Neisseria mucosa Does Not Inhibit the Growth of Neisseria gonorrhoeae

Antibiotic-sparing treatments are required to prevent the further emergence of antimicrobial resistance in Neisseria gonorrhoeae. Commensal Neisseria species have previously been found to inhibit the growth of pathogenic Neisseria species. For example, a previous study found that three out of five historical isolates of Neisseria mucosa could inhibit the growth of N. gonorrhoeae. In this study, we used agar overlay assays to assess if 24 circulating and historical isolates of Neisseria mucosa could inhibit the growth of 28 circulating and historical isolates of N. gonorrhoeae. Although pitting around each colony of N. mucosa created an optical illusion of decreased growth of N. gonorrhoeae, we found no evidence of inhibition (n = 24). In contrast, positive controls of Streptococcus pneumoniae and Escherichia coli demonstrated a strong inhibitory effect against the growth of N. gonorrhoeae.