Nosocomial valve endocarditis due to corynebacterium striatum: a case report
© Marull and Casares; licensee BioMed Central Ltd. 2008
Received: 01 September 2008
Accepted: 12 December 2008
Published: 12 December 2008
Staphylococcus aureus, Coagulase-negative staphylococci, and Enterococci sp. are the usual pathogens involved in nosocomial bacterial endocarditis. Corynebacterium species isolation in blood specimens is usually considered to be a contaminant. We present an interesting case of native mitral valve endocarditis in a 73 year old African American female that was diagnosed days after she was discharged from our institution. The infection was cleared with medical therapy alone.
Over the past twenty years, the epidemiological profile of infective endocarditis has been changing.  The number of cases of hospital-acquired endocarditis has been increasing. This entity carries a higher mortality rate compared with community-acquired cases. Indwelling catheters, intravenous lines, intravascular procedures and devices have increased the risk of bacteriemia.  The presentation is not always evident and especial importance should be given to the clinical history in a patient with fever and no evident source of infection. Positive blood cultures for Corynebacterium species, and Corynebacterium striatum in particular, should never be overlooked.
Basic metabolic panel and complete blood cell count
Hepatitis panel non-reactive
Antibiotic resistance profile
> 4 R
> 2 R
> 2 R
> 2 R
Two of the Duke major criteria were met, including the microbiology and echocardiographic findings, making a definitive diagnosis.  There is neither a recognized standard method nor specific MIC breakpoints or guidelines published by NICCS for antimicrobial testing of coryneform bacteria. National Committee for Clinical Laboratory Standards interpretive criteria currently valid for staphylococci, streptococci, or listeria monocytogenes was applied. Chester in 1901 and then Eberson in 1918 described for the first time the Striatum strain, and since then numerous corynebacterium species have been identified and reclassified, in different strains. 
In the 1980s and 1990s CS infections have been disregarded. It was only until recently that Corynebacterium diphtheria was considered to be the only pathogen of the coryneform species. Today, other species, such as C. jeikeium, C. urealiticum, C. amycolatum along with CS, are recognized as emerging hospital pathogens. The pathogenicity in non-diphtheriae corynebacteria species isn't well-known. Neither toxin nor other virulence factors explain the transition from colonization to infection.  Martin et al. isolated identical strains of CS from a leg ulcer and from the bloodstream in a patient with peripheral vascular disease, confirming the entry of the bacterium through the skin to the circulation.  The spectrum of diseases generated by CS is extensive, going from meningitis, keratitis, to arthritis, among others. 
The spread of CS from patient to patient and nosocomial outbreaks have been documented. Leonard et al., Iaria et al., and Brandenbrug described outbreaks caused by a single strain in intensive care unit settings. Leonard et al., described a selective pressure due to prior exposure to antibiotics favoring the overgrowth of CS in immune deficient patients. Brandenbrug et al recovered the strain in the air around infected patients and on the hands of the housestaff. [7–9]. Vancomycin is still the drug of choice for many authors since in vitro resistance has not been showed for this or any other Corynebacterium species. The spread of multidrug resistance strains of CS is concerning, although the mechanisms are not cleared. Ten years ago, CS was still sensitive to beta lactams, fluoroquinolones, carbapenems and linezolid. [10, 11]
In the hospital setting, positive blood cultures for Corynebacterium species, and CS in particular, should never be overlooked. Unlike other hospital-acquired pathogens such as staphylococcal or enterococcal species, that tend to infect patients with a predisposing condition such as a valvulopathy, CS endocarditis can be seen even in patients without prosthetic valves or structural heart disease. More research needs to be conducted to evidence what resistance mechanisms are involving this organism. Nowadays CS is being considered one of the emergent nosocomial agents implicated in endocarditis and serious infections.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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