Rapid Identification of Cardiobacterium hominis by MALDI-TOF Mass Spectrometry during Infective Endocarditis

We report a new case of Cardiobacterium hominis endocarditis identified during an acute coronary syndrome. The positivity of the blood cultures was confirmed rapidly (50 h) as a result of improvements to the automated detection system, whereby it is no longer necessary to incubate the vials for long periods of time when Aggregatibacter-Cardiobacterium-Eikenella-Kingella infections is suspected. The phenotype-based VITEK 2 NH identification system is not able to distinguish between the two species of Cardiobacterium, as it does not contain C. valvarum in its library. The method for 16S rRNA gene sequence analysis is able to separate the two species but is not available in all laboratories. We used MALDI-TOF mass spectrometry, as an alternative, to rapidly distinguish between C. hominis and C. valvarum, because both species are contained in the system library.