Endocarditis due to Corynebacterium pseudodiphtheriticum: five case reports, review, and antibiotic susceptibilities of nine strains.

Five cases of endocarditis due to Corynebacterium pseudodiphtheriticum are described. Two patients died, two patients with prosthetic valve endocarditis were successfully treated with antibiotics and valve replacement, and one patient with native valve endocarditis was successfully treated with penicillin alone. We also review 12 previously reported cases of C. pseudodiphtheriticum endocarditis. In vitro susceptibilities to 15 antibiotics were determined for nine isolates. The minimum inhibitory concentrations (MICs) of penicillin, amoxicillin, cefamandole, cephalexin, and rifampicin were all less than or equal to 0.12 mg/L. The MICs of vancomycin and ciprofloxacin for all strains were less than or equal to 0.5 mg/L. Tobramycin was the most active aminoglycoside, with MICs for all strains that were less than or equal to 0.12 mg/L. On the basis of in vitro data and the results of previous reports, penicillin alone or in combination with an aminoglycoside should achieve bacteriologic cure. Vancomycin should be used in patients who are allergic to penicillin.