Pleural space infection microbiology as assessed using a clinical sequencing-based assay: Fusobacterium nucleatum group, Streptococcus intermedius, and other oral normal microbiota are the most common bacteria identified in community-acquired pleural space infections.

The definition of the microbiology of pleural space infection has been challenging due to the poor yield of conventional culture. Here, the results of a 16S ribosomal RNA gene PCR/sequencing assay performed on pleural fluid in routine clinical practice between August 2020 and January 2023 were evaluated. Amplified 16S rRNA gene DNA was submitted to Sanger sequencing and/or next-generation sequencing or results were reported as negative, depending on PCR crossing threshold value. In all, 496 pleural fluids were tested at Mayo Clinic Laboratories, with 227 positive results, including 57 from Mayo Clinic patients. Among the 57 Mayo Clinic patients, pleural space infection was community acquired in 48 (84%); Fusobacterium nucleatum group and/or Streptococcus intermedius were detected in 31/57 (54%) cases [including 28/48 (58%) community-acquired cases], with additional facultative and/or anaerobic species also found in various combinations in 17/31 (55%). Results of this study suggest that the most frequent microorganism profile involved in community-acquired pleural space infection may be a combination of F. nucleatum group and/or S. intermedius, with or without other normal microbiota.

Importance: We describe here the most frequent microorganisms detected in community-acquired pleural space infection using a clinically performed sequencing-based assay. We found that the most common detection was the Fusobacterium nucleatum group and/or Streptococcus intermedius, with or without other normal microbiota. We propose the term e-FuSion (effusion with Fusobacterium nucleatum group, Streptococcus intermedius, and other oral normal microbiota) for this entity.