Pathogenic Neisseria gonorrhoeae causes the sexually-transmitted infection gonorrhea. N. gonorrhoeae has evolved high levels of antimicrobial resistance (AR) leading to therapeutic failures even in dual-therapy treatment with azithromycin and ceftriaxone. AR mechanisms can be acquired by genetic transfer from closely related species, such as naturally-competent commensal Neisseria species. At present, little is known about the antimicrobial resistance profiles of commensal Neisseria. Here, we characterized the phenotypic resistance profile of four commensal Neisseria species (N. lactamica, N. cinerea, N. mucosa, and N. elongata) against 10 commonly used antibiotics, and compared their profiles to 4 N. gonorrhoeae strains, using disk diffusion and minimal inhibitory concentration assays. Overall, we observed that 3 of the 4 commensals were more resistant to several antibiotics than pathogenic N. gonorrhoeae strains. Next, we compared the penicillin-binding-protein 2 (PBP2) sequences between commensal and N. gonorrhoeae strains. We found mutations in PBP2 known to confer resistance in N. gonorrhoeae also present in commensal Neisseria sequences. Our results suggest that commensal Neisseria have unexplored antibiotic resistance gene pools that may be exchanged with pathogenic N. gonorrhoeae, possibly impairing drug development and clinical treatment.

In the absence of a vaccine, current antibiotic-dependent efforts to reduce the prevalence of Neisseria gonorrhoeae in high prevalence populations have been shown to result in extremely high levels of antibiotic consumption. No randomized controlled trials have been conducted to validate this strategy and an important concern of this approach is that it may induce antimicrobial resistance. To contribute to this debate, we assessed if mass treatment in the related species, Neisseria meningitidis, was associated with the emergence of antimicrobial resistance. To this end, we conducted a historical review of the effect of mass meningococcal treatment programmes on the prevalence of N. meningitidis and the emergence of antimicrobial resistance. We found evidence that mass treatment programmes were associated with the emergence of antimicrobial resistance.