(P54) Alarmingly High Levels of Cephalosporin and Macrolide resistance in Oropharyngeal commensal Neisseria spp. from male patients, Seattle, WA, 2019–2022

Background: Some evidence suggests that oropharyngeal commensal Neisseria spp. act as a reservoir of antimicrobial resistance (AMR) leading to AMR Neisseria gonorrhoeae (Ng) through horizontal gene transfer. However, commensal Neisseria spp. are rarely cultured, there are limited data on their AMR profiles, and how often AMR in commensal Neisseria spp. leads to AMR Ng is unknown.

Methods: From 2019-2022, we cultured commensal Neisseria spp. using de-identified remnant pharyngeal specimens collected from male patients presenting to the municipal Sexual Health Clinic (SHC) and eight clinics in King County, WA who met clinical criteria for gonorrhea culture. Ng and Neisseria meningitidis (Nm) were confirmed by API NH and excluded from the study. Commensal Neisseria species confirmation was performed with the Bruker MALDI Biotyper and minimum inhibitory concentrations (MICs) for azithromycin (AZM), cefixime (CFX) and ceftriaxone (CRO) were determined by Etest. We defined cefixime resistance (CFX^R) and ceftriaxone resistance (CRO^R) as MIC ≥0.5 µg/ml, azithromycin resistance (AZM^R) as MIC ≥2 µg/ml, and high-level AZM^R (HL-AZM^R) as MIC≥256 µg/ml.

Results: We speciated 715 oropharyngeal non-Ng, non-Nm Neisseria spp. belonging to 10 different species by MALDI Biotyper, N. subflava (66.9%), N. macacae (9.5%), N. flavescens (9.5%), N. mucosa (5%), N. oralis (2.4%), N. perflava (2.1%), N. lactamica (1.4%), N. cinerea (1.1%), N. sicca (1.1%), and N. elongata (1%). Etest performed on 415 isolates of commensal Neisseria spp. showed high levels of AZM^R (95%), CFX^R (22%), and CRO^R (12%). The MIC ranges, MIC₅₀, and MIC₉₀ for the three antimicrobials were AZM 0.064 – >256, 128, and >256; CFX < 0.016 – 2μg/ml, 0.25 μg/ml, and 1 μg/ml; CRO 0.002 – 2μg/ml, 0.125 μg/ml, and 0.5 μg/ml, respectively. HL-AZM^R predominated among the commensal Neisseria spp.

Conclusion: Oropharyngeal commensal Neisseria spp. from male patients attending sexual health clinics in Seattle, WA, demonstrated high levels of macrolide and cephalosporin resistance suggesting that they harbor AMR determinants that can be transferred to Ng. However, given the rarity of CRO and CFX resistant Ng, transfer of AMR determinants from Neisseria spp. to Ng is likely a very rare event.