Neisseria mucosa Does Not Inhibit the Growth of Neisseria gonorrhoeae

Saïd Abdellati,Natalia Gonzalez,Irith De Baetselier,Sheeba S Manoharan-Basil,Tessa De Block,Delphine Martiny,Jolein Laumen,Christophe Van Dijck,Chris Kenyon

doi:10.3390/sci4010008

Abstract

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.

Highlights

Academic Editor: Claus JacobA number of countries worldwide are reporting an increasing incidence of sexually transmitted infections due to Neisseria gonorrhoeae [1]
If the use of the essential oil-based mouthwashes reduce the prevalence/abundance of N. mucosa, and N. mucosa inhibits the growth of N. gonorrhoeae, the essential oil-based mouthwash could increase the susceptibility for N. gonorrhoeae infection [2]
Our central objective was to assess if our locally circulating isolates of N. mucosa and other commensal Neisseria, including those circulating in the preventing resistance in gonorrhoea (PReGo) participants, were able to inhibit the growth of N. gonorrhoeae

Summary

Introduction

A number of countries worldwide are reporting an increasing incidence of sexually transmitted infections due to Neisseria gonorrhoeae [1]. One of these was the preventing resistance in gonorrhoea (PReGo) study conducted in our centre [2] This placebo-controlled trial randomized high-risk men who have sex with men to intensive use of an essential oil-based mouthwash and gargle, or placebo, to try to reduce the incidence of bacterial STIs in this population. One of the possible explanations for these surprising results is that essential oil-based mouthwashes could reduce the abundance of commensal bacteria that have an inhibitory effect on N. gonorrhoeae One such commensal bacteria is Neisseria mucosa, which has recently been shown to inhibit the growth of N. gonorrhoeae by Aho et al [11]. If the use of the essential oil-based mouthwashes reduce the prevalence/abundance of N. mucosa, and N. mucosa inhibits the growth of N. gonorrhoeae, the essential oil-based mouthwash could increase the susceptibility for N. gonorrhoeae infection [2]. Our central objective was to assess if our locally circulating isolates of N. mucosa and other commensal Neisseria, including those circulating in the PReGo participants, were able to inhibit the growth of N. gonorrhoeae

Results

Origin of Bacterial Isolates

Non-Neisseria Isolates

Agar Overlay Assay