Antimicrobial susceptibility of commensal Neisseria spp. In parents and their children in Belgium: a cross-sectional survey

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. N. subflava was detected in 77 of 88 (87.5%) individuals and N. mucosa in 64 of 88 (72.7%). N. mucosa was more prevalent in children (41/50 [82%]) than parents (23/38 [60.5%]; P < 0.05), while N. bacilliformis was more prevalent in parents (7/36 [19.4%]) than children (2/50 [4%]; P < 0.05). N. 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.