicuspid aortic valve endocarditis caused by methicillin- and gentamicin-resistant Staphylococcus aureus. Endocarditis led to root abscess formation, a complete heart block, and fistulous tract formation between the ascending aorta and the right ventricle. Although perivalvular abscess is not an unusual complication of native valve endocarditis, a fatal fistulous communication between the ascending aorta and the right ventricle is exceedingly rare.

Relationship between mutations in the gyrA gene and quinolone resistance in clinical isolates of Corynebacterium striatum and Corynebacterium amycolatum

Quinolone susceptibility was analyzed in 17 clinical isolates of Corynebacterium striatum and 9 strains of Corynebacterium amycolatum by the E-test method in Mueller-Hinton agar plates. The C. striatum ATCC 6940 strain was used as a control strain. The amplified quinolone resistance determining regions of the gyrA genes of C. amycolatum and C. striatum were characterized. Four in vitro quinolone-resistant mutants of C. amycolatum were selected and analyzed. Both in vivo and in vitro quinolone-resistant strains of C. amycolatum showed high levels of fluoroquinolone resistance in strains with a double mutation leading to an amino acid change in positions 87 and 91 or positions 87 and 88 (unusual mutation) of GyrA, whereas the same concomitant mutations at amino acid positions 87 and 91 in GyrA of C. striatum produced high levels of resistance to ciprofloxacin and levofloxacin but only showed a moderate increase in the MIC of moxifloxacin, suggesting that other mechanism(s) of quinolone resistance could be involved in moxifloxacin resistance in C. amycolatum. Moreover, a PCR-RFLP-NcoI of the gyrA gene was developed to distinguish between C. amycolatum and C. striatum species.