Antimicrobial susceptibility of commensal Neisseria species in the Japanese population
Izumo Kanesaka1, Sheeba Santhini Manoharan-Basil2, Tessa De Block2
1STI Unit, Department of Clinical Sciences, Institute of Tropical Medicine Antwerp, Nationalestraat 155, 2000, Antwerp, Belgium; Department of Infection Control and Prevention, Faculty of Nursing, Toho University, 4-16-20, Omori-nishi, Ota-ku, Tokyo, 143-0015, Japan.
Objectives:
We aimed to, for the first time, characterize the antimicrobial susceptibilities of commensal Neisseria species in the general population in Japan. In particular, we assessed if the tetracycline minimum inhibitory concentrations (MICs) of these isolates were changing over time and, given the recent interest in doxycycline post exposure prophylaxis (PEP), if the tetracycline MICs were associated with those of the other antimicrobials.
Methods:
Neisseria spp. were isolated from 1679 patients visiting dental clinics in Japan between 2018 and 2023. The MICs of tetracycline, ceftriaxone, cefixime, penicillin, azithromycin and ciprofloxacin against Neisseria spp. were determined using agar dilution. Linear regression was used to assess if there was an association between MIC and the year the isolate was obtained from, controlling for species identity.
Results:
Neisseria spp. were detected in 424 of 1679 individuals sampled. Of these, 417 (98.3 %) isolates were identified as Neisseria subflava, and the remaining 7 (1.7 %) as Neisseria mucosa. The median tetracycline MIC was 0.5 mg/L (IQR 0.5-1 mg/L). The MICs of penicillin, cefixime, ceftriaxone and ciprofloxacin were lower in N. mucosa than in N. subflava. The tetracycline MICs of Neisseria spp. were positively correlated with penicillin, azithromycin and ciprofloxacin. No significant correlations were found with cefixime or ceftriaxone.
Conclusions:
Our results suggest that despite the overall decline in antimicrobial use in Japan, MICs for several antimicrobials have increased over time. In particular, the MIC of tetracycline tends to be high in Japan. These results suggest the need to include surveillance of tetracycline MICs of commensal Neisseria spp. in doxycycline PEP implementation studies.
Insights
Antimicrobial resistance in common Neisseria bacteria is increasing in Japan, with high tetracycline minimum inhibitory concentrations (MICs). This highlights the need for monitoring resistance when considering doxycycline post-exposure prophylaxis.
Area of Science:
- Microbiology
- Antimicrobial Resistance
- Public Health
Background:
- Commensal Neisseria species are part of the normal human microbiota.
- Antimicrobial resistance in commensal bacteria can be an indicator of broader resistance trends.
- Understanding resistance patterns is crucial for effective treatment and prophylaxis strategies.
Purpose of the Study:
- To characterize antimicrobial susceptibilities of commensal Neisseria species in Japan.
- To assess temporal trends in tetracycline minimum inhibitory concentrations (MICs).
- To investigate associations between tetracycline MICs and other antimicrobials, particularly in the context of doxycycline post-exposure prophylaxis (PEP).
Main Methods:
- Isolation of Neisseria spp. from 1679 patients in Japanese dental clinics (2018-2023).
- Determination of MICs for tetracycline and other antimicrobials using agar dilution.
- Linear regression analysis to assess MIC trends over time and correlations between different antimicrobial agents.
Main Results:
- Neisseria subflava (98.3%) and Neisseria mucosa (1.7%) were identified.
- Median tetracycline MIC was 0.5 mg/L (IQR 0.5-1 mg/L).
- Tetracycline MICs positively correlated with penicillin, azithromycin, and ciprofloxacin, but not cefixime or ceftriaxone.
Conclusions:
- Antimicrobial MICs for commensal Neisseria species in Japan show an increasing trend over time.
- Tetracycline MICs are notably high in this population.
- Surveillance of tetracycline MICs in commensal Neisseria is recommended for doxycycline PEP implementation studies.
