Case report: Laboratory diagnosis methods on brain abscess pathogens caused by anaerobic species and Streptococci constellatus

Brain abscess (BA) represents a severe, intracranial infection associated with high morbidity and mortality. Multiple pathogens may contribute to BA development, some of which are difficult to detect using conventional diagnostic methods alone. With the wide utilization of metagenomic next-generation sequencing (mNGS), more experiences are concluded in authenticity practice except for being regarded as a comprehensive method for detecting all pathogens. Here, we report a severe case of BA in a patient diagnosed by CT imaging, who subsequently underwent surgical removal of the abscess. To identify the causative pathogen and support anti-infection treatment, Gram staining, culture, and mNGS were performed on the abscess specimen. Interesting, we found the results were discordant: the <i>Streptococcus constellatus</i> was identified by culture, whereas mNGS predominantly detected anaerobic bacteria. Following additional human DNA removal, sequencing detected <i>S. constellatus</i> in the specimen as well. In conclusion, we highlight that a combined diagnostic strategy, leveraging both conventional culture and mNGS, is critical for comprehensive pathogen identification and informed clinical decision-making in BA.