INTRODUCTIONCeftriaxone-resistant Neisseria gonorrhoeae (NG) poses a threat to successful first-line empirical treatment of gonorrhoeae. Ceftriaxone resistance is partially conferred through mosaic penA alleles, which are mainly obtained through transformation of DNA from commensal Neisseria species colonizing the oropharynx. These commensals themselves may exhibit high-level ceftriaxone resistance. Little is known about the effect of antibiotic treatment on their load and species-specific effect on presence within the oropharynx. Therefore, this study aimed to evaluate patterns in Neisseria species load and presence before and after antibiotic treatment.
METHODSA total of 96 oropharyngeal swabs were selected from follow-up consultations of 10 patients who visited our STI clinic between 2019 and 2021. Selection was based on frequency of positive PCR tests for NG. Samples were tested for bacterial load of commensal Neisseria and total bacterial load through PCR. Commensal Neisseria species identification was performed through targeted metagenomic sequencing of penA and flanking regions using Nanopore sequencing. Patients were treated with ceftriaxone 500mg IM according to national guidelines when testing positive for NG.
RESULTSPCR results showed that proportions of commensal Neisseria varied from 0.003% to 33%, with no clear observable difference between samples taken before and after antibiotic treatment. Targeted metagenomic sequencing showed a high degree of stable presence of N. subflava and stable absence of N. lactamica and N. oralis after antibiotic treatment. Other Neisseria species showed varying degrees of losses and gains after antibiotic treatment.
CONCLUSIONCommensal Neisseria form a reservoir of AMR for NG. Our results indicate that commensal Neisseria are not evidently affected in load after antibiotic treatment compared to other commensal bacterial species inhabiting the oropharynx. Furthermore, results indicate that some Neisseria species are more stable than others in response to antibiotic treatment, indicating that some Neisseria may provide a more suitable reservoir of AMR than others.
