Multiple Brain Microabscesses and a Lung Abscess Caused by Streptococcus intermedius Following COVID-19: A Case Report and Literature Review

Background: Secondary bacterial infections are increasingly recognized after coronavirus disease 2019 (COVID-19); however, bacterial abscess formation remains uncommon, and the simultaneous occurrence of brain and lung abscesses has not been previously reported. We report a rare case of Streptococcus intermedius infection presenting with multiple brain microabscesses and a lung abscess following COVID-19. Case Presentation: A 75-year-old man with no significant medical history except cholelithiasis experienced persistent fever following a diagnosis of COVID-19 and subsequently developed impaired consciousness 17 days later. Because bacterial meningitis was suspected, he was admitted to a neurology-specialized hospital on the same day. Brain MRI revealed more than 80 small enhancing lesions scattered throughout the brain parenchyma, consistent with multiple microabscesses. Chest CT demonstrated a mass-like lesion in the left lower lobe. Although cerebrospinal fluid cultures were negative, blood cultures obtained on admission yielded S. intermedius. Further investigation of the source of infection revealed moderate periodontitis, suggesting the oral cavity as the probable portal of entry. The patient was treated with intravenous antibiotics for eight weeks based on antimicrobial susceptibility testing, resulting in near-complete resolution of the lesions. Conclusions: Although a causal relationship between COVID-19 and abscess formation cannot be established, COVID-19-associated immune and mucosal barrier dysfunction may have contributed to the progression and dissemination of infection in this patient. Clinicians should be aware of the possibility of severe bacterial superinfection when fever or respiratory symptoms related to COVID-19 persist, even in patients without overt immunocompromise, particularly in those with pre-existing oral infections.