Critical illness caused by a difficult-to-diagnose Schaalia cardiffensis infection with septicemia, pulmonary involvement, and disseminated intravascular coagulation syndrome: A case report and literature review.

Infection caused by Schaalia cardiffensis, formerly Actinomyces cardiffensis, is uncommon, and its clinical characteristics remain largely unknown. This report presents a case of S. cardiffensis infection causing critical illness in an elderly patient, along with a literature review. An 82-year-old Japanese man presented with septicemia caused by gram-positive rod-shaped bacteria, as well as pulmonary involvement representing septic embolisms, and disseminated intravascular coagulation. S. cardiffensis was identified in the anaerobic blood culture samples through 16S rRNA sequencing and database analysis. The patient recovered from the critical illness through extended antimicrobial treatment, primarily penicillin, along with supportive care. To the best of our knowledge, only three cases of S. cardiffensis infection have been reported in the literature. Two of these cases, along with the present one, exhibited disseminated infections in the lungs, liver, or brain. This organism may be highly virulent and prone to disseminated infections, warranting further investigation in future studies.