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Endocarditis due to a penicillin-tolerant streptococcus bovis: microbiological findings and echocardiographic
Abstract:
We are presenting a case of endocarditis due to a penicillin-tolerant Streptococcus bovis in a 65-year-old patient. The minimal bactericidal concentration of penicillin (40 mg/l) was more than 100-fold the minimal inhibitory concentration (0.08 mg/l). The MBC of penicillin was 0.31 mg/l in the presence of 1.25 mg/l gentamicin. Cross-sectional echocardiography revealed endocarditis of the anterior leaflet of the tricuspid valve and a vegetation on the aortic valve which appeared to be pedunculated and which prolapsed into the left ventricular outflow tract during diastole. During therapy, the pedunculated part of the vegetation disappeared without signs of embolization. After initial clinical improvement, the patient died of cerebral bleeding caused by a mycotic aneurysm of the left median cerebral artery. The patient's final outcome suggested an asymptomatic embolus. Cross-sectional echocardiography was distinctly superior to M-mode echocardiography in estimating changes in the size and shape of the valve vegetation. The results of the post-mortem examination of the aortic and tricuspid valves corresponded to the echocardiographic findings.
Insights
This case study highlights endocarditis caused by penicillin-tolerant Streptococcus bovis. Echocardiography proved superior in monitoring valve vegetation changes, despite a fatal outcome from cerebral bleeding.
Area of Science:
- Cardiology
- Infectious Diseases
- Microbiology
Background:
- Endocarditis is a serious infection of the heart valves.
- Streptococcus bovis is a common cause of infective endocarditis, particularly in older adults.
- Penicillin tolerance, characterized by a high minimal bactericidal concentration (MBC) relative to the minimal inhibitory concentration (MIC), can complicate treatment.
Observation:
- A 65-year-old patient presented with endocarditis due to penicillin-tolerant Streptococcus bovis.
- Echocardiography revealed tricuspid valve endocarditis and a pedunculated aortic valve vegetation prolapsing into the left ventricular outflow tract.
- The vegetation's pedunculated portion regressed during therapy without apparent embolic events.
Findings:
- The patient's Streptococcus bovis exhibited significant penicillin tolerance (MBC/MIC ratio > 100).
- Gentamicin reduced the MBC of penicillin, suggesting synergistic potential.
- Cross-sectional echocardiography demonstrated superior visualization of valve vegetation changes compared to M-mode echocardiography.
- Despite initial improvement, the patient succumbed to cerebral bleeding secondary to a mycotic aneurysm, possibly from an undetected embolus.
Implications:
- Penicillin tolerance in Streptococcus bovis endocarditis necessitates careful monitoring and potentially combination therapy.
- Cross-sectional echocardiography is a valuable tool for assessing vegetation dynamics in endocarditis.
- Mycotic aneurysms remain a significant risk in infective endocarditis, even with apparent treatment success.
- This case underscores the complex interplay between bacterial tolerance, cardiac involvement, and cerebrovascular complications in endocarditis.