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Canadian Journal of Infectious Diseases and Medical Microbiology
Volume 26, Issue 1, Pages 41-43
Case Report

Subacute Bacterial Endocarditis Caused by Cardiobacterium hominis: A Case Report

Davie Wong,1 Julie Carson,2,3 and Andrew Johnson4

1Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
2Section of Microbiology, Department of Pathology and Laboratory Medicine, University of Calgary, Canada
3Calgary Laboratory Services, Canada
4Section of Infectious Diseases, Department of Medicine, University of Calgary, Calgary, Alberta, Canada

Copyright © 2015 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Cardiobacterium hominis, a member of the HACEK group of organisms, is an uncommon but important cause of subacute bacterial endocarditis. First-line therapy is a third-generation cephalosporin due to rare beta-lactamase production. The authors report a case involving endovascular infection due to C hominis that initially tested resistant to third-generation cephalosporins using an antibiotic gradient strip susceptibility method (nitrocephin negative), but later proved to be susceptible using broth microdilution reference methods (a ‘major’ error). There are limited studies to guide susceptibility testing and interpretive breakpoints for C hominis in the medical literature, and the present case illustrates some of the issues that may arise when performing susceptibility testing for fastidious organisms in the clinical microbiology laboratory.