A case of infectious endocarditis and vertebral discitis caused by Streptococcus pneumoniae serotype 23A

Streptococcus pneumoniae, is a Gram-positive diplococcus, causes various community-acquired infections. Although pneumococcal vaccination has reduced the incidence of invasive pneumococcal disease, relative incidence of non-vaccine serotype-associated infections has increased. Herein, we report a case of pneumococcal infectious endocarditis and vertebral discitis diagnosed concurrently. A 73-year-old man presented with a 1-week history of fever and back pain (day 0). Laboratory tests revealed elevated inflammatory markers and magnetic resonance imaging confirmed vertebral osteomyelitis. Empirical intravenous cefazolin and vancomycin were initiated, considering appropriate coverage for common causative organisms of vertebral osteomyelitis. On day 1, blood cultures yielded S. pneumoniae- later identified as penicillin G susceptible serotype 23A belonging to sequence type 5242 -and antibiotics were switched to ceftriaxone and vancomycin. On the same day, the patient developed worsening oxygenation and a systolic murmur. Echocardiography revealed a mitral valve vegetation with severe regurgitation. Cefepime and vancomycin were initiated on day 2, followed by meropenem and vancomycin on day 4 for potential nosocomial pneumonia. On day 6, cefepime monotherapy was continued after methicillin-resistant Staphylococcus aureus was not detected in sputum culture. To address persistent respiratory failure, mitral valve replacement was performed on day 7. Cultures of tissue removed from the mitral valve were negative; 16S rRNA sequencing using the excised valve confirmed S. pneumoniae infection. Postoperatively, ceftriaxone was resumed, followed by oral levofloxacin, and a 42-day antimicrobial course was completed. The patient recovered without any recurrence. Continued surveillance of pneumococcal serotypes and antimicrobial resistance is warranted.