Background Previous transformation experiments with Neisseria gonorrhoeae (Ng) have established that it is able to acquire high-level antibiotic resistance via transformation. We aimed to assess if a high-level ceftriaxone resistant Ng strain (WHO X) was able to acquire resistance to azithromycin (AZM) via this mechanism.

Methods A mid log phase culture of Ng WHO X (AZM MIC 0.25 µg/mL) was mixed with whole genomic DNA extracted from Ng WHO strain V (AZM ≥ 256 µg/mL). A concentration of 1,5x MIC of AZM was added as a stress factor for the selection of the resistance determinants. Control experiments were conducted by omitting the addition of AZM and/or DNA. Consecutively, the mixture was plated on blood agar plates and incubated at 36°C in a 6% CO₂ atmosphere. Of each blood agar plate 1 or 2 colonies were selected for E testing performed according to CLSI guidelines. Colonies growing alongside the E-test strip at the higher range of the MIC values were selected for further characterization, including whole genome sequencing, and to identify the acquired resistance mechanisms.

Results The MIC for AZM of WHO strain X increased to greater than 256 μg/ml. There was no change in the MICs of Ng in the control experiments. Whole genome sequencing results will be presented demonstrating the pathways to resistance.

Conclusion Neisseria gonorrhoeae is able to rapidly acquire high level macrolide resistance in the presence of both DNA of AZM highly resistant NG strains and AZM.

Disclosure No significant relationships.