[Endocarditis due to Corynebacterium xerosis]

Corynebacterium sp. are found as normal flora in skin and mucosal sites. They have been isolated in empyemas, brain abscesses, blood cultures and ventricular shunts. About 9-10% of early-onset and 4-5% late-onset prosthetic valve endocarditis are due to different species of the so-called "diphteroids". A 30 year-old white female was admitted after 30 days with fever of undetermined origin. A mitral prosthesis had been fitted in 1977. On physical examination a protomesosystolic mitral murmur, petechiae, retinal hemorrhages and hepatosplenomegaly were detected. Laboratory tests showed 37% hematocrit, 14,800/mm3 white blood cells, 78 mm ESR, urinary sediment: less than 30/h.p.f. red blood cells. A new first-degree A-V block was detected. Blood cultures were negative. Due to persistent fever, progressive anemia, leukocytosis and new vegetations on echocardiogram, surgery was performed. A mitral valve ring abscess was found. Corynebacterium xerosis was isolated from surgical specimens. The strain was found susceptible to penicillin, ampicillin, oxacillin, ticarcillin, piperacillin, cephalotin, cefoxitin, cefoperazone, rifampin, gentamicin, amikacin, and norfloxacin. Studies with clindamycin, disclosed MIC and MBC = 0.25 mg/l. The patient received 1800 mg/day clindamycin for 4 weeks. Serum cidal studies showed a peak concentration 1/128 and a titre of trough 1/4. Negative control blood cultures were obtained. She has remained well for nine months after treatment. Corynebacterium sp. can cause "apparently" negative blood cultures. Blood samples should be incubated for more than 15 days before they can be considered negative. Almost 50% of previously described cases have been detected during the six months after cardiac surgery. Mortality has been high (48%).(ABSTRACT TRUNCATED AT 250 WORDS)