The nonpathogenic commensal Neisseria friends and foes in infectious diseaseDorey, Robert B.a; Theodosiou, Anastasia A.a , b; Read, Robert C.a , b , c; Jones, Christine E.cCurrent Opinion in Infectious Diseases: October 2019 - Volume 32 - Issue 5 - p 490–496 doi: 10.1097/QCO.0000000000000585 PAEDIATRIC AND NEONATAL INFECTIONS: Edited by Saul N. Faust Buy Abstract Author InformationAuthors Article MetricsMetrics Purpose of review Nonpathogenic commensal Neisseria are rarely considered in the clinical setting despite evidence that they can cause invasive opportunistic infections. In contrast, they may offer protection against pathogenic Neisseria, and such relationships are being actively explored in experimental studies. Recent findings Recent case reports are presented of invasive infection caused by nonpathogenic Neisseria in patients on novel biologic therapies. On the other hand, Neisseria lactamica, a nonpathogenic commensal, has been shown in human challenge studies to inhibit colonization by Neisseria meningitidis. Experimental mouse models have also explored the inhibitory effects of nonpathogenic Neisseria on Neisseria gonnhoreae infection. Cutting-edge advances in metagenomics and microbiomics are being used to understand the mechanisms underpinning these effects. Summary Clinicians should have increased awareness of nonpathogenic Neisseria. First, as new immunomodulating therapies become licenced, the interactions that maintain balance between commensals and their human hosts may be altered. Second, these bacteria are showing promise in their capacity to exclude pathogenic Neisseria species from their anatomical niches. aClinical and Experimental Sciences, Faculty of Medicine, University of Southampton bSouthampton NIHR Biomedical Research Centre, University Hospital Southampton cFaculty of Medicine and Institute for Life Sciences, University of Southampton, Southampton, UK Correspondence to Robert B. Dorey, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK. E-mail: firstname.lastname@example.org Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.