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Non-pathogenic Neisseria are a reservoir of antimicrobial resistance genes for pathogenic Neisseria meningitidis and Neisseria gonorrhoeae. Men who have sex with men (MSM) are at risk of co-colonization with resistant non-pathogenic and pathogenic Neisseria. We assessed if the antimicrobial susceptibility of non-pathogenic Neisseria among MSM differs from a general population and if antimicrobial exposure impacts susceptibility. We recruited 96 participants at our center in Belgium: 32 employees, 32 MSM who did not use antibiotics in the previous 6 months, and 32 MSM who did. Oropharyngeal Neisseria were cultured and identified with MALDI-TOF–MS. Minimum inhibitory concentrations for azithromycin, ceftriaxone and ciprofloxacin were determined using E-tests® and compared between groups with non-parametric tests. Non-pathogenic Neisseria from employees as well as MSM were remarkably resistant. Those from MSM were significantly less susceptible than employees to azithromycin and ciprofloxacin (p < 0.0001, p < 0.001), but not ceftriaxone (p = 0.3). Susceptibility did not differ significantly according to recent antimicrobial exposure in MSM. Surveilling antimicrobial susceptibility of non-pathogenic Neisseria may be a sensitive way to assess impact of antimicrobial exposure in a population. The high levels of antimicrobial resistance in this survey indicate that novel resistance determinants may be readily available for future transfer from non-pathogenic to pathogenic Neisseria. [ABSTRACT FROM AUTHOR]

In this study, we characterized all oropharyngeal and anorectal isolates of Neisseria spp. in a cohort of men who have sex with men. This resulted in a panel of pathogenic Neisseria (N. gonorrhoeae [n = 5] and N. meningitidis [n = 5]) and nonpathogenic Neisseria (N. subflava [n = 11], N. mucosa [n = 3] and N. oralis [n = 2]). A high proportion of strains in this panel were resistant to azithromycin (18/26) and ceftriaxone (3/26). Whole genome sequencing (WGS) of these strains identified numerous mutations that are known to confer reduced susceptibility to azithromycin and ceftriaxone in N. gonorrhoeae. The presence or absence of these known mutations did not explain the high level resistance to azithromycin (>256 mg/L) in the nonpathogenic isolates (8/16). After screening for antimicrobial resistance (AMR) genes, we found a ribosomal protection protein, Msr(D), in these highly azithromycin resistant nonpathogenic strains. The complete integration site originated from Streptococcus pneumoniae and is associated with high level resistance to azithromycin in many other bacterial species. This novel AMR resistance mechanism to azithromycin in nonpathogenic Neisseria could be a public health concern if it were to be transmitted to pathogenic Neisseria. This study demonstrates the utility of WGS-based surveillance of nonpathogenic Neisseria. [ABSTRACT FROM AUTHOR]

Introduction. Commensal Neisseria spp. are highly prevalent in the oropharynx as part of the healthy microbiome. N. meningitidis can colonise the oropharynx too from where it can cause invasive meningococcal disease. To identify N. meningitidis , clinical microbiology laboratories often rely on Matrix Assisted Laser Desorption/Ionisation Time of Flight Mass Spectrometry (MALDI-TOF MS). Hypothesis/Gap statement. N. meningitidis may be misidentified by MALDI-TOF MS. Aim. To conduct genomic surveillance of oropharyngeal Neisseria spp. in order to: (i) verify MALDI-TOF MS species identification, and (ii) characterize commensal Neisseria spp. genomes. Methodology. We analysed whole genome sequence (WGS) data from 119 Neisseria spp. in Belgium. Different species identification methods were compared: (i) MALDI-TOF MS, (ii) Ribosomal Multilocus Sequence Typing (rMLST) and (iii) Neisseria spp. in Belgium. Different species identification methods were compared: (i) MALDI-TOF MS, (ii) Ribosomal Multilocus Sequence Typing (rMLST) and (iii) rplF gene species identification. WGS data were used to further characterize Neisseria species found with supplementary analyses of Neisseria cinerea genomes. Results. Based on genomic species identification, isolates from the oropharyngeal Neisseria surveilence study were composed of the following species: N. meningitidis ( n =23) , N. subflava ( n =61), N. mucosa ( n =15), N. oralis ( n =8), N. cinerea ( n =5), N. elongata ( n =3), N. lactamica ( n =2), N. bacilliformis ( n =1) and N. polysaccharea ( n =1). Of these 119 isolates, four isolates identified as N. meningitidis ( n =3) and N. subflava ( n =1) by MALDI-TOF MS , were determined to be N. polysaccharea ( n =1) , N. cinerea ( n =2) and N. mucosa ( n =1) by rMLST. Phylogenetic analyses revealed that N. cinerea isolates from the general population ( n =3, cluster one) were distinct from those obtained from men who have sex with men (MSM, n =2, cluster two). The latter contained genomes misidentified as N. meningitidis using MALDI-TOF MS. These two N. cinerea clusters persisted after the inclusion of published N. cinerea WGS ( n =42). Both N. cinerea clusters were further defined through pangenome and Average Nucleotide Identity (ANI) analyses. Conclusion. This study provides insights into the importance of genomic genus-wide Neisseria surveillance studies to improve the characterization and identification of the Neisseria genus.

Background: commensal Neisseria species are part of the oropharyngeal microbiome and play an important role in nitrate reduction and protecting against colonization by pathogenic bacteria. They do, however, also serve as a reservoir of antimicrobial resistance. Little is known about the prevalence of these species in the general population, how this varies by age and how antimicrobial susceptibility varies between species., Methods: we assessed the prevalence and antimicrobial susceptibility of commensal Neisseria species in the parents (n = 38) and children (n = 50) of 35 families in Belgium., Results: various commensal Neisseria (n = 5) could be isolated from the participants. Most abundant were N. subflava and N. mucosa. Neisseria subflava was detected in 77 of 88 (87.5%) individuals and N. mucosa in 64 of 88 (72.7%). Neisseria mucosa was more prevalent in children [41/50 (82%)] than parents [23/38 (60.5%); P < .05], while N. bacilliformis was more prevalent in parents [7/36 (19.4%)] than children [2/50 (4%); P < .05]. Neisseria bacilliformis had high ceftriaxone minimum inhibitory concentrations (MICs; median MIC 0.5 mg/l; IQR 0.38-0.75). The ceftriaxone MICs of all Neisseria isolates were higher in the parents than in the children. This could be explained by a higher prevalence of N. bacilliformis in the parents., Interpretation: the N. bacilliformis isolates had uniformly high ceftriaxone MICs which warrant further investigation., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)