Endocarditis Due to Streptococcus mitis With High-Level Resistance to Penicillin and Ceftriaxone
- Camille Sabella, MD;
- Daniel Murphy, MD;
- Jonathan Drummond-Webb, MB, ChB
To the Editor: Antimicrobial resistance is an increasing problem in the treatment of infections due to Streptococcus pneumoniae.1 Such resistance has also recently been reported in the United States among the viridans group of streptococci, especially Streptococcus mitis.2 We report a case of subacute bacterial endocarditis in a child, resulting from an infection caused by S mitis that was fully resistant to penicillin and ceftriaxone.
Report of a Case
A 22-month-old black male with a known history of a perimembranous ventricular septal defect was admitted to our hospital with a 10-day history of fever and irritability. The patient had otherwise been healthy. Both blood cultures drawn on admission grew S mitis. The sensitivity analyses showed a minimal inhibitory concentration (MIC) to penicillin of 4 µg/mL, an MIC to ceftriaxone of 4 µg/mL, and an MIC to vancomycin of 0.5 µg/mL or less. Transthoracic echocardiography revealed a large vegetation on the tricuspid valve.
The patient was treated with intravenous vancomycin (60 mg/kg per day) and ceftriaxone (100 mg/kg per day) for 6 weeks, as well as gentamicin (3 mg/kg per day) for the first 4 weeks of therapy. The results of blood cultures were negative 48 hours after initiation of antimicrobial therapy. Three weeks following the completion of antimicrobial therapy, the patient underwent primary closure of the ventricular septal defect and removal of the vegetation from the tricuspid valve. Gram staining and culture from the vegetation failed to reveal an organism and the pathology findings were consistent with acute and chronic inflammation. The patient remains clinically well 9 months after therapy.
Comment
We believe this is the first report of a healthy child with endocarditis caused by viridans streptococci with high-level resistance to penicillin and ceftriaxone. Group day care attendance was the only risk factor that we could elicit for multidrug-resistant infection. Endocarditis caused by viridans streptococci with high-level resistance to penicillin and cefotaxime was reported in an adult with human immunodeficiency virus infection (HIV).3 Additionally, Levitz4 reported an HIV-infected adult with prosthetic valve endocarditis caused by pencillin-resistant S mitis.
Because the optimal antibiotic therapy for endocarditis caused by resistant viridans streptococci is not known, it will be important to report clinical experiences with such cases in the hope that rational treatment recommendations can be developed.
